Facility layout is one of many document deliverables in a project. Do you know the philosophy to create facility layout? In this post, I want to share a siting and layout approach, as well as recommended safety distance for siting and layout of facilities by Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChe).

The siting philosophy begin with a review of the material and processing hazards, such as toxicity, flammability, explosivity, reactivity, or a combination of these hazards. Other potential hazards should also be considered since they may be unacceptable to their surrounding community, such as odors, loud noises, or the light from flares.

Once the type of hazards have been identified, their potential off-site and on-site impacts can be addressed. This step includes how the local terrains affects the release scenarios. At the same time, the layout of the process units and associated areas within the facility, such as storage tank areas or flares, should be arranged to reduce risks. The layout of the equipment, including both orientation and distance between them, may affect day-to-day operations. Therefore, it is important to address the balance between reduced or increased distances and the impact on accessibility when evaluating the on-site consequences.

Figure below shots a high level view of inter-related approach to create facility siting. It begins with understanding the hazards and potential consequences, understanding the effects of the location’s terrain, and then understanding both the potential off-site and on-site impacts due to process unit and equipment layout and accessibility.

CCPS recommended separation distance between equipment. The separation distances apply primarily to potential fire consequence scenarios between the process blocks, process units, process unit equipment, and facility’s industrial neighbors. The able can be used for preliminary process unit layout design.

Note: explosion, toxic releases, or security issues may require greater distances. 

For info, this figure illustrate how distances are measured.

Typical Facility and Layout Distances between Process Unit Equipment for Fire Consequences

Notes:

1. Distance are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
   1. Distance between one block to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary
   2. Distances between equipment to equipment: measure shortest distance between “points”or closes edge
2. These tables are not applicable for enclosed proses units
3. The typical distances cited are based on potential fire consequences and processes with “intermediate hazards”. Greater distances may be required based on modeled explosions and toxic release
4. Different distances may be warranted based on site-specific hazards and risks. Distances may be reduced or increased based on risk analysis or when additional layers of protection are implemented (such as: fire protection or emergency shutdown systems). Where unusual conditions required closer distances, appropriate risk reduction measures should be considered.

NA          Not Applicable

NM        No minimum distances requirement has been established for fire consequences. Use engineering judgement and provide sufficient space for maintenance and fire fighting access.

Typical Facility and Layout Distances between Tanks and Process Unit Equipment for Fire Consequences

Notes:

1. Distance are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
   1. Distance between one block to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary
   2. Distances between equipment to equipment: measure shortest distance between “points”or closes edge
2. These tables are not applicable for enclosed proses units
3. The typical distances cited are based on potential fire consequences and processes with “intermediate hazards”. Greater distances may be required based on modeled explosions and toxic release
4. Different distances may be warranted based on site-specific hazards and risks. Distances may be reduced or increased based on risk analysis or when additional layers of protection are implemented (such as: fire protection or emergency shutdown systems). Where unusual conditions required closer distances, appropriate risk reduction measures should be considered.

NA          Not Applicable

NM        No minimum distances requirement has been established for fire consequences. Use engineering judgement and provide sufficient space for maintenance and fire fighting access.

Typical Facility and Layout Distances between Tanks of Hazardous Materials for Fire Consequences

Notes:

1. Distance are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
   1. Distance between one block to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary
   2. Distances between equipment to equipment: measure shortest distance between “points”or closes edge
2. These tables are not applicable for enclosed proses units
3. The typical distances cited are based on potential fire consequences and processes with “intermediate hazards”. Greater distances may be required based on modeled explosions and toxic release
4. Different distances may be warranted based on site-specific hazards and risks. Distances may be reduced or increased based on risk analysis or when additional layers of protection are implemented (such as: fire protection or emergency shutdown systems). Where unusual conditions required closer distances, appropriate risk reduction measures should be considered.

Typical Facility and Layout Distances between On-site Buildings for Fire Consequences

Notes:

1. Distance are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
   1. Distance between one block to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary
   2. Distances between equipment to equipment: measure shortest distance between “points” or closes edge
2. These tables are not applicable for enclosed proses units
3. The typical distances cited are based on potential fire consequences and processes with “intermediate hazards”. Greater distances may be required based on modeled explosions and toxic release
4. Different distances may be warranted based on site-specific hazards and risks. Distances may be reduced or increased based on risk analysis or when additional layers of protection are implemented (such as: fire protection or emergency shutdown systems). Where unusual conditions required closer distances, appropriate risk reduction measures should be considered.
5. Substations and Satellite Instrument Houses (SIH) – normallly temperature controlled (i.e., air conditioned) buildings. SIHs are typically considered “unoccupied” for the facility siting studies. If personnel use Substations or SIHs, then evaluate them as “occupied”.
6. No direct comparable table for Substations in GAP 2.5.2. Interpretation for “More than one process unit” is the same as “Main”
7. The distictions between shelters: a simple weather overhang typically has three walls, a roof, and no windows or doors; wherease truck, railcar, barge unloading “shelters”are used for the paperwork and protection of the unloading personnel from the weather during the transfer of ther materials (rain, cold, or hot temperature)

NM No minimum distances requirement has been established for fire consequences. Use engineering judgement and provide sufficient space for maintenance and fire fighting access.

