RN Crimp Ferrules are chosen based on the length of the coupling barb and the actual hose outside diameter. Ferrule must fit snug over the cover of the hose prior to crimping.
As a general rule, ferrule should be about 1/4″ shorter than the barb – if the ferrule is longer than the barb it will start to compromise the structure if the hose is bent near the coupling, and if the ferrule is too short then the barb will dig into the tube and lead to premature failure – therefore it is important to choose the proper length.
SPECIAL NOTE: As with hose and couplings, crimp ferrules are subject to maximum pressures, temperatures, and mechanical forces like end-pull. As a rule, the higher the temperature, the lower the maximum pressure rating for crimp ferrules. Normal operating conditions are -40F to 70/F, above that the crimp ferrule integrity will diminish.
Temperature is affected by both – the media and the environment. Critical application hoses must always be tested or certified prior to field use.