Questions raised by several experts during the drawing defense for the unit’s certification renewal (answers are being sought with a prize)

Some are relatively simple, while others are difficult to answer. Please organize the answers; there will be extra points for that.

(The information is from the Internet; used here with permission.) 1. The value of b1 is taken as the width at the top of the ribbed plate, that is, b3 for a standard saddle. The height h does not include the thickness of the backing plate. 2. For saddle arrangement A, it should be no greater than 0.2L; in this case, the maximum bending moment between the saddles is equal to the bending moment at the cross-section of the saddle. If the head is to serve as a reinforcing element, then A must also be no greater than 0.5R. Place the side with more external connectors on the fixed end, and place the larger connectors on that same side. 3. Saddle failure results in flattening at the saddle area; it should be a sinking in the middle, right? (Is this term correct?) ) There are four types of equipment failure: strength failure (fracture), stiffness failure (deformation), instability failure (which is also considered a type of deformation), and leakage failure (leakage). Second, the issues related to safety valves are not clear. Third, 1. The formulas are not provided here; the values calculated by these formulas represent the minimum values. The test pressure must not be lower than the pressure value calculated by the formulas. At the same time, shell stress verification shall be carried out using the test pressure, with the condition that it must not exceed 0.9#### (0.8####). 3. The temperature condition for the test medium is primarily established in response to the requirement regarding the temperature without ductile transition

1. The value of 1.b is taken as the width at the top of the stiffening plate, that is, b3 of the standard saddle; h is the height from the bottom surface to the outer wall of the cylinder. 2. The value of A for the saddle arrangement should not be greater than 0.2L (where L is the distance between the centers of connection between the cylinder and the head); in this case, the maximum bending moment between the saddles is equal to the bending moment at the saddle sections. If the head is to serve a reinforcing role, then A must also be less than or equal to 0.5R. Place the side with more external connectors on the fixed end, and place the larger connectors on that same side. 3. Seat failure results in flattening at the seat area; the middle part should collapse. 4. Equipment failure can occur due to strength failure (fracture), stiffness failure (deformation), instability failure (which is also a form of deformation), or leakage failure (leakage). II.1. When the valve core reaches a measurable opening height, and the medium is discharged continuously, either visually or audibly, the pressure at this point is the opening pressure. “When the \"puff\" sound is heard, it is not due to an increase in pressure; rather, it is the normal operating pressure of the safety valve. 2. Discharge pressure refers to the set pressure plus the excess pressure (excess pressure is the amount of pressure that exceeds the set pressure of the safety valve, usually expressed as a percentage of the set pressure); in other words, it is the inlet pressure when the valve disc reaches the specified opening height. The upper limit of the discharge pressure must comply with the requirements of **relevant standards or specifications. 2, 3: Seat return pressure – the pressure at the valve inlet when, after the safety valve has discharged, its valve disc comes into contact with the seat again, that is, when the opening height becomes zero. 4. When there is only one safety valve on the container, its opening pressure must not be greater than the design pressure. (When there are multiple safety valves on the container, the opening pressure of one safety valve shall not be greater than the design pressure, while the opening pressure of the other safety valves may be greater than the design pressure.) ) III, 1.2: Refer to GB150; the temperature requirements for the testing medium are established primarily in regard to the threshold temperature at which no ductile transformation occurs. IV, 1: The scope of application can be found in GB150. 2. Calculated based on nominal thickness 3. Not very clear

