Hazardous Nature of Hydrogen FluorideAnhydrous Hydrogen Fluoride (AHF) is used as a catalyst in the reaction that combines C3 and C4 olefins and isobutane to produce alkylates, an important component of gasoline. AHF readily reacts with any available moisture to create the corrosive and toxic Hydrofluoric Acid.
For a great marksman, hitting the center of a target is not a problem. You set up a target, and he can hit it. In fact, he can hit it all day long; because this is what he does. However, all his skill and confidence won’t help him a bit if he’s presented with two targets and not told which one he is to hit. Which one should he focus on and which one should he ignore?
Such is the problem with many flange torqueing standards, especially in regard to heat exchangers. In the majority of cases, existing assembly procedures for heat exchangers call out a specific stud stress that should be targeted. That stress level may be 40%, 50%, or 60% of yield, and that same value is applied – almost without exception – to all heat exchangers in the plant, regardless of pressure ratings, the number and size of the studs, the gasket size, or a host of other factors. Success – in so far as tightening the exchanger is concerned – is defined by how much a stud is stretched. It’s an easy target to hit. But is it the right target?