ASME B31.3 vs ASME B31.1

ASME B31.1 vs. ASME B31.3: Know the Piping Design Codes

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Introduction

In piping design and engineering, selecting the appropriate piping code is essential for ensuring safety, efficiency, and compliance with industry standards. Two of the most widely recognized piping design codes are ASME B31.1 and ASME B31.3. While they both come from the American Society of Mechanical Engineers (ASME) and govern the design and construction of piping systems, their applications differ significantly. Understanding the ASME B31.1 vs. ASME B31.3 debate is crucial for selecting the correct code for your project, whether it involves power plants, chemical processing, or industrial facilities.

Overview: ASME B31.1 vs. ASME B31.3

What is ASME B31.3 or Process Piping Code?

ASME B31.1 is the standard that governs the design, construction, and maintenance of power plant piping systems. It applies to piping systems in power plants, industrial plants, and other facilities where power generation is involved. This code focuses heavily on the integrity of systems that handle high-pressure steam, water, and hot gases.

Typical Applications: Power plants, heating systems, turbines, and boiler systems.
Pressure Range: High-pressure steam and fluid systems.
Temperature Range: High-temperature service, especially for steam and gas applications.

What is ASME B31.1 or Power Piping Code?

ASME B31.3 applies to the design and construction of piping systems used in chemical, petrochemical, and pharmaceutical industries. It governs systems that transport chemicals, gases, or liquids under different pressure and temperature conditions, often including hazardous materials. This code also covers the associated support systems and the safety considerations of handling chemicals and dangerous substances.

Typical Applications: Chemical processing plants, refineries, pharmaceutical facilities, food and beverage plants.
Pressure Range: Generally lower than the pressure range in ASME B31.1, depending on fluid types and their classification.
Temperature Range: varies depending on the chemical fluids, but it is typically lower than the extreme conditions in ASME B31.1.

Difference Between ASME B31.3 and ASME B31.1 (ASME B31.3 vs ASME B31.1)

ASME B31.3 vs ASME B31.1

ASME B31.3 vs ASME B31.1

Sr No Parameter ASME B31.3-Process Piping ASME B31.1-Power Piping
1 Scope Provides rules for Process or Chemical Plants Provides rules for Power Plants
2 Basic Allowable Material Stress Basic allowable material stress value is higher (For example the allowable stress value for A 106 B material at 250 Deg C is 132117.328 Kpa as per ASME B31.3) Basic allowable material stress value is lower (For example the allowable stress value for A 106 B material at 250 Deg C is 117900.344 Kpa as per ASME B31.3)
3 Allowable Sagging (Sustained) The ASME B31.3 code does not specifically limit allowable sagging. An allowable sagging of up to 15 mm is generally acceptable. ASME B31.3 does not provide a suggested support span. ASME B31.1 clearly specifies the allowable sagging value as 2.5 mm. Table 121.5-1 of ASME B31.1 provides suggested support span.
4 SIF on Reducers Process Piping Code ASME B31.3 does not use SIF (SIF=1.0) for reducer stress calculation Power Piping code ASME B31.1 uses a maximum SIF of 2.0 for reducers while stress calculation.
5 Factor of Safety ASME B31.3 uses a factor of safety of 3; relatively lower than ASME B31.1. ASME B31.1 uses a safety factor of 4 to have higher reliability as compared to Process plants
6 SIF for Butt Welded Joints ASME B31.3 uses a SIF of 1.0 for buttwelded joints ASME B31.1 uses a SIF of up to 1.9 max in stress calculation.
7 Approach towards SIF ASME B31.3 uses a complex in-plane, out-of-plane SIF approach. ASME B31.1 uses a simplified single SIF Approach.
8 Maximum values of Sc and Sh As per the Process Piping code, the maximum value of Sc and Sh are limited to 138 Mpa or 20 ksi. For the Power piping code, the maximum value of Sc and Sh are 138 Mpa only if the minimum tensile strength of the material is 70 ksi (480Mpa); otherwise, it depends on the values provided in the mandatory appendix A as per temperature.
9 Allowable Stress for Occasional Stresses The allowable value of occasional stress is 1.33 times Sh As per ASME B31.1, the allowable value of occasional stress is 1.15 to 1.20 times Sh
10 The equation for Pipe Wall Thickness Calculation The equation for pipe wall thickness calculation is valid for t<D/6 There is no such limitation in the Power piping wall thickness calculation. However, they add a limitation on maximum design pressure.
11 Section Modulus, Z for Sustained and Occasional Stresses While Sustained and Occasional stress calculation the Process Piping code reduces the thickness by corrosion and other allowances. ASME B31.1 calculates the section modulus using nominal thickness. Thickness is not reduced by corrosion and other allowances.
12 Rules for material usage below -29 Deg. C ASME B31.3 provides extensive rules for the use of materials below -29 degrees C The power piping code provides no such rules for pipe materials below -29 degrees C.
13 Maximum Value of Cyclic Stress Range Factor The maximum value of cyclic stress range factor f is 1.2 The maximum value of is 1.0
14 Allowance for Pressure Temperature Variation As per clause 302.2.4 of ASME B31.3, occasional pressure temperature variation can exceed the allowable by (a) 33% for no more than 10 hours at any one time and no more than 100 hours/year, or (b) 20% for no more than 50 hours at any one time and no more than 500 hours/year. As per clause 102.2.4 of ASME B31.1, occasional pressure temperature variation can exceed the allowable by (a) 15% if the event duration occurs for no more than 8 hours at any one time and not more than 800 hours/year or (b) 20% if the event duration occurs for not more than 1 hour at any one time and not more than 80 hour/year.
15 Design Life Process Piping is normally designed for 20 to 30 years of service life. Power Piping is generally designed for 40 years or more of service life.
16 PSV reaction force ASME B31.3 does not provide specific equations for PSV reaction force calculation. ASME B31.1 provides specific equations for PSV reaction force calculation.

Conclusion

The critical difference in the ASME B31.1 vs. ASME B31.3 debate lies in the industry applications, material requirements, and safety considerations. ASME B31.1 is ideal for power generation and high-temperature systems, focusing on mechanical integrity. At the same time, ASME B31.3 is tailored for the chemical and process industries, emphasizing the safe handling of hazardous materials and chemical compatibility. By understanding the distinctions between these two standards, you can decide which code best suits your project’s requirements, ensuring compliance and safety throughout the project’s lifecycle. Whether you are involved in power plant design or system’ processing, choosing the correct piping code is crucial for a successful project.

ASME BPVC Section II Part A

ASME BPVC Section II Part A: Ferrous Material Specifications

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Introduction

ASME BPVC Section II Part A: Ferrous Material Specifications is a section of the ASME Boiler and Pressure Vessel Code (BPVC) that covers specifications for ferrous materials (primarily iron) used in the construction of boilers, pressure vessels and other pressure-retaining equipment. This section specifically addresses the requirements for steel and iron materials, including carbon steel, alloy steel, and stainless steel.

Related Material Specifications for Tubes & Plates

Tubes:

SA-178/SA-178M – Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler and Superheater Tubes
SA-179/SA-179M – Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes
SA-192/SA-192M – Seamless Carbon Steel Boiler Tubes for High-Pressure Service
SA-209/SA-209M – Seamless Carbon-Molybdenum Alloy-Steel Boiler and Superheater Tubes
SA-210/SA-210M – Seamless Medium-Carbon Steel Boiler and Superheater Tubes
SA-213/SA-213M – Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
SA-214/SA-214M – Electric-Resistance-Welded Carbon Steel Heat-Exchanger and Condenser Tubes
SA-249/SA-249M – Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes
SA-250/SA-250M – Electric-Resistance-Welded Ferritic Alloy-Steel Boiler and Superheater Tubes
SA-268/SA-268M – Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service
SA-334/SA-334M – Seamless and Welded Carbon and Alloy-Steel Tubes for Low-Temperature Service
SA-335/SA-335M – Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service
SA-423/SA-423M – Seamless and Electric-Welded Low-Alloy Steel Tubes
SA-450/SA-450M – General Requirements for Carbon and Low Alloy Steel Tubes
SA-556/SA-556M – Seamless Cold-Drawn Carbon Steel Feedwater Heater Tubes
SA-557/SA-557M – Electric-Resistance-Welded Carbon Steel Feedwater Heater Tubes
SA-688/SA-688M – Seamless and Welded Austenitic Stainless Steel Feedwater Heater Tubes
SA-789/SA-789M – Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service
SA-790/SA-790M – Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe
SA-803/SA-803M – Seamless and Welded Ferritic Stainless Steel Feedwater Heater Tubes
SA-813/SA-813M – Single- or Double-Welded Austenitic Stainless Steel Pipe
SA-814/SA-814M – Cold-Worked Welded Austenitic Stainless Steel Pipe

