API 599, Steel Plug Valves, Flanged and Butt-Welded
API 599 is the steel plug valve standard. It covers lubricated and sleeve designs, and it is the reference behind most tight-shut-off throttling valves on dirty service.
API 599, Steel Plug Valves, Flanged and Butt-Welded
A plug valve is a quarter-turn valve with a cylindrical or tapered plug rather than a ball. API 599 covers the steel versions in flanged and butt-welded construction, and it is the standard behind most plug valves quoted for tight throttling on media that would damage a ball seat.
The two families that matter commercially are the lubricated plug, where a sealant is injected between plug and body, and the sleeve type, where a polymeric sleeve provides the seal. They behave differently enough that they should not be treated as interchangeable.
Lubricated or sleeved
A lubricated plug depends on the sealant to fill the clearance and to lift the plug on operation. It seals exceptionally well and tolerates dirty media, but the sealant becomes part of the maintenance routine, and losing the injection path loses the seal.
A sleeve-type plug replaces the sealant with a sleeve that is compressed between plug and body. There is no sealant to maintain, and the temperature is limited by the sleeve rather than by the plug.
Temperature and medium limits
The published limits for our plug valve range are a working temperature band of about minus 29 to 80 degrees Celsius on water, oil and gas service. Above that band, a different valve family is normally the right answer rather than a different plug valve.
The shell and seat test pressures in our range follow the class, running from 3.0 MPa shell and 2.2 MPa seat at Class 150 up to 22.5 MPa shell and 16.5 MPa seat at Class 900. These are the seat test differentials the works applies before shipment.
Where a plug valve is the better answer
Plug valves come into their own where the medium is abrasive, where solids are present, or where throttling is required and a ball seat would be scored. They are also common where the line has to be opened frequently.
They are less attractive where the medium is very clean and tight shut-off is the only requirement, because a ball valve does that job with less maintenance. The choice is about the medium more than about the price.
From the works and the projects
Questions this page answers
Where the medium is abrasive or contains solids, where throttling is needed, or where the line is opened frequently and a ball seat would be scored. On clean media with simple isolation duty, a ball valve is usually the simpler answer.
The published range in our plug valve family is about minus 29 to 80 degrees Celsius on water, oil and gas. Above that, a different valve family is normally more appropriate.
Yes. The sealant is part of the sealing system, so the injection path and the sealant supply have to be maintained for the valve to keep sealing.