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DBB-ball Valve
Oct 30, 2018
1. Design of Double block & bleed (DBB Structure)

(1),Function   of double block & bleed

Ball seat   seal structure for the trunnion ball valve. The two seats of valve can block   the medium both import & export ends to achieve double block function ,   the mid-cavity and two end channels can be blocked though vavle closed &   both pressed on import & export ends, the remaining medium can be   discharged by bleeding valve
(2)   ,Automatic pressure relief of vave mid-cavity.

the   remaining liquid medium in valve gasifying dueto temperature increased and   caused abnormally high pressure, the medium in cavity can be released by   pushing the seat of the acting force itself to ensure the safety.

2.Design of   double isolation and discharge (Dl8 Structure)

(1),Double   isolation & two-way sealing function

The   trunnion ball valve supplies two-way sealing seat structure design. the two   seats can block the medium both import & export end independently,   meanwhile,block the pressure from cavity to achieve double isolation, the   medium of import & export end & cavity
are   isolated when valve closed; the seat of export end can seal when import end   of valve is leaking, and this makes the valve a double sealing function.
(2)Manual   & automatic discharge of valve cavity

The   remaining medium in cavity can be manual discharged by the bleeding valve on   the body; and the remaining medium in cavity which are gasifying due to high   temperature and caused abnormally high pressure which beyond the set value   can be automatic discharged by the safety valve on the body and to ensure the   safety of valve & pipeline.

3.Fire   protection design

Ball valve   sets two seals to the valve sealing position which are 0-ring & Metal   graphite spiral wound gasket, the Metal graphite

spiral   wound gasket can supply a assistant sealing when the seat seal, gasket,   O-ring are damaged when there's fire; the metal seat will make a metal   sealing automatically with ball under the force from spring when the seal   ring of seat is damaged, and control the internal& external leakage. The   fire prevention satisfy APl607, API6FA.BS6755 & JB/T6899 standard, and   achieve API 607 fire tesing.

4.Stem blow   out proof design

Stem uses   blow out proof design. the stem is with small top end & large bottom end,   this stem is positioned by gland & nut bolt,

this can   ensure the stem not blow out by medium though thers is abnormal pressure.

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