Articles

Manifold Solenoid Valve

In many automatic changeover manifold designs, the solenoid valve plays a critical role in the changeover
function.  In order for the manifold to retain a bank of compressed or liquefied gas in reserve, the solenoid valve must close and not leak.  When it is time for the reserve bank to become the service or bank in use, the solenoid valve must open.

 

The valve must be designed so that:
  • It is compatible with the gas service
  • Has a large enough orifice to provide sufficient flow Will automatically open if there is a power outage Will operate for many years of continuous usage
  • If there is a failure of other components to regulate, or maintain normal operating pressures it will open and provide life sustaining medical gases.

 

When we designed our med gas manifold system, we designated the solenoid valve as a critical component.  We decided that there were no acceptable commercially available solenoid valves that met our design standards, so we designed our own. The Tri-Tech solenoid valve has several advantages over the commercially supplied valves used by our competitors; higher flow rate, greater reliability and lifespan and most importantly a 400 psig differential pressure rating.  Our competitors utilize solenoid valves which have only a 150 psig differential rating.

 

Why is a solenoid valve with a 400 psig better than one with a 150 psig differential pressure rating?  It is safer and more reliable.  Every day in thousands of medical facilities there are tens of thousands of manifolds that must changeover automatically when one bank of gas is depleted to another full bank.  If the solenoid valve, which controls this changeover function fails to open, the life sustaining medgas will stop flowing thru the medical gas pipeline. Typical failures of other manifold components which can cause a solenoid valve to not open would be; leaks in certain areas of the manifold and/or regulators which are improperly adjusted or which fail to regulate properly. The differential pressure rating is simply:

inlet pressure minus the outlet pressure = X
(where if X > 150 the valve will not open because of mechanical design limitations)

A real-life example might be as follows:  the normal operating pressure of a medical gas entering the solenoid valve inlet is regulated to 200 psig and the pressure at the solenoid valve outlet is normally 100 psig at the time of changeover.  So when the valve is required to open the differential pressure across the solenoid valve is 100 psig (200 – 100 = 100).  If there is a leak on the outlet side of the solenoid valve and the pressure depletes to zero (which is a very real possibility since there are typically check valves which prevent replenishment of the gas from the opposite bank) we now have a failure scenario: 200 psig inlet pressure – 0 psig outlet pressure = 200 psig differential pressure.  In this scenario, a 150 psig differential rated solenoid valve will NOT open and the flow of medical gas will stop.

 

Why did we choose 400 psig?  Because there are no failure scenarios in our medical manifolds which could result in exceeding a 400 psig differential pressure across the solenoid valve.
          

“Improving Medical Gas Systems through innovation”


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