Basic Important points for Hydro-Test engineer
Basic And Important points for Hydro-Test engineer
I.
Making a detail testing
plans, Method Statements and procedures with industry standards, project
specifications, and safety regulations.
1 REFERENCE DOCUMENTS:
Ø Contract
Document
Ø Standard
specification for inspection, flushing and testing of piping systems.
2. EQUIPMENTS / MATERIALS
Ø Pressurizing
pump set of suitable capacity.
Ø Air
compressor.
Ø Calibrated
pressure gauges.
Ø Water/air
hoses pipe.
Ø Temporary
gaskets.
Ø Metallic end
blinds.
Ø Bolts &
nuts.
Ø Filling
Pumps.
Ø Other
miscellaneous items.
3. PREPARATION FOR TEST
Ø Piping
systems to be tested shall be divided into sections. The sections shall be
identified based on loop marked P&IDs, ISO Drawings, GADs, line schedule
& Test pressure.
Ø A test pack shall be prepared for each section
containing isometrics/line sketch of each line, P&ID, line history sheet,
mechanical clearance records by piping engineer.
Ø When section is mechanically ready the piping
engineer shall conduct a joint punch listing of the section to ensure to
complete all Hot work.
Ø After Mechanical clearance QC team shall
declare NDT clearance for the lines in the section. All NDT reports shall be completed
before start the pressure test.
4. PRE-HYDROTEST REQUIREMENTS
A. INSPECTION
Ø During various stages and after completion of
fabrication and erection, the piping system shall be inspected by the Engineer.
Ø Proper piping material has been used.
Ø PMI has been performed as per client
specification.
Ø Piping has been erected as per drawings and
instructions of Clients.
Ø All supports have been installed correctly.
Ø Test preparations mentioned in this
specification have been carried out.
B. FLUSHING
Ø Flushing of all lines shall be done before
pressure testing.
Ø Flushing shall be done by 'fresh potable
water' or by 'dry compressed air to clean the pipe of all dirt, debris or loose
foreign material.
Ø Required pressure for water flushing shall
meet the fire hydrant pressure or utility water pressure.
Ø For air flushing, the line/system shall be
pressurized by compressed air at the required pressure which shall be 3.5
kg/cm2g maximum. The pressure shall then be released by quick opening of a
valve, already in line or installed temporarily for this purpose.
Ø This
procedure shall be repeated as many times as required till the inside of the
pipe is fully cleaned.
Ø In line instruments like control valves,
orifice plates, rotameters, safety valves & column, vessel, exchanger etc. shall
not be included in flushing circuit.
Ø The screens/meshes shall be removed from all permanent strainers before flushing. Screens/meshes shall be reinstalled after flushing but before testing.
C. EXTENT OF TESTING
Ø All joints including welds shall be left
uninsulated for examination during the test; full painting of the welds is
unacceptable prior to hydro test.
Ø Check valves shall be removed and stored
securely and reinstalled after all works are completed.
Ø In a system all valves must be in the open
position, and for isolation spades or blinds shall be used downstream of any
valves.
Ø Rotating equipment shall not be included in Hydro test.
D. GENERAL REQUIREMENTS
Ø All vents
and other connections used as vents shall be left open while filling the line
with water for complete removal of air.
Ø All piping
systems to be hydrostatically tested shall be vented at the high points location (HPV).
Ø Wherever in
the line extra gap any reasons, like absence of control valves, safety valves,
check valves etc. Replace the valve by a temporary
spool and reinstall the valve after testing.
Ø All joints welded, screwed or flanged shall be
left exposed for examination during the test.
Ø Before pressurizing the lines, each weld joint
shall be cleaned by wire brush to free it from rust and any other foreign
matter.
Ø At these flanges, temporary gaskets shall be provided during testing and shall be replaced by permanent gaskets subsequently.
5. Testing Media, Test Pressure and Test Pressure Gauges
A. Testing Media
Ø All pressure tests shall be hydrostatic using
iron free water, which is clean and free of mud.
Ø Maximum chloride content in water for
hydrostatic testing for SS piping shall be 15-20 ppm.
Ø Air shall be used for testing only if water would cause corrosion of the system or overloading of supports etc. in special cases such as flare & vapor lines or as directed by client.
B . Test Pressure:
Ø The hydrostatic/ pneumatic test pressure shall
be as indicated in the line list/ isometric drawing or as per the instruction
of client.
Ø Section of HT depends on Loop file.
3. Test Pressure Gauges:
Ø All gauges used for field testing shall have
suitable range so that the test pressure of various systems falls in 35% to 65%
of gauge scale range.
Ø Pressure gage dial shall be minimum of 150 mm.
Ø Gauge shall be of a good quality and in first
class working condition.
Ø All test gauges shall be calibrated using a
standard dead weight gauge tester.
Ø Calibration certificate shall be well-appointed for the pressure gages
6. Testing Procedure
A. Hydrostatic Test
Ø All vents shall
be left open while filling the line with fluid for complete removal of air.
Ø In all lines for pressurizing and
depressurizing the system, temporary isolation valves shall be provided if vents,
drains do not exist in the system (HPD, LPD).
Ø Pressure shall be applied only after the
system / line is ready and approved by the Engineer.
Ø Pressure shall be applied by suitable test
pump.
Ø A pressure gauge shall be provided at the pump
discharge Section
Ø The pump shall be attended constantly during the
test by an authorized person.
Ø Test pressure shall be maintained for a
sufficient length of time 30minutes or pipeline 4 hours.
Ø Test pressure shall be released only after physical
checking of all the joints.
Ø Any joint found leaking during a pressure test
shall be retested to the specified pressure after repair.
Ø Care shall be taken to avoid increase in the pressure due to temperature variation during the test.
B. Pneumatic Test
Ø When testing with air, pressure shall be
supplied by means of a compressor.
Ø Piping to be tested by air shall have joints
covered with a soap and water solution so that the joints can be examined for
leaks.
Ø All other details shall be same as per hydro testing procedure.
7. COMPLETION OF TESTING
Ø After the hydrostatic test has been completed,
pressure shall be released by opening the vents.
Ø All vents shall be opened before the system is
to be drained and shall remain open till all draining is complete, so as to
prevent formation of vacuum in the system.
Ø After draining, lines / systems shall be dried
by air.
Ø After testing is completed the test blinds
shall be removed.
Ø Equipment / piping isolated during testing
shall be connected using the specified gaskets, bolts and nuts.
Ø Pressure test shall be considered complete
only after approved by the Clients.
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