PRESSURE TESTING OF PIPING

PRESSURE TESTING OF PIPING:

SCOPE:-• All installed piping, prior to initial operation shall be

pressure tested in accordance with the requirements of this specification.

• However, piping built, in conformance with the ASME Power Piping Code or Indian boiler Regulation etc. shall be pressure tested in compliance of such code or regulations.

• -Piping systems open to atmosphere, such as drains, vents outlet piping for relief valves discharging to atmosphere and underground severs shall not require any pressure testing.

• These lines shall be examined to determine that all joints are properly made up.

TEST METHODS:

• The following test methods are included in this specification:

a) Hydrostatic Testing b) Pneumatic Testing

TEST PREPARATION AND PRECAUTIONS:

• All joints, including welds, shall be left uninsulated and exposed for examination during the test.

• Major equipments, such as compressors, pumps, vessels and exchangers shall be isolated from pipe line during hydrostatic test.

• When necessary for practicability, exchangers and vessels may be included with the connected piping provided the piping test pressure is within the allowable cold pressure limits of the equipment.

• All air present in the system to be tested shall be vented while admitting the test fluid.

TEST PREPARATION AND PRECAUTIONS …..

• Piping designed for vapour and gas shall be provided with additional temporary supports, if tested hydraulically.

• Instruments, expansion joints, filters etc. for which the maximum permissible cold test pressures are lower than the specified hydrostatic test pressure shall be isolated or excluded from the test.

• Lines containing check valves have source of test pressure on the up-stream side.

TEST PREPARATION AND PRECAUTIONS ….

• Valves shall not be subjected to a test pressure in excess of manufacturer’s allowable test rating.

• When permitted, the installed valves shall be kept open.

• Relief valves shall be excluded of the test and suitably blanked off

• Orifice plates in horizontal lines shall not be installed till completion of test.

• Control valves shall not be field tested.

TEST PREPARATION AND PRECAUTIONS …

• All flanged control valves shall be removed before hydraulic testing of the pipe lines.

• Welding end control valves shall be welded after hydraulic test cleaning and blowing.

• Such field joints shall be made with root run in TIG/MIG welding and 100% radiographed in lieu of hydraulic test.

• Such joints are normally accepted by IBR inspector but in each project, formal approval of IBR Inspector may be obtained.

TEST PREPARATION AND PRECAUTIONS …

• Instrument take-off piping up to the first block valve shall be tested with piping to which it is connected.

• Testing of remainder of lead line up to instrument can also be done at the same time provided instruments are blocked off from source of pressure and vented to atmosphere.

TEST PREPARATION AND PRECAUTIONS ….

• Indicating pressure gauges mounted locally may be tested with the lines, provided the test pressure is not in excess of their scale ratings.

• The test shall be carried out at ambient temperature and the water temperature shall be limited between 5 °C and 38°C

• Flanged joints at which blinds are inserted to blank off other equipment during the test need not be tested.

• All vent valves during filling up as well as during draining must be fully open.

TEST FLUID:

• Test fluid shall normally be water.• Where the operating fluid would get adversely affected by

presence of water, hydro-carbon oil like kerosene may be substituted for water.

• Hydrocarbons shall not be permitted for oxygen service. • Hydraulic testing of ferritic material shall preferably be

carried out using suitably inhibited water, which pem1its an extended period between the start of testing and drying of components.

• Alternatively, uninhibited water may be used but the permitted period between the start of testing and drying of components is reduced.

• Hydraulic testing of austenitic material shall preferably be carried out using de-ionized water.

• Chloride content of water shall not exceed 15 ppm.

WATER QUALITY:

Ferritic parts and Ferritic parts associated with non-ferrous parts • The water shall be town’s main supply free from oil and suspended

matter. • If this water is to be inhibited, one of the inhibitors as specified below

shall be added; i) Sodium Benzoate -1.5 % W/W and Sodium Nitrite -0.1 % W/W or, ii) Sodium Fluorescein -50 ppm, Lissapol N -0.125%V/V Monoethanolamine -0.625% V/V

Austenitic parts and ferritic parts associated with Austenitic parts

• Water shall be de-ionized water having conductivity not greater than 1 micro mho/cm at 25°C.

• In case of works testing of un-erected components towns’ main water free from oil and suspended matter may be used.

