Purpose: ON-OFF / Isolation valve
P&ID symbol:
General points:
- Ball valves can be manufactured from minimum of 1/4" to maximum of 10" (some manufacturers also give upto 16")
- Due to cost and bulkiness of the valve,Butterfly valves are always preferred over globe and ball for larger sizes i.e. more than 6" or 8".
- For smaller size Ball valves are favorite of all, from cost, handling and installation and service point of view.
- In most household applications, ball valves are used.
Types of Ball valve:
- Full bore: Valve size = line size
- Reduced port: Valve size < Line size (by 1 inch)
Advantages:
- Requires only 1/4th turn to operate.
- Excellent for shut-off application & preferred over gate & globe valve (for sizes < 60 mm)
- Ease of operation
- Supports & sustain high P (<10,000 psi), T (<200 C) & Q (flow).
- Long service life.
- Better sealing.
- Sturdy device.
- Relatively low cost.
- Inspection & repair of seats & seals can be done without removing of valve body from the pipeline.
Disadvantages:
- Flow control is not possible.
- Tightens with age, implies require more maintenance.
- Regular replacement of seal is required.
- Abrasive solids will damage seal & ball surface.
I would take issue with the following statements:
ReplyDelete•Due to cost and bulkiness of the valve, Butterfly valves are always preferred over globe and ball for larger sizes i.e. more than 6" or 8".
For positive cycling applications where a positive seal is required, ball valves are preferred. AT least if you look at the installed base of large gas phase polypropylene/polyethylene production.
•In most household applications, ball valves are used.
Last I checked in my US home, the water supply valves under the kitchen/bathroom sinks, and the outside hosecocks are NOT ball valves. Neither are the actual faucets on the sinks or tubs. The gas supply main is a plug valve.
nice technical detail given
ReplyDeletesimple content but attractive words used
"Ashok Polytech"
It's really interesting to read about these details on ball valves.
ReplyDeleteAre there ball valves with capability for throttling gas flow to some extend? For use in pig launchers/receivers kicker pipelines during pigging operation.
ReplyDeleteI read "Reduced port: Valve size < Line size (by 1 inch)" let me know if I am wrong but it seems the author wanted to say (by 1 diam.).
ReplyDeleteTo throttle the flow with a ball fall is possible but accuracy is difficult with the hand valve. Ball valve are generally used as isolation. When ball valves are used for throttling, the internals are arranged to appreciate the cv and with a specific internal.
One advantage is the low pressure drop.
When the ball valve is equipped with the actuator, pneumatic or electric, the overall dimensions is interesting compared to the others technologies.
another advantage is ball valve accepts a high differential pressure and can be used with large range of piping class up to 2500# and more.
Yes, you read it right. For reduced port, valve size < line size usually by 1" in terms of diameter. With your other points I agree with you. Thank you
DeleteI read "Reduced port: Valve size < Line size (by 1 inch)" let me know if I am wrong but it seems the author wanted to say (by 1 diam.).
ReplyDeleteTo throttle the flow with a ball fall is possible but accuracy is difficult with the hand valve. Ball valve are generally used as isolation. When ball valves are used for throttling, the internals are arranged to appreciate the cv and with a specific internal.
One advantage is the low pressure drop.
When the ball valve is equipped with the actuator, pneumatic or electric, the overall dimensions is interesting compared to the others technologies.
another advantage is ball valve accepts a high differential pressure and can be used with large range of piping class up to 2500# and more.