1300 Layout and Spacing

Abstract
This section discusses plant layout and facility and equipment spacing to minimize
the potential for fire to spread to adjacent facilities. Figure 1300-1 and 1300-2 at the
end of this section offer guidelines for plant-to-plant and plant-to-equipment
spacing.
This section covers layout and spacing requirements for process plants. Requirements for other types of facilities are covered in Sections 3100 to 4100. Drainage is
discussed in Section 1400. Location and protection of critical controls are discussed
in Section 1700. Tank spacing is discussed in the Tank Manual.
Contents

Page

1310 Layout Considerations

1300-3

1311 General
1312 Legal Requirements
1313 Design for Local Conditions
1314 Layout Objectives
1315 Block Layout and Roads
1316 Drainage
1320 Plant Spacing

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1321 Spacing Tables

1322 Protection of the Public Through Spacing
1323 Plant-to-Plant Spacing
1324 Plant-to-Offplot Facilities Spacing
1325 Spacing of Unrelated Facilities
1330 Process Equipment Spacing

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1331 General Philosophy

1332 Pumps and Compressors
1333 Air-Cooled Heat Exchangers

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1334 Process Piping

1335 Other Equipment Spacing Concerns

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1340 Specific Facilities

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1350 Building Siting in Process Plants

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1360 References

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1300 Layout and Spacing

1310 Layout Considerations

1311 General
The primary consideration in the layout of a petroleum handling facility is its
impact on the public and the environment. Assessment of this impact requires
knowledge of the process or operation and an understanding of laws and regulations
concerning fire protection designs, public safety, and environmental controls.
Economics is another consideration in the layout of facilities. The designer must
balance the incremental benefit resulting from greater spacing against the additional
cost.
Legal and safety spacing requirements in plant layout apply to alterations and additions as well as to new installations.

1312 Legal Requirements

Of primary importance in laying out an oil handling facility are the laws and regulations concerning fire protection design and public safety. Most communities, states
and countries have such requirements. They may establish limitations such as
minimum distances of structures from property lines and from the nearest side of a
public way. Legal requirements must be followed unless variances or other specific
approvals for deviation are obtained from the enforcing authority.

1313 Design for Local Conditions

New facilities and modifications should be designed to accommodate local conditions that may affect the safety of personnel and equipment. Where the historical
record indicates a reasonable probability of extreme conditions, the designer should
make appropriate provisions in laying out facilities. Extreme conditions include
hurricanes, tornadoes, violent hailstorms, heavy snow loads, severe and prolonged
freezing temperatures, airborne salt water spray, cooling tower fog, lightning
storms, floods, and exposure to earth slides, rock slides or earthquakes.

1314 Layout Objectives

Understanding the safety requirements for plant layout is important in planning new
installations and in making alterations and extensions to existing facilities. From
the standpoint of fire safety, general requirements for layout of an oil handling
facility are summarized as follows:

Separation from Adjacent Public Property

It is important to protect the public from exposure to spills, fires, explosions, heat,
smoke, odors, hazardous releases, or noise. Consider both present and possible
future activities on land adjacent to the plant site, and operations on any rights-ofway for highways, railroads, and pipelines that may traverse the property.

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Separation of Facilities
Protect Company personnel and equipment by separating independent elements,
such as process units, storage tanks, and control houses. This helps to prevent fire,
explosions, radiant heat, spills, etc. in one element from significantly affecting adjacent elements.

Protection of Critical Equipment

Critical equipment should be located and designed for maximum protection. For the
purposes of this section, critical equipment is defined as that equipment necessary
for safe, normal plant operation and control as well as equipment necessary for safe
shutdown during plant upsets, fires, and other emergencies. Critical equipment may
include instrument air supplies, process control systems, electrical power, substations, main process block valves, certain pumps and compressors, emergency shutdown (ESD) and depressuring systems, and fire water systems. The location and
protection of critical controls is discussed in Section 1700.

Separation of Hazardous Areas

Separate high-hazard plants from each other and from low-hazard plants. Highhazard units typically involve high pressure (greater than 500 psig), high temperature, and volatile processes with flammable materials and fast chemical reaction
rates. These units have a greater chance for a release, fire or explosion than lowhazard units (such as storage tank areas, power generating plants, and boilers).
Although low hazard units have a lower probability of incident, the consequences
can be much greater.

Protection for Utilities

Power-generating plants, boiler plants, and substations generally serve several
process plants. They should remain operable when one or more of the process
plants is in distress. It may be prudent to have greater spacing between boiler plants
and a high-pressure process plant than between two process plants.

Protection Against Flooding

Provide good drainage and protection against flooding of vital areas of the plant.

Meteorological Conditions
Consider general climatic, meteorological, and related conditions such as direction
of prevailing winds, maximum storm wind velocities, frequency of thunderstorms,
maximum and minimum temperatures, and the occurrence of earthquakes.

