Switchover Manifold

WHAT IS A SWITCHOVER MANIFOLD?

A changeover manifold is a system of valves and pressure regulators that delivers gas to a process without gas flow interruption. Most changeovers consist of a regulator scheme that reduces the pressure in two stages to achieve a constant outlet pressure.

It should be noted that there are systems offered that do not provide two stages of pressure reduction and that the resultant outlet pressure will fluctuate considerably as the system operates, thus requiring the addition of a line regulator downstream from the switchover to provide a consistent pressure to the process.

 SELECTION CRITERIA FOR SWITCHOVER MANIFOLDS

Each application has a different set of operating parameters that must be evaluated and satisfied. A few of those parameters are outlined below.

 1. Automatic or semi-automatic?

A semi-automatic switchover operates by opposing pressure differential. It switches from the “in-service” side to the “reserve” side automatically, but requires an action by the operator to switch it back from the new “in-service” side to the “reserve side”. Typically this is accomplished by turning a knob or lever.

An automatic switchover manifold functions electronically. The only action required by an operator for this unit to reverse the changeover is to replace empty cylinders and to re-pressurize the depleted side.

2. What is the gas supply source?

The gas supply source to a switchover may include any combination of the following:

• A standard high pressure cylinder.
• A cylinder of liquefied gas.
• A six pack or 12 pack manifold of cylinders.
• A high pressure cryogenic container of argon, nitrogen, oxygen, or carbon dioxide.
• A tube trailer.
• A high pressure bulk storage tank.

The above gas sources and their combinations will drive your choice of switchover manifolds.

3. What is the maximum required flow?

This is often the most difficult parameter to specify. Knowing the maximum flow is important for two reasons. First, you must ensure that the changeover has sufficient capacity to feed the process. Second, you must ensure that the gas sources are sufficient to meet the operating parameters of the application.

4. Determine the desired gas source change out frequency.

To determine the gas source frequency change out time, consider the flow rate, the total hours of operation, and the time period to obtain full containers to replace the empty side of the changeover.