Abstract： ASME PTC 25:1998 pdf download.Pressure Relief Devices. The valve shall be equipped with an atmospheric discharge, as shown in Fig. 2. Test procedure shall be in accordance with paras. 4.5.3 (a) through (n), performing such portions of the p...

ASME PTC 25:1998 pdf download.Pressure Relief Devices.

The valve shall be equipped with an atmospheric discharge, as shown in Fig. 2. Test procedure shall be in accordance with paras. 4.5.3 (a) through (n), performing such portions of the procedure and recording such data as has been agreed upon.

NOTE: The objectives of this portion of the test may be only to determine and record the set pressure and closing pressure of the

valve; and the lift of the valve at the flow-rating pressure, when the valve is discharging to atmosphere. In this case, the

portions of paras. 4.5.3 (a) through (h) relating to capacity determination may be eliminated.

(b) Back-Pressure Test. Following the atmospheric back-pressure test, if performed, install the discharge arrangement required by

Fig. 5 or 6, depending on type of back pressure desired

4.8.4 Testing With Superimposed Back Pressure (fig. 5)

(a) Adjust the back pressure on the valve and discharge piping to the required value. Increase the pressure at the valve inlet.

During the pressure interval starting at 90% of the expected set pressure, the rate of pressure increase shall not exceed 2.0 psi!

sec, or whatever lesser rate of increase is necessary for the accurate reading of the pressure. Observe and record the set pressure of the valve, the back pressure, and any other desired or pertinent characteristics.

(b) Continue increasing the pessure at the valve inlet until the valve remains open. Observe the action of the valve. Gradually

decrease the inlet pressure until the valve closes. Record the reseating pressure of the valve and the back pressure. Observe the

action of the valve.

NOTE: During (a) and (b) above, care shall be exercised to maintain the back pressure at as uniform a value as possible.

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