Plug Valve Applications

Hi valveman,

Notwithstanding the appropriateness or otherwise of your 'moniker', the answer to your question is that plug valves are the most primative for of isolation available. Their history can be traced back to Roman times when bronze versions were to be found outside 'villas' supplied with piped water. You can see examples in Pompeii. This really describes their modern use also. Plenty were to be found in domestic applications such as draining the contents of hot water urns and 'coppers' (wash boilers). Also much favoured by the 19th century gas supply industry.

Bearing in mind that the whole thing is held together by a nut and washer on the bottom end of the taper, which controls leakage but causes friction/stiction if the nut is overtightened,this can render the thing in-operable in some circumstances.

Therefore the modern application would only be as a basic drain control device on say an oil tank or other low static head storage vessel.

Good luck with the name change!

Massey.

Plug valves are still quite widely used in gas services. In foundries and heat treating furnaces they are used as the main stop in gas lines just before regulators. There are also plug valves designed as three way for switching fuel sources to burners.

They are a simple design so casting them is not as complex as a globe valve for example or even a gate valve. Ball valves are often used instead of plug valves in smaller sizes.

Cast in all bronze they are non sparking and there is less chance of corrosion preventing their operation especially when there is a lubricant supplied at installation between the plug and the body. Nothing worse than a gas valve that won't close when you want it to. Could lead to an explosive situation.

Natural gas distribution companies in the U.S. have thousands of these installed thru out their system. The are probably the cheapest valve available, much cheaper than ball valves. They are the lubricated design, have no nut on the bottom, totally accessible from the top, required no maintenance, and worked well 99% of the time. Occasionally, one would be difficult to turn. A shot of grease from grade thru the 4" diameter valvebox is all that was needed. The majority of lines were 2 and 4" IPS steel 60 psig, but they could also be used on higher pressure lines by selecting ones suitable for the higher pressure (usually steel valves). Most of them were of the venturi type, which caused an ever-so-slight, probably almost immeasurable, pressure drop. You had to have 125 psig feeder lines every so often anyway, so it was of no consequence. For corrosion protection, they were totally encased in mastic and tape, and became part of the pipe protection cover.