Typical Facility and Layout Distances between Other Types of Equipment and Operations for Fire Consequences

Notes:

1. Distance are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
   1. Distance between one block to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary
   2. Distances between equipment to equipment: measure shortest distance between “points”or closes edge
2. These tables are not applicable for enclosed proses units
3. The typical distances cited are based on potential fire consequences and processes with “intermediate hazards”. Greater distances may be required based on modeled explosions and toxic release
4. Different distances may be warranted based on site-specific hazards and risks. Distances may be reduced or increased based on risk analysis or when additional layers of protection are implemented (such as: fire protection or emergency shutdown systems). Where unusual conditions required closer distances, appropriate risk reduction measures should be considered.

Typical Facility and Layout Distances for Emergency Response and Operation Accessibility

	Ground Level, Horizontal Plane, or Grade Distance
No	Spacing From	To	Maximum Distance (ft)
1	One process unit access way	Another access way	200
2	Fire hydrants protecting process unit	Another fire hydrant	200
3	Fire hydrants in tank farms	Another fire hydrant	200
4	Firewater monitors	Fire risk area	50
5	Access way	Access way	100

Access way should be at least 20 ft wide; basis for this distance is the typical fire hose length of 100 ft.

Notes:

1. Distance are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
2. Distance between one block to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary
3. Distances between equipment to equipment: measure shortest distance between “points” or closes edge
4. Different distances may be warranted based on site-specific hazards and risks. Distances may be reduced or increased based on risk analysis or when additional layers of protection are implemented (such as: fire protection or emergency shutdown systems). Where unusual conditions required closer distances, appropriate risk reduction measures should be considered.

Typical facility and Layout Distance for Flare Systems

	Ground Level, Horizontal Plane, or Grade Distance
No	Spacing From	To	Minimum Distance (ft)
1	Elevated and grade level flares and burn pits (if radiation level calculations do not exist)	All other facilities	500
2	Enclosed ground flares	Property line, equipment handling flammables	100

 

Guidelines for Radiant Heat calculations

No	Permissible Design Level in kW/m2 (Btu/h-ft2)	Condition
1	1.58 (500)	Maximum radiant heat intensity at any location where personnel with appropriate clothing can be continously exposed
2	4.73 (1,500)	Maximum radiant heat transfer in areas where emergency actions lasting 2 min to 3 min can be required by personnel without shielding but with appropriate clothing
3	6.31 (2,000)	Maximum radiant heat transfer in areas where emergency actions lasting up to 30 second can be required by personnel without shielding but with appropriate clothing
4	9.46 (3,000)	·         Maximum radiant heat intensity at any location where urgent emergency action by personnel is required. When personnel eneter or work in an area with potential for radiant heat intensity greater than 6.31 kW/m2 (2,000 Btu/h-ft2), then radiation shielding and/or special protective apparel (e.g. fire approach suit) should be considered ·         Personnel with appropriate clothing cannot tolerate thermal radiation at 6.31 kW/m2 (2,000 Btu/h-ft2) fot more than a few seconds.

 

No	Thermal Radiation in kW/m2 (Btu/h-ft2)	Effect
1	1.5 (500)	Fire fighters can operate for long duration under normal conditions
2	5 (1,500)	Fire fighter can fight fire with normal protective clothing for a short time
3	8 (2,500)	·         Fire fighters can fight fire for short time if special cooled protective clothing is worn ·         Fire unlikely to propagate beyond this point, even if no fire water applied
4	12 to 30 (4,000 to 9,000)	Fire should not propagate beyond this point if sufficient fire water applied
5	36 (11,000)	Fire likely to propagate no matter how much fire water applied

Note:

1. Distances here are measured with the shortest line from one point to another point at ground level, horizontal plane, or grade.
2. Distance between one block (e.g. building or structure) to another block or boundary: measure the shortest distance between the edge of the block and the other block or boundary. This could be on the corner of a block. For flare calculation, the distance is measured from the perimeter of the calculated circle.

References:

Guidelines for Siting and Layout of Facilities, CCPS AIChe.