Gate Valves for piggable service

[ione]

Yeah, valves can be listed amongst biggest obstacles of piggability, if not properly designed. Full bore valves, without any protrusion inside the line, should be the way to go.

 

[kpanand]

Thank you ione for the reply. Can some one tell me whether there are any gate valves which are not piggable and how can i find out. Some supplier told me gate valves designed to API600 by default is not piggable .. any comments ?

 

[gerhardl]

As there is a number of pig types and design your customer should advice you on details: type of pig, pressure used, fluid used, temperature and how often.

A qualifiedvalve producer will then be able to give you a detailed answer, and eventual limitation on use.

For some types of gatevalves, for certain pressure classes and sizes, there might be limitations, and it might be necessary to go one dimension higher than nominal for the pipeline. (This is not a given general rule, especially if the valve else is 'pure' full bore without protrusions).

Trim details and geometry is an issue both for piggabillity (not to damage valve or stop pig) and not to tear pig outer surface apart.

The clue is that the valve producer (if the valve producer shall give a warranty for the use) is the one to answer your question, while the customer should be able to give you an answer on a typical sample valve brand and construction which trough practical experience qualifies.

The last answer should give you an idea at what you are up against.

 

[stewbaby]

Surely they meant API 6D (sometimes we customers don't really know what we are asking for). API 6D is the spec for pipeline valves (Gate, Ball and such). An API 6D valves is designed to be full bore and minimally obtrusive...aka, piggable. Put any old API 600 gate in there and you are asking for trouble. Even if a vendor said his API 600 was 'piggable', which i haven't seen many i'd put anything but a foam pig thru (no intelligent pigs), you'd have to inspect each one they sent to make sure it was thru full bore.

 

[Duwe6]

"Is there gate valves which are not piggable ???" Almost all of them.

Get one with a *signed* certification that it will allow a smart-pig to pass through it.

 

[valvit]

In general, API 600 gate valves make use of wedge style gates. The wedge angle varies from manufacturer to manufacturer, but is usually somewhere from 6-10 degrees. From a fluid flow standpoint, leaning the circular diameter of the seat ring over at a 6-10 degree angle has little or no effect on the flow, but can interfere with the passage of smart, dumb, semi-smart, MBA smart, been-there-done-that smart, and any other kind of pig.

For a piggable gate valve, you should specify full-bore, through conduit, such as are found in API 6D.

 

[kpanand]

Thank you all for the replies.