This article provides the basic considerations for the development of plant layout in a presentation form. For more details in any of the listed points you can refer to any standard piping books. This presentation will provide an overview on basic considerations.
Basis of Site Selection:
- Area Allocation
- Transport Facilities
- Manpower availability
- Industrial Infrastructure
- Community Infrastructure
- Availability of Water
- Availability of Power
- Effluent Disposal
- Availability of Industrial Gas
- Site Size
What is Plot Plan & its requirement?
Plot plan is the master plan locating each unit/facility within the plot boundary for a process industry such as
- Chemical /Agro Chemical / Petro Chemical / Organic Chemical / Inorganic Chemical
- Power Generation
It is used to locate the unit/facility.
The following main aspects shall be considered during development of the layout.
- Process requirement
- Economy of piping material and cables
- Erection & Construction requirements
- Safety requirements.
- Operation and Maintenance requirements.
- Grouping of similar equipment for convenience of maintenance & safety wherever possible.
Data to be collected before starting:
- Plane table survey map.
- Contour survey map.
- Soil bearing capacity.
- Nature of Soil
- Rail/Road Access.
- Location of Electric Supply Point.
- Supply voltage levels.
- Fault Levels.
- Voltage Levels required within the unit.
- Proposed distribution scheme.
Non Plant Facilities
- Administrative Block
- R&D, QC Lab and Pilot Plant
- Gate House/Time office
- Security Arrangements
- Vehicle Parking
- Medical Centre
- Ware House
- Covered Area
- Open Area
- Solid Warehouse
- Liquid Warehouse
- Steel / Scrap Yard
- Fire Station
- Weigh Bridge
- Staff Colony
- Minimum, Maximum and Normal Temperature during the year
- Intensity and Direction of the wind (wind rose)
- Seismic zone
- Wet and Dry Bulb temperatures
- Relative humidity
- Flood level
- Size/Capacity of the process unit
- Knowledge on the type of plant
- Sequence of process flow
- Hazardous nature of the plant
- The Overall operating philosophy
- Fully Automatic
- Partially Automatic
- Raw material receipt and product dispatch philosophy
- Storage Philosophy
- Effluent plant capacity and discharge points, incineration requirements, etc.
- Type of Hazard
- No of flares
Data on Utilities
- Source and/or supply point of raw water
- Quality of Water available
- Water Consumption for the process
- Requirement of different types of utilities such as Steam, Air, Nitrogen, DM water, Fire water, Brine, etc.
- Capacities and Grouping philosophy.
- State Industrial Development Corporation (SIDC)
- Central / State Environmental Pollution Control Boards (PCBS)
- Factory Inspectorate
- State Electricity Boards (SEB)
- Chief Controller of Explosives (CCOE)
- Static and Mobile Pressure Vessel Rules (SMPV)
- Tariff Advisory Committee (TAC)
- National Fire Protection Association (NFPA)
- Aviation Laws
- Chief Inspector of Boilers (CIB)
- Oil Industry Safety Directorate (OISD)
- Food and Drug Administration (FDA)
- Ministry of Environment and Forest (MoEF)
- Within the unit
- Additional Units
- Near future expansion
- Far future expansion
Points to Note
- Normally Construction is permitted on maximum 50% of the plot area with total built up area equal to area of the plot (i.e. F.S.I. = 1 (Depending upon the regulation governing the area and the type of industry))
- Area reserved for tree plantation shall be 1/3 of the area occupied.
- Water storage capacity – 24 hr. minimum.
- Domestic water – 100 litres per person per day
- Water requirement for Boiler – Steam rating x Working factor
- Cooling tower – 11/4 % of capacity as drift and blow down losses
- Washing – 10-15 litres per day per sq.ft. of floor area of the plant
- Gardening – 5 litres per day per sq.ft. of garden area
- Parking space – 10% of the plot area
Roads & Paving
- Roads in the plant shall be planned for effective movement of the trucks, cranes & emergency vehicles etc. Road width (Black top) shall be generally as follows unless specially requested.
- Main plant road & roads connecting to Plant boundaries, roads for fire fighting access is 6 meters wide (Min)
- Secondary roads 4 meters wide (Min)
- Turning radius of the road shall be adequate for the mobile equipment & shall clear of any obstruction. Minimum turning radius to be same as the length of vehicle.
- The finish of road i.e. graded or black top shall be decided in the beginning while developing plot layout.
- Paving should be provided around the equipments where spillage is likely occurring. For example: Pumps or machineries, below furnace or fire heaters, compressor etc.
- Also paving should be provided below Air fin cooler those are located at grade.
- Area handling acids, alkalis or toxic material shall be paved and bunded. Proper surface treatment shall be provided to paving to meet service requirement.