ASME BPVC

ASME BPVC

Plates:

SA-203/SA-203M – Pressure Vessel Plates, Alloy Steel, Nickel
SA-204/SA-204M – Pressure Vessel Plates, Alloy Steel, Molybdenum
SA-285/SA-285M – Pressure Vessel Plates, Carbon Steel, Low- and Intermediate-Tensile Strength
SA-299/SA-299M – Pressure Vessel Plates, Carbon Steel, Manganese-Silicon
SA-302/SA-302M – Pressure Vessel Plates, Alloy Steel, Manganese-Molybdenum and Manganese-Molybdenum-Nickel
SA-353/SA-353M – Pressure Vessel Plates, Alloy Steel, Double-Normalized and Tempered 9% Nickel
SA-387/SA-387M – Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum
SA-516/SA-516M – Pressure Vessel Plates, Carbon Steel, for Moderate- and Lower-Temperature Service
SA-517/SA-517M – Pressure Vessel Plates, Alloy Steel, High-Strength, Quenched and Tempered
SA-533/SA-533M – Pressure Vessel Plates, Alloy Steel, Quenched and Tempered, Manganese-Molybdenum and Manganese-Molybdenum-Nickel
SA-537/SA-537M – Pressure Vessel Plates, Heat-Treated, Carbon-Manganese-Silicon Steel
SA-542/SA-542M – Pressure Vessel Plates, Alloy Steel, Quenched-and-Tempered, Chromium-Molybdenum, and Chromium-Molybdenum-Vanadium
SA-543/SA-543M – Pressure Vessel Plates, Alloy Steel, Quenched and Tempered, Nickel-Chromium-Molybdenum
SA-553/SA-553M – Pressure Vessel Plates, Alloy Steel, Quenched and Tempered 7, 8, and 9% Nickel
SA-612/SA-612M – Pressure Vessel Plates, Carbon Steel, High Strength, for Moderate and Lower Temperature Service
SA-662/SA-662M – Pressure Vessel Plates, Carbon-Manganese-Silicon Steel, for Moderate and Lower Temperature Service
SA-841/SA-841M – Pressure Vessel Plates, Produced by Thermo-Mechanical Control Process (TMCP)

Conclusion

In conclusion, ASME BPVC Section II Part A: Ferrous Material Specifications is a critical resource for ensuring the safety, reliability, and quality of ferrous materials used to construct boilers, pressure vessels, and other pressure-retaining equipment. By providing comprehensive specifications on the mechanical and chemical properties of materials like carbon steels, alloy steels, and stainless steels, this section ensures that materials meet the rigorous standards required for high-pressure and high-temperature applications. Its detailed guidance on product forms, testing procedures, and compliance with industry standards makes it indispensable for engineers, manufacturers, and inspectors involved in pressure equipment design and construction. As such, ASME BPVC Section II Part A is crucial for petrochemical, nuclear, and power generation industries, where pressure vessels and boilers must operate safely and efficiently under stringent mechanical stress conditions.

Quenching SAE4140 Seamless Steel Pipe

Analysis of the Causes of Ring-shaped Cracks in Quenched SAE 4140 Seamless Steel Pipe

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The reason for the ring-shaped crack at the pipe end of the SAE 4140 seamless steel pipe was studied by chemical composition exam, hardness test, metallographic observation, scanning electron microscope, and energy spectrum analysis. The results show that the ring-shaped crack of SAE 4140 seamless steel pipe is a quenching crack, generally occurring at the pipe’s end. The reason for the quenching crack is the different cooling rates between the inside and outside walls, and the outside wall cooling rate is much higher than that of the inside wall, which results in cracking failure caused by stress concentration near the inside wall position. The ring -shape crack can be eliminated by increasing the cooling rate of the inside wall of the steel pipe during quenching, improving the uniformity of the cooling rate between the inside and outside wall, and controlling the temperature after quenching to be within 150 ~200 ℃ to reduce the quenching stress by self-tempering.

SAE 4140 is a CrMo low alloy structural steel, is the American ASTM A519 standard grade, in the national standard 42CrMo based on the increase in the Mn content; therefore, SAE 4140 hardenability has been further improved. SAE 4140 seamless steel pipe, instead of solid forgings, rolling billet production of various types of hollow shafts, cylinders, sleeves, and other parts can significantly improve production efficiency and save steel; SAE 4140 steel pipe is widely used in oil and gas field mining screw drilling tools and other drilling equipment. SAE 4140 seamless steel pipe tempering treatment can meet the requirements of different steel strengths and toughness matching by optimizing the heat treatment process. Still, it is often found to affect product delivery defects in the production process. This paper mainly focuses on SAE 4140 steel pipe in the quenching process in the middle of the wall thickness of the end of the pipe, produces a ring-shaped crack defect analysis, and puts forward improvement measures.

1. Test Materials and Methods

A company produced specifications for ∅ 139.7 × 31.75 mm SAE 4140 steel grade seamless steel pipe, the production process for the billet heating → piercing → rolling → sizing → tempering (850 ℃ soaking time of 70 min quenching + pipe rotating outside the water shower cooling +735 ℃ soaking time of 2 h tempering) → Flaw Detection and Inspection. After the tempering treatment, the flaw detection inspection revealed that there was an annular crack in the middle of the wall thickness at the pipe end, as shown in Fig. 1; the annular crack appeared at about 21~24 mm away from the exterior, circled the circumference of the pipe, and was partially discontinuous, while no such defect was found in the pipe body.

Fig.1 The Ring-shaped Crack at Pipe End

Fig.1 The Ring-shaped Crack at Pipe End

Take the batch of steel pipe quenching samples for quenching analysis and quenching organization observation, and spectral analysis of the composition of the steel pipe, at the same time, in the tempered steel pipe cracks to take high power samples to observe the crack micro-morphology, grain size level, and in the scanning electron microscope with a spectrometer for the cracks in the internal composition of the micro-area analysis.

2. Test Results

2.1 Chemical composition

Table 1 shows the chemical composition spectral analysis results, and the composition of the elements is in accordance with the requirements of the ASTM A519 standard.

Table 1 Chemical composition analysis results (mass fraction, %)

Element C Si Mn P S Cr Mo Cu Ni
Content 0.39 0.20 0.82 0.01 0.005 0.94 0.18 0.05 0.02
ASTM A519 Requirement 0.38-0.43 0.15-0.35 0.75-1.00 ≤ 0.04 ≤ 0.04 0.8-1.1 0.15-0.25 ≤ 0.35 ≤ 0.25

2.2 Tube Hardenability Test

On the quenched samples of the total wall thickness quenching hardness test, the total wall thickness hardness results, as shown in Figure 2, can be seen in Figure 2, in 21 ~ 24 mm from the outside of the quenching hardness began to drop significantly, and from the outside of the 21 ~ 24 mm is the high-temperature tempering of the pipe found in the region of the ring crack, the area below and above the wall thickness of the hardness of the extreme difference between the position of the wall thickness of the region reached 5 ( HRC) or so. The hardness difference between this area’s lower and upper wall thicknesses is about 5 (HRC). The metallographic organization in the quenched state is shown in Fig. 3. From the metallographic organization in Fig. 3; it can be seen that the organization in the outer region of the pipe is a small amount of ferrite + martensite, while the organization near the inner surface is not quenched, with a small amount of ferrite and bainite, which leads to the low quenching hardness from the outer surface of the pipe to the inner surface of the pipe at a distance of 21 mm. The high degree of consistency of ring cracks in the pipe wall and the position of extreme difference in quenching hardness suggest that ring cracks are likely to be produced in the quenching process. The high consistency between the ring cracks’ location and the inferior quench hardness indicates that the ring cracks may have been produced during the quenching process.

Fig.2 The Quenching Hardness Value in Full Wall Thickness

Fig.2 The Quenching Hardness Value in Full Wall Thickness

Fig.3 Quenching Structure of Steel Pipe

Fig.3 Quenching Structure of Steel Pipe

2.3 The metallographic results of the steel pipe are shown in Fig. 4 and Fig. 5, respectively.

The matrix organization of the steel pipe is tempered austenite + a small amount of ferrite + a small amount of bainite, with a grain size of 8, which is an average tempered organization; the cracks extend along the longitudinal direction, which belongs along the crystalline cracking, and the two sides of the cracks have the typical characteristics of engaging; there is the phenomenon of decarburization on both sides, and high-temperature grey oxide layer is observable on the surface of the cracks. There is decarburization on both sides, and a high-temperature gray oxide layer can be observed on the crack surface, and no non-metallic inclusions can be seen in the vicinity of the crack.

