# What is Cold Differential Test Pressure (CDTP)

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PRV – Cold Differential Test Pressure;

The Cold Differential Test Pressure (CDTP) of the Pressure Relief Valve (PRV) is a set pressure that is adjusted to be used for the PRV (Bench Testing). Because in actual use conditions, the PRV may be affected by the Backpressure. And the operating temperature. Therefore, when testing at room temperature and without backpressure, it is necessary to adjust the set pressure to compensate for these factors. In other words, the shop test pressure = CDTP.

PRV – Cold Differential Test Pressure (Example 1);

An example of a Cold Differential Test Pressure (CDTP) with a backpressure (superimposed) effect. In this case, CDTP is equal to Set Pressure minus Backpressure.

Refer to:

What is Backpressure, Superimposed Backpressure?

What is Backpressure testing of PRV?

What is Built-up Backpressure of PRV?

PRV – Cold Differential Test Pressure (Example 2);

An example of a Cold Differential Test Pressure (CDTP) with different temperature compensations for use and testing. And an example of CDTP that has been adjusted to compensate for both Backpressure (Superimposed) and temperature  effects.

PRV Testing – Test Stand or Test Bench;

Test Stand or Test Bench is a set of equipment used for Pressure Relief Valve (PRV) in Pop Test (Set Pressure Test), Blowdown and Seat Tightness Test (Leakage Test)

The above concept is typical used for “Conventional” type of PRV.

In case of Using “Pilot” or “Bellow” type, the Back-pressure from Outlet side will be exempted following explainations:

Refer to: What is Balanced Bellow of PRV ?

PRV – Cold Differential Test Pressure for Balanced Bellow PRV;

As for the Balanced Bellow Pressure Relief Valve, which has a bellow for reducing the impact of the Backpressure, the Cold Differential Test Pressure (CDTP) of the Balanced Bellow Type PRV will compensate only for the impact of different temperatures  between the Shop Test and In-service.

PRV – Cold Differential Test Pressure for Balanced Bellow Type (Example 1);

Examples of the Cold Differential Test Pressure (CDTP) of the Balanced Bellow PRV is adjusted compensation by the High Temperature applies only.