How is the cold-state test differential pressure (CDTP) calculated when there is a variable additional back pressure on the safety valve?
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How is the cold-state test differential pressure (CDTP) calculated when there is a variable additional back pressure on the safety valve? For example, with a fixed pressure of 1.0 MPa(g), a constant additional backpressure of 0.1 MPa(g), a variable additional backpressure ranging from 0 to 0.05 MPa(g), and an exhaust backpressure of 0.05 MPa, what would be the CDTP if a conventional safety valve is used?
Under these conditions, the calculation method for the cold-test differential pressure (CDTP) of a safety valve is as follows: 1. Set pressure: 1.0 MPa (g). 2. Constant additional backpressure: 0.1 MPa (g). 3. Variable negative pressure range: 0 – 0.05 MPa (g). Since the set pressure already takes into account the constant additional backpressure, the cold-test differential pressure (CDTP) can be obtained by simply subtracting the discharge backpressure from the set pressure. Therefore, for a conventional safety valve, its cold-test differential pressure (CDTP) is 0.95 MPa(g). .