A gas that follows the perfect gas laws without deviation. Although theoretical, it is the basis from which calculations are made and corrections applied.

The condition when a perfect gas is isentropically compressed, and the gas, inlet temperature, and amount of work spent is the same for each stage.

Incapable of being mixed without separation phases. Water and petroleum oil are immiscible under most conditions, although they can be made miscible with the addition of an emulsifier.

The part of the rotating element of a dynamic compressor that imparts energy to the flowing medium by means of centrifugal force.  It consists of a number of blades mounted so that they rotate with the shaft.

A measurement of vacuum or pressure and is used to measure an airflow restriction.

Inches of water gauge or column (in-wg or in-wc) is a unit of air pressure measurement equal to the pressure exerted by a column of water 1 inch high.

The charge for compressed air consumed above the BAR (base air requirement) and is charged based on the quantity consumed.

The quantity of air required in excess of the Base Air Requirement. Air compressors are designed as frame sizes. Each frame size will deliver up to a certain amount of flow.  Many times the air requirement of a customer will fall in the middle to bottom of a compressor frame. This creates additional available capacity from the compressor or air station. This additional capacity may not be utilized initially, but is available, usually at a reduced rate, to the customer in the future. Incremental air capacity can be intentionally built into the air station, but this usually results in additional capital cost. which is reflected in the facility fee.

Power as calculated from compressor-indicator diagrams.

A pressure - volume diagram for a compressor or engine cylinder, produced by direct measurement by a device called an indicator.

An indicator that signals pressure conditions.

An air flow caused by a fan that draws air through the heat exchanger core in a uniform pattern to dissipate the sensible heat.

A curved inlet section on an impeller.

Process of purging a container or covering a product with a non-reactive atmosphere such as nitrogen, carbon dioxide, argon, or helium.

A gas that does not enter into known chemical combination, either with itself or another element and does not supply any of the needs of combustion.  There are four known gases of this type: helium; neon; argon and krypton.

A concrete foundation with lateral supports which rests upon a number of steel springs and designed to mitigate disturbing frequencies in vibration isolation.

When reciprocating compressors run, the moving parts (pistons, rods, crossheads, connecting rods) are repeatedly accelerated and retarded. These velocity changes set up pulsating inertia forces. The forces are of the first and second order. The first order forces have the same frequency as the compressor shaft speed and the second order forces have a frequency twice the shaft speed.

The fluid entering a component.

Environmental contaminant that ingresses due to the action of the system or machine.

A Valve fitted on the inlet of most types of compressors, and the valve opens and closes to throttle the air flow. However, the term IBV is usually associated with turbo compressors.

CFM flowing through the compressor inlet filter or inlet valve under rated conditions.

A valve assembly at the air inlet of a "blower" (single stage, low pressure, centrifugal air compressor). Usually it is intended to be mounted in very close proximity to the "blower" impeller. It provides "pre-swirl" of air flow in the same rotational direction as the "blower" impeller. It has proven to improve efficiency (reduced bhp) during throttled-down modulation of the "blowers". Its effectiveness, when used with multi-stage centrifugal air compressors, degrades rapidly.

The total pressure (static plus velocity) at the inlet flange of the compressor.

The temperature at the inlet flange of the compressor.

A compressor control mechanism designed to control performance output of the compressor to the demands of the plant process.

A filter assembly in which the inlet, outlet and filter element axes are in a straight line.

Insoluble material suspended in the lubricating oil. This material may come from contamination or oil degradation.

The quality of compressed air for use with pneumatic instruments and controls and is usually dry and free from contaminants.

A device for separating solids or suspended particles in the air before they enter the air intake of the compressor.

A device for separating solids or suspended particles in the air before they enter the air intake of the compressor and reduce intake noise as on reciprocating compressors through a silencing chamber in the filter housing.

A valve designed to prevent air volume and pressure from escaping the compressor tank back into the compressor heads while the compressor is not in operation.

Heat exchangers for removing the heat of compression between stages of a compressor.

The removal of heat from the air or gas between stages.

The difference in air or gas temperatures between the inlet of the compressor and the outlet of the intercooler.

When the temperature of the air or gas leaving the intercooler is equal to the temperature of the air or gas entering the inlet of the compressor.

Energy which a substance possesses because of the motion and configuration of its atoms, molecules, and subatomic particles.

International Organization for Standardization.

One in which a portion of the original system energy is dissipated and cannot be returned to the system through its own operation. The system and/or surroundings cannot be returned to their original state.

A process taking place without any heat exchange with the surroundings.

An adiabatic compression with no increase in entropy; a reversible-adiabatic compression.

The ratio of the real gas isentropic power consumption to shaft input.

The power which is theoretically required to compress a gas under constant entropy from a given inlet pressure to a given discharge pressure and is calculated assuming ideal conditions.

A process taking place under constant pressure. To change the volume from state 1 to state 2, heat must be removed. The temperature change is proportional to the change in specific volume.

A process taking place under constant volume. To raise the pressure from state 1 to state 2, heat must be added. The pressure change is proportional to the change in temperature.

A process taking place under constant temperature. To compress the gas from state 1 to state 2, heat must be removed to keep the temperature constant. The pressure change is reciprocal to the change in specific volume.

A compression in which the temperature of a gas remains constant.

The ratio of the isothermal power consumption to shaft input.

The power which is theoretically required to compress a gas under constant temperature, in a compressor free from losses, from a given inlet pressure to a given discharge pressure.

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