Fig.4 Observations of Crack Morphology

Fig.4 Observations of Crack Morphology

Fig.5 Microstructure of Crack

Fig.5 Microstructure of Crack

2.4 Crack fracture morphology and energy spectrum analysis results

After the fracture is opened, the micro-morphology of the fracture is observed under the scanning electron microscope, as shown in Fig. 6, which shows that the fracture has been subjected to high temperatures and high-temperature oxidation has occurred on the surface. The fracture is mainly along the crystal fracture, with the grain size ranging from 20 to 30 μm, and no coarse grains and abnormal organizational defects are found; the energy spectrum analysis shows that the surface of the fracture is mainly composed of iron and its oxides, and no abnormal foreign elements are seen. Spectral analysis shows that the fracture surface is primarily iron and its oxides, with no abnormal foreign element.

Fig.6 Fracture Morphology of Crack

Fig.6 Fracture Morphology of Crack

3 Analysis and Discussion

3.1 Analysis of crack defects

From the viewpoint of crack micro-morphology, the crack opening is straight; the tail is curved and sharp; the crack extension path shows the characteristics of cracking along the crystal, and the two sides of the crack have typical meshing characteristics, which are the usual characteristics of quenching cracks. Still, the metallographic examination found that there are decarburization phenomena on both sides of the crack, which is not in line with the characteristics of the traditional quenching cracks, taking into account the fact that the tempering temperature of the steel pipe is 735 ℃, and Ac1 is 738 ℃ in SAE 4140, which is not in line with the conventional characteristics of quenching cracks. Considering that the tempering temperature used for the pipe is 735 °C and the Ac1 of SAE 4140 is 738 °C, which are very close to each other, it is assumed that the decarburization on both sides of the crack is related to the high-temperature tempering during the tempering (735 °C) and is not a crack that already existed before the heat treatment of the pipe.

3.2 Cracking causes

The causes of quenching cracks are generally related to the quenching heating temperature, quenching cooling rate, metallurgical defects, and quenching stresses. From the results of compositional analysis, the chemical composition of the pipe meets the requirements of SAE 4140 steel grade in ASTM A519 standard, and no exceeding elements were found; no non-metallic inclusions were found near the cracks, and the energy spectrum analysis at the crack fracture showed that the gray oxidation products in the cracks were Fe and its oxides, and no abnormal foreign elements were seen, so it can be ruled out that metallurgical defects caused the annular cracks; the grain size grade of the pipe was Grade 8, and the grain size grade was Grade 7, and the grain size was Grade 8, and the grain size was Grade 8. The grain size level of the pipe is 8; the grain is refined and not coarse, which indicates that the quenching crack has nothing to do with the quenching heating temperature.

The formation of quench cracks is closely related to the quenching stresses, divided into thermal and organizational stresses. Thermal stress is due to the cooling process of the steel pipe; the surface layer and the heart of the steel pipe cooling rate are not consistent, resulting in uneven contraction of the material and internal stresses; the result is the surface layer of the steel pipe is subjected to compressive stresses and the heart of the tensile stresses; tissue stresses is the quenching of the steel pipe organization to the martensite transformation, along with the expansion of the volume of inconsistency in the generation of the internal stresses, the organization of stresses generated by the result is the surface layer of tensile stresses, the center of the tensile stresses. These two kinds of stresses in the steel pipe exist in the same part, but the direction role is the opposite; the combined effect of the result is that one of the two stresses’ dominant factor, thermal stress dominant role is the result of the workpiece heart tensile, surface pressure; tissue stress dominant role is the result of the workpiece heart tensile pressure surface tensile.

SAE 4140 steel pipe quenching using rotating outer shower cooling production, the cooling rate of the outer surface is much greater than the inner surface, the outer metal of the steel pipe all quenched, while the inner metal is not entirely quenched to produce part of the ferrite and bainite organization, the inner metal due to the inner metal can not be fully converted into martensitic organization, the inner metal of the steel pipe is inevitably subjected to the tensile stress generated by the expansion of the outer wall of the martensite, and at the same time, due to the different types of organization, its specific volume is different between the inner and outer metal At the same time, due to the various kinds of organization, the particular volume of the inner and outer layers of the metal is different, and the shrinkage rate is not the same during cooling, tensile stress will also be generated at the interface of the two types of organization, and the distribution of the stress is dominated by the thermal stresses, and the tensile stress generated at the interface of the two types of organization inside the pipe is the largest, resulting in the ring quenching cracks occurring in the area of the wall thickness of the pipe close to the inner surface (21~24 mm away from the outer surface); in addition, the end of the steel pipe is a geometry-sensitive part of the whole pipe, prone to generate stress. In addition, the end of the pipe is a geometrically sensitive part of the entire pipe, which is prone to stress concentration. This ring crack usually occurs only at the end of the pipe, and such cracks have not been found in the pipe body.

In summary, quenched SAE 4140 thick-walled steel pipe ring-shaped cracks are caused by uneven cooling of the inner and outer walls; the cooling rate of the outer wall is much higher than that of the inner wall; production of SAE 4140 thick-walled steel pipe to change the existing cooling method, can not be used only outside the cooling process, the need to strengthen the cooling of the inner wall of the steel pipe, to improve the uniformity of the cooling rate of the inner and outer walls of the thick-walled steel pipe to reduce the stress concentration, eliminating the ring cracks. Ring cracks.

3.3 Improvement measures

To avoid quenching cracks, in the quenching process design, all the conditions that contribute to the development of quenching tensile stresses are factors for the formation of cracks, including the heating temperature, cooling process, and discharge temperature. Improved process measures proposed include: quenching temperature of 830-850 ℃; the use of an internal nozzle matched with the centerline of the pipe, control of the appropriate internal spray flow, improving the cooling rate of the inner hole to ensure that the cooling rate of the inner and outer walls of thick-walled steel pipe cooling rate uniformity; control of the post-quenching temperature of 150-200 ℃, the use of steel pipe residual temperature of the self-tempering, reduce the quenching stresses in the steel pipe.

The use of improved technology produces ∅158.75 × 34.93 mm, ∅139.7 × 31.75 mm, ∅254 × 38.1 mm, ∅224 × 26 mm, and so on, according to dozens of steel pipe specifications. After ultrasonic flaw inspection, the products are qualified, with no ring-quenching cracks.

4. Conclusion

(1) According to the macroscopic and microscopic characteristics of pipe cracks, the annular cracks at the pipe ends of SAE 4140 steel pipes belong to the cracking failure caused by quenching stress, which usually occurs at the pipe ends.

(2) Quenched SAE 4140 thick-walled steel pipe ring-shaped cracks are caused by uneven cooling of the inner and outer walls. The cooling rate of the outer wall is much higher than the inner wall’s. To improve the uniformity of the cooling rate of the inner and outer walls of the thick-walled steel pipe, the production of SAE 4140 thick-walled steel pipe needs to strengthen the cooling of the inner wall.

ASME SA213 T91 Seamless Steel Tube

ASME SA213 T91: How Much Do You Know?

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Background & Introduction

ASME SA213 T91, the steel number in the ASME SA213/SA213M standard, belongs to the improved 9Cr-1Mo steel, which was developed from the 1970s to the 1980s by the U.S. Rubber Ridge National Laboratory and the Metallurgical Materials Laboratory of the U.S. Combustion Engineering Corporation in cooperation. Developed based on the earlier 9Cr-1Mo steel, used in nuclear power (can also be used in other areas) high-temperature pressurized parts materials, is the third generation of hot-strength steel products; its main feature is to reduce the carbon content, in the limitation of the upper and lower limits of the carbon content, and more stringent control of the content of residual elements, such as P and S, at the same time, adding a trace of 0.030-0.070% of the N, and traces of the solid carbide-forming elements 0.18-0.25% of V and 0.06-0.10% of Nb, to refine the grain requirements, thereby improving the plastic toughness and weldability of steel, improve the stability of steel at high temperatures, after this multi-composite reinforcement, the formation of a new type of martensitic high-chromium heat-resistant alloy steel.

ASME SA213 T91, usually producing products for small-diameter tubes, is mainly used in boilers, superheaters, and heat exchangers.

International Corresponding Grades of T91 Steel

Country

 USA Germany Japan France China
Equivalent Steel Grade SA-213 T91 X10CrMoVNNb91 HCM95 TUZ10CDVNb0901 10Cr9Mo1VNbN

We will recognize this steel from several aspects here.