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1300 Layout and Spacing

Plant Equipment Access

Equipment access and layout is also critical to safe normal operation and emergency response. The Piping Manual includes three engineering forms illustrating
typical piping and equipment layouts.
PIM-EF-579

Process Plant Cross-Section Equipment and Pumps

on Same Side of Pipeway

PIM-EF-580

Process Plant Cross-Section Equipment Separated

from Pumps by Pipeway

PIM-EF-883

Process Plant Cross-Section Two-Sided Plant with

Air Coolers

Security
Plant location and degree of public access may indicate that plant borders and
entrances should be supervised and protected.

Evacuation
Evacuation routes should take into account the location of potential releases,
prevailing winds, drainage patterns, etc.

1315 Block Layout and Roads

A large plant composed of several major units should be laid out in a rectangular or
block pattern with adequate roadways giving access to major elements. Streets that
separate blocks are excellent fire breaks and facilitate movement and use of firefighting equipment.
For purposes of fire protection, economy of operations, and maintenance, main
access roadways are needed. Within operating areas, every unit and facility should
have roadways that allow for firefighting equipment.
During an emergency, it may be necessary to block certain roadways; therefore,
each unit should have two or more approaches. Block layout will generally provide
two-direction access.
On tank farms, roads should provide ready access to tanks. These roads may be
narrow, but they should be all-weather roads and have turnouts at convenient intervals.
Maintenance considerations should include access by large lift vehicles, if appropriate. Roadways and pipeway crossings should be able to handle expected weight
loads.

Restricted and Unrestricted Roads

As discussed in Section 2000, vehicles are ignition sources. To minimize the risk of
a vehicle igniting flammable material in a facility, any road within 25 feet of potential release sources of flammable or toxic material is designated as a restricted road.

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Restricted roads should not be used for routine plant travel of operations and maintenance vehicles.
Traffic on restricted roads can be closely controlled by installing barriers and signs
at the entrance to the facility, and by requiring procedures such as hot work permits
for vehicles that must enter the facilities. This usually requires that the operators
test for combustibles in the area prior to vehicular entry.
Unrestricted roads are those roads located more than 25 feet from release sources.
They do not require traffic control.

1316 Drainage
In process units, area drainage prevents spills from accumulating under vessels or
piping. Drainage design requirements are described in the Civil and Structural
Manual, Section 500, and in Section 1400 of this manual. Firefighting water
requirements are determined by the size of fire that could occur and the fire control
techniques and equipment likely to be used.

1320 Plant Spacing

1321 Spacing Tables
The spacing tables in Figures 1300-1 (sheets 1 and 2) and 1300-2 give minimum
spacing guidelines for the following:

Plant to plant
Plant to property line
Plant to equipment
Equipment to equipment

These guidelines have been developed through Company experience and industry
standards. Where special circumstances allow less spacing, the facility or project
team should document the rationale and mitigation efforts. Following are examples
for using the spacing tables.

Plant-to-Plant or Plant-to-Property Line Spacing

Note

Figures 1300-1 and 1300-2 are foldouts located at the end of this section.

Refer to Figure 1300-1, sheet 1 for your situation. Sheet 1 gives the codes to use on
sheet 2 to locate the minimum spacing.
Example: Spacing of control house to high pressure plant.
From Figure 1300-1, sheet 1, the code is B13. B on the diagonal and 13 on the horizontal gives you 50 feet accompanied by Note 16.

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1300 Layout and Spacing

Plant-to-Equipment or Equipment-to-Equipment Spacing

Refer to Figures 1300-1 (sheet 2) and 1300-2.
Choose one type of equipment on the diagonal and go down or across to the other
type of equipment.
Example: Spacing of motor control center to air cooler.
Locate motor control center on the diagonal (column 25). Drop down column 25 to
the row corresponding to air coolers (row 30). Where they intersect is the minimum
spacing numberin this case, 50 feet.

1322 Protection of the Public Through Spacing

Where practical, use offices, warehouses, and other low-risk buildings as buffers
between the process plants and the public. Greenbelts and planted areas are often
used to this end. These areas give the industrial facility a friendly, modern image
that can make them more acceptable to the public.
Protection of the public and the environment is a Company priority and this area is
becoming increasingly regulated.

