Pressure testing in API 6D

Pressure Testing In API 6D

General

Each  valve shall be tested prior to shipment. The purchaser shall specify which particular supplementary tests in Annex B shall be performed.

If the valve has been previously tested in accordance with this International Standard, subsequent repeat testing may be performed without removal of the valve external coating.

Test fluid shall be fresh water or, by agreement, light-weight oil having a viscosity not exceeding that of water. Water shall contain a corrosion inhibitor and, by agreement, antifreeze. The chloride content of test water in contact with austenitic and duplex stainless steel wetted components of valves shall not exceed 30 IJg/g (30 ppm by mass).

API 6D Ball Valves shall be tested with the seating and sealing surfaces free from sealant except where the sealant is the primary means of sealing. A secondary sealant system, if provided, shall not be used before or during tests.

Tests specified with the valve half-open may also be performed with the valve fully open, provided the body cavity is simultaneously filled and pressurized through a cavity connection.

If valve-body connections are not available for direct monitoring, methods for monitoring pressures and/or leakage shall be determined.

Supply pressure shall be stabilized prior to the start of pressure testing and shall be held for the minimum test durations listed in Tables 1 and 2.

Pressure testing shall be performed in accordance with documented procedures.

Stem backseat test

Testing of the backseat shall commence with the packing gland loose. Self-energized packing or seals shall be removed unless a test port is provided for this test.

The valves shall be filled with the ends closed off and the obturator in the partially open position until leakage of the test fluid around the stem is observed. The backseat shall then be closed and a minimum pressure of 1,1 times the pressure rating determined in accordance with 7.2 for material at 38°C (100 OF) applied for the duration specified in Table 1.

Monitoring for leakage shall be through a test access port or by monitoring leakage around the loosened packing.

No visible leakage is permitted at this test pressure.

NOTE This test is performed prior to hydrostatic shell test.

Table 1 – Minimum duration of stem backseat tests

Hydrostatic shell test

Valve ends shall be closed off and the obturator placed in the partially open position during the test. If specified by the purchaser, the method of closing the ends shall permit the transmission of the full-pressure force acting on the end blanks to the valve body. If present, external relief valves shall be removed and their connections plugged.

The test pressure shall be 1,5 or more times the pressure rating determined in accordance with 7.2 for material at 38°C (100 OF). The duration shall not be less than that specified in Table 2.

Table 2- Minimum duration of hydrostatic shell tests

No visible leakage is permitted during the hydrostatic shell test.

After hydrostatic shell testing, external relief valves shall be fitted to the valve. The connection to the valve body shall be tested at 95 % of the set pressure of the relief valve for 2 min for valve sizes up to and including ON 100 (NPS 4), and 5 min for valve sizes ON 150 (NPS 6) and larger. The relief-valve connection shall be free of visible leakage during this period.