I. Chemical Composition of ASME SA213 T91

Element C Mn P S Si Cr Mo Ni V Nb N Al
Content 0.07-0.14 0.30-0.60 ≤0.020 ≤0.010 0.20-0.50 8.00-9.50 0.85-1.05 ≤0.40 0.18-0.25 0.06-0.10 0.030-0.070 ≤0.020

II. Performance Analysis

2.1 The role of alloying elements on the material properties: T91 steel alloying elements play a solid solution strengthening and diffusion strengthening role and improve the steel’s oxidation and corrosion resistance, analyzed explicitly as follows.
2.1.1 Carbon is the most apparent solid solution strengthening effect of steel elements; with the increase in carbon content, the short-term strength of steel, plasticity, and toughness decline, the T91 such steel, the rise in carbon content will accelerate the speed of carbide spheroidization and aggregation speed, accelerate the redistribution of alloying elements, reducing the weldability, corrosion resistance and oxidation resistance of steel, so heat-resistant steel generally want to reduce the amount of carbon content. Still, the strength of steel will be decreased if the carbon content is too low. T91 steel, compared with 12Cr1MoV steel, has a reduced carbon content of 20%, which is a careful consideration of the impact of the above factors.
2.1.2 T91 steel contains traces of nitrogen; the role of nitrogen is reflected in two aspects. On the one hand, the role of solid solution strengthening, nitrogen at room temperature in the steel solubility is minimal, T91 steel welded heat-affected zone in the process of welding heating and post-weld heat treatment, there will be a succession of solid solution and precipitation process of V.N.: Welding heating heat-affected zone has been formed within the austenitic organization due to the solubility of the V.N., nitrogen content increases, and after that, the degree of supersaturation in the organization of the room temperature increases in the subsequent heat treatment of the weld there is slight V.N. precipitation, which increases the stability of the organization and improves the value of the lasting strength of the heat affected zone. On the other hand, T91 steel also contains a small amount of A1; nitrogen can be formed with its A1N, A1N in more than 1 100 ℃ only a large number of dissolved into the matrix, and then re-precipitated at lower temperatures, which can play a better diffusion strengthening effect.
2.1.3 add chromium mainly to improve the oxidation resistance of heat-resistant steel, corrosion resistance, chromium content of less than 5%, 600 ℃ began to oxidize violently, while the amount of chromium content up to 5% has an excellent oxidation resistance. 12Cr1MoV steel in the following 580 ℃ has a good oxidation resistance, the depth of corrosion of 0.05 mm/a, 600 ℃ when the performance began to deteriorate, the depth of corrosion of 0.13 mm / a. T91 containing chromium content of 1 100 ℃ before a large number of dissolved into the matrix, and at lower temperatures and re-precipitation can play a sound diffusion strengthening effect. /T91 chromium content increased to about 9%, the use of temperature can reach 650 ℃, the primary measure is to make the matrix dissolved in more chromium.
2.1.4 vanadium and niobium are vital carbide-forming elements. When added to form a fine and stable alloy carbide with Carbon, there is a solid diffusion-strengthening effect.
2.1.5 Adding molybdenum mainly improves the thermal strength of the steel and strengthens solid solutions.

2.2 Mechanical Properties

T91 billet, after the final heat treatment for normalizing + high-temperature tempering, has a room temperature tensile strength ≥ 585 MPa, room temperature yield strength ≥ 415 MPa, hardness ≤ 250 HB, elongation (50 mm spacing of the standard circular specimen) ≥ 20%, the permissible stress value [σ] 650 ℃ = 30 MPa.

Heat treatment process: normalizing temperature of 1040 ℃, holding time of not less than 10 min, tempering temperature of 730 ~ 780 ℃, holding time of not less than one h.

2.3 Welding performance

In accordance with the International Welding Institute’s recommended Carbon equivalent formula, T91 steel carbon equivalent is calculated at 2.43%, and visible T91 weldability is poor.
The steel does not tend to reheat Cracking.

2.3.1 Problems with T91 welding

2.3.1.1 Cracking of hardened organization in the heat-affected zone
T91 cooling critical speed is low, austenite is very stable, and cooling does not quickly occur during standard pearlite transformation. It must be cooled to a lower temperature (about 400 ℃) to be transformed into martensite and coarse organization.
Welding produced by the heat-affected zone of the various organizations has different densities, coefficients of expansion, and different lattice forms in the heating and cooling process will inevitably be accompanied by different volume expansion and contraction; on the other hand, due to the welding heating has uneven and high-temperature characteristics, so the T91 welded joints are enormous internal stresses. Hardened coarse martensite organization joints that are in a complex stress state, at the same time, the weld cooling process hydrogen diffusion from the weld to the near-seam area, the presence of hydrogen has contributed to the martensite embrittlement, this combination of effects, it is easy to produce cold cracks in the quenched area.

2.3.1.2 Heat-affected zone grain growth
Welding thermal cycling significantly affects grain growth in the heat-affected zone of welded joints, especially in the fusion zone immediately adjacent to the maximum heating temperature. When the cooling rate is minor, the welded heat-affected zone will appear coarse massive ferrite and carbide organization so that the plasticity of the steel decreases significantly; the cooling rate is significant due to the production of coarse martensite organization, but also the plasticity of welded joints will be reduced.

2.3.1.3 Generation of softened layer
T91 steel welded in the tempered state, the heat-affected zone produces an inevitable softening layer, which is more severe than the softening of pearlite heat-resistant steel. Softening is more remarkable when using specifications with slower heating and cooling rates. In addition, the width of the softened layer and its distance from the fusion line are related to the heating conditions and characteristics of welding, preheating, and post-weld heat treatment.

2.3.1.4 Stress corrosion cracking
T91 steel in the post-weld heat treatment before the cooling temperature is generally not less than 100 ℃. If the cooling is at room temperature and the environment is relatively humid, it is easy to stress corrosion cracking. German regulations: Before the post-weld heat treatment, it must be cooled to below 150 ℃. In the case of thicker workpieces, fillet welds, and poor geometry, the cooling temperature is not less than 100 ℃. If cooling at room temperature and humidity is strictly prohibited, otherwise it is easy to produce stress corrosion cracks.

2.3.2 Welding process

2.3.2.1 Welding method: Manual welding, tungsten-pole gas-shielded, or melting-pole automatic welding can be used.
2.3.2.2 Welding material: can choose WE690 welding wire or welding rod.

Welding material selection:
(1) Welding of the same kind of steel – if manual welding can be used to make CM-9Cb manual welding rod, tungsten gas shielded welding can be used to make TGS-9Cb, melting pole automatic welding can be used to make MGS-9Cb wire;
(2) dissimilar steel welding – such as welding with austenitic stainless steel available ERNiCr-3 welding consumables.

2.3.2.3 Welding process points:
(1) the choice of preheating temperature before welding
T91 steel Ms point is about 400 ℃; preheating temperature is generally selected at 200 ~ 250 ℃. The preheating temperature can not be too high. Otherwise, the joint cooling rate is reduced, which may be caused in the welded joints at the grain boundaries of carbide precipitation and the formation of ferrite organization, thus significantly reducing the impact toughness of the steel welded joints at room temperature. Germany provides a preheating temperature of 180 ~ 250 ℃; the U.S. C.E. provides a preheating temperature of 120 ~ 205 ℃.

(2) the choice of welding channel / interlayer temperature
Interlayer temperature shall not be lower than the lower limit of the preheating temperature. Still, as with the selection of preheating temperature, the interlayer temperature can not be too high.T91 welding interlayer temperature is generally controlled at 200 ~ 300 ℃. French regulations: the interlayer temperature does not exceed 300 ℃. U.S. regulations: interlayer temperature can be located between 170 ~ 230 ℃.

(3) the choice of post-weld heat treatment starting temperature
T91 requires post-weld cooling to below the Ms point and hold for a certain period before tempering treatment, with a post-weld cooling rate of 80 ~ 100 ℃ / h. If not insulated, the joint austenitic organization may not be fully transformed; tempering heating will promote carbide precipitation along the austenitic grain boundaries, making the organization very brittle. However, T91 cannot be cooled to room temperature before tempering after welding because cold Cracking is dangerous when its welded joints are cooled to room temperature. For T91, the best post-weld heat treatment starting temperature of 100 ~ 150 ℃ and holding for one hour can ensure complete organization transformation.

