Hoses testing procedures

The use of steam at 100°C or above would provide an accelerating effect, although this would probably be considered too severe for most applications. Such a test would, however, be relevant for a product such as hose intended for use with steam and the particular test procedure would be found in the product specification. In designing any tests for exposure to steam it is necessary to control the amount of air (if any) present since oxygen at the temperatures used would have a strong deteriorating action. 

Any hose used to transfer a liquid, including refrigerants, that has an agency-reportable quantity listed for a spill. It does not include normal utility hoses such as steam, water, nitrogen, and air. It does not include hoses that are supplied by a contract carrier. It does not include hydraulic hoses or other such hoses that are permanently mounted as a part of equipment that has its own inspection schedule. Fire hoses are not included, but do have testing procedures for that particular service. NOTE that good judgment should be exercised with the use of all hoses, and any obvious defects should be addressed. 

After the explosion, investigators confiimed that the 8-inch DEMCO block valve was open at the lime of the accident. Furthermore, tests showed that the compressed air hoses were improperly connected in a reversed position. This unauthorized step during maintenance activity allowed the DEMCO isolation valve to open when the actuator switch was in the closed position. [7] Over time, somehow, the company s maintenance procedures had been modified and this tragedy resulted. 

Weep Test - This is a test to determine the integrity of a high pressure hose. In this procedure (MIL-S-3136, type III and MIL-H-25579) unbraided samples of the tube are pressurized by filling with a specified fuel (70% i-octane + 30% toluene) to a calculated initial pressure. Pressure is incrementally (0.035 MPa) increased until seepage occurs. This pressure is recorded as weep pressure. 

Pressure hoses are tested by the procedure of DIN 14 811 Teil 4-1976. Depending on the type, a 400 or 500 mm long section of the hose is filled with water at 5 bar and 8 to 12 °C and then placed in a test chamber of 260 mm x 260 mm base area and 500 mm in length. A propane flame is applied for 10 s. The hose complies with the requirements if four of five specimens have not blown out and afterflame and afterglow time is less than 3 s. 

Lower the sampling hose approximately 6 inches through the hold in the manhole cover to make the first pre-entry test. If no combustible gas is found, remove the cover and proceed. If the flammable gas concentration is above 60 percent LEL (lower explosive limit), suspend operations and follow company procedures. 

Note Self-test fit testing can be conducted for both positive and negative pressure checks on SCBA respirators by crimping the hoses with one s fingers and blocking airways with the palms of one s hands. If either test shows leakage, the following procedure should be followed ... 

As one illustration of quality control lapses causing failure, nitrile/PVC hoses analysed by the author failed from ozone cracking. Although suitably formulated, there had been a processing error and because the quality assurance (QA) testing for ozone resistance had not been carried out this went undetected. For this case, there was in theory a control procedure which is one stage better than no provisions for control, although the result was the same. 

Chip seal Loose chips from a freshly paved road are the major safety concern for chip seal operation, and several attempts were reported in the literature to develop a laboratory procedure to simulate the field experience. A modified fretting test (also know as the abrasion cohesion test Esso, ACTE) appears to be the most success-fid [26, 27]. In this test a known amount of CRS-2 asphalt emulsion and aggregates are spread on a roofing felt, and then rolled with a 301 rabber roller. The sample is subjected to the shearing action of a horizontal steam-hose, which is attached to a Hobart sun and planet mixer, and the percentage of retained chips is recorded as a function of curing time. 

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