When a cross fitting is constructed with a three piece system comprising of a main body, nut and ferrule, wherein the ferrule acts as a spring, it is called a flareless bite type cross fitting. The function of this cross is again holding four pipes sections together whereas the captive ferrule in this cross fitting bites the outer surface of the tubing with sufficient strength to hold the tube against pressure.

This system works by forcing the ferrule cutting edge into the tubing wall to create a seal. The resulting spring-action joint offers a leak proof seal and resistance to vibration. Flareless fittings do not require a flaring operation and are used on medium to heavy walled tubing.

Like all metal-to-metal tube fitting systems, the flareless cross is limited in the number of disassemblies and reassemblies the tubing can withstand as the ferrule bites deeper and deeper into the tubing wall with each reassembly. Hence, the intermixing of components from different manufacturers is discouraged.

Standard material for the fitting body is Type 316 stainless steel for the body and nut, and Carpenter Custom 630 (17Cr - 4Ni) stainless steel for the ferrule. The ferrule can be slightly discolored because it is treated to give extra hardness for biting. One must take care that the ferrule must be harder than the tubing to form the bite that seals the assembly.

A look at commonly used flareless Cross fittings:

Union cross elbows are amongst the most important type of elbow fittings and find their utility in sectors such as oil, gas, power, petrochem, pharmaceutical etc.