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Q: What is a pneumatic test? What do I need to know about it?

Here are some things you need to know about pneumatic tests:

(a) Subject to the provisions of UG-99 (a) (1) and UG-99 (a) (2), a pneumatic test prescribed in this paragraph may be used in lieu of the standard hydrostatic test prescribed in UG-99 for vessels:

  1. that are so designed and/or supported that they cannot safely be filled with water
  2. not readily dried, that are to be used in services where traces of the testing liquid cannot be tolerated and the parts of which have, where possible, been previously tested by hydrostatic pressure to the pressure required in UG-99.

(b) Except for enameled vessels, for which the pneumatic test shall be at least equal to but not exceed, the maximum allowable working pressure to be marked on the vessel, the pneumatic test pressure at every point in the vessel shall be at least equal to 1.1 times the maxi-mum allowable working pressure 36 multiplied by the lowest stress ratio (LSR) for the pressure-boundary materials of which the vessel is constructed. The stress ratio for each pressure-boundary material is the ratio of the stress value Sat its test temperature to the stress value Sat its design temperature (refer UG-21).

Bolting shall not be included in the determination of the LSR, except when 1.1 times the LSR multiplied by the allowable stress of the bolt at its design temperature exceeds 90% of the bolt material specified minimum yield strength at the test temperature. All loadings that may exist during this test shall be given consideration. In no case shall the pneumatic test pressure exceed 1.1 times the basis for the calculated test pressure as defined in 3-2.

(c) The metal temperature during pneumatic test shall be maintained at least 30°F (17°C) above the minimum design metal temperature to minimize the risk of brittle fracture. [refer UG-20 and Figure UCS-66.2, Note (6)]

(d) The pressure in the vessel shall be gradually increased to not more than one‐half of the test pressure.Thereafter, the test pressure shall be increased in steps of approximately one‐tenth of the test pressure until the required test pressure has been reached. Then the pres-sure shall be reduced to a value equal to the test pressure divided by 1.1 and held for a sufficient time to permit inspection of the vessel.

Any leaks that are present, except for leakage that might occur at temporary test closures for those openings intended for welded connections, shall be corrected, and the vessel shall be retested.

The visual inspection of the vessel at the required test pressure divided by 1.1 may be waived, provided:

  • a suitable gas leak test is applied;
  • substitution of the gas leak test is by agreement reached between Manufacturer and Inspector;
  • all welded seams that will be hidden by assembly are given a visual examination for workmanship prior to assembly;
  • the vessel will not contain a“lethal”substance.

(e) Painting and Coating:

  • Unless permitted by the user or his designated agent, pressure-retaining welds of vessels shall not be painted or otherwise coated either internally or externally prior to the pneumatic pressure test.
  • When painting or coating prior to the pneumatic test is permitted, or when internal linings are to be applied, the pressure-retaining welds shall first be leak tested in accordance with Section V, Article 10. Such a test may be waived with the approval of the user or his designated agent.
  • Vessels for lethal service [refer UW-2(a)] shall not be painted or otherwise coated or lined either internally or externally prior to the pneumatic pressure test

Kami bakal mengadakan Webinar Kuasai ASME VIII pada ketetapan berikut:

  • Tarikh: 15 Januari 2022
  • Hari: Sabtu
  • Masa: 9.00 pagi – 12.00 tengah hari
  • Tempat: Platform Zoom

Untuk mendaftar, sila klik pautan ini:

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