Hydrocarbon Drains & Vents Design 1

[ghamsa]

In our plant all drains or vents, which are attached hydrocarbon lines, discharging to the atmosphere have an isolation valve with:
1) plug ,or
2) blind

The insurance company inspector is asking for double isolation valves for these drains and vents.
1) Is double isolation valves requirement is part of the industry codes???

2) Do not you think that a plug or blind should do a similar job like a second isolation valve???

Thanks for participation.

Thanks for your participation

 

[BSMP]

Double isolation valve is a good engineering practice for high pressure systems and not a requirement by any code. Some operators do insist double isolation for all 300# pressure rating and above though 600# is more common.

In your case, you need to evaluate whether drains and vents under scrutiny are regular process vents or not. Sometimes hydrotest vents are left in the piping system with blinds or plugs and never be used in the regular operation. If it is a regular process vent or drain, assessment has to be made based on the piping pressure rating/operating pressure.

 

[jalvarez]

Insurance inspectors usually give good advices, but being humans, sometimes they go to far, not to say they are wrong. And the worse is that you may do whatever they like, but the cost of the insurance will be the same.
For 1" or less, a single valve is enough, ended with a thread and a plug. If the drain or vent is unfrequently used, it is very advisable to tack weld the plug. For pipe that can be exposed to vibrations, the use of goosets is also recommended. Some refineries use goosets for all purges and vents, with or without vibrations.
If the purge or vent is being used frequently, like in start ups or shutdowns, you must judge, for each case, the convenience of a second valve.
For purges and vents larger than 1", moderate to high pressures (let's say more than 10 psig) a double block is preferable.

Have a safe day

J. Alvarez

 

[TD2K]

At the plant I'm currently working in, the requirement for all vents and drains is for either double valves or a single valve with a plug or blind. The purpose here I've been told is to limit potential VOC emissions.

The site's practice is to prefer double valves from an operating point of view but they will accept a flange or plug on some applications where operation is infrequent. The main concern I have with relying on plugs or flanges is ensuring they are reinstalled after use. It's easier to close a second valve than reinstall a flange (with a new gasket of course), find where you've put the plug, etc.

One previous plant I worked at used threaded caps on all drains and attached them to the piping with a short chain so they couldn't be misplaced.

 

[sshep]

Our own standard is generally to use double valves on 600# systems, and plug the lower pressure systems. Valves which must remain plugged for environmental compliance reasons are spray painted to make them more visible. State fines in Louisiana for unplugged valves are ridiculous (I think up to $1000/valve/day).

In mentioning site practices, last year I was on a start-up team for a new plant where only flanged valves were used for vents and drains. At first it seemed like it would be hard to live without the 3/4" threaded (and plugged) valves I have been used to. As there are only 4 bolts to a small flanged valve, I actually found it to be not at all inconvenient and I feel sure the integrity is much better in many services once the long term effects of corrosion are considered.

 

[IPGBen]

Hi,

at the plants I've worked and also at the one I still work each shift has it own section of the plant. This includes the staff.

This shift/group is responsible for housekeeping, blinds & plugs, etc.

The first responsability is for the operator who uses the drains/vents. After this it's the responsability from the team to which this area is assigned to, to make sure they're in place after usage.

Grtz
Ben

 

[mrtangent]

ghamsa,

Some info for you on vent and drains.

I completed a startup a few years ago. Our site is close to the local community so we cannot afford any environtental spills or risk fines or shutdowns to prevent us running while investigation - so we are very caucious. On all the plants startup plans we have a vent and drain check list so before we start up we had a documented record to know we'd checked everything. At the time I throught it was a bit excessive but we did't have one spill from an open vent or drain.

The check list if well organsed (ie by floor level) etc does take long even on a big plant.

 

[BenThayer]

We typically use the plug following the valve. If it is a valve we will use relatively frequently, we use a spring to close mechanism on it.

For some reason, the safety department and insurance company did not like the more common term of "dead man" handle. Maybe it was a sexist term?

If the insurance company requires it as a matter of coverage, then just accept it. quarter turn valves in particular have a poor track record of accidental opening due to someone walking by and brushing it open or getting it caught on a coat sleeve, etc.

 

[saxon]

ghamsa, I've seen both single blocks with plugs or blinds and double blocks with plugs or blinds used; based on service or pressure used in the same plant. Check your piping spec. and detail sheets, these things were put together as they are for a reason. If the plant insurance coverage is tied to or dependant on implementing the insurance carriers design guidelines you have no choice but to comply. This will neccesitate an ECO (engineering change order or how ever your company handles design changes and documentation) to reflect the new design conditions. If it is simply the design preference of the inspector, then perhaps, you need to open a discussion with the inspector.

Hope this helps.
saxon

 

[sshep]

BenThayer's comment on quarter turn valves being accidently brushed open is a very real hazard. I expect that I will have either seen or read about (in accident reports) this happening over 100 times by the end of my career. Our current facility discourages these, and (if needed) only allows oval handles (as opposed to straight) in this service.