Air bottle being a pressure vessel is one of the most crucial item for survey. But before the survey is carried out following procedure is carried out:-
First the work permit is filled and bottles are isolated. an authorized personnel should be present all the time while work is going on.
- Air bottle is depressurized and air bottle is drained fully to remove any oil water present in the bottom of the bottle.
- If both the bottles are surveyed simultaneously then all the mountings are removed. if not then the other bottle valves are fully shut and then the mountings are removed and then the interconected lines are blanked to allow the working of the second bottle efficiently.
- The mountings are sent to the workshop for overhauling and testing.
- Now removal of any rusted part inside the bottle is removed and bottle is throughly cleaned by dry cotton cloth is carried out. while removing the rust if any precaution to be taken that coating inside the bottle should not be damaged. the rust is mainly due to damage of epoxy coating.
- Now surveyors are informed to carry out the survey.
There are following points which a surveyor see while doing the survey:-
- The condition of coating inside the bottle which is important as the coating protect the bottle from corrosion. corrosion is mainly due to the oily water mixture formed due to carry over from compressor. this may lead to thinning of the compressor walls and hence the pressure carrying capacity of the bottle. if corrsion is found than surveyor may ask to carry ultrasonic testing of the wall thickness.
- The condition of openings to the mountings. openings should not be having any kind of wire drawing.
- Condition of drain and to check that drain is fully clear.
- Mountings are fully opened and checked for any wire drawing and leakages and pitting marks.
- Relief valve is opened and inspected and pressure tested in front of surveyor.
- The manhole door area is also checked for pitting, wire drawing and corrosion
NOTE:- AIR BOTTLES ARE COATED WITH EPOXY COATING.