1323 Plant-to-Plant Spacing

These are the major concerns in plant-to-plant spacing:

Personnel safety and operator access

Explosion damage prevention
Spill spread control
Vapor releases and vapor cloud travel
Fire and fire spread
Flood control
Maintenance access
Firefighter access
Radiant heat from fire
Economical construction

Spacing between process units is based on the estimated hazard of one or both facilities.
Once the overall risk is agreed upon, it is important to determine what effect a fire
or explosion would have on the surroundings. This effect is a function of the degree
of explosive violence possible in the process and/or the rate of flow, total volume,
volatility, temperature, and toxicity of the liquid or vapors that might be accidentally released. This determination should further help to establish the justified
spacing between units.
Close spacing of operating units permits shorter runs of transfer pipe, more centralization of plant control, and more compact electrical supply systems. Close spacing

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minimizes surge between plants and has other tangible economic benefits.
However, close spacing increases the likelihood of fire spreading between units,
increases the problems of major maintenance work, and may hamper firefighting
activities.
Each foot of separation costs money, and there is a point at which additional separation may increase the fire hazard, especially if control is highly automated and
centralized. Leaks may go undetected and operators may be restricted in their
visual observation of the unit.
In general, spacing between major process units should not be less than 75 feet
between equipment setback lines. Spacing greater than 200 feet, except for specialized operations such as emergency high capacity flare systems, provides little
decrease in risk and may actually increase the overall hazard.
It is acceptable for an overhead or grade-level pipe rack to cross a segregation space
transversely. A pipe rack may also be routed longitudinally along a segregation
space, provided that it does not occupy the full width. At least 20 feet (6 meters) of
the segregation space should be left clear of the pipe rack as a firebreak and to
permit fire fighting access.
The likelihood of future expansion of any major process unit should be considered
in the spacing layout. The minimum spacing between units should not be viewed as
a location for possible unit expansion.

1324 Plant-to-Offplot Facilities Spacing

Refer to Figure 1300-2 for offplot facility spacing.
A block layout of plants and roads conveniently separates process units from
nonprocess equipment such as cooling towers, storage tanks, utility plants, electrical substations, and fire water pumps. See Section 1315 for more considerations
on the layout of roads.
Firefighting facilities, critical instrumentation systems, and utility plants should be
able to operate in the worst-case plant failure. They are the last line of defense in
fire and accident control. Therefore, the plant layout should allow greater spacing
between these facilities and those that may be sources of toxic releases. See
Figure 1300-2.
Separators and holding ponds also require special attention to spacing. These are
electrically classified areas because they often contain oil.
In general, shops and warehouses can be placed closer to the process units than can
office buildings.

1325 Spacing of Unrelated Facilities

Nonprocessing facilities involved in packaging, shipping, and pipeline marketing
may be located near process plants. Examples of such facilities are pipeline pump
stations, marketing terminals, warehousing distribution, and marine terminals.

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These facilities should be treated as offplot facilities and spaced accordingly.

Consider the prevailing winds when siting tank truck loading racks and gas bottling
plants, to minimize vapor release travel into other plants or to ignition source
should a spill occur.
The vehicle traffic pattern should not interfere with vehicle traffic to the refinery or
process area parking lot. For example, tank truck loading-rack traffic is normally
heaviest in early morning, when employees begin to arrive at work. Heavy traffic
may interfere with fire equipment access.

1330 Process Equipment Spacing

1331 General Philosophy
Process flow generally dictates the layout of equipment within an operating unit.
The spacing between individual pieces of equipment is determined by requirements
for piping flexibility, access for operation and maintenance, and fire protection.
Equipment spacing for fire protection is calculated to provide:

Protection against flammable vapor reaching sources of ignition

Access for fire control
Protection of important equipment from fire

Keep fired equipment away from equipment and portions of the plant where a flammable vapor release might occur. Where possible, locate furnaces on the outside
edge of plants, upwind of other equipment.
General spacing recommendations are shown in Figure 1300-2.

1332 Pumps and Compressors

Mechanical equipment, such as pumps and compressors handling flammable fluids
and vapors, is the equipment most likely to be a source of accidental leakage to the
atmosphere. Locate this equipment at least 40 feet from sources of ignition, such as
furnaces, and far enough from other equipment to prevent a gland fire from overheating adjoining or overhead equipment.
In general, locate pumps alongside in-plant overhead pipeways, with the process
ends of flammable liquid pumps 5 feet outside the extremities of the overhead
pipeway.
Consider locating LPG and hot pumps on the outside edge of plants to improve
access, drainage, and fire water coverage.

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Pumps Handling Hydrocarbon Above its Auto-ignition Temperature

(or 600F):
Use the following guidelines:

Locate pumps at least 25 feet from furnaces; both are sources of ignition
should a pump leak occur.

Place pumps 5 feet apart

Pumps should be 10 feet from equipment handling other flammables so that a

packing gland fire or mechanical seal fire will not expose adjacent equipment.

Locate pumps along the outer edge of the plot limit, outboard of columns and
vessels, and with no equipment installed overhead. If it is necessary to locate
such pumps alongside in-plant overhead pipeways, the process ends should be
10 feet outside the extremities of the overhead pipeway. Where desirable to
further reduce risk of fire loss, a pump may be separated from its spare by
another pump or by increased spacing.

