Plug Vlave Type

[Pavis1968]

Hi,

I wonder if someone could help me to find out what is a difference between lubricated plug valve and sleeved plug valve. We are going to buy plug valve for sulphur service, the maximum operating temprature of sulphur line is 210 DEG C and operating presure is 6 bar.
In my opinion the sleeved type is better rather than lubricated lubricated plug valveds due to less attiontion during operation. During operation very often, the lubrication schedule is missed by the operators. Could anybody help me on this matter?
Many thanks in advance.

 

[JimCasey]

You pretty much nailed it.

LUBRICATED plug valves require the injection of "Sealant" (often called "grease") before they can be positioned. The sealant's job is (1) to be compatible and non contaminating to the process fluid (2) to lubricate (3) to seal. Sealants are formulated specifically to be compatible with the process fluid. Lubricated valves can handle higher temps and pressures since they have no polymers.

NON Lubricted plug valves have a plastic leeve or liner. Usually PTFE, but other fluorocarbons, with or without additives, are offered. You rightly point out that they don't require quite as much attention or brute force to cycle them. Your application appears to be too hot for Virgin PTFE, but Flowserve offers a material called Durlon II good for up to 232C. The Durco plug valve is also available with jacketed bodies which is very convenient feature for handling sulfur.

I found a catalog for you on the Flowserve website.

http://www.flowserve.com/vgnfiles/F...Literature/FlowControl/Durco/DVABR0024-00.pdf

 

[UNSR60001]

Sleeved Plug Valves are ideal for Molten Sulfur service. They offer distinct advantages inherent in its design.

There are three main advantages and they are as follows:

The most important advantage would be that of being so called “Cavity-Free” In this case, what I mean by Cavity-Free is that there are no other possible leak paths or cavities where the flow can accumulate other than the cover/steam areas. In the case of Lubricated Plugs the body is drilled in one or more locations in order to install injector to facilitate the inclusion of lubricants. Why is this essential in a Sulfur Plant application? Cavities enable the flow of molten sulfur, which at that service temperature has a high viscosity, to remain trapped and in turn offer the possibility of solidification and reduction or complete elimination of the sealing capabilities of the valve. Even without a proper solidification, the infiltration of those cavities by the slurry-like flow greatly reduces the capability of the valve to operate.

The second most important feature Sleeved Plug Valve over other designs is that the sleeve protects the flow openings and the plug from erosion as well as its ability to be adjusted. All damage due to particulate vehicle in the flow is absorbed by the polymer sleeve, contrary to other designs. Sleeves are not only adjustable, meaning that as the sleeve wears, the tapered plug can be pushed further in and by its taper achieve again a perfect seal, they are also quickly and easily field serviced in the event of complete wear the sleeve can be changed in the field.. These two features not only translate into time savings and extended service life through adjustment, quick and easy re-sleeving but also in significant monetary savings do to lengthy shut downs to disassemble and machine worn metal components that Lubricated Plug valves require during schedule or unforeseen turnarounds.

Finally, the third most important feature would be the lack of regular maintenance required in continuous operation of our valves, unlike lubricated plug valves for example where a lubricant injection is necessary at each actuation. In the case Sleeved Plug Valves, the only maintenance required is the occasional adjustment of the plug depth in order to ensure a perfect seal.

Additionally it is highly recommended, in my opinion a requirement for Molten Sulfur Applications to specify high performance sleeve materials and jacketed valve. In your particular case, given the process temperature of 210° C., you should seek higher performance (polymer) materials other than PTFE. For two reasons:

1- PTFE will start breaking up above 204° C. in continuous service, unless it is used only intermittently, in which case it could withstand the elevated temperature.

2- Higher performance polymers are slightly more rigid and are not only suitable for continuous applications up to 260° C.; they can also withstand higher pressures associated with the type of flow and temperature of the process.

Please let me know if I can be of additional help and can provide more information on the high performance sleeve materials.

NOTE. The reason why I did not mention any particular brand names of the high performance sleeve materials is do to the fact that all mayor sleeve plug manufacturers offer this in a "Proprietary" brand name. Thereby making different claims as to there attributes. However it should be consider that all this materials outperform PTFE.

 

[caihui]

I think it's better to use ball valve instead plug valve. At first ball valve is cheaper and function is the same.
And if use actuator the torque is much smaller than plug valve. At the same time the valve should be jacket. I think the ball valve jacket is easy then plug valve.
As for the seat ring, for ball valve you can use metal to metal or PEEK as seat ring. As I know, PEEK can stand the temp to 280 degree but I'm not sure. Hoping can help you on this matter.

 

[Pavis1968]

First, many thanks from every body that spent time and make me a reply.

I am agree with UNSR60001. I think the sleeved plug valve is better selection than lubricated plug valves.
Although the PTFE will start breaking up above 204° C as UNSR60001 mentioned it but I can fix the operating temparature on 165° C which is steam jacket temprature.