LUG IS BETTER THAN DOUBLE FLANGE END CONNECTION
Lugged end connections are better than flange connections in Triple offset butterfly valve in critical application due to the following reasons:-
- In critical application like LPG gas where medium is susceptible to react to atmospheric air a valve with compact design is required which prevents medium from any leakage ,due to this requirement lugged is more preferred than double flange. As per seen in below diagram one long stud is inserted from one end of pipe flange which passes through hole of valve body end connection and then passes through other flange end of pipe and are tightened through bolts atboth the ends which tightens the grip of valve with pipe flange and prevents it from loosening in comparison to double flange design where flanges at both the end of valve, mate with pipe flanges at both ends with small nuts and bolts tightening separately , but as per API 609 CAT.B Face to face of Double Flange is more than lugged design which result in more weight in valve and more pressure on nuts and bolts in hanging and containing the weight of valve due to which after some time due to wear and tear and expansion and contraction due to medium and atmospheric conditions nuts start getting loosen up hence start leakage insides of valve and this leakage of medium could be catastrophic if it is critical and susceptible to oxygen due to this double flange is more favorable in bigger sizes and water application.
- Big advantage of lug in comparison to double flange is after commissioning and execution during maintenance of valve and pipe, pipe can be easily opened from one side without removing the valve and valve will remain attached with the other end of pipe flange and there is no need to remove the valve and realigning it.
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