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WHAT IS HOT BOLTING? AND WHERE IT IS USED?

Posted by Antony Thomas at Saturday, February 01, 2014

WHAT IS HOT BOLTING? AND WHERE IT IS USED?


The removal and replacement of flange bolts on live piping and
Equipment is practiced for several reasons:
• For replacing corroded or damaged bolts;
• for upgrading the material specification/grades of bolts; or
• to minimise the time spent freeing bolts during plant shutdown.


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The practice of removing and replacing or freeing and re-tightening bolts on live equipment is potentially hazardous and the utmost caution therefore needs to be exercised when planning and carrying these operations.
The replacement must only be carried out under permit, and under controlled conditions. Because it involves working on live equipment, each application must be specially reviewed beforehand.
Detailed procedures must be in place for the control of hot bolting and must be observed.
For further information, see EEMUA Information Sheet No. 17 Rev.1, dated May 1999.

Restrictions on Hot and Odd Bolting
a) Marginal time savings during shutdowns on disjointing should not be considered sufficient incentive for Hot Bolting operations.
b) A formal engineering review of the proposed Hot Bolting operation must be carried out to establish that there are no unacceptably high external loads and bending moments acting on
the joint.


The review should consider, as a minimum, the following:
                i) Contents of the line or equipment.
                ii) Design and operating pressures and temperatures.
                iii) Possible upset conditions.
                iv) Position and functionality of piping supports.
                v) Position and type of expansion bellows fitted.
                vi) Maintenance history of the joint.

c) Flanges should have a minimum of 8 bolts.
d) Hot Bolting shall not be considered when the operating pressure exceeds 60% of that specified in ASME/ANSI B16.5, Annex G, Table G for any given flange rating.
e) A thorough inspection of the flange assembly should be conducted to verify the integrity of the flange and fasteners. These operations should not be allowed if bolts and nuts show signs of corrosion, necking or are suspected of having cracks.
f) Equipment containing toxic materials shall not be Hot Bolted.
g) Consideration must be given to the accessibility of the area and that adequate escape routes are available, should uncontrolled flange leakage occur.

To repeat - it is essential that each application is reviewed beforehand. The operation must be carried out under strictly controlled conditions.
Taken from : Piping Joints Hand Book-BP Amoco

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