pressure relief valve on NG pipeline 1

[aady001]

Hello for all
I have 10 km length nat. gas pipeline. My question : Is it important to put PRV on it. and how can I know where it is will be and, is one PRV is enough or not.
Thaaaanks

 

[LittleInch]

It is important to prevent the pressure in the pipeline from exceeding the design pressure.

This could mean no Pressure Relief Valve, one at the inlet, one at the outlet or any version inbetween.

It is not normal to place any PRV at any intermediate point.

your question has few details, so unfortunately so does the answer....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[zdas04]

As LittleInch says, it is common to rely on the PSV at the supply sources and at compressor stations rather than place PSV equipment on the system itself. The major exception to this (and the reason I chimed in) is that several governments have "helped" us and created a requirement to put PSV on pig launchers and receivers.

Engineering practice has long been to either write procedures to prevent isolating a launcher/receiver barrel that could be liquid full or to place thermal relief on them. A couple of barrel failures caused regulators to step up and write confusing/conflicting regulations that require protection against a (usually) non-existent scenario of overpressure in gas.

There is no piping code that requires over-pressure protection for natural gas pipelines, and the emerging requirements to put protection on launchers/receivers are sort of assuming that the barrel is isolated from the pipeline.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[aady001]

Thank you LittleInch
Please what is the data which is used to specify the numbers of PRV's

 

[EmmanuelTop]

Based on the governing relief scenario, you will establish the required size of the PSV orifice. If the calculated size is larger than the highest conventional orifice size, the design will probably consists of several PSV's with staggered set points. Go through API520 for more detailed information on sizing. Here is one online reference:

http://www.isibang.ac.in/~library/onlinerz/resources/enghandbook3.pdf

Once you determine the size and the number of PSV's, you need to see where the discharge stream will be released. Unless you are by a miracle allowed to vent 10km pipeline to atmosphere, you would need a dedicated relief system. If the pipeline is linked to a compressor station (whether upstream or downstream), this will likely be the best place to locate the PSV.

Dejan IVANOVIC
Process Engineer, MSChE

 

[LittleInch]

Like we are all saying, you need to look at your system and establish where the pressure sources are and in what circumstances an over pressure situation can occur.

This is normally only about what happens if the end is shut in and the input pressure can exceed the design pressure.

otherwise you don't normally need PRVs on a gas pipeline.

you haven't given out any details so the answer has few details....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[dcasto]

Let me iterate again, a PSV is not required on a pipeline. The codes say an over pressure protection system, they do not specify a PSV.

 

[georgeverghese]

Pls note that there is are major differences between B31.8 code for pipelines and B31.3 code for inplant piping in the treatment of overpressure.

B31.8 code allows the use of an an instrumented safeguarding system (without PSV) of a certain integrity and configuration to allow a design pressure break, provided the hydrotest(??) pressure of the protected downstream component is in excess of the upstream components max operating pressure. My language may be a little loose here, and perhaps a pipeline engineer may correct me, but this is the general hang of it.

Your perception of the use of PSV when dealing with design pressure breaks is what is used in ANSI B31.3, so pls check if this pipeline is a B31.8 or a B31.3 line.

 

[TD2K]

11 days and the original poster is still missing in action.

 

[aady001]

Thank you All for these important notes.

 

[roslanhamid]

What is the cause of overpressure on the pipeline? If none then it is not required.