Failure Analysis Case History No. 018

Several LPG product loading hoses failed due to bulging and tearing of the outer rubber layer. The hoses contained LPG (propane, butane, isobutane) at approximately 150-200 psig.

The as-received hoses all contained deflated bulges, splits and tears to the outer rubber cover. Researching the manufacture and use of rubber hoses in LPG service indicted that LPG hoses were supposed to contain pin pricks, holes, or other means of venting gases that permeated through the hose to the outer cover. As the aneurisms and tears suggested build up of pressure under the outer cover, a test procedure was devised to test good sections of the hoses for permeability. A gouge was made on the I.D. of the hoses to a depth of the outer cover. End caps were placed on the cut ends of the hoses and they were pressured up using shop air with the hose under water to facilitate observation of air bubbles. All submitted hoses bulged indicating that the hose outer covers did not contain adequate gas venting means.