The piping system will be pressure tested to prove the pressure integrity of the main components (pipe, valves, flanges, gaskets) of the system. The test shall be performed in accordance with Standard Construction specification, supplemented by the Contractor’s standard hydrostatic test procedure
approved by RPL. For test purposes, the piping system has been divided into a series in Document “Line Designation Table”.
All the piping systems will be hydrostatically tested except specific system where hydraulic fluids are not allowed due to operation reasons. Those systems will be subject to pneumatic testing.
A pressure test report will be completed for each test loop for record purposes using Reliance Standard Form. All untested joints shall be clearly shown on the hydrotest diagrams.
SAFETY NOTE: Hydrostatic testing is carried out to prove the pressure
integrity of the piping system under test. Accidents, sometimes fatal, have been recorded during such testing. Manning levels in areas where hydrostatic testing is to be performed should be kept to a minimum. All personnel engaged in the test should be fully briefed and all precautions taken in respect of personnel safety. Danger signs and notices should be erected at all strategic locations. Piping routed outside of the main plant boundary should be cordoned off and manned to prevent accidental access by unauthorised or third party personnel. All safety equipment shall be on site for the duration of testing. All personnel directly or indirectly engaged during the test shall be equipped with personnel protective and safety equipment.
Important Checks and Guidelines
a. On line instruments and instrument impulse lines will be temporarily removed and / or disconnected before testing.
b. Check that hydrotest pump, valve, fittings, pressure gauge are in good working order. Filling line/ test equipment shall be connected at lowest possible point to avoid entrapment of air in the system while filling.
c. Check that all test gauges are available with relevant latest test certificates, with direct reading gauge and suitable range so that test pressure readable in 40-60% range. The test gauge shall be mounted at lowest point to account liquid head of system.
d. Check that all in-line valves are in fully open position.
e. Check that all safety equipment like cordoning rope, sign board, etc. are available at testing site and placed at strategic location.
f. Check that check valves are removed from the line or its internal removed, if required.
g. All welds shall be free of slag, grease, oil, paint and any other foreign materials, which prevent proper examination.
h. Vents to be provided on test fittings if it is not provided on the line i. Blinds used shall be in accordance with Pipe Line Class
j. There are sufficient numbers of vents/ drains located in suitable position. While filling the piping, ensure that all air is vented at highest point and system is full of test fluid.
k. Vessel and water temperature should be always above 15 0C to eliminate the possibility of cold fracturing of the metal.
l. Hydrotest pressure should be as per LDT (line designation table) or as per piping class & should not be higher than lowest rated component of system. ANSI B 31.3 must be followed while testing piping system.
m. The weld joints, flange connections and the sections of greatest strain (the areas close to opening and those where two different types of materials are
connected) must be checked visually. The test is acceptable if no loses, sweating or fall of pressure are detected for the time of test.
n. Test pressure will be held for sufficient time to visually determine if there are any leaks, but not less than 2 hours.
o. Drain out the water from the section after the hydrotest is completed.
Note:
Ensure that under no circumstances the pressure applied does not exceed the allowable test pressure of the lowest rated component in the loop.
Keep the vents open to prevent from pulling a vacuum and possibly collapsing equipment, while draining the system after hydrotest.
Ensure that, chloride content of the treated water used for hydrotest of the section that contains austenitic steel is below 50-ppm wt%. If this is not possible then the test water should have a max. of 0.5 wt% sodium nitrate / specific chemical added to it. Such system should be drained and dried after hydrotest as soon as possible.
4.3.1.3 Flushing
The piping system will be flushed in order to remove construction debris, accumulated corrosion products and scale to prevent blockages and damage to equipment during actual start-up
Prior to commencing the flushing operation, the contractor will divide the piping system into a series of flushing loops. Configuration of flushing loop mostly remains as hydrotest loop. The loops will be presented in diagrammatic form, as a markup to the plant P & Ids using local site knowledge and the guidelines
presented below, as the basis for determining the extent and the number of flushing loops needed. Use this opportunities to break in and run in as many pumps as possible (High head pumps should not be run on water). Water flushing helps in spotting the problems and correcting the problems before the start-up. The progress of the flushing operation will be recorded by marking up the flushing loop diagrams.
Important Checks and Guidelines
a. Install blinds the flanges of the equipment, which will not be operated on water. b. Install fine mesh screens on the pump suction lines.
c. Bypass the filters and traps in line, as per requirement.
d. Identify and ensure suitable water hose connection points and draining points for injection and draining of water.
e. In case of exchangers, flush the inlet line upto the exchanger inlet flanges and then connect the inlet flanges, and flush the exchangers.
f. Restriction orifices must be removed prior to flushing.
g. Control Valves and in line instrumentation must be removed prior to flushing h. Instrument impulse lines and sampling systems will be disconnected prior to
flushing. During flushing, each process valve on instrument process connections should be opened to flush the connection and be checked for tightness after closure.
i. Check valves should be removed, or installed in reverse (subject to selected direction of flow for flushing) and all other valves fully opened.
j. Flow rates should be maintained in the range 3 to 4 m/s for water flushing, 30 to 40 m/s for air blowing.
k. The flushing water is fully drained (properly) and system dried with air immediately after completion of flushing, water containing upto 20 mg/kg chlorides may be used for flushing of austenitic stainless steel piping systems or sub-systems. In cases where proper drainage is not possible, and the metal temperature in operation exceeds 50 0C, general recommended practice is to use water containing less than 1 mg/kg chloride; i.e. condensate or demineralised water for austenitic SS piping.
l. Isolate vessels and equipment from the flushing loop to prevent damage/ accumulation of debris within these items.
m. Flush through open end lines. Do not restrict flow in principle. n. Flush through all drains and vents.
o. Where possible, flush downward or horizontally
p. Flush the main header from source-to-end, each lateral header from the main- to-end, and each branch line from the lateral header to end.
q. Always flush through bypasses, where provided, to an open end before flushing through equipment.
r. On completion of flushing, reinstate all removed equipment items (control valves and in-line instrumentation), install orifice plates and reconnect instrument lines to process valve connections.
s. On completion of flushing, standard RPL form, duly signed by the RPL / Bechtel/ UOP / Contractor representative will be prepared and placed on file for record purposes