Tuesday, September 16, 2014

[PPT] Under Ground Piping (Trench, Culvert, Buried)

Types of Under Ground Piping:

Ø Trench Piping

Ø Culvert Piping

Ø Buried Piping

Trench Piping

Trench: This is three sided concrete trough located in the ground whose top is flush with grade. It is used to house piping systems below grade.

Many times trenches are avoided due to problems associated with it ,like:

Ø High initial cost

Ø Fire hazard

Ø Under ground piping header should be run together in trench to minimize the amount of trenches required.

Ø Plan pipe trenches not to undermine any building or equipment foundations.

Ø Maintain 8” minimum separation between pipes in trench for tape wrapping of pipes at but weld joints.

Ø Maintain 24” minimum separation between cooling water supply and return lines to prevent heat transfer.

Ø Avoid to locate in line instruments and valves etc. in trench

Ø For supporting of pipes in trench use H Beam

Buried Piping

Buried Piping generally avoided due to high cost involved. Following are common pipe lines buried in power plant:

Ø Cooling water lines

Ø Fire fighting line

Ø Potable water

Ø Service water

While pipes are routed buried following points to be kept in mind:

Ø Minimum pipe size to be routed shall not be less than 1 inch

Ø All buried piping shall be designed in order to with stand the loading from covering soil as well as from traffic

Ø Avoid flange joint in buried piping

Ø If pipe leaks it will be difficult to detect , so avoid buried routing of pipes carrying hazardous fluid.

Ø Pipe preferably be routed so that excavation if required does not reach the surface of pipe.

Ø Top of buried pipe must be below the frost level to ensure that soil does not cool the flowing medium.

Ø Insulating joints or flange insulation kit shall be required when pipe line goes under ground then it comes over ground to reduce the danger of electric shock.

Ø For marking high density polythene should be provided that will indicated after this pipe surface will come so it will work as protecting cover for pipe lines during excavation.

Ø Pipe sleeves have to provided to protect the line from traffic load.

Ø For buried piping both carbon steel and plastic pipes (GRP/FRP) can be used.

Ø Carbon steel pipes should be coated with protective coating if deemed required then provide Cathodic protection to protect from corrosion.

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