(4) post-weld heat treatment tempering temperature, holding time, tempering cooling rate selection
Tempering temperature: T91 steel cold cracking tendency is more significant, and under certain conditions, it is prone to delayed Cracking, so the welded joints must be tempered within 24 hours after welding. T91 post-weld state of the organization of the lath martensite, after tempering, can be changed to tempered martensite; its performance is superior to the lath martensite. The tempering temperature is low; the tempering effect is not apparent; the weld metal is easy to age and embrittlement; the tempering temperature is too high (more than the AC1 line), the joint may be austenitized again, and in the subsequent cooling process to re-quench. At the same time, as described earlier in this paper, determining the tempering temperature should also consider the influence of the joint softening layer. In general, T91 tempering temperature of 730 ~ 780 ℃.
Holding time: T91 requires a post-weld tempering holding time of at least one hour to ensure its organization is wholly transformed into tempered martensite.
Tempering cooling rate: To reduce the residual stress of T91 steel welded joints, the cooling rate must be less than five ℃ / min.
Overall, the T91 steel welding process in the temperature control process can be briefly expressed in the figure below:

Temperature control process in the welding process of T91 steel tube

Temperature control process in the welding process of T91 steel tube

III. Understanding of ASME SA213 T91

3.1 T91 steel, by the principle of alloying, especially adding a small amount of niobium, vanadium, and other trace elements, significantly improves high-temperature strength and oxidation resistance compared to 12 Cr1MoV steel, but its welding performance is poor.
3.2 T91 steel has a greater tendency to cold Cracking during welding and needs to be pre-welding preheated to 200 ~ 250 ℃, maintaining the interlayer temperature at 200 ~ 300 ℃, which can effectively prevent cold cracks.
3.3 T91 steel post-welding heat treatment must be cooled to 100 ~ 150 ℃, insulation one hour, warming and tempering temperature to 730 ~ 780 ℃, insulation time of not less than one h, and finally, not more than 5 ℃ / min speed cooling to room temperature.

IV. Manufacturing Process of ASME SA213 T91

The manufacturing process of SA213 T91 requires several methods, including smelting, piercing, and rolling. The smelting process must control the chemical composition to ensure the steel pipe has excellent corrosion resistance. The piercing and rolling processes require precise temperature and pressure control to obtain the required mechanical properties and dimensional accuracy. In addition, steel pipes need to be heat-treated to remove internal stresses and improve corrosion resistance.

V. Applications of ASME SA213 T91

ASME SA213 T91 is a high-chromium heat-resistant steel, mainly used in the manufacture of high-temperature superheaters and reheaters and other pressurized parts of subcritical and supercritical power station boilers with metal wall temperatures not exceeding 625°C, and can also be used as high-temperature pressurized parts of pressure vessels and nuclear power. SA213 T91 has excellent creep resistance and can maintain stable size and shape at high temperatures and under long-term loads. Its main applications include boilers, superheaters, heat exchangers, and other equipment in the power, chemical, and petroleum industries. It is widely used in the petrochemical industry’s water-cooled walls of high-pressure boilers, economizer tubes, superheaters, reheaters, and tubes.

NACE MR0175 ISO 15156 vs NACE MR0103 ISO 17495-1

NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1

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Introduction

In the oil and gas industry, particularly in onshore and offshore environments, ensuring the longevity and reliability of materials exposed to aggressive conditions is paramount. This is where standards like NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1 come into play. Both standards provide critical guidance for material selection in sour service environments. However, understanding the differences between them is essential for selecting the right materials for your operations.

In this blog post, we will explore the key differences between NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1, and offer practical advice for oil and gas professionals navigating these standards. We will also discuss the specific applications, challenges, and solutions these standards provide, especially in the context of harsh oil and gas field environments.

What Are NACE MR0175/ISO 15156 and NACE MR0103/ISO 17495-1?

NACE MR0175/ISO 15156:
This standard is globally recognized for governing material selection and corrosion control in sour gas environments, where hydrogen sulfide (H₂S) is present. It provides guidelines for the design, manufacturing, and maintenance of materials used in onshore and offshore oil and gas operations. The goal is to mitigate the risks associated with hydrogen-induced cracking (HIC), sulfide stress cracking (SSC), and stress corrosion cracking (SCC), which can compromise the integrity of critical equipment like pipelines, valves, and wellheads.

NACE MR0103/ISO 17495-1:
On the other hand, NACE MR0103/ISO 17495-1 is primarily focused on materials used in refining and chemical processing environments, where exposure to sour service may occur, but with a slightly different scope. It covers the requirements for equipment exposed to mildly corrosive conditions, with an emphasis on ensuring materials can withstand the aggressive nature of specific refining processes like distillation or cracking, where the corrosion risk is comparatively lower than in upstream oil and gas operations.

NACE MR0175 ISO 15156 vs NACE MR0103 ISO 17495-1

NACE MR0175 ISO 15156 vs NACE MR0103 ISO 17495-1

Main Differences: NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1

Now that we have an overview of each standard, it is important to highlight the differences that may impact material selection in the field. These distinctions can significantly affect the performance of materials and the safety of operations.

1. Scope of Application

The primary difference between NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1 lies in the scope of their application.

NACE MR0175/ISO 15156 is tailored for equipment used in sour service environments where hydrogen sulfide is present. It is crucial in upstream activities such as exploration, production, and transportation of oil and gas, especially in offshore and onshore fields that deal with sour gas (gas containing hydrogen sulfide).

NACE MR0103/ISO 17495-1, while still addressing sour service, is more focused on refining and chemical industries, particularly where sour gas is involved in processes like refining, distillation, and cracking.

2. Environmental Severity

The environmental conditions are also a key factor in the application of these standards. NACE MR0175/ISO 15156 addresses more severe conditions of sour service. For instance, it covers higher concentrations of hydrogen sulfide, which is more corrosive and presents a higher risk for material degradation through mechanisms such as hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC).

In contrast, NACE MR0103/ISO 17495-1 considers environments that may be less severe in terms of hydrogen sulfide exposure, though still critical in refinery and chemical plant environments. The chemical composition of the fluids involved in the refining processes may not be as aggressive as those encountered in sour gas fields but still presents risks for corrosion.

3. Material Requirements

Both standards provide specific criteria for material selection, but they differ in their stringent requirements. NACE MR0175/ISO 15156 places greater emphasis on preventing hydrogen-related corrosion in materials, which can occur even in very low concentrations of hydrogen sulfide. This standard calls for materials that are resistant to SSC, HIC, and corrosion fatigue in sour environments.

On the other hand, NACE MR0103/ISO 17495-1 is less prescriptive in terms of hydrogen-related cracking but requires materials that can handle corrosive agents in refining processes, often focusing more on general corrosion resistance rather than specific hydrogen-related risks.

4. Testing and Verification

Both standards require testing and verification to ensure materials will perform in their respective environments. However, NACE MR0175/ISO 15156 demands more extensive testing and more detailed verification of material performance under sour service conditions. The tests include specific guidelines for SSC, HIC, and other failure modes associated with sour gas environments.

NACE MR0103/ISO 17495-1, while also requiring material testing, is often more flexible in terms of the testing criteria, focusing on ensuring that materials meet general corrosion resistance standards rather than focusing specifically on hydrogen sulfide-related risks.

Why Should You Care About NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1?

Understanding these differences can help prevent material failures, ensure operational safety, and comply with industry regulations. Whether you are working on an offshore oil rig, a pipeline project, or in a refinery, using the appropriate materials per these standards will safeguard against costly failures, unexpected downtime, and potential environmental hazards.

For oil and gas operations, especially in onshore and offshore sour service environments, NACE MR0175/ISO 15156 is the go-to standard. It ensures that materials withstand the harshest environments, mitigating risks like SSC and HIC that can lead to catastrophic failures.

In contrast, for operations in refining or chemical processing, NACE MR0103/ISO 17495-1 offers more tailored guidance. It allows materials to be used effectively in environments with sour gas but with less aggressive conditions compared to oil and gas extraction. The focus here is more on general corrosion resistance in processing environments.

Practical Guidance for Oil and Gas Professionals

When selecting materials for projects in either category, consider the following:

Understand Your Environment: Evaluate whether your operation is involved in sour gas extraction (upstream) or refining and chemical processing (downstream). This will help you determine which standard to apply.

Material Selection: Choose materials that are compliant with the relevant standard based on environmental conditions and the type of service (sour gas vs. refining). Stainless steels, high-alloy materials, and corrosion-resistant alloys are often recommended based on the severity of the environment.

Testing and Verification: Ensure that all materials are tested according to the respective standards. For sour gas environments, additional testing for SSC, HIC, and corrosion fatigue may be necessary.

Consult with Experts: It is always a good idea to consult with corrosion specialists or material engineers familiar with NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1 to ensure optimal material performance.

Conclusion

In conclusion, understanding the distinction between NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1 is essential for making informed decisions on material selection for both upstream and downstream oil and gas applications. By choosing the appropriate standard for your operation, you ensure the long-term integrity of your equipment and help prevent catastrophic failures that can arise from improperly specified materials. Whether you are working with sour gas in offshore fields or chemical processing in refineries, these standards will provide the necessary guidelines to protect your assets and maintain safety.

If you are unsure which standard to follow or need further assistance with material selection, reach out to a materials expert for tailored advice on NACE MR0175/ISO 15156 vs NACE MR0103/ISO 17495-1 and ensure your projects are both safe and compliant with industry best practices.