WATER QUALITY .....

Period between the start of testing and drying • The period between the start of testing and

drying a component shall not be longer than 48 hours in case of inhibited water and 4 hours in case of uninhibited water.

• Where difficulty may be experienced in draining and therefore in achieving the drying specified above, drying shall be accomplished in as short a time as is practicable.

TEST PRESSURE:

• Generally, the test pressure shall be as indicated in "Schedule of pipe Test Pressure" and not less than 1.5 times the maximum working pressure.

• For piping with design temperatures above 340°C (650°F) the test pressure shall be calculated by the following formula:

• PT = (1.5 x P x ST)/S • Where, PT = Hydrostatic test pressure, Kg/cm2 • P = Maximum working pressure, Kg/cm2 • ST = Allowable stress at 340°C (650°F), Kg/cm2 • S = Allowable stress at design temp., Kg/cm2 • The maximum working pressure is the pressure representing

the most severe condition of coincident pressure and temperature expected in normal operation considering fluid head, set pressure of safety valves in the line and pump shut off head.

TEST PRESSURE …..

• Tested and properly calibrated pressure gauges shall be used and appropriate corrections shall be made during the hydrostatic test for any static heads in any component of the piping under test.

• The range of the pressure gauge shall not be more than 1.7 times the test pressure and the error of the pressure gauge shall not be more than 1 % of the range.

• If the pipe lines are to be tested along with the equipment the test pressure shall not exceed the equipment test pressure.

• However it shall be checked that stress due to testing does not exceed 90% of yield stress.

Lines at Atmospheric Pressure

(a) All gas lines at atmospheric pressure (<= 1 Kg/cm2) shall be tested pneumatically at 0.5 kg/cm2 .

(b) All liquid lines at atmospheric pressure (<= 1 kg/cm2) shall be tested hydrostatically at 2 Kg/cm2.

GENERAL GUIDE LINES:

Vacuum Services • Lines in vacuum services shall be tested at a minimum internal

pressure of 1.5 Kg/cm2 unless limited to a lower value by design.

• Where it is not possible to test hydrostatically, the pipe lines shall be tested pneumatically at 1 kg/cm2 .

Jacketed Piping and Piping under External Pressure • In jacketed lines, the jacket shall be tested on the basis of jacket

pressure. • The internal pipe shall be tested on the basis of the internal or

external pressure, whichever is critical. • Lines in external pressure service shall be subjected to an

internal pressure test at not less than the external design pressure.

GENERAL GUIDE LINES ….

Hammer Testing

• While under the hydrostatic pressure, all welded joints shall be struck with 1 kg hammer on both sides of and within 100 mm of joint for detection of weakness, cracks or leaks, avoiding regular, rhythmic hammering. Hammer shall have rounded edges.

PNEUMATIC TESTING:

• Piping may be tested pneumatically if these cannot be safely filled with water, or where traces of water cannot be tolerated, or if these have been previously tested hydrostatically.

PNEUMATIC TEST PRESSURE:

• The test pressure for piping shall be 110 % of maximum working pressure.

• Any pneumatic test shall include a preliminary check at not more than 2 Kg/cm2 for detection of any major leaks.

• The pressure subsequently shall be increased gradually in steps to the specified test pressure, providing sufficient time to allow the piping to equalize the strains during the test and to check for leakage.

• After reaching maximum test pressure, pressure shall be reduced to design pressure and kept for sufficient time to inspect the piping.

• Hammering is strictly prohibited.

TEST PROCEDURE:

RETEST

• Any leaks shall be repaired and the system retested to the extent required by the provisions of this Standard.

DURATION OF TEST • Test pressure shall be maintained for half

an hour or the time taken for inspection which ever is more.

RADIOGRAPHY:

• Radiography inspection of welding may be used in lieu of hydrostatic or pneumatic pressure testing at the discretion of Purchaser's Engineer for field welded joints, which join together piping components previously pressure tested.

• Such radiographic examination and interpretation of the resulting radiographs shall be in accordance with Section VIII of ASME Boiler and Pressure Vessel code.

TEST RECORDS:

• Records shall be made of each piping installation during the testing. These records shall include:

• a) Date of Test. • b) Identification of the piping tested. • c) Test Method. • d) Test Pressure and duration. • e) Approval by the Inspector.