Where possible, blow steam lines free of condensate before turning steam into ejector. A single-stage ejector can be put into operation by simply turning on steam valve. For multi-stage systems, always start the last stage (Z) pump or jet and progress backward to the first stage (see cooling water and liquid ring vacuum pump paragraphs below).

Ejectors are usually vertically installed to discharge downward and provide the best possible drainage. They will, however, operate in any position if exhaust and vacuum lines are properly configured.

Most single-stage ejectors are designed to build to a full vacuum of 28” Hg. when blanked off. Steam pressure only a few points below design will cause a sharp break in vacuum; but steam pressure cannot be used to control the vacuum or capacity of this type of ejector. Excessively high steam pressure may result in poorer vacuum.

A low vacuum single-stage ejector is designed for operation with absolute pressures above 15” Hg. Steam pressure can be used to control the vacuum and capacity with this type of ejector.

Checking steam quality: A steam jet ejector can be used as a throttling calorimeter. A thermometer in the ejector exhaust line can be used to check the steam quality. Tests should be made with the ejector blanked off. A 220 °F exhaust temperature is too low for good performance. 240 °F and upward is acceptable. Actual steam quality can be obtained from these temperature readings by referring to a Mollier Chart.

For multi-stage steam jet systems utilizing condensers, the cooling water must be turned on before putting steam to any ejectors. The cooling water temperature must not exceed the maximum design temperature of the condensers (see nameplate). Flow rate must also match design spec(see nameplate).

For hybrid systems using liquid-ring vacuum pumps, the liquid ring inside the pumps must be present and at the correct level. Cooling water must also be flowing to the cooler (if equipped) or to the pump for once-thru or partial recalculating systems. Cooling water temperatures and flow rates should match the design spec.

Discharge pressure should not be more than 1 psig unless the ejector is designed for higher backpressure.

It is desirable to break system vacuum by letting in air before turning off an ejector. If the ejector is turned off first, air is sucked back through the ejector exhaust line bringing vapor and condensate back into the vacuum system

To shut down a multi-stage system, shut off the steam to the first stage then the second stage and so on after bleeding in air to prevent suck-back. When the steam is off to all stages, cooling water to the condensers can be shut off.

If the system has a liquid-ring vacuum pump as the last stage, follow this procedure. Shut off the steam to upstream ejectors, then turn off pump and then turn off cooling water to pump.