6'' 800LB CF8 / CF8M Control Fluid Flow Either Manually Globe Valve
How Does It Work?
Globe valves are usually controlled by an automatic actuator that regulates the flow by moving the disk perpendicular to the seat. Globe valves can control fluid flow either manually or automatically.
The right angles produce less leakage than you’d find in a gate valve.
When turned in a clockwise motion the disk lowers to the seat which physically obstructs the liquid’s path, either reducing it or blocking it completely, depending on how low the disk moves.
|SPECIFICATIONS FOR STEEL GLOBE VALVES
|Pressure rating and size:
|DN40 to DN600
||Body : A216-WCB,A325-LCB,A217-WC6,CF8,CF8M
|Disc : A105+13Cr, SS304, SS316
|Stem : A182+F6a,A182-F6a
||stopcock for water
||-20 to 425°C
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
- 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
- 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
Globe Valve Disk Types
Globe valve is available in many different types of disc arrangement. The most used disk designs are listed below.
The ball disk design is used in low-pressure and low-temperature systems. It is capable of throttling flow, but in principle, it is used to stop and start the flow.
Needle disk design provides better throttling as compared to ball or composition disk design. A wide verity of long and tapered plug disks are available to suit different flow conditions.
Composition disk is used to achieve better shutoff. A hard, non-metallic insert ring is used in composition disk design.