For drawings that require the indication of the maximum allowable operating pressure, how do people handle the design parameters?
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This post was last edited by yechao25038 on 2019-3-22 at 14:12. According to the fixed-volume regulations, equipment must undergo a gas-tightness test and be equipped with a safety relief device; the maximum allowable operating pressure must also be indicated. Let me first talk about what I do. The input design pressure used in the calculations is taken directly as the final maximum allowable operating pressure; thereafter, the design pressure on the calculation sheets and drawings is adjusted according to the positive or negative deviations of the safety valve or rupture disc. The unit’s review team said what I’m doing is incorrect and increases costs ； It is said that to determine the maximum allowable operating pressure, one only needs to follow the calculations provided in the manual, that is, to use the effective thickness of the tank head of 150.3 to calculate the maximum allowable operating pressure ； Will this ensure the strength of the hole reinforcement (without considering the allowance)? There’s another issue: the customer saw the \"maximum allowable operating pressure\" indicated on the drawings and asked me whether the operating pressure could reach that value. My answer was no; the actual operating pressure cannot be higher than the maximum allowable operating pressure (I have no basis for this, but it’s something I’ve always assumed subconsciously: lol). However, the review team’s response was that as long as the safety valve does not activate, there is no problem (that is, when the actual operating pressure is higher than the design pressure but the safety valve does not trigger). What do you all think?
It’s an old problem, 1. There are differences in understanding; the MAWP is derived from ASME. When designing according to China’s standards, there are also two approaches: one involves calculating the MAWP, while the other does not. For pressure vessels whose MAWP is not taken into account, design can be carried out using traditional methods. If the equipment is designed based on the calculated MAWP, it becomes more complex. China’s SW6 software can only calculate the MAWP of major components such as the cylinder and head; it lacks the capability to calculate the MAWP of pipe flanges, openings for reinforcement, or the tube sheets of heat exchangers. Therefore, it can be said that this tool is inadequate. (It also needs to be reviewed using other software). 3. That’s why the equipment is designed based on the calculated MAWP; if the tools available aren’t sufficient, it’s very difficult to determine the actual MAWP indicated on the drawings. .
The simpler approach might be to use the design pressure entered in the software as the MAWP on the final drawings, and then work backwards to determine the design pressure.
First, the process parameters are determined: the design pressure is calculated based on the maximum operating pressure, the set pressure is derived from the design pressure, and the maximum allowable operating pressure is obtained from the set pressure. The maximum allowable operating pressure is then used as the pressure value for strength calculations. It’s not the manufacturing unit, so we don’t pay much attention to costs; the manufacturing unit is likely to be more strict about costs.
The maximum allowable operating pressure is, by definition, a value that is calculated inversely, but in practice, as mentioned on the second floor, it is very difficult to determine such a value. I believe that during the airtightness test, the relationship between the three pressures should be: design pressure < relief valve setting pressure < maximum allowable operating pressure ； The maximum allowable pressure we set now is a value that is slightly higher than the setting pressure of the safety valve along with its tolerance. It is artificially assigned.
No, just don’t include the MAWP; follow the conventional design methods used in the past.
1) If a gas-tightness test is to be conducted, your maximum allowable operating pressure must be calculated based on the effective thickness of all pressure-bearing components. Then, the sealing pressure of the safety valve (which is generally 90% of the set pressure) must be higher than the design pressure; otherwise, the airtightness test must be conducted at the design pressure, and the safety valve should activate. 2) The reinforcement calculation is fine, as it is based on the effective thickness anyway. 3) With the maximum allowable operating pressure defined, the setting pressure of the safety valve can be determined based on this maximum allowable operating pressure, which meets the requirements of the Pressure Vessel Regulations. 4) For leakage tests, it is not necessary to use the airtightness testing method; alternatives such as ammonia leak detection, helium leak detection, and halogen leak detection are also available. The test pressure for these methods is specified in the design documents, and it is not required to use the design pressure exactly. Therefore, if these methods are chosen, there is no need to consider the maximum allowable operating pressure.
The manufacturer’s facility needs to conduct a airtightness test. Unless the highest allowable operating pressure is considered, the setting pressure of the safety valve must not exceed the design pressure; as a result, the pressure used in the airtightness test will inevitably be lower than the design pressure, which does not meet the standard requirements.
Is it correct to use the maximum allowable operating pressure as the calculation pressure for strength calculations? There must be something wrong with this procedure
Actually, that’s what I do right now. The maximum allowable operating pressure is used as the calculation pressure for strength calculations, from which the design pressure and set pressure or burst pressure are then determined. I’m not sure if this is reasonable.
After reviewing the standards and calculation software, for cylinders, heads, container flanges, flat covers, and cylinder ends – which are the pressure-bearing components commonly used by our company – the software or standards can determine the maximum allowable operating pressure. As for reinforcement due to openings, I just can’t figure it out: how is it possible that for other pressure-bearing components, the maximum allowable operating pressure can be determined while ensuring that reinforcement is sufficient? I haven’t worked with other types of leak tests. It turns out that for ammonia leak detection, a pressure of 1 MPa is sufficient; it’s not related to the design pressure of the equipment either. Thank you~:handshake