8 replies to this topic

[tsaravanan1976]

We have  filter vessel in Naphtha service  to remove  particles like iron rust material. This filter is handling @ flow rate  of 180 m3/hr. The volume of the filter is ~1 m3.

As per the HAZOP study, it was recommended to provide PSV  based on firer case.

My question is " Is there any standard guidelines to confirm the requirement of PSVs based on volume of  vessel?                                              

[Chemitofreak]

1) What does the local regulation say ?

 

2) Does the filter has full body flanges ? If yes, then the relief might be through flanges.

 

3) Is Fire the only overpressure scenario ? Maybe fire water, sprinklers etc will come into picture.

 

There are companies that follow the volume concept to get away with the fire case, but there are other things you need to take into consideration, not sure that is acceptable counter argument in your case

[christopherchoa]

ASME VIII Code has that clause on requirement of PSV.

 

But as you mentioned, it was already required by HAZOP. If all qualified HAZOP participant already agreed to have one, it will be difficult to overturn it.

Edited by christopherchoa, 25 November 2022 - 05:49 AM.

[Pilesar]

Calculate PSV size and if it is impractical, discuss the results with the HAZOP team to reconsider recommendation. Owner is the final decider for risk, not the HAZOP, and owner is the judge of what risks are acceptable. Consider the effect on fire case calculations if the vessel were insulated or provided with dedicated fire protection system. Fire case would be for a blocked-in vessel so the small volume vessel might be considered expendable and not deserving of expensive protections. If fire case is the only case, then consider whether a rupture disk might be a better option than a PSV.

[seuenergy]

For PSV, I think there are two requirement for consideration:

1. risk base

    The philosophy is what kind of risk(normally, from risk matrix)? Then what kind of protection device is needed to cover the risk.

2. regulation

    In some region, PSV is needed to protect pressure vessel. And there is definition about what is pressure vessel(working pressure, volume).

[breizh]

Hi,

You should acknowledge the requirement from the Hazop team. Otherwise, what is the point to perform safety reviews?

Breizh 

[latexman]

In my company, to take a credit for a PRD in a PHA we must/shall have a valid, peer reviewed PRD sizing/calculation showing adequacy.  If not, no credit!  If the process owner says no PRD, then that's what the PHA/HAZOP must show.  Otherwise, the documentation does not show reality, and at worst it can be interpreted as fraudulent and at best misinformation.

 

tsaravanan1976, ASME UG-125 says, "all pressure vessels within the scope of this Division, irrespective of size or pressure, shall be provided with overpressure protection in accordance with the requirements of UG-125 through UG-138, or with overpressure protection by system design in accordance with the requirements of UG-140, or a combination of the two."  Bolding is mine.  If owner decides to not provide overpressure protection for whatever reason, like small volume, then it seems to me the system design must conform to UG-140.  What do others think?

[seuenergy]

For PSV, the designer need scenario for calculation. For your question, hazop team need to describe the scenario for which this PSV protect.   

[shvet1]

@tsaravanan1976

Is there any standard guidelines to confirm the requirement of PSVs based on volume of  vessel?

 

No, there is not. But there are requirements based on Design Codes.

 

It is possible to eliminate PSV if pressure parts of filter will be part of pipe (not vessel) and the rest overpressure cases has been already excluded. Piping Codes do not require to protect piping from firecase and by this reason many companies have practice to provide design of small vessels based on combination of pipe elements (not vessel) to avoid strict requirements of Pressure Vessel Codes.

 

You need this filter will filter, who cares formulas its was calculated? If a device looks like a pipe segment and acts as a pipe segment what is the difference between a pipe and a device? Internals and function only? Why a device that looks and functions as a pipe has to have features of a large storage drum?

 

Check with procurement team if filter has been already manufactured. If not then talk with Manufacturer to change design code from ASME VIII to ASME B31.3. 

 

PS

 

All differences are inside of our heads. Does not matter what it is, the question is what we see when look at it.

 

Also note my experience with naphtha filters.

If design pressure of filter is high enough situation is possible when temperature of relief is higher than design temperature of vessel or associated piping. This means that in case of fire filter will failure regardless of PSV because of failure of gaskets or local overstress of piping or vessel wall caused by combination of P+T during fire. This situation is common for vessels designed for high pressure, fully filled with liquid and containing low MW liquids like naphtha or LPG. The point is that in case of fire a fluid this kind of will become overheated above critical temperature and become a vessel filled with gas only what leads to very low pressure rise vs temperature. I have encountered many vessels (including naphtha) where firecase was excluded because of exceeding of liquid critical temperature.

Edited by shvet1, 08 December 2022 - 12:53 AM.