Basic Globe Valve Seating Designs

Globe Valve Seating Designs...

Plug Type Disc

Long taper with corresponding seat, giving a wide area of seating contact, makes the plug-type disc superior to all others for severe throttling service, such as blow-off, soot-blower, boiler feed.

Because of wide seat bearing, most cuts and nicks by dirt, scale, and other foreign matter in flow are seldom big enough to cause leakage.

Plug disc shape, in proper combination of metals for service, is most effective in resisting erosive effects of close throttling.

Construction permits replacement of seat if necessary.

Conventional (ordinary) Disc

A good seating design for many not-too-severe services, but not for close throttling.

Disc has relatively narrow contact with body seat - virtually a line bearing. This narrow metal area, in closely throttled high-velocity flow, is subject to erosion and wire-drawing.

Deposit of particles of foreign matter on seat makes tight closure virtually impossible.

Yet uniform deposit on seat, such as coking action in oil refineries, is more easily broken down by the narrow bearing. It makes a tight metal-to-metal contact easier than a wide seat.

Seat and disc can be conveniently serviced.

Needle Point Disc and Seat

Needle point valves are designed to give fine control of flow in small-diameter piping. Their name is derived from their sharp-pointed conical disc and matching seat. They come in globe and angle patterns, in bronze and steel, and find usage on steam, air, water, oil, gas, light liquid, fuel oil, and similar services.

Stem threads are finer than usual so that considerable movement of stem is required to increase or decrease opening through seat.

Usually, these valves have reduced seat diameter in relation to pipe size.

Their Service Characteristics

Composition Disc

A useful design in bronze and iron valves for adaptability to many services and for quick repairs.

Discs available in compositions suitable for steam, hot water, cold water, oil, air, gas, gasoline, and many other fluids. Disc change is quickly made with slip-on disc holder.

Highly regarded for dependable, tight seating on hard-to-hold fluids such as compressed air. Flat face relatively "soft" disc seats against a raised crown in body.

Small particles of foreign matter are imbedded in disc, preventing seat damage and leakage.

Suited for all moderate pressure services except close regulating and throttling, which can rapidly cut out the disc.

Angle Valve Seating

It is well to note and remember the angle valve when looking for globe valves. If there's a right angle turn in the line near where you need a valve, an angle pattern gives you important advantages.

It's available with the same seating variations as shown here for globe valves: plug-type disc, conventional, and composition disc.

Has considerably reduced turbulence, restriction of flow, and pressure drop because flow makes one less change of direction than in globe valve.

Angle valve cuts down on piping installation time, labor, and materials, also reduces number of joints or potential leaks by serving as a valve and a 90 degree elbow.