PISTON VALVES
DESCRIPTION
The Pennant Piston Valve (PPV) is a linear movement valve in which a stainless-steel piston travels between the upper and lower seal ring. These rings are separated by a lantern bushing, which supports the piston and creates a bubble tight seal. When the valve is in the open position, the upper seal ring in conjunction with the piston prevents leakage through the stem. In the closed position, the lower seal ring seals the valve – passage and provides a tight shutoff. Known for their extraordinary performance and long life, Piston Valves can handle a variety of media such as steam, thermal fluid, condensate and many other liquids and gasses. They can be used in on/off and throttling applications.
FEATURES
- Bubble tight (ANSI leakage class VI) shutoff
- Can be used for throttling applications
- Piston valve is robust and maintenance free
- Long service life
- Effective sealing area is large, as compared to the conventional linear movement valves
- Compensates for thermal expansions with reinforced Grafoil sealing rings and Belleville washers
- Can be easily serviced inline
- Easy to repair: The only wearing parts are sealing rings which are easily replaceable
- Low cost of ownership (Cost of ownership includes maintenance, inventory cost in addition to the purchase cost)
RANGE OF PISTON VALVES
Pennant Piston Valves are available in wide variety of Pressure class as below:-
- Cast Steel Construction :- #150, #300 as per ASME B16.34
PN40 as per BSEN 1092-1 - Forged Steel Construction : – #800 as per ASME B16.34
TYPES OF PISTON VALVE
- BALANCED PISTON VALVE – For higher size piston valves above NPS. 2, higher torques is required to operate (close/open) an unbalanced valve against inlet pressure. Balanced piston valves overcome this higher torque requirement, by balancing the pressure above and below the piston.
- UNBALANCED PISTON VALVE – It can be used for lower sizes (Below NPS 2½”)
TYPICAL APPLICATIONS OF PISTON VALVES
- Thermic Fluid Supply, Return & Balancing Line Isolation
- Pressure Reducing Stations
- Main steam isolation valves on Steam header
- Steam Trap isolation valves
- Pressure Reducing & De-superheating Stations
- Steam Manifolds
- Condensate Manifolds
Difference Between Coventional Piston Valve and Pennant Piston Valve
| FEATURES | PENNANT PISTON VALVE | CONVENTIONAL PISTON VALVE |
|---|---|---|
| Manufacturing standard of piston valve | API-602- more stringent standard followed | ANSI 800 standard followed |
| Flanged connections | Integral flanges available from 15nb | Add on flanges provided for 15 to 40nb size |
| Multiple pattern option | Angle pattern option available in 15 to 25 nb to ensure lower pressure drop in flow | Only straight pattern option available, higher pressure drop compared to angle patterns |
| Operating life of rings of piston valve | Rings are tested for 1,00,000 cycles of operation | Rings are tested for 2000 to 8000 cycles of operation only |
| Weight of piston valve | Considerable safety factor considered while designing resulting higher weight of valve | To cut down cost, little or no safety margins considered while designing of weight, resulting in light |
| Hand wheels | Cast steel MOC minimizes hand wheel damages | Cast steel moc minimizes hand wheel damages |
| Bolted design | 4 bolt design helps to exert uniform pressure on the seal rings resulting prolonged operating life | 2 bolt design results in uneven pressure exertion on the rings resulting in increased failure rate |
Imperial
| Sizes | Materials | Pressure Range |
|---|---|---|
| ½” to 8” | Cast/ Forged Carbon Steel | Forged – #800 Cast – #150, #300, PN40 |
Metric
| Sizes | Materials | Pressure Range |
|---|---|---|
| DN15 to DN200 | Cast/ Forged Carbon Steel | Forged – #800 Cast – #150, #300, PN40 |