Why can’t a water seal be used for safety isolation in confined space operations?
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As the title suggests, why can’t a water seal be used? Why must a cut-off or blind flange be used?
The water seal is not a mandatory barrier; there may be dissolved substances in the water seal
The water seal has a pressure limit; once the pressure exceeds this limit, the water seal ceases to function and can no longer provide a safe barrier.
A water seal cannot be used; it is necessary to implement complete isolation or the use of blind flanges in order to prevent pressure fluctuations from having an impact
A water seal is installed, as there is a possibility of a breach under abnormal conditions.
The water seal is unreliable; pressure and water level may change, resulting in poor isolation performance
A water seal is not the most reliable form of isolation; blind valve and butterfly valves provide a better and more reliable isolation effect
Reference can be made to HG 30011-2013 \"Safety Specifications for Work in Confined Spaces in Production Areas\"; a water seal cannot provide absolute isolation, and effective isolation must be achieved by installing blind flanges or removing a section of pipeline.
The water seal is highly affected by pressure and cannot provide absolute isolation.
First, some harmful substances dissolve in water; when they evaporate, they can cause fatal damage. Second, excessive pressure makes it impossible to seal off the area； For example, gas often leaks into the gas cooling water, leading to explosions when welding is carried out
The water seal is unreliable; even the simplest ones develop leaks, and what’s the use of it once all the water has leaked out?