1. Issue with inputting b and h values when calculating SW6? (This question is not about that; it’s an error I made while reviewing a colleague’s calculation sheets for a defense presentation.) The value of the saddle width that needs to be entered in the calculation software should be the axial width of the saddle at the point where it contacts the cylinder, and not the width of the saddle’s base plate. For JB4712—92 saddle supports, the value b3 should be used instead of b1. h is the height from the top surface of the saddle base plate to the outer wall of the cylinder. 2. Principles for determining the placement of saddles – why? What are the principles for setting the fixed end? The placement of the saddles should be as close as possible to the head; that is, A should be less than or equal to D0/4 and not exceed 0.2L, because in this case the maximum bending moment between the saddles is equal to the bending moment at the saddle section. The fixed end should be located at the pipeline end. 3. What are the various manifestations of failure in the saddle? Three cases exhibit flattening at the saddle area, resulting in failure in strength and stiffness ； The top middle part is subject to instability failure. 4. There are several types of equipment failure; examples for each include strength failure (fracture), stiffness failure (minor deformation), and instability failure (major deformation). II. Issues related to safety valves 1.2.3. Not very clear. 4. Can the opening pressure of a safety valve be higher than the design pressure (when there is only one safety valve on the equipment)? If so, under what circumstances? Article 146 of the Code: When only one safety valve is installed on a fixed-pressure vessel, its opening pressure shall not be greater than the design pressure of the vessel. When multiple safety valves are installed on the vessel, the opening pressure of one of them shall not be greater than the vessel’s design pressure, while the opening pressure of the remaining safety valves may be increased appropriately. III. Hydrostatic test issues 1. The expression for the pressure test – what do the various symbols represent? See GB150 3.8.1 IV. Issues related to reinforcement of openings 1. What is the scope of application of GB150-1998 regarding openings in cylinders and heads? Refer to GB150 8.2 2. When calculating the reinforcement for openings, how is the area that needs to be reinforced determined? (What is the basis used for calculating this thickness?) Nominal thickness 3. How to calculate it for overall reinforcement? (What kind of stresses, etc.) V. Heat treatment issues 1. How many categories are there for heat treatment? Post-weld heat treatment ； Heat treatment for restoring mechanical properties ； Heat treatment to change mechanical properties ； Dehydrogenation heat treatment 2. What types of equipment require heat treatment (mention general categories such as media, etc.). GB150 10.4: Containers specified in the drawings as being susceptible to stress corrosion, such as those used for storing liquefied petroleum gas, liquid ammonia, etc.; containers specified in the drawings as holding media with extremely high or high toxicity levels. VIII. Material selection issues 1. What are the principles for selecting materials resistant to hydrogen sulfide corrosion? 2. What are the requirements for materials when the hydrogen sulfide concentration is greater than 100 mg/l? Carbon steel and low-alloy steel sheets should be ultrasonically inspected one by one. 3. What issues should be considered in the design of thick plates? 4. What are the requirements for sheets in the three types of containers? The materials require re-inspection. 5. Should low-temperature impact tests be conducted on the spherical tanks intended for Shandong? 6. Is it sufficient to specify GB3531 for low-temperature steel? What other requirements should be stated or what additional information should be included? Technical requirement: The steel plate must be retested ； Charpy impact test with V-notch at low temperatures. IX. Basic issues: What are the calculation formulas for internal pressure cylinders according to GB150-1998? What is its scope of application? Why? See GB150-1998 5.2. Last edited by Yajiong on 2009-3-13 11:33.]

