Friday 27th October 2023:Bi-Weekly Internal Tool Box Talk
Prepared by: Anton Chulannikov
Pre-Commissioning/Commissioning: Piping MOP &
GALT Pressure Tests
MOP/GALT Approach/Methodology
Agenda:
 MOP/GALT General Information
 MOP/GALT prerequisites: PCC & Construction
 Sequencing
 MOP/GALT precautions prior to start
 MOP/GALT performing
 Potential/typical piping problems which can fail MOP/GALT. Potential Leak
points.
 Possible consequences after of non-proper Leak tests.
 Hazards examples during MOP/GALT.
 Area for Improvement. Recommendations.
MOP/GALT General Information
 What does it mean, MOP/GALT? MOP: Maximum Operating Pressure Test. GALT:
Gross Air Leak Test. Pressurization and leak testing.
 MOP: MOP Leak Test is performed to check system/subsystem connections
(flanges, instruments, tubing, screws, valves, plugs, etc…) tightness against leaks.
Pressure value: 90% from PRV’s Set Pressure or Design pressure. Test Medium is N2
(for the equipment inside buildings is Air).
 GALT: tightness test activity it’s a way to ensure that any previous activity which
required the temporary removal of equipment and/or disconnecting flanges,
the following reinstatements have been carried out correctly and according to
the project specification. Tightness test activity precedes the Commissioning
activities, where hazardous process gas or liquids will be introduced into the
systems, therefore it’s a guarantee of avoiding any uncontrolled release to
atmosphere or any human risk. Pressure value: 7 bar, or 90% from Design
pressure. Test Medium is Air.
MOP/GALT prerequisites: PCC & Construction
 Construction test packs tested and reinstated; respective QCFs are signed
off; Punches category “A” are closed:
 RO (restriction orifices) and FE (flow elements) inspected by PCC
 Strainers inspected by PCC
 Tubing tested
 Temporary (additional) welded caps/flanges for MOP RT/FM performed
 Golden joints identified
 Equipment box-up done
 Valves stroke tested (preferably)
 Flanges/valves/instruments insulation not done
 PCC Test pack with all supported docs is approved/signed off
Sequencing
 As a general rule MOP/GALT shall follow the following:
 MOP/GALT can be combined if they are at the same pressure
 2 MOP can’t be performed together if they aren’t same pressure
and even if they are adjacent
MOP/GALT precautions prior to start
 Maximum Operating Pressure Leak Tests & Gross Air Leak Tests are activity that create
potential hazards as they involve high pressure, large testing volume, specific equipment and
material (such as cryogenic pumps, cryogenic storage, Liquid nitrogen, Air under high
pressure). Consequently, these activities must be carefully prepared and risks assessed.
 Be in a possession of a valid PTW, notification.
 Ensure all barriers and warning signs are in place. Restricted area (in all directions) for any
non-related activities is to be set according to the criteria (across the entire length of piping
under pressure): Piping up to 6 inches in diameter: 3 meters. Piping above 8 inches in
diameter: 5 meters if pressure 10 bar or below. Area must be increased by an additional 1.5
meters (in all directions) for every10 bar increase above the initial 10 bar pressure.
 Ensure risk assessment mitigations are in place.
 Ensure all check list have been signed off and confirm Test Pack is protected for overpressurization.
 Ensure Lined-up is done properly. System under test is properly isolated.
 Ensure Pressure Recorder is properly installed, and the disk range is accurate for the test
pressure.
 Tool box talk is performed.
 Specific equipment (Cryogenic pumps and tanks or Nitrogen generator, Air compressors and
dryers, Diesel generators, hoses, manifolds, PRVs and fittings etc) are tested and ready for use.
MOP/GALT performing
Pressurizing
 First to pressurize only Pressurization unit with hoses and fittings to prove the
integrity (value: MOP or GALT pressure)
 Start pressurization of subsystem. Steps: 7 bar; 25%; 50%; 75%; 100% (MOP
pressure value). 10 min for stabilization at each step. At 50% First leak
detection. At 100% Final leak detection.
 Acceptance criteria: fall in pressure is equal or less than 0.05 bar/h; no
visible leaks identified following the flange to flange check; Hold-up test
duration is 4 hours (1 hour for GALT).
 Depressurize system safely after Hold up test finished or immediately if leaks
detected (for rectification).
 If no leaks detected & Hold up is successful: Mop/GALT accepted.
 If leaks detected: repair after depressurization, then Test again.
Potential/typical piping problems which can fail
MOP/GALT. Potential Leak points.
Possible consequences after of non-proper Leak tests.
Hazards examples during MOP/GALT.
 Gas under pressure contains approx. 200 times more energy than the
equivalent volume of water under pressure.
 The release of that energy in an “uncontrolled” manner can be
instantaneous and extremely destructive.
 Nitrogen can KILL if not handled correctly. Gaseous nitrogen can be
hazardous where it occurs in high concentrations, most commonly in
confined spaces.
 Over-pressurization of equipment can occur if precautions not observed.
 Sections of pipe-work may be left with trapped gas in “Dead-legs” after
system has been de-pressured.
 Hoses under pressure and not adequately secured can be a major hazard
to equipment and personnel if they fail.
Area for Improvement.
Recommendations.
 All personnel be made aware of hazards associated with
this activity.
 Clear communication of planned activities prior to
starting each shift.
 Experienced sub-contractor, experienced crew.
 Close supervision and monitoring of concurrent
activities.
 First pressure-ups done on nights with minimal personnel
on site.
Last but not Least!
Any Questions?