The design of knife gate valves of PA 550 series
Description of basic structural elements
PA 550 series valve elastic seat is made of a pair of rubber inserts reinforced inside with a stainless ring, which prevents their deformation. In the open position, both inserts are in constant tight contact, providing the required tightness and the absence of stagnant zones. This design ensures the medium flow in two directions, eliminates accumulation of solid particles that prevent the valve closure. The seat is made of the following materials:
Natural rubber. Has high mechanical properties. It is designed for operating temperature up to 90 °С. Recommended for abrasive products.
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 550 series gate valves are full-opening, that ensures a high working medium flow rate at low pressure drops. The valve body is cast, has a sealed bottom cover to remove the working medium residues that can enter the body during the opening and closing process, and special holes can be made in the body to wash the valve interior cavity.
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)
Knife material is stainless steel CF8. The knife is polished on both sides, the edge has a sharpened shape, which allows shutting off the working medium flow. It is possible to make a knife made of stainless and special steels of various grades.
Gland follower packing
Gland packing ensures tightness between the body and the knife, preventing any leakage to the environment. Gland 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.