Boundary: Boundary of the equipment is the term used in a processing facility, by an imaginary line that completely encompassed the defined site.
Dike: Dike is an earth or concrete wall providing a specified liquid retention capacity.
Diversion Wall: It is an earth or concrete wall which directs spills to a safe disposal area.
Fire Resistive: Fire resistance rating, as the time in minutes or hours, that materials or assemblies have withstand a fire exposure as established in accordance with the test of NFPA 251.
High Flash Stock: Those having a closed cup flash point of 55°C or over (such as heavy fuel oil, lubricating oils, transformer oils etc.). This category does not include any stock that may be stored at temperatures above or within 8°C of its flash point.
Low-Flash Stocks: Are those having a closed cup flash point under 55°C such as gasoline, kerosene, jet fuels, some heating oils, diesel fuels and any other stock that may be stored at temperatures above or within 8°C of it’s flash point.
Non-Combustible: Material incapable of igniting or supporting combustion.
Pipe Rack: The pipe rack is the elevated supporting structure used to convey piping between equipment. This structure is also utilized for cable trays associated with electric-power distribution and for instrument tray.
Plot Plan: The plot plan is the scaled plan drawing of the processing facility.
Sleepers: The sleepers comprise the grade-level supporting structure for piping between equipment for facilities, e.g., tank farm or other remote areas.
Tank Diameter: Where tank spacing is expressed in terms of tank diameter, the following criteria governs:
(a) If tanks are in different services, or different types of tanks are used, the diameter of the tank which requires the greater spacing is used.
(b) If tanks are in similar services, the diameter of the largest tank is used.
Tank Spacing: It is the unobstructed distance between tank shells, or between tank shells and the nearest edge of adjacent equipment, property lines, or buildings.
Toe Wall: It is a low earth, concrete, or masonry unit curb without capacity requirements for the retention of small leaks or spills.
Vessel Diameter: Where vessel spacing is expressed in terms of vessel diameter, the diameter of the largest vessel is used. For spheroids, the diameter at the maximum equator is used.
Vessel Spacing: It is the unobstructed distance between vessel shells or between vessel shells and nearest edge of adjacent equipment, property lines, or buildings.
Some Key Issues Related To Layout:
1. For operator access via a central aisle.
2. The need that the outlet sides of two lines of equipment (pumps, for instance) point toward each other so that they can be readily hooked to one common line.
The plant layout shall be arranged to:
1. maximize safety.
2. prevent spread of fire.
3. Facilitate easy operation and maintenance.
4. Consider future expansion.
5. Economize project.
Blocking: The plant site shall be blocked in consideration of hazards attendant to plant operation in the area. All blocked areas shall be formed as square as possible by divided access roads and/or boundary lines.
Location and Weather: The plant layout shall be arranged in consideration of geographic location and weather in the region of the site.
Prevailing Wind: Where the prevailing wind is defined, the administration and service facilities and directly fired equipment, etc., shall not be located windward of process Units and storage tanks, etc.
Layout Indication: The basic requirements to be met in the appropriate diagram when making a piping and equipment layout are:
1. All equipment, ladders, structures, davits, trolley beams, shall be indicated.
2. All instruments shall be located and indicated.
3. All valves and hand wheel orientations shall be indicated.
4. Drip funnel locations for underground drains shall be indicated.
5. All electrical switch gear, lighting panels shall be indicated.
6. All sample systems shall be indicated.
Classification of Hazards: The plant layout shall be determined in consideration of classified hazardous areas.
Area Arrangement: Classified blocked areas, such as process areas, storage areas, utilities areas, administration and service areas, and other areas shall be decided on the bases of following factors:
1. Soil characteristics.
2. Main road, rail access ways, and jetty.
3. Location of pipelines to and from plant.
4. Direction of prevailing wind.
5. Local law and regulation which may affect the location of units and storage facilities.
6. Natural elevation for location of upstream / downstream units and equipment (such as feed and product storage tanks, wastewater plant, oil/ water separator, etc.) and arranged as follows:
Pipe racks and Sleepers:
1. In general, pipe racks for process Units and pipe sleepers for the off-site facilities shall be considered as the principals support of the pipe way. Run pipe lines overhead should be grouped in pipe racks in a systematic manner.
2. Pipe rack runs oriented in the same direction shall be at consistent elevations. Pipe rack runs oriented opposite to these runs shall be at other elevations to accommodate crossing of lines at pipe racks junctions and to accommodate branch line intersections.
3. Single level pipe racks are preferred, if more than one level is required, the distance between levels oriented in the same direction shall be adequate for maintenance but not less than 1.25 meters.
4. Maximum pipe rack widths shall be 10 m. If widths larger than 10 m are required, the pipe rack shall be designed to be of two stages. Actual widths shall be 110% of the required widths or the required widths plus 1m. In cases where air fin coolers are to be placed on the pipe racks, the pipe rack widths shall be adjusted based on the length of the air coolers.
