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.
