Tuesday, April 12, 2011

Hot Bolting Procedure

When contemplating hot bolting a number of factors need to be considered. These include, but are not limited to:
·         Working procedures and guidelines
·         The piping system and the system's operating pressures and temperatures
·         Flange joints considered for hot bolting should have a minimum of 8 (eight) bolts. The bolt material should have a minimum strength equal to or greater than grades B7/2H
·         Prior to the commencement of work, the supervisor should review the maintenance history of the joint under consideration, and any joints of a similar type which have been hot bolted in the past.
·         The supervisor should also carry out a visual assessment of the joint. Hot bolting should not be carried out on joints which show significant signs of corrosion or necking, or which have worn or cracked threads on the fasteners
·         Hot bolting should only be attempted under operating conditions when the history of the flange assembly is known, i.e. records exist for the bolt load
·         The consequences of joint leakage during hot bolting should be considered (for example, toxicity, flammability and temperature of escaping fluids) and all necessary precautions taken. Contingency plans should also be put in place for an escape or emergency, e.g. means of communications and provision of standby equipment
·         Pipework within the vicinity of the joint to be hot bolted should also be reviewed. Pipe supports for the local section should be checked to ascertain whether they are taking the load on the pipe, along with their overall condition. If the pipework displays any significant signs of vibration around the specific flange, then hot bolting should not be considered as an option
·         The site supervisor shall check that all the necessary personnel, materials and equipment are at the worksite
·         Each bolt shall be checked for tightness, with any abnormal conditions, such as loose bolts, reported to the supervisor
·         Carry out hot bolting on one bolt at a time in accordance with the operator's correct sequence
·         Remove, examine, clean and lubricate each bolt, complete with nuts, for reuse. Any damaged bolts or nuts shall be disposed of and replaced with new items to the correct piping specification. If there is any doubt, the materials shall be replaced. All exposed flange surfaces must be cleaned and the area under the nuts lubricated
Note: Bolt cutting by any hot methods, including burning and grinding, is not usually permitted during hot bolting operations. Any cold bolt cutting, including hydraulic nut splitting, is usually only permitted by specific approval of the relevant authority
·         Ensure that the bolt has been correctly tightened before moving onto the next bolt in the sequence. Initial retightening of refitted bolts shall not introduce additional local compression of the gasket
·         After all the bolts have been replaced, a final tightness check shall be carried out again.
This work will be executed on flanges of live facilities, therefore in order to avoid potential risk of gas leakage rising through the flanges connection, the bolts shall be released and reinstated one by one. Sequence of bolts tightening arranged as such way to minimize the risk as defined in work steps hereafter.

Due to short length of existing bolt, torque wrench or hammer wrench will be used for bolting / unbolting. Prior to unbolting a complete check of all new bolts nuts (number + diameter + length + material) must be performed. Thread of existing bolts shall be cleaned up first from any dirt, paint or corrosion by means of paints removal and to be brushed by hand wire brush.

After one bolt has been released, then the all threads of bolt and nut shall be properly greased prior to reinstatement.

Monitoring gas leakage by gas detector shall be continuously conducted on the flanges during unbolting process, In case of gas detection, re-tighten immediately the concerned bolt and inform operators.

Unbolting and bolting shall be done according to the following steps :
1.              Using gas detector, ensure there is no gas leakage on flange connection on where hot bolting will be applied as well as existing facilities located close to the bolting area
2.              Smear the bolt no. 1 until the last bolt by paint removal and leave it for about 15 minutes
3.              Clean up the bolt by hand wire brush from dirt, paint or corrosion
4.              Install torque wrench or hammer wrench on the bolt
5.              Loosen the bolt’s nut just a little bit, then check this flange connection by gas detector if there is gas leakage ,especially at the position of bolt being loosened
6.              If the condition is safe, then continue unbolting process while monitoring by gas detector
7.              Grease all threads of bolt and nuts
8.              Reinstate the bolt and properly tighten it using torque wrench
9.              Mark the bolt that has been completed using marker
           10.     For hot bolting work, the bolts shall be released & reinstated one by one