Boiler and Heat Exchanger

Boiler and Heat Exchanger: Seamless Tubes Selection Guide

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Introduction

In industries such as power generation, oil and gas, petrochemicals, and refineries, seamless tubes are essential components, especially in equipment that must withstand extreme temperatures, high pressures, and harsh, corrosive environments.  Boilers, heat exchangers, condensers, superheaters, air preheaters, and economizers use these tubes. Each of these applications demands specific material properties to ensure performance, safety, and longevity. The selection of seamless tubes for the boiler and heat exchanger depends on the specific temperature, pressure, corrosion resistance, and mechanical strength.

This guide provides an in-depth look into the various materials used for seamless tubes, including carbon steel, alloy steel, stainless steel, titanium alloys, nickel-based alloys, copper alloys, and zirconium alloys. We will also explore the relevant standards and grades, thereby helping you make more informed decisions for your Boiler and Heat Exchanger projects.

Overview of CS, AS, SS, Nickel Alloys, Titanium and Zirconium Alloys, Copper & Copper Alloys

1. Corrosion Resistance Properties

Each material used for seamless tubes has specific corrosion resistance properties that determine its suitability for different environments.

Carbon Steel: Limited corrosion resistance, typically used with protective coatings or linings. Subject to rusting in the presence of water and oxygen unless treated.
Alloy Steel: Moderate resistance to oxidation and corrosion. Alloy additions like chromium and molybdenum improve corrosion resistance at high temperatures.
Stainless Steel: Excellent resistance to general corrosion, stress corrosion cracking, and pitting due to its chromium content. Higher grades, such as 316L, have improved resistance to chloride-induced corrosion.
Nickel-Based Alloys: Outstanding resistance to aggressive environments like acidic, alkaline, and chloride-rich environments. Highly corrosive applications use alloys like Inconel 625, Hastelloy C276, and Alloy 825.
Titanium and Zirconium: Superior resistance to seawater brines, and other highly corrosive media. Titanium is especially resistant to chloride and acidic environments, while zirconium alloys excel in highly acidic conditions.
Copper and Copper Alloys: Excellent resistance to corrosion in freshwater and seawater, with copper-nickel alloys showing exceptional resistance in marine environments.

2. Physical and Thermal Properties

Carbon Steel:
Density: 7.85 g/cm³
Melting Point: 1,425-1,500°C
Thermal Conductivity: ~50 W/m·K
Alloy Steel:
Density: Varies slightly by alloying elements, typically around 7.85 g/cm³
Melting Point: 1,450-1,530°C
Thermal Conductivity: Lower than carbon steel due to alloying elements.
Stainless Steel:
Density: 7.75-8.0 g/cm³
Melting Point: ~1,400-1,530°C
Thermal Conductivity: ~16 W/m·K (lower than carbon steel).
Nickel-Based Alloys:
Density: 8.4-8.9 g/cm³ (depends on alloy)
Melting Point: 1,300-1,400°C
Thermal Conductivity: Typically low, ~10-16 W/m·K.
Titanium:
Density: 4.51 g/cm³
Melting Point: 1,668°C
Thermal Conductivity: ~22 W/m·K (relatively low).
Copper:
Density: 8.94 g/cm³
Melting Point: 1,084°C
Thermal Conductivity: ~390 W/m·K (excellent thermal conductivity).

3. Chemical Composition

Carbon Steel: Primarily iron with 0.3%-1.2% carbon and small amounts of manganese, silicon, and sulfur.
Alloy Steel: Includes elements like chromium, molybdenum, vanadium, and tungsten to improve strength and temperature resistance.
Stainless Steel: Typically contains 10.5%-30% chromium, along with nickel, molybdenum, and other elements depending on the grade.
Nickel-Based Alloys: Predominantly nickel (40%-70%) with chromium, molybdenum, and other alloying elements to enhance corrosion resistance.
Titanium: Grade 1 and 2 are commercially pure titanium, while Grade 5 (Ti-6Al-4V) includes 6% aluminum and 4% vanadium.
Copper Alloys: Copper alloys contain various elements like nickel (10%-30%) for corrosion resistance (e.g., Cu-Ni 90/10).

4. Mechanical Properties

Carbon Steel: Tensile Strength: 400-500 MPa, Yield Strength: 250-350 MPa, Elongation: 15%-25%
Alloy Steel: Tensile Strength: 500-900 MPa, Yield Strength: 300-700 MPa, Elongation: 10%-25%
Stainless Steel: Tensile Strength: 485-690 MPa (304/316), Yield Strength: 170-300 MPa, Elongation: 35%-40%
Nickel-Based Alloys: Tensile Strength: 550-1,000 MPa (Inconel 625), Yield Strength: 300-600 MPa, Elongation: 25%-50%
Titanium: Tensile Strength: 240-900 MPa (varies by grade), Yield Strength: 170-880 MPa, Elongation: 15%-30%
Copper Alloys: Tensile Strength: 200-500 MPa (depends on the alloy), Yield Strength: 100-300 MPa, Elongation: 20%-35%

5. Heat Treatment (Delivery Condition)

Carbon and Alloy Steel: Delivered in annealed or normalized condition. Heat treatments include quenching and tempering to improve strength and toughness.
Stainless Steel: Delivered in an annealed condition to remove internal stresses and improve ductility.
Nickel-Based Alloys: Solution annealed to optimize mechanical properties and corrosion resistance.
Titanium and Zirconium: Typically delivered in an annealed condition to maximize ductility and toughness.
Copper Alloys: Delivered in soft annealed condition, especially for forming applications.

6. Forming

Carbon and Alloy Steel: Can be hot or cold-formed, but alloy steels require more effort due to their higher strength.
Stainless Steel: Cold forming is common, though work-hardening rates are higher than carbon steel.
Nickel-Based Alloys: More challenging to form due to high strength and work-hardening rates; often requires hot working.
Titanium: Forming is best done at elevated temperatures due to its high strength at room temperature.
Copper Alloys: Easy to form due to good ductility.

7. Welding

Carbon and Alloy Steel: Generally easy to weld using conventional techniques, but preheat and post-weld heat treatment (PWHT) may be required.
Stainless Steel: Common welding methods include TIG, MIG, and arc welding. Careful control of heat input is necessary to avoid sensitization.
Nickel-Based Alloys: Challenging to weld due to high thermal expansion and susceptibility to cracking.
Titanium: Welded in a shielded environment (inert gas) to avoid contamination. Precautions are needed due to titanium’s reactivity at high temperatures.
Copper Alloys: Easy to weld, especially copper-nickel alloys, but preheating may be required to prevent cracking.

8. Corrosion of Welds

Stainless Steel: Can suffer from localized corrosion (e.g., pitting, crevice corrosion) at the weld heat-affected zone if not properly controlled.
Nickel-Based Alloys: Susceptible to stress corrosion cracking if exposed to chlorides at high temperatures.
Titanium: Welds must be properly shielded from oxygen to avoid embrittlement.

9. Descaling, Pickling, and Cleaning

Carbon and Alloy Steel: Pickling removes surface oxides after heat treatment. Common acids include hydrochloric and sulfuric acids.
Stainless Steel and Nickel Alloys: Pickling with nitric/hydrofluoric acid is used to remove heat tint and restore corrosion resistance after welding.
Titanium: Mild acid pickling solutions are used to clean the surface and remove oxides without damaging the metal.
Copper Alloys: Acid cleaning is used to remove surface tarnishes and oxides.

10. Surface Process (AP, BA, MP, EP, etc.)

AP (Annealed & Pickled): Standard finish for most stainless and nickel alloys after annealing and pickling.
BA (Bright Annealed): Achieved by annealing in a controlled atmosphere to produce a smooth, reflective surface.
MP (Mechanically Polished): Mechanical polishing improves surface smoothness, reducing the risk of contamination and corrosion initiation.
EP (Electropolished): An electrochemical process that removes surface material to create an ultra-smooth finish, reducing the surface roughness and improving corrosion resistance.

Stainless Heat Exchanger

                                                                                                                Stainless Heat Exchanger

I. Understanding Seamless Tubes

Seamless tubes differ from welded tubes in that they do not have a welded seam, which can be a weak point in some high-pressure applications. Seamless tubes are initially formed from a solid billet, which is then heated, and subsequently, it is either extruded or drawn over a mandrel to create the tube shape. The absence of seams gives them superior strength and reliability, making them ideal for high-pressure and high-temperature environments.

Common Applications:

Boilers: Seamless tubes are essential in the construction of water-tube and fire-tube boilers, where high temperatures and pressures are present.
Heat Exchangers: Used to transfer heat between two fluids, seamless tubes in heat exchangers must resist corrosion and maintain thermal efficiency.
Condensers: Seamless tubes help condense steam into water in power generation and refrigeration systems.
Superheaters: Seamless tubes are used to superheat steam in boilers, enhancing the efficiency of turbines in power plants.
Air Preheaters: These tubes transfer heat from flue gases to air, improving boiler efficiency.
Economizers: Seamless tubes in economizers preheat the feedwater using waste heat from boiler exhaust, boosting thermal efficiency.

