ARTICLE KT-3HYDROSTATIC TESTS

KT-300 SCOPE

Each completed vessel shall be subjected to a hydro-static test pressure which, at every point in the vessel,is within the range specified in KT-310. Vessels de-signed for vacuum conditions do not require an addi-tional external pressure hydrotest.

KT-301 Layered Vessels

See additional requirements for hydrotest of layered,wire-wound, and strip-wound vessels in Articles KF-8, KF-9, and KF-10.

KT-302 Nonmetallic Lined Vessels

Vessels which are to be lined with a nonmetallicmaterial shall be pressure tested before the applicationof such lining.

KT-303 Autofrettaged Vessels

Autofrettaged vessels may be exempt from hydrostatictesting. See KT-340.

KT-310 LIMITS OF HYDROSTATIC TESTPRESSURE

KT-311 Lower Limit

The test pressure shall not be less than 1.25 times thedesign pressure to be marked on the vessel, multiplied bythe lowest ratio (for materials of which the vessel isconstructed) of the specified yield strength valueSy forthe test temperature of the vessel to the specified yieldstrength valueSy for the design temperature.

KT-312 Upper Limit

Except for the provision in KT-312.3, the test pressureshall not exceed the limits in KT-312.1 or KT-312.2,as applicable.

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KT-312.1 For Single Wall Vessels

Pt p Syln(Y)

whereSyp specified yield strength at test temperatureYp DO /DI diameter ratio

DOp outside diameterDIp inside diameter

KT-312.2 For Layered Vessels

Pt p ∑Syiln(Yi )

where Syi and Yi are the specified yield strength anddiameter ratio for each individual layer.

KT-312.3 Pressures Beyond Code Limit.If thehydrostatic test pressure exceeds the value determinedas prescribed in KT-312.1 or KT-312.2, as applicable,the suitability and integrity of the vessel shall beevaluated by the Designer and the results of thisevaluation shall be included with the Manufacturer’sDesign Report.

KT-320 FLUID MEDIA FORHYDROSTATIC TESTS 1

Only fluid which is liquid at the hydrotest temperatureand pressure and is not corrosive to the vessel partsshall be used for the hydrostatic test. The Manufacturershall consider the effect of increase in fluid viscositywith pressure. To minimize the risk of brittle fracture,the test temperature shall be a minimum of 30°F (17°C)higher than the material impact test temperature, butbelow the boiling point of the pressurized fluid. Thetest pressure shall not be applied until the vessel

1 To decrease the pressure energy of the fluid during hydrostatic test,filler bars may be inserted into vessels. Safety precautions shouldbe scaled according to the test location, fluid properties, and thepressure energy contained in the vessel under test.

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KT-320 PART KT — TESTING REQUIREMENTS KT-340

and the pressurizing fluid are within 10°F (5.6°C) ofeach other.

KT-330 TEST PROCEDURE

(a) The test pressure shall be increased in incrementsof not more than 20% of the test pressure. The pressureshall be stabilized at each increment and maintainedwithout the aid of the pump. If the pressure dropsmore than 5% at any increment, the pressure shall bereleased to a safe level. Following the release of thehydrostatic test pressure to a safe level, examinationfor leakage shall be made of all joints, connections,and regions of high stress, such as head knuckles,regions around openings, and thickness transition sec-tions. The examination shall be made immediately afterpressure is released and shall be witnessed by theInspector. Any evidence of leaks shall be investigatedand leaks corrected, after which the vessel shall beretested in accordance with these requirements.

(b) After the test pressure has been maintained with-out the aid of the pump for a minimum of 5 min, the

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pressure shall be reduced to the design pressure. Athorough inspection for leakage shall be conducted inaccordance with KT-330(a). If no leaks are found orif leaks are found to be from a fitting or other attachment,external to the vessel itself, the test may be acceptedas satisfactory.

KT-340 EXEMPTION FORAUTOFRETTAGED VESSELS

Autofrettaged vessels may be exempt from hydrostatictesting if all the following conditions are met:

(a) the vessel, when autofrettaged, is in its finalassembled form;

(b) no access ports or nozzles will be cut or attachedafter the autofrettage;

(c) the heads, closures, seal carriers, or other sealingmembers but not necessarily the seals that will be usedin the completed vessel are used as sealing membersduring the autofrettage process;

(d) the autofrettage pressure equals or exceeds therequirements of KT-311 as limited by KT-312.

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