Which one could be chose between Plug valves- metal seated/ soft seated For fluid service of fuel gas (design conditions, temp 100 deg C and pr- 5.0kg/sq sm) and sour water acid gas (temp 160 deg C and pr- 5.0 kg/sq cm)?Cast Gate, Globe, Check Valves

"Lubricated" plug valves are all metal.They use a sealant that is injected under pressure to seal and lubricate the plugforged Gate, Globe, Check Valves .The sealant is formulated to be compatible with and noncontaminting for the specific process fluid in the valve.Lubricated plug valve are usually manual because they are complicated to automate.It's necessary to activate the lubricator before turning the valve, and most automation does not have that functionality.

"Nonlubricated" plug valves have the plug running in a TFE sleeve usually, but other polymers may be used.In this configuration they may be cast in exotic alloys for corrosion resistance.No additional lubrication is required.A variation is the fully-lined plug valve that has a TFE lining and a PFA encapsulated plugBall Valves. That lets the user run corrosive chemicals through a valve with a ductile iron body because the body never gets wet-just the (chemically inert) TFE liner

It is easy to automate the nonlubricated valve because they only need to be twisted to operate.Nonlubricated valves are even available for modulating controlResilient Seated Gate Valves.They require a lot of torque, but for control they just slap a big enough actuator and a positioner on them and they serve well in appropriate applications.

Lubricated valves are inherently fire-safe.Nonlubricated valves are considered prone to lose the liner in a fire but they may be offered as fire-SEALED, where they are certified not to leak to atmosphere as a result of fire.

Both types are manufactured by Flowserve.Additional information for lubricated valves is in Flowserve.com under the Nordstrom heritage name, and for nonlubricated valves use Durco for the heritage name.

Non-Lubricatedplug valves are also available from MTS in Spain. They are the industry standard for desalination plant. Materials such as super duplex are readily availableAutomatic Control Valves.

One advantage of plug valves: If they leak, the tapered plug allows them to be readjusted to restore tightness.

Another: There is essentially no cavity for contamination or polymerization to accumulate in a plug valve.

And what's simpler than a plug valve? Heck, it's HARD to machine a round ball but any goober with a lathe can make a tapered plug.

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