Standards for Piping System Layout

▣ General Layout Standards

• Piping should be arranged based on the General Arrangement (G/A) drawing and the flow diagram (P&ID).
• Piping should be laid out in the shortest possible distance considering operation and maintenance space, space utilization, and aesthetics. High-temperature piping should maintain flexibility to absorb thermal expansion and contraction.
• High-temperature and large-diameter piping should be prioritized considering flexibility, cost-effectiveness, and support positions. Small-diameter piping should be arranged later (grouping and support).
• Except for main system piping with slopes, large-diameter, alloy steel, and main steam piping, piping that crosses east-west and north-south directions should be arranged at different heights.
• Piping should be arranged to avoid penetrating and transmitting vibrations to control rooms, electric rooms, etc.
• When piping passes through building walls, floors, and roofs, sleeves should be installed, and all roof sleeves should be weatherproof shielded (size and location should be agreed upon with the design team, considering the maximum displacement expected during operation).
• Insulated piping should adjust spacing by adding insulation thickness, and increase spacing if thermal expansion or orifice flanges are expected during operation.
• Piperacks should secure at least 15% spare space for future piping installation, and pipe support design should align the height of non-insulated piping based on the bottom of the pipe and insulated piping based on the bottom of the pipe shoe.
• If there are no special design criteria for vents and drains, install a single block valve for ASME B16.5 600 Class and below, and two block valves for ASME B16.5 900 Class and above.
• Piping connected to pumps, turbines, compressors, and heat exchangers should be designed to minimize stress and reaction, and not exceed the manufacturer's allowable stress.
• The discharge piping of pressure relief valves on steam lines should be installed at least 3100mm above the floor.

 

▣ Spacing Between Piping and Equipment

• Piping should be arranged to suit installation, operation, and maintenance requirements, considering maximum displacement due to thermal expansion.
• When designing indoor piping, ensure space for duct and cable tray installation under beams and above piping and insulation materials, considering maximum displacement (not placed above the piping).
• Piping around equipment should secure necessary space for maintenance and operation (ensure space for pulling out tube bundles of condensers, heat exchangers, etc.).
• All piping should maintain the following heights from the floor, considering operation and shut-off positions, covers, and devices:
  • Walkway areas: 2.1m
  • Outdoor areas and maintenance paths: 3.0m
  • Roads and construction vehicle entry: 5.0m

 

 

▣ Vents and Drains

• Equipment and piping should allow natural drainage and minimize the number of drain points.
• The slope direction of steam piping should match the fluid flow direction, using the same material as the main piping.
• Steam piping should always allow drainage under any operating condition, giving a slope of about 2% (minimum 1%) towards the drain, considering thermal expansion of the piping.
• All valves should be arranged for easy operation from the floor or platform of each level.
• Control valves, bypass valves, and shut-off valves should have maintenance space for easy dismantling and be installed on the floor or inside the platform.
• All manual valves should have stems installed as vertically as possible (maintaining a horizontal height), and control valves should be installed on horizontal piping with stems vertical.
• Maintain a certain distance when installing wafer-type check valves close to butterfly valves to avoid internal disc interference.
• All valve actuators should be easily accessible, with space for disassembly, and electric valve position indicators and bypass valves should be installed in accessible and visible locations.

 

 

▣ Pump Piping

• Use top flat eccentric reducers for the horizontal suction piping of pumps to prevent bubble formation during operation.
• Pump connection piping should prevent excessive loads on pump casing due to thermal expansion and self-weight of the piping.
• Install check valves and shut-off valves close to the pump discharge side, with check valves close to the shut-off valves.
• Arrange pump suction piping in short distances to prevent air pockets and satisfy the pump's NPSH.