Boilers, heat exchangers, condensers, superheaters, air preheaters, and economizers are integral components in several industries, particularly those involved in heat transfer, energy production, and fluid management. Specifically, these components find primary use in the following industries:

1. Power Generation Industry

Boilers: Used in power plants to convert chemical energy into thermal energy, often for steam generation.
Superheaters, Economizers, and Air Preheaters: These components improve efficiency by preheating the combustion air, recovering heat from exhaust gases, and further heating the steam.
Heat Exchangers and Condensers: Used for cooling and heat recovery in thermal power plants, particularly in steam-driven turbines and cooling cycles.

2. Oil & Gas Industry

Heat Exchangers: Crucial in refining processes, where heat is transferred between fluids, such as in crude oil distillation or in offshore platforms for gas processing.
Boilers and Economizers: Found in refineries and petrochemical plants for steam generation and energy recovery.
Condensers: Used to condense gases into liquids during the distillation processes.

3. Chemical Industry

Heat Exchangers: Used extensively to heat or cool chemical reactions, and to recover heat from exothermic reactions.
Boilers and Superheaters: Used to produce the steam required for various chemical processes, and to provide energy for distillation and reaction steps.
Air Preheaters and Economizers: Improve efficiency in energy-intensive chemical processes by recovering heat from exhaust gases and reducing fuel consumption.

4. Marine Industry

Boilers and Heat Exchangers: Essential in marine vessels for steam generation, heating, and cooling systems. Marine heat exchangers are often used to cool the ship’s engines and generate power.
Condensers: Used to convert exhaust steam back into water for reuse in the ship’s boiler systems.

5. Food and Beverage Industry

Heat Exchangers: Commonly used for pasteurization, sterilization, and evaporative processes.
Boilers and Economizers: Used to produce steam for food processing operations and to recover heat from the exhaust to save on fuel consumption.

6. HVAC (Heating, Ventilation, and Air Conditioning)

Heat Exchangers and Air Preheaters: Used in HVAC systems for efficient heat transfer between fluids or gases, providing heating or cooling for buildings and industrial facilities.
Condensers: Used in air conditioning systems to reject heat from the refrigerant.

7. Pulp and Paper Industry

Boilers, Heat Exchangers, and Economizers: Provide steam and heat recovery in processes such as pulping, paper drying, and chemical recovery.
Superheaters and Air Preheaters: Enhance energy efficiency in the recovery boilers and the overall heat balance of paper mills.

8. Metallurgical and Steel Industry

Heat Exchangers: Used for cooling hot gases and liquids in steel production and metallurgical processes.
Boilers and Economizers: Provide heat for various processes like blast furnace operation, heat treatment, and rolling.

9. Pharmaceutical Industry

Heat Exchangers: Used for controlling temperature during drug production, fermentation processes, and sterile environments.
Boilers: Generate the steam required for sterilization and heating of pharmaceutical equipment.

10. Waste-to-Energy Plants

Boilers, Condensers, and Economizers: Used for converting waste into energy through combustion, while recovering heat to improve efficiency.

Now, let’s dive into the materials that make seamless tubes suitable for these demanding applications.

II. Carbon Steel Tubes for Boiler and Heat Exchanger

Carbon steel is one of the most widely used materials for seamless tubes in industrial applications, primarily due to its excellent strength, as well as its affordability and widespread availability. Carbon steel tubes offer moderate temperature and pressure resistance, making them suitable for a wide range of applications.

Properties of Carbon Steel:
High Strength: Carbon steel tubes can withstand significant pressure and stress, making them ideal for use in boilers and heat exchangers.
Cost-Effective: Compared to other materials, carbon steel is relatively inexpensive, which makes it a popular choice in large-scale industrial applications.
Moderate Corrosion Resistance: While carbon steel is not as corrosion-resistant as stainless steel, it can be treated with coatings or linings to improve its longevity in corrosive environments.

Main Standards and Grades:

ASTM A179: This standard covers seamless cold-drawn low-carbon steel tubes used for heat exchanger and condenser applications. These tubes have excellent heat transfer properties and are commonly used in low to moderate-temperature and pressure applications.
ASTM A192: Seamless carbon steel boiler tubes designed for high-pressure service. These tubes are used in steam generation and other high-pressure environments.
ASTM A210: This standard covers seamless medium-carbon steel tubes for boiler and superheater applications. The A-1 and C grades offer varying levels of strength and temperature resistance.
ASTM A334 (Grades 1, 3, 6): Seamless and welded carbon steel tubes designed for low-temperature service. These grades are used in heat exchangers, condensers, and other low-temperature applications.
EN 10216-2 (P235GH, P265GH TC1/TC2): European standard for seamless steel tubes used in pressure applications, particularly in boilers and high-temperature service.

Carbon steel tubes are an excellent choice for Boiler and Heat Exchanger applications where high strength and moderate corrosion resistance are required.  However, for applications involving not only extremely high temperatures but also harsh corrosive environments, alloy or stainless steel tubes are often preferred due to their superior resistance and durability.

III. Alloy Steel Tubes for Boiler and Heat Exchanger

Alloy steel tubes are designed for high-temperature and high-pressure Boiler and Heat exchanger applications. These tubes are alloyed with elements like chromium, molybdenum, and vanadium to enhance their strength, hardness, and resistance to corrosion and heat. Alloy steel tubes are widely used in critical applications, such as superheaters, economizers, and high-temperature heat exchangers, due to their exceptional strength and resistance to heat and pressure.

Properties of Alloy Steel:
High Heat Resistance: Alloying elements such as chromium and molybdenum improve the high-temperature performance of these tubes, making them suitable for applications with extreme temperatures.
Improved Corrosion Resistance: Alloy steel tubes offer better resistance to oxidation and corrosion compared to carbon steel, particularly in high-temperature environments.
Enhanced Strength: Alloying elements also increase the strength of these tubes, allowing them to withstand high pressure in boilers and other critical equipment.

Main Standards and Grades:

ASTM A213 (Grades T5, T9, T11, T22, T91, T92): This standard covers seamless ferritic and austenitic alloy-steel tubes for use in boilers, superheaters, and heat exchangers. The grades differ in their alloying composition and are selected based on the specific temperature and pressure requirements.
T5 and T9: Suitable for moderate to high-temperature service.
T11 and T22: Commonly used in high-temperature applications, offering improved heat resistance.
T91 and T92: Advanced high-strength alloys designed for ultra-high-temperature service in power plants.
EN 10216-2 (16Mo3, 13CrMo4-5, 10CrMo9-10, 15NiCuMoNb5-6-4, X20CrMoV11-1): European standards for seamless alloy steel tubes used in high-temperature applications. These tubes are commonly used in boilers, superheaters, and economizers in power plants.
16Mo3: An alloy steel with good high-temperature properties, suitable for use in boilers and pressure vessels.
13CrMo4-5 and 10CrMo9-10: Chromium-molybdenum alloys that offer excellent heat and corrosion resistance for high-temperature applications.

Alloy steel tubes are the go-to option for high-temperature and high-pressure environments where carbon steel may not provide sufficient performance for the Boiler and Heat Exchanger.

IV. Stainless Steel Tubes for Boiler and Heat Exchanger

Stainless steel tubes offer exceptional corrosion resistance, making them ideal for Boiler and Heat Exchanger applications involving corrosive fluids, high temperatures, and harsh environments. They are widely used in heat exchangers, superheaters, and boilers, where, in addition to corrosion resistance, high-temperature strength is also required for optimal performance.

Properties of Stainless Steel:
Corrosion Resistance: Stainless steel’s resistance to corrosion comes from its chromium content, which forms a protective oxide layer on the surface.
High Strength at Elevated Temperatures: Stainless steel maintains its mechanical properties even at high temperatures, making it suitable for superheaters and other heat-intensive applications.
Long-Term Durability: Stainless steel’s resistance to corrosion and oxidation ensures a long service life, even in harsh environments.

