On shipyard normally have 2 time pressure test. Like on ABS Steel Vessel Rule 4.6.2 / 7.3 Hydrostatic Test.
1. On shop pressure test, this test doing after workshop fabrication complete and accepted by owner. On this test to check welding quality, any leaking or not on shop weld position. This is refer to ABS Rule 7.3.1 "Hydrostatic Test of Pipes Before Installation Onboard"
2. On site pressure tested, this teste doing after on site pipe erection complete and accepted by class and owner. On this test to check flange spool joint and field weld position. This refer to ABS rule 7.3.3 "Test After Installation"
On pressure test there is some rule must be followed :
- Pressure tust must 1.5 working pressure.
- Pressure gauge must have active calibration certivicate.
- Pipe line must accepted for final pipe line inspection by owner and class.
- Pressure test must aware with safety oriented, like using HP square ball valve etc.
On Shipyard industry, normally have 2 methode pressure test.
- Hydrotest thats mean pressure test using water pressure
- Pneumatic test pressure thats mean pressure test using air pressure.
For item no 2 or pneumatic test, following ABS Steel rule 2012 no 4.6.2 / 7.3.4 "Pneumatic Test in Lieu of Hydrostatic Test" on this rule mention that's In general, Pneumatic test in lieu of hydrostatic test are not permitted. Only on special case, where it is impracticable to carry out the required hydrostatic tests, pneumatic tests may be considered. In such cases, the procedure for carrying out pneumatic test, having regard to safety of personnel, is to be submitted to the surveyor review.
Why pneumatic not permitted for pressure test, may be this is about safety reason. On pneumatic test we use compress air, the nature of the air is easy to expands. this is dangerous if we doing on open area, the weather will give dirrect effect to air, if we start test on morning and then we keep pressure untill noon, the air pressure will increase fastly and some time air pressure will be over presure requirement and will be explosion.
Other reason is, pneumatic difficult to check leaking position. This is not like on hydrotest, on hydrotest at least we will found seepage water on pipe joint when pipe leaking but on pneumatic test for small leaking difficult to identify althought we use shoap water to spry around pipe joint but this one not evective action.
Last reason, to avoid cheating trick, If we compare between pneumatic test and hydrotest, hydrotest is more difficult to cheat, because if any little leaking will show or identify with water drops, and for that case very easy to looking for. I f we use pneumatic test, we need good water foam to make air bubbles for leaking identification. And sometime, we can not see this air bubbles.
Why pneumatic not permitted for pressure test, may be this is about safety reason. On pneumatic test we use compress air, the nature of the air is easy to expands. this is dangerous if we doing on open area, the weather will give dirrect effect to air, if we start test on morning and then we keep pressure untill noon, the air pressure will increase fastly and some time air pressure will be over presure requirement and will be explosion.
Other reason is, pneumatic difficult to check leaking position. This is not like on hydrotest, on hydrotest at least we will found seepage water on pipe joint when pipe leaking but on pneumatic test for small leaking difficult to identify althought we use shoap water to spry around pipe joint but this one not evective action.
Last reason, to avoid cheating trick, If we compare between pneumatic test and hydrotest, hydrotest is more difficult to cheat, because if any little leaking will show or identify with water drops, and for that case very easy to looking for. I f we use pneumatic test, we need good water foam to make air bubbles for leaking identification. And sometime, we can not see this air bubbles.
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