What is a difference between lubricated plug valve and sleeved plug valve.Forged Steel Valves

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.Hydraulic control valvesSealants are formulated specifically to be compatible withthe 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.Water Control valves

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