Main Standards and Grades:

ASTM A213 / ASTM A249: These standards cover seamless and welded stainless steel tubes for use in boilers, superheaters, and heat exchangers. Common grades include:
TP304 / TP304L (EN 1.4301 / 1.4307): Austenitic stainless steel grades are widely used for their corrosion resistance and strength.
TP310S / TP310MoLN (EN 1.4845 / 1.4466): High-temperature stainless steel grades with excellent oxidation resistance.
TP316 / TP316L (EN 1.4401 / 1.4404): Molybdenum-bearing grades with enhanced corrosion resistance, particularly in chloride environments.
TP321 (EN 1.4541): Stabilized stainless steel grade used in high-temperature environments to prevent intergranular corrosion.
TP347H / TP347HFG (EN 1.4550 / 1.4961): High-carbon, stabilized grades for high-temperature applications such as superheaters and boilers.
UNS N08904 (904L) (EN 1.4539): Super austenitic stainless steel with excellent corrosion resistance, particularly in acidic environments.
ASTM A269: Covers seamless and welded austenitic stainless steel tubes for general corrosion-resistant service.
ASTM A789: Standard for duplex stainless steel tubes, offering a combination of excellent corrosion resistance and high strength.
UNS S31803, S32205, S32750, S32760: Duplex and super duplex stainless steel grades, offering superior corrosion resistance, especially in chloride-containing environments.
EN 10216-5: European standard covering stainless steel seamless tubes, including the following grades:
1.4301 / 1.4307 (TP304 / TP304L)
1.4401 / 1.4404 (TP316 / TP316L)
1.4845 (TP310S)
1.4466 (TP310MoLN)
1.4539 (UNS N08904 / 904L)

Stainless steel tubes are highly versatile and are used in a wide range of applications, including heat exchangers, boilers, and superheaters, where both corrosion resistance and high-temperature strength are not only required but also essential for optimal performance.

V. Nickel-based alloys for Boiler and Heat Exchanger

Nickel-based alloys are among the most corrosion-resistant materials available and are commonly used in Boiler and Heat exchanger applications involving extreme temperatures, corrosive environments, and high-pressure conditions. Nickel alloys provide outstanding resistance to oxidation, sulfidation, and carburization, making them ideal for heat exchangers, boilers, and superheaters in harsh environments.

Properties of Nickel-Based Alloys:
Exceptional Corrosion Resistance: Nickel alloys resist corrosion in acidic, alkaline, and chloride environments.
High-Temperature Stability: Nickel alloys maintain their strength and corrosion resistance even at elevated temperatures, making them suitable for high-temperature applications.
Oxidation and Sulfidation Resistance: Nickel alloys are resistant to oxidation and sulfidation, which can occur in high-temperature environments involving sulfur-bearing compounds.

Main Standards and Grades:

ASTM B163 / ASTM B407 / ASTM B444: These standards cover nickel-based alloys for seamless tubes used in boilers, heat exchangers, and superheaters. Common grades include:
Inconel 600 / 601: Excellent resistance to oxidation and high-temperature corrosion, making these alloys ideal for superheaters and high-temperature heat exchangers.
Inconel 625: Offers superior resistance to a wide range of corrosive environments, including acidic and chloride-rich environments.
Incoloy 800 / 800H / 800HT: Used in high-temperature applications due to their excellent resistance to oxidation and carburization.
Hastelloy C276 / C22: These nickel-molybdenum-chromium alloys are known for their outstanding corrosion resistance in highly corrosive environments, including acidic and chloride-containing media.
ASTM B423: Covers seamless tubes made from nickel-iron-chromium-molybdenum alloys such as Alloy 825, which offers excellent resistance to stress corrosion cracking and general corrosion in various environments.
EN 10216-5: European standard for nickel-based alloys used in seamless tubes for high-temperature and corrosive applications, including grades such as:
2.4816 (Inconel 600)
2.4851 (Inconel 601)
2.4856 (Inconel 625)
2.4858 (Alloy 825)

Nickel-based alloys are often chosen for critical applications where corrosion resistance and high-temperature performance are essential, such as in power plants, chemical processing, and oil and gas refineries Boiler and Heat Exchanger.

VI. Titanium and Zirconium Alloys for Boiler and Heat Exchanger

Titanium and zirconium alloys offer a unique combination of strength, corrosion resistance, and lightweight properties, making them ideal for specific applications in heat exchangers, condensers, and boilers.

Properties of Titanium Alloys:
High Strength-to-Weight Ratio: Titanium is as strong as steel but significantly lighter, making it suitable for weight-sensitive applications.
Excellent Corrosion Resistance: Titanium alloys are highly resistant to corrosion in seawater, acidic environments, and chloride-containing media.
Good Heat Resistance: Titanium alloys maintain their mechanical properties at elevated temperatures, making them suitable for heat exchanger tubes in power plants and chemical processing.
Properties of Zirconium Alloys:
Outstanding Corrosion Resistance: Zirconium alloys are highly resistant to corrosion in acidic environments, including sulfuric acid, nitric acid, and hydrochloric acid.
High-Temperature Stability: Zirconium alloys maintain their strength and corrosion resistance at elevated temperatures, making them ideal for high-temperature heat exchanger applications.

Main Standards and Grades:

ASTM B338: This standard covers seamless and welded titanium alloy tubes for use in heat exchangers and condensers. Common grades include:
Grade 1 / Grade 2: Commercially pure titanium grades with excellent corrosion resistance.
Grade 5 (Ti-6Al-4V): A titanium alloy with enhanced strength and high-temperature performance.
ASTM B523: Covers seamless and welded zirconium alloy tubes for use in heat exchangers and condensers. Common grades include:
Zirconium 702: A commercially pure zirconium alloy with outstanding corrosion resistance.
Zirconium 705: An alloyed zirconium grade with improved mechanical properties and high-temperature stability.

Titanium and zirconium alloys are commonly used in highly corrosive environments such as seawater desalination plants, chemical processing industries, and nuclear power plants Boiler and Heat Exchanger due to their superior corrosion resistance and lightweight properties.

VII. Copper and Copper Alloys for Boiler and Heat Exchanger

Copper and its alloys, including brass, bronze, and copper-nickel, are widely used in heat exchangers, condensers, and boilers due to their excellent thermal conductivity and corrosion resistance.

Properties of Copper Alloys:
Excellent Thermal Conductivity: Copper alloys are known for their high thermal conductivity, making them ideal for heat exchangers and condensers.
Corrosion Resistance: Copper alloys resist corrosion in water, including seawater, making them suitable for marine and desalination applications.
Antimicrobial Properties: Copper alloys have natural antimicrobial properties, making them suitable for applications in healthcare and water treatment.

Main Standards and Grades:

ASTM B111: This standard covers seamless copper and copper-alloy tubes for use in heat exchangers, condensers, and evaporators. Common grades include:
C44300 (Admiralty Brass): A copper-zinc alloy with good corrosion resistance, particularly in seawater applications.
C70600 (Copper-Nickel 90/10): A copper-nickel alloy with excellent corrosion resistance in seawater and marine environments.
C71500 (Copper-Nickel 70/30): Another copper-nickel alloy with higher nickel content for enhanced corrosion resistance.

Copper and copper alloys are widely used in marine Boiler and Heat Exchanger applications, power plants, and HVAC systems due to their excellent thermal conductivity and resistance to seawater corrosion.

In addition to the boiler and heat exchanger, condensers, superheaters, air preheaters, and economizers are also vital components that significantly optimize energy efficiency. For instance, the condenser cools the exhaust gases from both the boiler and heat exchanger, while the superheater, on the other hand, increases the steam temperature for improved performance. Meanwhile, the air preheater utilizes exhaust gases to heat incoming air, thereby further enhancing the overall efficiency of the boiler and heat exchanger system. Lastly, economizers play a crucial role by recovering waste heat from flue gases to preheat water, which ultimately reduces energy consumption and boosts the efficiency of both the boiler and heat exchanger.

VIII. Conclusion: Choosing the Right Materials for the Boiler and Heat Exchanger

Seamless tubes are integral to the performance of boilers, heat exchangers, condensers, superheaters, air preheaters, and economizers in industries such as power generation, oil and gas, and chemical processing. The choice of material for seamless tubes depends on the specific application requirements, including temperature, pressure, corrosion resistance, and mechanical strength.

Carbon steel offers affordability and strength for moderate temperature and pressure applications.
Alloy steel provides superior high-temperature performance and strength in boilers and superheaters.
Stainless steel delivers excellent corrosion resistance and durability in heat exchangers and superheaters.
Nickel-based alloys are the best choice for extremely corrosive and high-temperature environments.
Titanium and zirconium alloys are ideal for lightweight and highly corrosive applications.
Copper and copper alloys are preferred for their thermal conductivity and corrosion resistance in heat exchangers and condensers.

Boiler and heat exchanger systems play a crucial role in various industries by efficiently transferring heat from one medium to another. A boiler and heat exchanger work together to generate and transfer heat, providing essential heat for steam production in power plants and manufacturing processes.

By understanding the properties and applications of these materials, engineers and designers can make informed decisions, ensuring the safe and efficient operation of their equipment. When selecting materials for the Boiler and Heat Exchanger, it is crucial to consider the specific requirements of your application. Additionally, you should consult the relevant standards to ensure compatibility and optimal performance.