What is proceduer for hydrotest?

Answer 1

see ASME VIII div 1 UG-99 STANDARD HYDROSTATIC TEST(a) A hydrostatic test shall be conducted on all vesselsafter:(1) all fabrication has been completed, except foroperations which could not be performed prior to the testsuch as weld end preparation [see U-1(e)(1)(a)], cosmeticgrinding on the base material which does not affect therequired thickness; and(2) all examinations have been performed, exceptthose required after the test.The completed vessels, except those tested in accordancewith the requirements of UG-100 and UG-101, shall havesatisfactorily passed the hydrostatic test prescribed in thisparagraph.(b) Except as otherwise permitted in (a) above and 27-4, vessels designed for internal pressure shall be subjectedto a hydrostatic test pressure which at every point in thevessel is at least equal to 1.3 times the maximum allowableworking pressure34 to be marked on the vessel multipliedby the lowest ratio (for the materials of which the vesselis constructed) of the stress value S for the test temperatureon the vessel to the stress value S for the design temperature(see UG-21). All loadings that may exist during this testshall be given consideration.(c) A hydrostatic test based on a calculated pressuremay be used by agreement between the user and the Manufacturer.The hydrostatic test pressure at the top of thevessel shall be the minimum of the test pressures calculatedby multiplying the basis for calculated test pressure asdefined in 3-2 for each pressure element by 1.3 and reducingthis value by the hydrostatic head on that element.When this pressure is used, the Inspector shall reserve theright to require the Manufacturer or the designer to furnishthe calculations used for determining the hydrostatic testpressure for any part of the vessel.(d) The requirements of (b) above represent the minimumstandard hydrostatic test pressure required by thisDivision. The requirements of (c) above represent a specialtest based on calculations. Any intermediate value of pressuremay be used. This Division does not specify an upperlimit for hydrostatic test pressure. However, if the hydrostatictest pressure is allowed to exceed, either intentionallyor accidentally, the value determined as prescribed in (c)above to the degree that the vessel is subjected to visiblepermanent distortion, the Inspector shall reserve the rightto reject the vessel.(e) Combination units [see UG-19(a) and UG-21] shallbe tested by one of the following methods.(1) Pressure chambers of combination units that havebeen designed to operate independently shall be hydrostaticallytested as separate vessels, that is, each chamber shallbe tested without pressure in the adjacent chamber. If thecommon elements of a combination unit are designed fora larger differential pressure than the higher maximumallowable working pressure to be marked on the adjacentchambers, the hydrostatic test shall subject the commonelements to at least their design differential pressure, correctedfor temperature as in (b) above, as well as meet therequirements of (b) or (c) above for each independentchamber.(2) When pressure chambers of combination unitshave their common elements designed for the maximumdifferential pressure that can possibly occur during startup,operation, and shutdown, and the differential pressure isless than the higher pressure in the adjacent chambers, thecommon elements shall be subjected to a hydrostatic testpressure of at least 1.3 times the differential pressure Tobe marked on the unit, corrected for temperature as inUG-99(b).Following the test of the common elements and theirinspection as required by (g) below, the adjacent chambersshall be hydrostatically tested simultaneously [see (b) or(c) above]. Care must be taken to limit the differentialpressure between the chambers to the pressure used whentesting the common elements.The vessel stamping and the vessel Data Report mustdescribe the common elements and their limiting differentialpressure. See UG-116(j) and UG-120(b).(f) Single-wall vessels designed for a vacuum or partialvacuum only, and chambers of multichamber vesselsdesigned for a vacuum or partial vacuum only, shall besubjected to an internal hydrostatic test or when a hydrostatictest is not practicable, to a pneumatic test in accordancewith the provisions of UG-100. Either type of testshall be made at a pressure not less than 1.3 times thedifference between normal atmospheric pressure and theminimum design internal absolute pressure.(g) Following the application of the hydrostatic testpressure, an inspection shall be made of all joints andconnections. This inspection shall be made at a pressurenot less than the test pressure divided by 1.3. Except forleakage that might occur at temporary test closures forthose openings intended for welded connections, leakageis not allowed at the time of the required visual inspection.Leakage from temporary seals shall be directed away soas to avoid masking leaks from other joints.The visual inspection of joints and connections for leaksat the test pressure divided by 1.3 may be waived provided:(1) a suitable gas leak test is applied;(2) substitution of the gas leak test is by agreementreached between Manufacturer and Inspector;(3) all welded seams which will be hidden by assemblybe given a visual examination for workmanship priorto assembly;(4) the vessel will not contain a "lethal" substance.(h) Any nonhazardous liquid at any temperature maybe used for the hydrostatic test if below its boiling point.Combustible liquids having a flash point less than 110°F(43°C), such as petroleum distillates, may be used onlyfor near atmospheric temperature tests. It is recommendedthat the metal temperature during hydrostatic test be maintainedat least 30°F (17°C) above the minimum designmetal temperature, but need not exceed 120°F (48°C), tominimize the risk of brittle fracture. [See UG-20 and GeneralNote (6) to Fig. UCS-66.2.] The test pressure shallnot be applied until the vessel and its contents are at aboutthe same temperature. If the test temperature exceeds 120°F(48°C), it is recommended that inspection of the vesselrequired by (g) above be delayed until the temperature isreduced to 120°F (48°C) or less.CAUTION: A small liquid relief valve set to 11⁄3 times the test pressureis recommended for the pressure test system, in case a vessel, while undertest, is likely to be warmed up materially with personnel absent.(i) Vents shall be provided at all high points of thevessel in the position in which it is to be tested to purgepossible air pockets while the vessel is filling.(j) Before applying pressure, the test equipment shallbe examined to see that it is tight and that all low-pressurefilling lines and other appurtenances that should not besubjected to the test pressure have been disconnected.(k) Vessels, except for those in lethal service, may bepainted or otherwise coated either internally or externally,and may be lined internally, prior to the pressure test.However, the user is cautioned that such painting /coating /lining may mask leaks that would otherwise havebeen detected during the pressure test.