TYPICAL MEDICAL GAS CYLINDRES, VOLUMES, WEIGHT cylinder size dimension weight (ib) Air CO2 oxygen Nitrous oxide B 3 1/2 x 13 5 370 200 D 4 1/2 x 17 11 375 940 400 940 E 41/4 x 26 14 625 1590 660 1590 M 7 x 43 63 2850 7570 3450 7570 G 8 1/2 x 51 97 5050 12300 13800
Strips are cut longitudinally from the cylinder and stretched until they elongated The yield point should not be less than15 tons per square inch
One cylinder is kept between two compression blocks and then oressure is applied to flatten it til distance of becomes six times the thickness of walls.
Three longitudinal and three transverse strips from a finished cylinder are taken and struck by a mechanical hammer .The mean energy needed to produce a crack should not be less than 5 feet lb for tranverse strip and 10 ft lb for longitudinal strip
A ring of 25 mm width is cut from that cylinder and equally divided into four strips.each strip is than bent inward until the inner edge are apart not greater than the diameter of the strip. The approved cylinder should not develop any crack
Hydraulic test or pressure test
The test is usually done by the water jacket method. here the proof pressure applied inside is 236.2kgf/cm this test also determines wether it is leak proof or not
Before any fitting is applied to cylinder valve , the valve should be opened slowly and briefly to remove dust or any other particle ( cracking)
A sealing washer or gasket in good condition should always be used with small cylinder valve . If more than one seal is used the pin on yoke may not extrude far enough to engage mating whole or safety pin index
A cylinder valve should be opened slowly ,because if gases passes quickly into the space between valve and the yoke or the regulator , the rapid recompression in this space will generate large amount of heat .because there is no space for dissipation of heat , this constitutes an adiabatic process. Particle of dust, grease, etc present in that space may be ignited by the heat causing a flash fire or explosion.
Definition : It is defined by NFPA as , regardless its sources, has no detectable liquid hydrocarbon, less than 25 ppm gaseous hydrocarbon , less than 5mg/m3 of particulates of 1 micron size or greater at normal atmospheric pressure and a dew point of less than 4° c
After the pipelines have been installed , but before the installation of terminal units, the line must be blown clear using oil free dry nitrogen
Initial pressure test
Each section of piping system must be subjected to 1.5 times of working pressure ( minimum1034 kpa) with oil free nitrogen with source valve closed. It is maintained and each join has been checked for leakage