5. Avoid flat turns. When changing directions, change elevation.
6. Allow ample space for routing instrument lines and electrical conduit. Provide 25% additional space for future instrument lines and electrical conduit adjacent to that required.
7. Provide 20% additional space on the pipe rack for future piping. This space shall be continued and clear on each level for the full length of the rack. The width allocation may be split in two sections but not more than two.
8. Allow a continuous clear area of 4 meters high by 4 meters wide below main racks in process Units for maintenance access ways.
9. Pipe racks outside process areas shall have the following minimum overhead refinery/plant clearances: main roadway: 5 meters, access roads: 4.5 meters, railroads: 6.7 meters above top of rail.
10.Typical layout of pipe rack, for process plants depending on the number of process Units incorporated and the process complexities are given in Figures with reference descriptions as follow:
12.Overhead racks may contain more than one level. For steel pipe racks, the height of levels shall have one of the following elevations:
a. Main pipe racks : 4.60, 6.20, 7.80 m
b. Individual or secondary pipe rack: 3.80, 5.40, 7.00 m. In special cases for large size pipes or concrete pipe racks, the distance between the various floors may be increased.
13.Except for special cases, minimum width of pipe rack shall be 6 m. The width of pipe rack shall be designed to accommodate all pipes involved plus 20% space for future expansion or modification. Where the pipe rack supports air coolers, the preferred width shall be the width of air coolers.
14. In multi-level pipe racks, pipe carrying corrosive fluids shall be on the lower level, and utility lines should be at the upper floor. Large size or heavy weight pipes shall be located at the lower level and on extreme sides.
Layout of Control Room and Electrical Sub-Station
1. The control room and substation shall be located as close as possible to the plant equipment, maintaining a minimum distance from viewpoint of noise and safety requirements.
2. The control rooms, and substation shall be spaced at least 15 m from the nearest process equipment surface.
3. The control room and substation shall be located with consideration to convenience in daily operation.
4. The control room and substation shall be located from an economical standpoint so as to minimize the length of electrical and instrument cables entering and leaving therefore.
5. The control room shall be positioned so that the operator can command a view of the whole system which is under control. Large buildings, or equipment shall not be placed in front of the control room.
Fire Fighting Requirements
1. Each individual process Unit shall be provided with sufficient open spaces there around that, fire trucks can be run and operated thereat. The width of access way there to, shall be 6 meters minimum.
2. Process Units consisting of large hazardous material storage tanks should be located desirably in outer area in the complex site.
3. High-pressure gas lines shall not pass through a process area or run within 30 m of important structures or equipment without shutdown valve to insure that portions of piping within the process area can be isolated from the main gas line and depressurized in the event of an emergency. However, extensive use of shutdown valves may not be needed, since the increased complexity of the system will require a greater degree of preventive maintenance if unwarranted shutdowns are to be avoided. Shutoff valves, sometimes known as "station isolation valves", shall be provided on all gas and product pipelines into and out of the plant.
A bypass line with a normally shut valve may be required between plant inlet and discharge lines. All station isolation valves-and bypass valves, if any should be located at a minimum distance of 75 m but not more than 150 m from any part of the plant operations. Care should be taken in locating these valves so that they will not be exposed to damage by plant equipment or vehicular traffic.
4. At least two remote emergency shutdown stations, located at a minimum distance of 75m apart, shall be provided. Locate actuating points at least 30m from compressor buildings and high pressure gas lines. More than two shutdown stations may be required, depending on the size and complexity of a given plant. One of the actuating stations shall be located in the control room. It shall be distinctively marked and equipped with signs stating the proper method of actuation in the event of an emergency.
5. Wastewater separators handling hydrocarbons should be spaced at least 30 m from process unit equipment handling flammable liquids and 60 m from heaters or other continuous sources of ignition. Preferably, wastewater separators should be located downgrade of process equipment and tanks.
6. Fire training areas are ignition sources when in use. Because of the smoke produced, they can also create a nuisance for the refinery and neighboring facilities. Fire training areas shall be 60 m from process unit battery limits, main control rooms, fired steam generators, fire pumps, cooling towers and all types of storage tanks. They shall also be 75 m from property boundaries, administration, shops, and similar buildings and from the main substation.
1. Service buildings include offices, control rooms, laboratories, houses, shops, warehouses, garages, cafeterias and hospitals.
2. These structures and areas require protection of personnel from possible fires and explosions of major plant equipment and may require additional spacing from high risk facilities.
3. The service buildings shall be located near the entrance of the plant and be readily accessible to a public road or highway.
4. Spacing at refineries, petrochemicals, chemicals, and gas plants for buildings shall be in accordance with Insurance recommendation.
Access Requirements: Access ways within the plant shall be provided for maintenance, emergency case, and for fire fighting from the road around the plant. Piping system shall be laid in such a way to make possible passage of mobile equipment. Operating passageway between equipment or piping and adjacent equipment generally is 1050 mm minimum except when otherwise shown on drawings.
