Working on a project and wondering on why is it necessary for there to be "long bolted"  safety valves? For example I noticed long bolted wafer valves in a fire hazard the bolt melt off and simply leak material. In a petrochemical industry which I work for that is bad news and makes fires worse! I understand a steel sheeting wrapped around the valve is a proper way to fireproof but the actual question is why use this valve? Why not use a short bolted valve? Why not use a flangeless valve where no bolts will be exposed? What are the pros and cons to using "long bolted" valves where the bolts protrude and expose themselves for say 6'' or more? Can a different material be used to aid in this fire hazard to promote a longer time of exposure to flame impengement so fire fighters or personel can shut down the flow? You could argue that thermal expansion of unprotected threaded bar/partially threaded bolt (normal as long bolts tend to be either threaded bar + 2 nuts, or long bolts, partially threaded + 1 nut) is far greater than a shorter bolt.
Obviously thermal expansion of a component that is keeping a pressurised line "integral" can be disastrous if allows leakage due to a fire (9 times out-of 10 flammable leakage).

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