The design of knife gate valves of PA 520 series
Description of basic structural elements
Elastic seat is inserted into the body of the knife gate valve and reinforced with a steel wire to keep the shape and prevent slipping under the influence of the working medium flow. The seat has a U-shape repeating the knife shape. This design allows the flow of medium in two directions, eliminating accumulation of solid particles that prevent the gate closure.
Elastomeric materials used as seats
EPDM. It has high mechanical properties, to be used mainly for water and aqueous solutions. It is designed for operating temperature up to 90 °С in the constant mode, and not higher than 125 °С in the short-term mode. It can also be used for abrasive products.
NBR. Has a high hardness and relatively high abrasion resistance, to be used for liquids containing fats and oils. It is designed for operating temperature not exceeding 80 °С
VITON. It has high resistance to temperatures and chemicals, to be used for corrosive liquids. It is designed for operating temperature up to 180 °C in the constant mode and up to 200 °C in the short-term mode.
All the above materials provide 100% tightness
PA 520 knife gate valves are full-opening, that ensures a high working medium flow rate at low pressure drops. The internal body structure does not allow accumulation of solid deposits.
The knife gate valve body can be made of the following materials:
– ductile cast iron GGG40
– carbon steel WCB
– corrosion-resistant steel CF8
– Corrosion-resistant steel with molybdenum CF8M
– special steels and alloys (upon the order)
Standard valves have an epoxy corrosion-resistant coating 250 microns thick.
Application of another protective coating is available.
By default, the knife material is stainless steel. The knife is polished on both sides, the edge has a rounded shape.
Gland follower packing
Packing ensures tightness between the body and the knife, preventing any leakage to the environment. Packing is located in an easily accessible point and can be replaced without removing the gate from the pipeline.
The knife gate valve stem is made of stainless steel. This ensures its high strength and excellent corrosion resistance. The knife gate valve design provides for both a rising and non-rising stem.