Globe Valves With Fully Body-Guided Disc Handles Flow At High-Pressure Differentials

Globe Valves With Fully Body-Guided Disc Handles Flow At High-Pressure Differentials

The new generation of globe valves with fully body-guided disc have an excellent ability to handle flow at high-pressure differentials.

API 623 in it's new edition requires that all globe valves must have there disc fully body guided, in order to hold the disc for supporting the hydraulic forces and vibrations when the valve is in severe throttling. The main purpose of this design is not to tractor lateral forces to the stem, because the allowances between the stem and the disc are larger than the allowances between the body guides and the disc. This keeps the valve packing in position and prevents leakage.

When selecting a Globe valve, the parameters of:

a) Type of fluid
b) Inlet pressure & Inlet temperature
c) Flowrate
d) Required pressure drop across the valve

Globe valves

A Globe valves is a linear motion valve and are primarily designed to stop, start and regulate flow.

The disk of a Globe valve can be totally removed from the flowpath or it can completely close the flowpath.

Conventional Globe valves may be used for isolation and throttling services. Although these valves exhibit slightly

higher pressure drops than straight=through valves (e.g., gate, plug, ball, etc.), they may be used where the pressure

drop through the valve is not a controlling factor.

Because the entire system pressure exerted on the disc is transferred to the valve stem, the practical size limit for these

valves is NPS 12 (DN 300). Globe valves larger than NPS 12 (DN 300) are an exception rather than the rule. Larger

valves would require that enormous forces be exerted on the stem to open or close the valve under pressure. Globe

valves in sizes up to NPS 48 (DN 1200) have been manufactured and used.

Globe valves are extensively employed to control flow. The range of flow control, pressure drop, and duty must be

considered in the design of the valve to avert premature failure and to assure satisfactory service. Valves subjected

to high-differential pressure-throttling service require specially designed valve trim.

Generally the maximum differential pressure across the valve disc should not exceed 20 percent of the maximum

upstream pressure or 200 psi (1380 kPa), whichever is less. Valves with special trim may be designed for applications

exceeding these differential pressure limits.

Advantages and disadvantages of Globe valves

ADVANTAGES:

• Good shutoff capability
• Moderate to good throttling capability
• Shorter stroke (compared to a gate valve)
• Available in tee, wye, and angle patterns, each offering unique capabilities
• Easy to machine or resurface the seats
• With disc not attached to the stem, valve can be used as a stop-check valve

DISADVANTAGES:

• Higher pressure drop (compared to a gate valve)
• Requires greater force or a larger actuator to seat the valve (with pressure under the seat)
• Throttling flow under the seat and shutoff flow over the seat

Typical Applications of Globe valves

The following are some of the typical applications of Globe valves:

• Cooling water systems where flow needs to be regulated
• Fuel oil system where flow is regulated and leaktightness is of importance
• High-point vents and low-point drains when leaktightness and safety are major considerations
• Feedwater, chemical feed, condenser air extraction, and extraction drain systems
• Boiler vents and drains, main steam vents and drains, and heater drains
• Turbine seals and drains
• Turbine lube oil system and others

Packing Details:

We choose suitable wood cases according to different valves and arrange skilled workers to pack in case of bruise. Long term cooperated forwarder will book space, clear customs and transport for us without delay. There are three ways for transportation, by sea, by air and by train. We will arrange transportation according to customers' needs.

Delivery Details: According to the order, 7~60days