Greasing of Packing 3

[benensky]

Is it legal to grease packing before testing a valve? API 598 (section 4.4.1) infers that the packing should not be greased because it is a "sealing surface." Also, MSSP-61 (4.1.2) also says that seat surfaces should be clean. It could be inferred that the packing should also be clean because it creates a seal on the stem of the valve. Some people in our company interpret this as strictly the seat of the valve and therefore it is perfectly fine to grease the packing to get the valve to pass a pressure test. Not having much experience in the industry, I ask others opinions interpreting this.

 

[vpl]

In nuclear industry, for safety-related valves, answer would be "no."

Can't speak for other industries.

Patricia Lougheed

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[moltenmetal]

It stands to reason that unless the valve is a lubricated design, any pretty much any lubricant you use in manufacture or testing won't be there after some time in service. In a sense, what you're asking is "do you care if the owner later notices packing leakage which potentially cannot be repaired merely by a packing adjustment"?

That said, it's been my experience that certain types of packings and seals, particularly o-rings, NEED an initial application of a film lubricant to ease installation to AVOID future problems. Skipping the lubricant in this case is not in the owners' interest!

Some valve manufacturers list the lubricants they use, so clients will know if these are suitable or if substitutions will need to be made. I've always presumed that if a lubricant was used, some of this stuff will end up on wetted parts inside the valve.

 

[JimCasey]

Assemble the valve according to the manufacturer's assembly/service procedure. Unless you have a lubricated plug valve there should be no grease(Sealant) inside the valve.

On most of the valves I have seen:
TFE packings are not usually lubricated.
Grafoil packings are put together with a dab of never-seez

Certainly the old days of asbestos packing and a grease injector on the side of the bonnet are gone.

 

[valvehowker]

Could you tell us a bit more about the use of Neverseez on Grafoil packings.

Is this to aid assembly or to help the graphite packing surface bed in? Does it allow a less polished surface on the valve stem? Does it significantly reduce friction and valve operating torque? Does the Neverseez usually stay in place or wash/wear away?

Kind regards
Bill

 

[JimCasey]

Valvehowker:
I am glad you asked the question because it prompted me to go back and review the instruction manual.

I had seen the guys in the shop using never-seez in graphite packing. I believe it would fill the pores in the packing with the microscopic particles of nickel, and act as both a lubricant and sealant. The valves in question were rotary valves, so anything in the packing box tends to stay put-not being dragged in and out by a reciprocating stem.

However, as I suggested that one follow the manufacturer's assembly procedure, when I checked the literature the Mfr only says to use never-seez on the stem thrust bearing.

So I must apologize that what I witnessed and reported may not be best practice. I will research it further and if I find additional information I will report here.

 

[roydm]

I believe the standard is referring the plug & seat not the packing.
Roy