Lubricated & Non-Lubricated Plug Valves? 5

[NAPB]

As far as I know there are Lubricated Plug Valves & Nun-Lubricated Plug Valves.

According to my short experience Non-Lubricated Plug Valves are mainly used in process industries like petrochemical or refining & Lubricated Plug Valves are used in Crude Oil Pipelines.

Can anyone tell my why?

Thanks,

Nerio.

 

[JimCasey]

Nonlubricated plug valves are used in Chemical and process services. They actually ARE lubricated: The plug rides in a PTFE sleeve or liner.

Lubricated plug valves are used in applications where the lubricant will not render the process contaminated. Mining, gas, petroleum are reasonably typical. To cycle a nonlubricated plug valve, it is appropriate to first exercise the lubricator, forcing sealant between the plug and the body. This "floats" the plug clear of the body so it can be turned. Sealant (frequently called "grease" is specially formulated for the intended application, and the sealant selected should not be washed away nor react with the process fluid.

Take a look at the Flowserve.com website under "Durco" for nonlubricated plug valves and for "Nordstrom" for Lubed valves.

 

[dtn6770]

The petroleum refinery I worked at uses lubricated valves, plug or otherwise. However, they are bad-mouthed because the "don't work." The irony is that they don't work because nobody lubricates them, properly if at all.

Too much or not enough grease can cause problems and we could never get the operations & maintenance folks to do the right thing, even with training. Debating union job duties came into play.

 

[NAPB]

It would be too bad if I mount a Non-Lubricated Plug Valve on Crude Oil Service?

Thanks,

 

[zdas04]

There are those of us that feel that the only reason to use plug valves is if ball valves have not yet been invented (they were a huge improvement over gate valves in the 1960's).

I spent a lot of time and money ripping them out of a natural gas gathering system I operated because we simply did not have the attention span to keep them properly lubricated.

David

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[stanier]

Non lubricated plug valves are used for RO plants. Contamination of the mebranes cannot be tolerated and hence a lubricated plug valve is of no use. Butt welded plug valves up to Class 600 are common in RO plants. MTs from Spain are a key manufacturer.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[JimCasey]

>>It would be too bad if I mount a Non-Lubricated Plug Valve on Crude Oil Service?
<<

Not a problem as long as the crude oil service is within the published ratings of the plug valve.

zdas04, One big difference between plug valves and ball valves: If the plug valve leaks, it can be adjusted to restore shutoff. This is particularly true of nonlubricated plug valves. If a ball valve starts to leak, you shut down the line, pull the valve, strip out the guts, and replace the seat(s).

 

[zdas04]

I've seen few "properly maintained" plug valves in upstream service. One that was greased on schedule and exercised quarterly started leaking through. We tried all the adjustments available and finally pulled it out. The plug was badly gouged by trash and had a significant leakage path.

In upstream, if a ball valve leaks through and injecting grease doesn't fix it, we replace the whole valve--the downtime to kit it is worth more than the savings.

David