To identify and manage risks associated with welding, cutting drilling and other process boundary-penetration on live equipment and pipelines, so that fires or explosions that could result in personal injuries, property damage, community impacts, environmental impacts, or business impacts are prevented.
Considerations during the development of a Hot Tapping SWP include:
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Hot Tapping is an inherently hazardous process, as it always results in the penetration of an operating process boundary—in effect, Hot Tapping is a controlled loss-of-containment (LOC) event. The first step in any hot tap SWP is a mandatory evaluation to ensure that the operation cannot be performed under normal maintenance conditions; i.e., a “cold tap”, where equipment is de-energized, empty, at ambient temperature conditions, and cleaned prior to the procedure.
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If a routine maintenance operation cannot be performed, strong consideration should be given to a “warm tap” process; i.e., one where the equipment is not out of service and cleaned, but where enough isolation has been performed so as to limit any release of material should the tap fail.
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Although hot tapping on live equipment and pipelines is practiced widely across the process industries, and even though sufficient experience has been obtained, the risks remain the same every time the activity is performed.
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No two activities involving welding on live systems are identical. The risks differ for each case and extreme caution must be exercised from the task design stage to completion of execution.
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Strong consideration should be given during procedural development to circumstances where hot tapping should be absolutely forbidden. These situations might include
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Equipment containing highly toxic materials
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Equipment containing heat transfer fluid (HTF), either vapor or liquid, above 250 C
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Steam above 600 psig
Background
Hot tapping refers to a two-step process.
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The first step is to weld a branch nozzle on the live operating equipment or pipeline.
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During the second step, after welding the branch nozzle, the nozzle coupon is drilled and removed by a specially-designed drilling machine.
The combined activity of welding and drilling to create a new nozzle on live systems is termed as hot tapping. There are also instances when only welding is carried out on live systems with no drilling required. For clarity, in this document the term “hot tapping” to refers to all types of welding on live equipment (with or without drilling).
Hot tapping on live equipment depends on the following characteristics of the system:
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Metallurgy of the parent equipment / pipeline
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Operating pressure
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Operating temperature
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Chemistry and physical properties (hazardous properties) of the operating fluid
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Condition of the equipment / pipeline on which the activity will be performed.
Hot tapping on live systems containing pressurized fluids is one of the most hazardous activities in an operating unit. A loss of containment during welding or drilling on live equipment or pipeline can cause serious damage to the personnel involved in the welding jobs. The consequences can include serious injuries with a potential leading to fatalities. Damage to the assets near the workplace can also occur, dependent on location and process chemicals within.
Potential incidents can occur if:
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The pipeline or equipment on which the hot tapping is to be done is not inspected and certified fit for hot tapping. A common situation that can disqualify equipment for hot tapping is wall thinning.
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The metallurgy of the pipeline or equipment is not fit for hot tapping.
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The fluid flow is not maintained as required to adequately cool the weld metal.
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The procedure is done by untrained personnel with the possibility of not controlling the heat input for welding.
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The hot tap connection is inadequately or improperly designed.