Leak prevention in an HF alkylation unit

The high volatility and toxicity of HF mean that very special precautions have to be taken to ensure that circuits are completely tight at flanges and valves. The essential nature of the measures taken in the acid section of the unit can be listed as follows  

Tightening of boltwork using a torque wrench is the rule. 

The condition of joint surfaces is of smooth finish quahty. 

All valves subject to inspection are tested with gas oil (testing of the body, tests upstream and downstream of the opening) in circuits containing acid, internals are of solid Alloy 400, bearing surfaces of PTFE, gland packing of graphite, threaded rods of B7M. 

An HF-sensitive paint (colour change) is applied to all flanges and stuffing boxes. 

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