Thursday, October 17, 2013

Superior Design Check Valve Better Than Swing Check


Proquip Check Valve Design
Many engineers apply swing check valves because they are inexpensive and their use is pretty wide spread. Our experience tells us there are better alternatives. Here are the reasons RENCOR favors Velan-Proquip valves over conventional swing check valves.

Reduced Size – Weight – Cost: 

The inherent design of the double flapper check valves results in a significantly reduced weight as compared to the conventional full bodied check valve. As the valves increase in size the Velan-Proquip valve will be as little as one fifth the weight of the full bodied unit. This results in savings in initial cost, space, and pipe support element installation.

Reduced Line Shock: 

To minimize/eliminate line shock, check valves must close as quickly as possible prior to the flow having an opportunity to reverse. As each of the flappers in the Velan-Proquip check valve is only half the size of that of a full bodied check, they experience reduced fluid drag and can move more quickly to the closed position. Their swing radius is one half that of the conven- tional check valves. The leading edge distance from open to closed position is halved, in turn reducing the travel time by 50%.

The reduced weight of a dual disc valve flapper versus the full bodied swing check is a major factor in
conventional swing check design
minimizing water hammer. The heavier full bodied disc has greater momentum when swinging closed, causing it to slam into the valve seat resulting in severe damage, (in large valve sizes the disc can weigh up to a ton).

For potentially severe applications, Velan-Proquip offers a high torsion spring to ensure the valve closes as quickly as possible.

Lower Pressure Drop – Reduced Energy Costs:

The inherent design of the double flapper check valves results in a significantly reduced weight as compared to the conventional full bodied check valve. As the valves increase in size the Velan-Proquip valve will be as little as one fifth the weight of the full bodied unit. This results in savings in initial cost, space, and pipe support element installation.

The two factors that affect pressure drop across any valve are:
  1. The unobstructed flow area. 
  2. The energy required to maintain the valve in the open position. 
Specifically, full-bodied swing check valves have a disc which is hinged at the top with gravity working to keep it in the closed position. Flow must provide sufficient energy to overcome this force of gravity and lift the disc. This energy requirement increases dramatically in larger sizes.

Velan-Proquip valves are installed such that the flappers are hinged at their sides like a door. Thus, the effect of gravity is eliminated. Consequently, very little energy is needed to open the valve and maintain this position, resulting in lower energy costs.