You should discuss any exceptions to these guidelines with the CRTC Fire &
Process Safety Team.

1333 Air-Cooled Heat Exchangers

It is preferable to locate air-cooled heat exchangers over areas where risks of
serious fires are minimal. Do not locate them near pumps or other mechanical
equipment.

1334 Process Piping

Process piping should be run above ground and preferably overhead. Do not install
new below-grade pipe trenches. Upgrade existing below grade pipeways that
contain flammable materials. Overhead pipeways provide excellent separation
between equipment and generally run through the center of an operating unit. They
also are less prone to external corrosion and can be inspected more easily. Do not
locate mechanical equipment under overhead pipeways.

1335 Other Equipment Spacing Concerns

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Spacing between furnaces and pumps, columns, vessels, etc. (see

Figure 1300-1).

Spacing between the control house and process equipment (See Figure 1300-1).

Spacing for access by operating personnel, maintenance personnel, and fire

fighting crews.

Hydrocarbon vent locations (Section 1900).

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Where vents and relief valves are piped to a closed system, locate the relief
line away from fire hazardous equipment. If it is located onplot, it should be
properly supported or have fireproofed supports.

Place instruments, instrument leads, and critical power cables out of the fire
hazard area. If this is not possible, protect them or place them underground as
discussed in Section 1700.

Spacing between process plant equipment and fire suppression equipment,

including portable extinguishers (Section 1652), wheeled dry chemical extinguishers (Section 1657), hydrants (Section 1624), and fire water monitors
(Section 1636).

1340 Specific Facilities

Spacing and layout guidelines specific to a certain type of facility are found in
Sections 3100 to 4100.
Spacing and layout guidelines related to tanks and tankfields are found in the Tank
Manual.

1350 Building Siting in Process Plants

Buildings and Control Rooms at facilities should be analyzed to determine if the
location and construction type are appropriate for potential hazards from the
process areas. Potential hazards include: fire, toxic release and Vapor Cloud Explosion (VCE). For new control rooms and buildings (at facilities handling flammable
or toxic materials), a hazard assessment should be done to insure that the design
requirements are sufficient to mitigate potential hazards. This could include blast
resistant design, protected ventilation systems, or gas detectors. The Process Risk
Team at CRTC can conduct the hazard assessment or provide guidance.
Existing buildings at a facility can also be reviewed to understand and manage the
associated risk from the hazards in the plant. API's "Recommended Practice 752 Management of Hazards Associated with Location of Process Plant Buildings"
provides a framework for conducting a Building Siting Assessment. Following this
practice will meet the requirement for OSHA's PSM Rule 1910.119(e) for facility
siting.
API RP 752 outlines a three-stage analysis process for identifying hazards and
managing risk to building occupants from fires, toxic releases, and explosions. The
staged approach systematically identifies and evaluates buildings in which occupants may be at risk.

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Stage 1 of the study will identify each building at the facility, verify potential
hazards, and screen out buildings based on occupancy levels and function
during an emergency.

During Stage 2, the buildings that met the previous screening criteria are evaluated with consequence modeling for vapor cloud explosion and toxic release

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hazards; and they are evaluated against current Company design standards for
fire hazards. If the team determines that a building(s) has a sufficient hazard,
then a Stage 3 is justified.

During the Stage 3, the study team identifies and analyzes the frequency of
potential scenarios either qualitatively or quantitatively. Recommendations are
then developed to mitigate the risks where appropriate. This is the final evaluation step in the API RP 752 facility siting assessment methodology. Specific
guidance and criteria for such a study are in CRTC's "Building Siting Assessment: Supplemental Guidelines for API RP 752", and is included in Appendix
H of this manual.

1360 References
American Petroleum Industry (API)
API 500

Classification of Locations for Electrical Installations in

Petroleum Facilities

API 2510

Design and Construction of LP Gas Installations at

Marine and Pipeline Terminals, Natural Gas Processing
Plants, Refineries, Petrochemical Plants and Tank Farms
(included in the Piping Manual)

API RP 752

Management of Hazards Associated with Location of

Process Plant Buildings

Chevron References
Civil and Structural Manual
Electrical Manual
Tank Manual

National Fire Protection (NFPA)

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NFPA 30

Flammable and Combustible Liquids Code (included in

this manual)

NFPA 50A

Gaseous Hydrogen Systems at Consumer Sites

NFPA 58

Storage and Handling of Liquefied Petroleum Gases

NFPA 59

Storage and Handling of Liquefied Petroleum Gases at

Utility Gas Plants

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Fig. 1300-1 Plant and Equipment Spacing (1 of 2)

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Fig. 1300-1 Plant and Equipment Spacing (2 of 2)

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Fig. 1300-2 Process Units to Offplot Facility Spacing

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