The Type 75 Relay uses signal pressure to accurately control output pressure over a wide range of flow and supply pressure variation. Under varying flow conditions output pressure is maintained by use of an aspirator tube, which adjusts the air supply valve opening in accordance with the flow velocity. A balanced supply valve, utilizing a rolling diaphragm, makes the relay virtually immune to changes in supply pressure. Maintenance is simple due to the unit construction, and the relay can be serviced without removing it from the line. Signal to output pressure ratios of 1:1, 1:2, 1:4 and 1:6 are available. The Type 75 is designed to regulate output pressure up to 150 psi with a maximum supply pressure of 250 psi.

The Type 75 relays are most commonly used when increased flow capacity, pressure amplification, or remote pressure control is required. These applications include; Volume Boosting, Dancer Roll Loading, Calendar Roll Loading, Cylinder Bucking Control, Clutch and Brake Controls, Gas Flow Control, Tensioning Control, Valve Motor Loading.

The Type 75HR High-Relief Relay provides all the features of the standard Type 75 with maximum exhaust capacity for when fast relief of pressure is required.

Type 75 Relay with Fixed Negative Bias
The Type 75 Relay is also available with a 4 ±1 psig negative bias spring mounted internally. This bias spring automatically subtracts 4 ±1 psig from any signal pressure introduced. The relay then multiplies the net signal pressure by its ratio value to obtain final output pressure. This option is particularly useful in obtaining zero pressure from pneumatic devices such as I/P transducers that normally cannot be adjusted this low, as well as obtaining higher outputs from such devices. Typical applications of the Type 75 Relay with fixed negative bias include the electronic control of the applications listed for the standard Type 75 Relay.