Would You Place an EIV in the Lateral or the Main Line?

[drywall]

Our firm has been involved in relocating some scraper traps in NGL service. In one case there are two EIV's (Emergency Isolation Valves)in series on the lateral downstream and in another case the single EIV is upstream of the trap. It seems logical to me that the EIV is ahead of the trap so that if there is a problem the entire kit and caboodle is shut down rather than just the line feeding the bullets. (On the other hand there is a double block and bleed ball valve upstream anyhow.) Isn't the best rationale safety and isn't it safest to locate the EIV just as the pipe comes inside the scraper trap enclosure about 18 meters from the trap?

 

[BigInch]

Its more common in my experience to have the trap on the pipeline and ONE single (unless you're paranoid) EIV or ESD (emergency shut down) valve between the trap/trap and the plant. That is a convenient point for operation, maintenance and code break points too.

The accepted definition is that traps are pipeline facilities and bullets, tanks, meters, scrubbers, slug catchers, separation columns, etc. are plant facilities and never the two shall come together, as well as that isolation valves are required at plant or unit boundaries, hence the isolation valves are convient points to make that distinction.

It will make OPS record keeping, maintenance and operation duties and responsibilities easier to separate between departments later on, as pipeline ops and maintenance is often separate from plant ops and maintenance and federally required pipeline records don't get mixed and become confused with plant records.

Aside from the widely held belief that you could get unlucky and have an iso valve closing down on a scrapper, if you locate iso valves within the pipeline. Plausable, since scrapers can cause pressure glitches that just might trip an iso valve.

http://virtualpipeline.spaces.msn.com

 

[dcasto]

Typically, the lines in and out of the pipeline are one size smaller, saves money on the ESD valve.

 

[drywall]

Gentlemen:


Thanks, what you said makes sense.


Drywall