Features of soft sealed gate valves and differences from hard-sealed gate valves

Soft sealed gate valves are mainly used in water supply and drainage systems. Temperature ≤80℃, nominal pressure ≤PN25, diameter ≤800mm. The valve body material is cast iron or ductile iron, cast steel or stainless steel. Adopted standards: CJ/T216-2013 Soft sealed gate valve for water supply and drainage, GB/T 24924-2010 Resilient sealing gate valve for water supply system, AWWA C509:2001.

Main features of soft sealed gate valve

  1. The outer surface of the metal gate adopts molding vulcanization or injection vulcanization molding process, and is entirely covered with rubber EPDM or NBR. When closing, the elastic deformation of the rubber on the gate sealing surface completes the sealing. Corrosion-resistant, good sealing, zero leakage can be achieved. The gate is wedge-shaped, which reduces the wear of the valve plate sealing surface.
  2. There are no grooves at the bottom of the valve body. Fine particles in the medium will pass through the valve body along with the medium and will not accumulate impurities. The inner diameter of the flow channel at the valve seat is equal to that of the pipe and is consistent with the nominal size. Almost no flow resistance.
  3. Use epoxy resin powder electrostatic spraying. The coating does not dissolve in water after curing and does not affect water quality. Epoxy resin powder coating is a dry solid ultra-fine powder. During coating, an electrostatic spray gun is used to adsorb the charged coating particles on the surface of the valve body driven by compressed air. The valve body is then sent to the furnace for baking at a temperature of 180° to 200° to melt the paint and form a coating on the surface of the valve body. Epoxy powder coating has the following advantages: its melt viscosity is low, so its coating film has good leveling properties, and its adhesion to metal substrates is very good, so it does not require primer. The paint film has high hardness, good scratch resistance and good impact strength and other mechanical properties. The paint film has good water resistance, acid resistance, alkali resistance and salt water resistance.
  4. The gate valve stem position is sealed with three O-rings. Effectively prevent valve stem position leakage. At the same time, a dust ring is set on the top to prevent impurities and dust from entering. Can be replaced online under pressure.

The main replacement of soft sealed gate valve is: GB/T12232-2005 general valve flange connection iron gate valve. Including nominal pressure PN1 ~ 25, nominal diameter DN50 ~ 2000 flange connection gray cast iron and ductile iron gate valves.

The main differences between the two are

  1. The gate plate of the soft sealed gate valve is entirely wrapped with rubber, forming a soft seal with the sealing surface of the valve body, and has good sealing performance. During maintenance, it is generally only necessary to replace the gate with a new one, which is easy to maintain. The hard seal gate valve body and gate plate sealing surface are made of body material, copper alloy and stainless steel. After wear and tear, the valve body and gate need to be repaired at the same time, which is relatively complicated.
  2. The body of the soft sealed gate valve adopts a groove-free design. Will not cause impurities to accumulate. Due to the sealing surfaces on both sides of the valve body, the hard-sealed gate valve has grooves at the bottom of the valve body. Over time, some impurities will be deposited in the grooves. Block the gate from falling, causing sealing failure.
  3. The body of the soft sealed gate valve is sprayed with epoxy resin paint. Epoxy resin coating is corrosion-resistant, pollution-free, and can be used in tap water pipes. Hard-sealed gate valves are mostly spray-painted, which pollutes water quality to a certain extent, but now hard-sealed gate valves in tap water pipelines are also sprayed with epoxy resin.
  4. The standard for soft sealed gate valves stipulates that the valve stem shaft seal must have at least three O-ring seals, which can be replaced when the gate valve is fully open under working pressure. The hard seal gate valve standard GB/T12232-2005 stipulates no less than two sealing rings. Also provide a dust seal.
  5. The upper valve cover of the soft sealed gate valve adopts hexagon socket screws. After tightening, wax is poured on top to seal. This prevents rust between the screws and the valve body threads. Convenient for later screw removal and repair. The original hard seal gate valve usually uses hexagonal bolts. However, there are also some hard-sealed gate valves with similar structures.
  6. The applicable medium temperatures are different. On water pipelines, soft sealed gate valves are increasingly used. Hard-sealed gate valves for some high-temperature medium pipelines are also the main products.