Minimum widths of access way shall be as follows:
1. Vehicular access ways within units: 4.0 m
2. Pedestrian access ways and elevated walkway: 1.2 m
3. Stairways and platforms: 0.8 m
4. Footpaths in tanks areas: 0.6 m
5. Maintenance access around equipment: 1m
6. Fire truck access way: 6m
Minimum headroom clearance for access ways shall be as follows:
1. Over railways or main road: 6.8 m
2. Over access roads for heavy trucks: 6 m
3. For passage of truck: 4 m
4. For passage of personnel: 2.1 m
5. Over fork-lift truck access: 2.7 m
Preparation of Plot Plan Drawing
The general plot plan drawing shall give the layout of the whole plant(s). It should be prepared in accordance with one of the following scales: 1:500, 1:1000, 1:2000.
The following items shall be shown in plot plan drawing:
1. Battery limits of complex (area boundary).
2. Plant geographical and conventional north.
3. Elevation, with regard to the nominal plant 0 (zero) elevation.
4. Coordinates of main roads, process units, utility units, buildings, storage tanks and main pipe rack.
5. Location of flares and burn pit.
6. Direction of prevailing wind.
Plant coordinates may be started from point N=0, and E= 0
Layout in Process Units:
1. In cases where process fluid is run by gravity head, elevated layouts must be considered. Unless there are any such limitations as indoor arrangement and confined locations, equipment shall be placed at grade as a rule except in cases where gravity flow is specifically required for any reason.
2. Since the directions of the incoming feed stocks, outgoing products and utility supply are determined on the overall plot plan, first the direction of the pipe rack in the Unit shall be decided.
3. Equipment shall be arranged to minimize piping runs (particularly, for large sized piping and alloy piping) as far as possible. Clear access ways having minimum width of 600 mm shall be provided for the operators access around equipment.
4. Large capacity storage tanks containing flammable and explosive fluids shall be located in outer areas as far as possible.
5. Space shall be allowed for the provision of future spare equipment. Consideration shall also be given to future plant expansion.
6. The drawing shall be prepared in one of the following scales: 1:1500, 1:1200.
7. The drawing shall show the following items:
a. Conventional North.
b. Coordinates of battery limits and roads.
c. Symbols for equipment and coordinates of their centerlines.
d. Finished floor elevation.
e. Equipment index list.
8. The area of any unit shall not exceed 20,000 m2, and the length of each side should not exceed 200 m.
9. For units processing flammable fluids, the central control building shall be adjacent to a road. It shall not be located in any area classified as zone 0 to 1.
1. Equipment shall be laid out along the flows on the process flow diagram.
2. Especially, the fractionators and the reboiler, condensers and overhead receivers shall be collectively located.
3. Gravity flow lines shall be laid out with consideration given to related elevations, so that their lengths will become minimum. Especially in the case of lines in which liquids will flow near at their boiling points, related equipment shall be located close to each other so that the lines need not be elevated.
4. Pieces of equipment which are to be connected by large-size piping or alloy piping shall be located close to each other.
5. Air coolers shall be laid out so that no heated air may be recirculated.
1. All process equipment should be kept at least 15 meters from fired heaters. Exception are permitted for certain pieces of equipment where the heater in question is being used to heat the process flow of the equipment and where any leakage from the equipment would probably ignite instantly, thus no additional fire hazard. Such an exception is permitted when locating reactors on a reforming Unit (an example). Each exception must be individually investigated as to its potential hazards and must not violate any process practices in OGP plants and governing codes.
2. Locate fire heaters on the side of the process Unit from which the prevailing wind blows. This is done to blow gas away from the heaters instead of towards them. Fired equipment shall not be located in "Hazardous Area Classification". Generally, fired equipment shall be located at a distance of more than 15 meters from any sources of hazards (hot oil pumps, light end pumps, compressors etc.).
3. Emergency showers, if required in a certain process, should be located as near the hazard as possible and indicated in the Plot Plan.
4. Adequate and easy access and egress must be considered for not only safety, but operation and maintenance requirements.
5. Control rooms and their roadways shall not be located in hazardous area, classified in project specification; generally, they shall be located at a distance of more than 15 meters from the nearest equipment.
6. High pressure gas compressors shall be located at leeward locations.
7. Large-Capacity hazardous material storage tanks shall be located in outer areas as far as possible.
8. Pumps intended to handle flammable materials (which fall under the control of the hazardous area classification), shall be located on the following basis.
9. Fired heater stacks shall be located at such points that the performance of the air coolers and operators on tower tops may not be adversely affected by hot flue gas emitted through them: the directions of prevailing wind shall be taken into consideration in the determination of the stack locations.
A good piping layout is essential for proper handling of liquid products. Piping cost is generally 20 to 25% of project cost. There are 2 areas of Piping layouts.