control valve

What is a blow-down valve?

A blowdown valve is a widely used pipe valve and it is used in many industrial applications. The blowdown valve is mostly used for open position operations, the major function of a blowdown valve is to control the flow under high differential pressure. The important feature of this type of valve is that it can maintain fluid-tightness and it can be operated without any wedging action. The blowdown valves are mostly made up of stainless steel, these valves can blow out unwanted loose material that is collected in the strainer element. Blow-down valves can also be used to blow down the system pressure from the device during the shutdown. These valves can be seen in boilers to drain the dissolved solids from the boiler water and it will be fitted in the drain lines of the boilers.

What are the uses of blow-down valves?

  • It can be used with an air compressor
  • These valves are very useful for the removal of slugs and unwanted material after cleaning the pipe
  • It is used in the water feeders
  • It can be very helpful to lower water cut-offs
  • These valves can control the solid concentration in the boiler

What are the features of blow-down valves?

  • It is made up of stainless steel so it is corrosion resistant
  • It provides tight shutoff in closed condition
  • It is available in various size
  • Easy to operate
  • Maintenance-free
  • The design material of the blowdown valve would reduce the effect of the fluid stream in conditions when the water sometimes have abrasive material
  • It has a stroke indicator which would show the disk position
  • The design of this valve is bonnet-less, so it will be very easy to do the inspection, maintenance, and dismantling.
  • The outlet of these valves are venture tube-shaped, the stem is rising non-rotating there is a local stroke indicator which shows the disk position.

How does a blow down valve work?

During the start-up, the valve closes and this would lead to the air-oil separator pressure build-up. During the shut-down, the valve would open to bleed the air-oil separator to the atmosphere, and pressure will be provided during this time.

How to select a blow down valve?

We must select the dimension of the blow down valve according to the operating conditions like

  • Working pressure
  • Working temperature
  • Exhausting capability
  • Material
  • Size
  • Type and durability
  • End connection and end usage

How to install a blow-down valve?

The blow-down valves will be installed in a drain point or it would be connected near to the strainer element. The direction of the outlet of the blow-down valve should be pointing away from the working area. We must make sure that only a wrench is used for operating the blow-down valve and this will protect the operator.

A blowdown piping system would have a shipside blow-down valve which would discharge the boiler effluent overboard. This blow-down cock is connected to the bottom blow-down valve by a non-return valve. The non-return valve would prevent any backflow either from other discharging boilers.

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