Let’s take our time and answer gradually: lol Please don’t delete it, Banzhu: handshake 1. The saddle seat issue – it has already been answered upstairs. 2. The safety valve issue: 1. What is the opening pressure of a safety valve? Is the pressure at which the ‘puff’ sound starts to be heard the opening pressure? When the medium pressure rises to the specified value, the valve disc opens automatically and the medium is discharged rapidly; the pressure at the inlet of the valve at this point is known as the opening pressure. Yes. 2. What is the discharge pressure of a safety valve? Describe the state of the valve disc and indicate the height it rises to Once the valve disc is opened, if the pressure of the medium in the equipment’s pipeline continues to rise, the valve disc should remain fully open to discharge the rated volume of medium; at this point, the pressure at the valve inlet is referred to as the discharge pressure. It consists of two parts: the design pressure and the overpressure limit, with the valve disc fully open ； The maximum rising height is 3. What is the reset pressure of the safety valve, and what is the state of the valve disc? The inlet pressure at which the valve disc presses back against the seat after the safety valve has discharged, and flow stops. The return seat pressure is an important parameter that indicates the quality of a safety valve’s performance; it is generally required to be at least 80% of the operating pressure, with an upper limit set such that the valve disc does not experience frequent bouncing. The valve disc presses back against the valve seat. 4. Can the opening pressure of the safety valve be higher than the design pressure (when there is only one safety valve on the equipment)? If so, under what circumstances? No. According to Article 146 of the Regulatory Regulations, when only one safety valve is installed on a fixed-pressure vessel, the opening pressure Pz of that safety valve shall not be greater than the design pressure P of the vessel; moreover, the sealing test pressure Pt of the safety valve shall be greater than the highest operating pressure Pw of the vessel. That is: Pz ≤ P and Pt > Pw. When multiple safety valves are installed on a fixed-pressure vessel, the opening pressure of one of these valves shall not exceed the design pressure of the vessel, while the opening pressures of the other valves can be increased appropriately, but must not exceed 1.05 times the design pressure. Article 147: The opening pressure of the safety valve on mobile pressure vessels shall be 1.05 to 1.10 times the design pressure of the vessel. The rated discharge pressure of the safety valve shall not exceed 1.2 times the design pressure of the vessel, and the reseating pressure shall not be less than 0.8 times the opening pressure. III. Issues related to hydrostatic testing 1. What is the formula for the pressure test, and what do the various symbols represent? 2. What considerations should be taken regarding the pressure value for pressure testing? (What are the principles for determining the pressure value in pressure tests, and what conditions must the stress in the cylinder meet during the test?) )sT must satisfy the following conditions: During hydrostatic testing, sT ≤ 0.9φσs(σ0.2); during pneumatic testing, sT ≤ 0.8φσs(σ0.2). Where: σs(σ0.2) is the yield point (or 0.2% yield strength) of the cylinder material at the testing temperature, in MPa ； φ —— Weld joint coefficient of the cylinder. 3. Why are specified test medium temperatures set for various materials? IV. Issues related to reinforcement of openings 1. What is the scope of application of GB150-1998 regarding openings in cylinders and heads? 2. When calculating the reinforcement for openings, how is the area that needs to be reinforced determined? (What is the basis used for calculating this thickness?) 3. How should it be calculated for overall reinforcement? (What kind of stresses, etc.) V. Heat treatment issues 1. How many categories are there for heat treatment? 2. What types of equipment require heat treatment (mention general categories such as media, etc.)? 1) What thicknesses need heat treatment, and which components are used the most? Why? Is the heat treatment at this stage a post-weld stress-relief heat treatment, and what is it? VI. Issues with welding test plates (liquid chlorine: operating temperature -30, operating pressure 0.3 ； The designer set the design temperature at 50 degrees and the design pressure at 1.57 Mpa ； The material used is 16MnDR. 1. How should the design temperature be specified, and how should the design pressure be determined? 2. How many weld test pieces are required for low-temperature vessels? Where are they located respectively? VII. Non-destructive testing issues: What has been added to the 2005 version of non-destructive testing compared to the 1994 version? (This way of asking is related to the training we organized for those who attended the promotion event in Hainan after they returned.) I’ll ask it differently: what are the requirements for RT and UT transillumination, and in what situations are they applicable respectively? VIII. Material selection issues 1. What are the principles for material selection in cases of hydrogen sulfide corrosion? 2. What are the requirements for materials when the hydrogen sulfide concentration is greater than 100 mg/l? 3. What issues should be considered in the thick plate design process? 4. What are the requirements for sheets in the three types of containers? 5. Should spherical tanks used in Shandong undergo low-temperature impact testing? 6. Is it sufficient to specify GB3531 for low-temperature steel? What other requirements should be stated or what additional information should be included? IX. Basic question: What is the calculation formula for internal pressure cylinders in GB150-1998? What is its scope of application? Why? Last edited by 263525689 on 2009-3-18 20:04]

1. What is the opening pressure of a safety valve? Is the pressure at which the \"puff\" sound starts to be heard the opening pressure? Answer: When the medium pressure rises to the specified value, the valve disc opens automatically and the medium is discharged rapidly; the pressure at the inlet of the valve at this point is called the opening pressure. However, the pressure at which the \"puff\" sounds begin is not the opening pressure; it is rather the pressure at which relief occurs. The safety valve will open only when the pressure continues to rise. In other words, the relief pressure is less than the opening pressure. This post was last edited by 263525689 on 2009-3-18 at 20:05.]

In response to what was said above: The pressure that appears when there are \"pfft\" sounds is not the opening pressure; it is rather the pressure being released. It is only when the pressure continues to rise that the safety valve opens. In other words, it is not accurate to say that the relief pressure is less than the opening pressure. The opening pressure of a safety valve is the pressure at which it starts to operate; it is less than the discharge pressure of the safety valve (the pressure at which the safety valve opens fully)

This post is excellent and very practical; it’s definitely a great post. I hope it gets pinned as a highlight.

Are there any material selection principles for hydrogen sulfide corrosion? No one has answered this question yet; I think the new standard to use is 20R, with Q245R being the appropriate choice

It seems these questions have been asked before, and there aren’t many comprehensive and systematic answers available

1. Issue with inputting b and h values when calculating SW6? (This question is not about that; it’s an error I made while reviewing a colleague’s calculation sheets for a presentation.) b refers to the thickness of the saddle plate’s web, while h denotes the height of the saddle plate (excluding the thickness of the reinforcement plates and the bottom plate). 2. Principles for the placement of the saddle, why? What are the principles for setting the fixed end? The distance A from the center of the support to the head should be kept as small as possible, at or less than 0.5Ra; when this cannot be achieved, the value of A should not exceed 0.2L. For double-saddle supports, the fixed end is usually located on the side of the container where there are more and larger nozzles. For triple-saddle supports, the fixed end is placed in the middle to reduce the displacement of the sliding end. 3.3. Why are specified test medium temperatures for various materials established? As the temperature drops, the risk of brittle fracture in steel increases, which is particularly important when conducting pressure tests outdoors during cold winters; therefore, a limit is set for the test temperature, which must be 30 degrees higher than the material’s transition temperature to loss of ductility. 4.2 When calculating the reinforcement for openings, how is the area that needs to be reinforced determined? (What is the basis used for calculating this thickness?) Based on the calculated thickness at the opening of the cylinder or spherical shell. This post was last edited by LIJINQIANG on 2009-3-18 14:07.]

