Piston Valve Working Principle
They perform their duties by cutting and opening the fluid passage by inserting, lowering and lifting the piston attached to the end of a shaft into the fluid passage hole, passing through the non-metal seal packages.
Piston Valve Specification
Clean, neutral or aggressive liquid, gaseous fluids
It indicated. Otherwise flow is not recommended.
Hot and Cold Water Installations, Steam Installations, Hot Oil Installations
Manually, with pneumatic actuators
It can be from DN 15 to DN 200.
Up to PN 63 can be reached.
Working Temperature Range:
It can expand from -100C to + 3500C. However, they are generally manufactured for the range of –100C and + 3000C.
Cast Iron, Ductile Iron and Steel
Connection to Installation:
Screwed, Flanged, Welding Mouth
Piston Valve Advantage and Disadvantage
They provide flow control.
A good tightness is ensured by the environmentally tight contact of the metal piston to the non-metal seal packs.
The circumference of the piston can also be used for liquids containing solid particles, as it travels by sealing packs during opening and closing.
They are also suitable for gaseous fluids.
Since the pistons move in non-metal gaskets, they are not easily worn. Worn gaskets can be easily renewed.
Pressure losses are high due to their structure.
They contain dead volume. Residues may accumulate inside the valve.
In large nominal dimensions, enormous forces act on the opening and closing spindle. This force makes it difficult to close. It is appropriate to switch to “Balance piston” type valve with nominal sizes larger than DN 65.
Piston Valve Types
According to pressure force balances:
Normal piston: In these types, the piston must overcome the force exerted by the fluid against the area arising from the piston diameter during closing. (This force was mentioned in seated-globe valves)
Balance piston: Equal pressure is created at the bottom and top of the piston with the holes extending from the piston to the back of the piston, and during closing, the operator tries to overcome the friction force that occurs only between the piston and the sealing rings, and the force it needs to spend is significantly reduced. It is used in dimensions of DN 65 and above.
Piston Valve Application Examples
If the fluid used may be freezing or solidifying when the temperature drops, the body should be heated in a pattern such as a serpentine and jacket.
In terms of overall energy saving; It should not be forgotten that the valves have large surfaces that will cause heat loss to the environment, and the valves where different fluid passes from the ambient temperature must be isolated.
Piston Valve Maintenance
The most common problems in such valves are; sealing of the gaskets and lack of compression.
Piston seal kits can be easily replaced by obtaining new ones from the manufacturer. By opening the cover, the piston and old gaskets are removed.
The piston surface is cleaned and polished. The lower seal set, the metal spacer and the upper seal set are placed in the housing, respectively.
The piston is placed so that both gaskets pass through it. The cover stud nuts are tightened mutually and the cover is mounted.
In Balance Piston Valves; In the case of leakage from the shaft seal, the packing must be compressed to prevent leaks. But; If the valves have been in the warehouse for a long time before they are connected to the installation or have reached the limit of compressibility,
the seals may lose their elasticity and become unable to prevent leakage. In this case, repair is not possible and the packing must be replaced.