The below sketch (Fig. 1) shows minimum distance required between the road and the facility. This distance shall be reviewed to case to case basis for the project.
- Below data for the elevations should be generally followed.
- Under side the base plate of Structural steel: Min150 mm. above HP of finished grade/paving.
- Stair or ladder pads: Min75 mm. above HP of finished grade/paving.
- Top of Pedestal of Vessel & Tower: Min300 mm. above HP of finished grade/paving.
- Top of Pump pedestal: Min200 mm. above HP of finished grade/paving.
Insulation & Fire Proofing
- Fire proofing requirements for pipe rack, vessel supports, process structure should be considered as these reduces the clearances with access, pipe work, instrument & electrical equipment.
- Proper insulation thickness should be considered for pipe work & equipment clearances.
- Pumps: Locate pumps close to suction source considering NPSH requirement. Pumps & driver axis should be located perpendicular to pipe rack or other equipment to minimize fire exposure in case of pump seal failure.
- Gas compressor or Expanders: Gas compressors should be located downwind of the fired heaters, flare or any open flame equipment. They may be grouped together for maintenance & operations (Common EOT / drop down area, single sunshade can be made)
- Plant Air & Instrument air compressors: Plant air & instrument air is vital service for the plant. These units should be located near the control room & shall be kept in safe area sufficiently away from HAC of equipment.
- Heat Exchangers: Heat exchangers are generally placed on grade unless otherwise due to process or technical reasons. (Platform for vertical heat exchangers, Tube bundle removal area, access to mobile crane or monorail with hoist shall be considered)
- Air cooler: Air cooler located such a way to allow the access to mobile lifting equipment. Preferably air cooler is located in a main equipment row in accordance with process requirement.
- Cooling Towers: Cooling towers shall be located away from the process equipment & downwind of process equipment, substation, main pipe rack.
- Offsite Tanks: Storage tanks (Grouped and shall be surrounded by dike wall, Primary/secondary roads for adequate firefighting accessibility, Lower elevations than the other occupancies and downwind of flares, furnace heaters). Emergency shutdown valve, pumps, manifold & transfer piping shall be outside dike area.
Pipe ways / Pipe racks
- Pipe ways or pipe racks should be overhead in process main unit and at grade in off site.
- Width is determined based on present need + 10% at outset the job + 15% for future requirement or as specified by client.
- Requirement of expansion bays, anchor bays & bracing shall be checked with stress / structural engineer at the beginning of the rack layout.
Relief valve and Flare systems
- Closed relief valve system
- No pocket to avoid condensation & back pressure.
- Flare shall be located upwind process unit & storage.
Clearance at Pig Receiver
- Area at the end closure of Receiver shall be kept free to avoid any incident.
- Provide concrete wall minimum 20 meter away (Fig. 2) from the end closure if area needs to be utilized for any equipment.
- Eye wash and emergency showers shall be provided in area where operators are subject to hazardous sprays or spills.
- Breathing air stations in the facilities handling extremely toxic gases / fluids.
Fig. 3 shows a typical plant layout.
What is Hazard Classification?
- Hazardous area classification is the risk locating plan for each unit/facility within the plot boundary for a process industry.
- The Plot plan will be used by indicating boundaries of risk area.
- HAC drawings are generally used by operator while issuing work permits.
- HAZARDOUS AREA: An area in which an explosive gas atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of apparatus.
- NON-HAZARDOUS AREA: An area in which an explosive gas atmosphere is not expected to be present, in quantities such as to require special precautions for the construction, installation and use of apparatus.
- Proper interconnection between equipment to achieve intended process parameters.
- Normally equipment is arranged in the process fluid flow sequence. Requirement like gravity flow (Equipment Drain piping), Thermo syphon system should be considered, Limitation of pressure & temperature (process parameters) to be considered
- Requirement of upstream and downstream pipe lengths for instruments.
- Hazardous & Toxic fluid shall be identified. (H2S, Cyanide, Methanol etc.)
- Equipment handling hazardous fluids like flare and direct fired equipment containing open flame shall be located separately.
- Similarly equipment handling toxic material shall be located with the restricted access or in accordance with local statutory regulation.
- Equipment shall be located without affecting the process requirement for maximum economy of pipe work & supporting steel with consistent standard clearances, construction, and maintenance & safety requirements.
- Runs of exotic material & large bore piping shall be minimized.
- Optimum utilization of the structure to be ensured.
Erection & Construction
- Road access for erection of pipe support / pipes and equipment.
- Clear area for crane to erect equipment on the location from the trucks.
- Minimum one side of pipe rack shall be kept clear.
Fig. 4 shows relative locations for area Layout.