Unclear of Valve Packing Specification 3

[ashaari]

Dear all,

Hope you can clear my query. I am planning to purchase two gate valves used for steam service. I am not clear of the valve packing specification.

The first gate valve (Gate valve A) is for steam service with max 51.1 barg, with temperature up to 300degC.

The second gate valve (Gate valve B) is also for steam service with max 36.7 barg, with temperature up to 399degC.

The packing specification for Gate valve A is as follows:
1. Special lubricant impregnated carbon fiber braided packing, and suitable for temperature 50degC to 350degC with class 600 pressure rating of oil, gas and chemical services.

While the packing specification for Gate valve B is as follows:
1. Special lubricant impregnated carbon fiber braided packing, and suitable for temperature 50degC to 350degC with class 600 pressure rating of oil, gas and chemical services.
2. Stainless steel wire mesh inserted pure graphite packing.

My questions are:
1. I know what is a special lubricant impregnated carbon fiber braided packing. However, I don't know what is a stainless steel wire mesh inserted pure graphite packing. Can someone help me to explain what this is?

2. In API 603 mentions about material for Stem Packing: "Unless otherwise specified in the purchase order, the stem packing shall be flexible graphite, suitable for a temperature range of 29degC to 538degC. Graphite packing, when used, shall contain a corrosion inhibitor."
If I were to purchase a gate valve with a packing that meets this API specification, does it also meet the "stainless steel wire mesh" requirement?

I'm working in a 20 year-old gas plant, so I am following our piping specification the same age as my plant.

Thanks for your help

 

[reverman]

Most packing vendors have types of packing with wire mesh core for "increased service life" the majority of the ones I'm aware of have an inconel wire mesh (do a search for Garlock 127-AFP for example). But I'm sure some packing suppliers have sackings with stainless wire as well.

Most standard off the shelf API gate valves with graphite packing do not have a wire mesh in the packing. This will need to be specified. It will add a little cost to the valve an perhaps a couple days lead time for somebody to switch out the packing.