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+91 9904000336

Unitech Valves & Automation
+(91) 9904000336

Piston Valve

Piston Valve

Piston Valve

Description

The Mechseal piston valve (MSV) 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. Known for their extraordinary performance and long life, piston valves can handle a variety of media such as steam thermic fluid condensate and many other liquids and gasses. They can be used in on/off and throttling application. Mechseal valve offers glandless piston valve for reliable long-term performance in steam, condensate as well as process lines. The versatile valve can be used for both solation and throttling application.

Installation

The valve should be installed in the direction of flow indicated on the body. The valve can be installed in any plane, except with the hand wheel on the lower side Sealing is affected by the linear motion of the piston, between upper and lower valve rings- when the piston engages with the lower ring, the valve closes and when the piston aligns with the upper ring, the valve opens. Further, the piston is conjunction with the upper ring prevent leakage to atmosphere.

Conformity To Standard & Codes

→ Bubble tight (ANSI leakage class VI) → Reinforced sealing rings and Belleville washer-compensates for thermal expansion, rellability. → Sealing not affected by the presence of dirt or any other impurities in the media. → Other serviceable-sealing rings can be replaced without removing the valve from line. → Can be used for throttling applications → Robust and maintenance free. → No erosion of sealing surface. → Long service life. → Effective sealing area is large, as compared to the conventional linear movement of valves. → 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 included maintenance, inventory cost in addition to the purchase cost).

Maintenance

In case any leakage is observed the bonnet nuts should be tightened with the valve in the fully closed position. Tightened the bonnet nuts may be repeated as and when required until the rings are worn out and no further adjustment or tightening is possible. At this stage the sealing rings need to be replaced.

No under force should be used when tightening the nuts, as they should rotate easily with a standard spanner. Care should be taken while tightening the nuts to avoid titing of the Undue force should not be used to shut the valve as this may damage the spindle or the wheel.

To Stop Stem Leakage

→ In piston valve, the bonnet must be tightened down to prevent stem gland seal & lower seat leakage. Applying the recommended torque to nut wil ensure any steam leaks are avoided → The piston valve is designed for either bonnet assembly replacement which includes all the necessary internal parts, or simple in-line replacement of the upper andlower sealing rings. → The valve spindle should be checked at regular interval to ensure adequate grease is present to ensure efficient valve operation. → When piston valve fitted on high temperature application or where server weather condition prevails, the grease should be checked more rapidly.

To Replace Sealing Ring & Position

→ Close the piston valve. → Remove the bonnet nuts and washer. → Withdraw the bonnet complete with spindle and piston. → Remove the upper sealing rings, lantern bush and lower sealing ring. → Ensure the inside surface & sealing ring's sitting surface of the valve are clean. → Fit the new lower sealing ring, lantern bush (it available) and upper sealing ring. → Refit the bonnet complete with spindle and piston and tighten nuts to the recommended torque.

Comparision Between Bellow Seal, Piston & Traditional Valves

Bellow Seal Valve Piston Valve Conventional Valve
Sream Seal Metallic Bellow Gland Packing Sealing Ring Gland Packing
Stem Leakage Not Possible Since Metallic Bellow are designed to several thousands cycle Not Possible till the ring wear out Very Common Due to friction between stem & gland
Equipment Downtime Nil Low for replacing ring Very High for replacing gland packing
Safety Can be used safely for almost any media can be used for limited media steam, hot water Highly unsafe when the media is poisonous / hazardous
Valve Life Very High in Years High compared to Conventinal Valve Very low due to leakage throught gland occur in some month

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