the situation described by you indicated following
1. There is leakage of joint (through gasket) suggests that the bolts
are not able to exert necessary force Wm1 ( of appendix 2)
Wm1 is in the operating condition scenario in which bolt shall
resist the hydrostatic end force H and additional force Hp to maintain
the joint (gasket) contact surface under required compression to avoid
leak.
Wm1 = H + Hp
= 0.785 G2 P + (2b x 3.14 G m P)
This force Hp is specified as multiple m of internal pressure and
gasket contact width.
2. Look at the flange design calculation and you should find the
operating condition govering.
here check if correct value of m is used. There is a possibility
of using lesser value of m which has resulted into smaller force Hp
hence resulting the leak.
3. If the calculations (and the m factor of gasket ) are ok then there
is possibilty of actulal value of gasket m factor being different than
those used in calculation ( the actual value will be higher); here try
replacing the gaskets.
5. i wont advice you to go for higher strength bolts until flange is
analysed for this higher bolt strength.
Deepak
On Aug 12, 5:39 pm, M S R K S Prasad <MSRKSPra...@nagarjunagroup.com>
wrote:
> Dear members,
> I am thinking of changing MOC of one of the exchanger channel cover bolts
> from B7 to B16 as the exchanger channel cover is leaking very frequently.
> Whenever it leaks we tighten it manually the leak minimizes after few days
> it resurfaces.In each tightening the nuts are moving by about 10 to 15
> deg.
>
> I request members to suggest whether the choice of B16 is OK are any other
> bolting material is better than B16 is available.
> with regards
--
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