Determining hose assembly pressure ratings

A word (or two) on working pressure:

Rubber industrial hose is typically marked with the working pressure rating by the manufacturer directly on the hose. This is calculated based on a burst test at the factory, without taking into account what couplings will be installed, how they will be installed, and how the hose will be used. The actual assembly rating may be much different than what is stated. For example, air hose is typically rated at 200 or 300 PSI and therefore will state this along the hose layline, but your assembly pressure may be much lower…

An assembly maximum working pressure cannot be higher than its lowest rated component.  In the above air hose example, Chicago universal couplings are factory rated at 150 PSI, when installed properly.  This rating also assumes they are used at ambient temperature without any added stress.  The hose clamp is another key factor in establishing a working pressure rating.  Ensuring that the clamp does not decrease your assembly working pressure rating is two-fold.  First, it must be compatible with the hose type, and application, with an equal or greater maximum pressure capability.  Second, it must be installed per manufacturer procedure and torque or tightness recommendation.  Make sure the clamp is installed tightly, but not gouging deep into the hose, and ensure that the coupling is inserted fully and the clamp is seated properly.

Additional factors can decrease working pressure rating including temperature and stresses such as end pull or pulsation.  A hose hung from its coupling without any bracing or support and under pressure can cause a failure even when operating within the hose assembly’s capable  pressure range.  Elevated temperature can reduce an industrial hose working pressure by more than half.  Refer to the chart and additional info here.

All of these factors can reduce the rating marked on the hose significantly.  Determine your safe operating pressure and inform all potential users of the hose assembly, and tag the assembly with its proper rating.

Also install hose safety cables or whip checks to reduce the risk of injury if an accident were to occur. Inspect hoses regularly as well, and remove them from service BEFORE they fail.