what material is suitable for Dp type pressure transmitter which is measuring flow of Ethylene ( -90 degc)? what measure should be considered to not let cell and impulse line not frozen in case of leakage around tubing and manifold? is heat tracing suitable and is not it dangerous? sharing any same experience would be appreciated.

 

There's no flow through an impulse tube, it is dead-headed.

Transfer of heat from ambient air will heat impulse tubing and the valve manifold and vaporize the cryogenic liquid. On initial installation, keep the block valves closed for a period of time to allow vaporization to occur and component temperatures to equilibrate.