Friday, April 26, 2013

Ball Valve

                      




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:
  1. Full bore: Valve size = line size 

  2. Reduced port: Valve size < Line size (by 1 inch)


Advantages
  1. Requires only 1/4th turn to operate.
  2. Excellent for shut-off application & preferred over gate & globe valve (for sizes < 60 mm)
  3. Ease of operation
  4. Supports & sustain high P (<10,000 psi), T (<200 C) & Q (flow).
  5. Long service life.
  6. Better sealing.
  7. Sturdy device.
  8. Relatively low cost.
  9. Inspection & repair of seats & seals can be done without removing of valve body from the pipeline. 
Disadvantages: 
  1. Flow control is not possible
  2. Tightens with age, implies require more maintenance.
  3. Regular replacement of seal is required. 
  4. Abrasive solids will damage seal & ball surface.

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