Equipment failure can be categorized into several types, each with examples: elastic failure, plastic failure, elastoplastic failure, plastic instability–progressive collapse failure, explosive failure, fatigue failure, fracture failure, creep and stress relaxation failure, corrosion failure, and stiffness failure (for liquid chlorine: operating temperature of -30, operating pressure of 0.3； The designer set the design temperature at 50 degrees and the design pressure at 1.57 Mpa ； The material used is 16MnDR. 1. How should the design temperature be specified, and how should the design pressure be determined? The design temperature is -35°C/50°C; the corresponding protective steam pressures are 0.1/1.47 MPa in absolute terms. The design pressure is 1.37 MPa (many people use 1.62 MPa; for safety reasons, I have also chosen 1.62 MPa). 8.1 What are the principles for selecting materials resistant to hydrogen sulfide corrosion? See Specification P128, 8.2: What are the requirements for materials when the hydrogen sulfide concentration is greater than 100 mg/l? Carbon steel and low-alloy steel plates used for manufacturing pressure vessel shells shall be subjected to ultrasonic testing on a sheet-by-sheet basis, with the acceptance level being no lower than Grade II. 8.4. What are the requirements for sheets in the three types of containers? The regulatory requirements state that the steel plates used to manufacture Class 3 pressure vessels must be retested. 5. Should spherical tanks used in Shandong undergo low-temperature impact testing? Regions across the country where the average monthly minimum temperature is below minus 20 and minus 10 do not include Shandong; therefore, low-temperature stress tests should not be conducted due to environmental factors

Some know, some don’t; please announce the correct answer.

Not even a repost was made; it was simply copied outright. These issues related to certificate renewal were those that arose during the certificate renewal defense process by Liaoning Jinhua Chemical Engineering Design Co., Ltd. in 2006. I noticed that some of the responses were also copied directly from chemical engineering forums. I am deeply disappointed and disgusted by the fact that the original poster and some members chose to copy answers directly. Those looking for answers should go to the chemical engineering forums

Is this about renewing design qualifications? Our company will also start preparing for a renewal in the second half of the year; it’s related to manufacturing, so we’ll prepare a document as well: lol

VIII. Material selection issues 1. What are the principles for material selection in cases of hydrogen sulfide corrosion? Carbon steels and low-alloy steels used in wet H2S stress corrosion environments shall meet the requirements of each item in the series: a. The yield strength σs specified in the material standards shall be ≤ 355 MPa ； b. The actual measured tensile strength σb of the material ≤ 603 MPa ； c. The material should be in at least one of the following conditions: normalized, normalized + tempered, reverted, or quenched and tempered ； d. Carbon equivalent limit: For carbon steel and carbon-manganese steel, Ce≤0.40; Ce=C+Mn/6. For low-alloy steel (including low-temperature nickel steel), Ce≤0.45; Ce=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15. e. For non-welded parts or materials that have been normalized or tempered after welding, the hardness requirements are as follows: For low-carbon steel, HV(10) ≤220 (single value); for low-alloy steel, HV(10) ≤245 (single value). f. When the thickness of the steel plate used for the shell is greater than 20 mm, ultrasonic testing shall be carried out in accordance with JB4730, with results meeting Grade II requirements.

2. When calculating the reinforcement for openings, how is the area that needs to be reinforced determined? (What is the basis used for calculating this thickness?) The calculated thickness of the shell at the opening and the effective thickness of the nozzle (page P76 of GB150). 3. What issues should be considered in the design of thick plates? Requirements for ultrasonic testing of carbon steel and low-alloy steel plates; Requirements for the supply and service condition of steel; Requirements regarding forging grades; Requirements for impact testing; Requirements for heat treatment; Non-destructive testing

Thank you for such a great post. Please don’t delete it, OP – give me a chance to learn from it, and also provide a platform for everyone to learn and communicate. I’m extremely grateful

Learned* Saved Looking forward to new posts