Environmental and

Mechanical Testing Chamber.

Flexible hoses are used in a wide variety of environments. Engine air intake and cooling water hoses in particular are subject to extremes of temperature and vibration. A hose manufacture required a test rig in which samples of hoses could be subjected to continuous temperatures cycles, ranging from -50°C to 250°C. At the same time the hoses were to be pulse pressurised at up to 5 bar, with both hot and ambient air, and continuously flexed at up to 15 Hz. The hoses are mounted inside an environmental test chamber which can accommodate two to four hoses.
A temperature cycle typically consists of several ramps between the defined temperatures with dwells at each temperature; the duration is generally several hours. The cycle is repeated continuously throughout the duration of the test.
The pressure is applied to the hoses in short pulses of a few seconds duration.
A system has been developed in which all these cycles can be flexibly programmed to run asynchronously for continuous periods of up to several weeks in duration. Test sequences can be scheduled to cover all combinations of temperature, pressure and mechanical cycling. As well as controlling the operation of the oven, the variable speed motor, and the pressure cycles, the computer system monitors that the required test temperatures are being achieved inside the hoses and that the required test pressure is being achieved. A full test log is maintained and regular test progress reports are generated. Algorithms are incorporated to detect failure of the hose; if this should occur then the system is automatically shut down and the failure condition noted.
One end of the hoses is fixed and the other is connected to a motor driven crankshaft via a connecting rod which passes through seals in the floor of the environmental chamber.