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Is it possible to weld on to a pipe, or vessel, that contains an inflammable fluid?


Frequently Asked Questions

Yes, subject to stringent control of welding to ensure a safe operation. This may include restrictions on the welding parameters to keep the inner wall of the carrier pipe low enough to avoid combustion, or changing the pressure or flow rate within the system in order to reduce the risks. TWI can provide advice regarding any in-service welding, including safety assessments and information on applying the selected guidelines, along with development and assistance with qualification of welding procedures for in-service welding.

Making a welded connection to a 'live' pipeline, or vessel, is commonly known as 'hot tapping' or in-service welding and there are National (and proprietary) Standards that provide details of the controls that are necessary.

Examples of these Standards are:

BS 6990 Code of practice for welding on steel pipes containing fluids
Transco SP/P9 The welding of fittings to pipelines operating under pressure (Supplementary to BS 6990)
Transco P9 Supplement The welding of fittings to pipelines under pressure and having a wall thickness not less than 5mm; Notes for Guidance
EEMUA 185 Guide to hot tapping
API RP 2201 Procedure for hot tapping
API STD 653 Repairs to storage tanks

Further information

For more information, please contact us.

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