OISD-STD-118

Revision - II

FOR RESTRICTED
CIRCULATION

LAYOUTS
FOR

OIL AND GAS INSTALLATIONS

OISD – STANDARD – 118

Revision – II, September 2004

Oil Industry Safety Directorate

Government of India
Ministry of Petroleum & Natural Gas
 OISD-STD-118
Revision – II
September 2004

FOR RESTRICTED
CIRCULATION

LAYOUTS
FOR

OIL AND GAS INSTALLATIONS

Prepared by
Committee on
Layouts for Oil and Gas Installations

OIL INDUSTRY SAFETY DIRECTORATE

7TH FLOOR, NEW DELHI HOUSE
27, BARAKHAMBA ROAD
NEW DELHI – 110 001
 NOTE

OISD Publications are prepared for the use in the Oil and Gas Industry
under the Ministry of Petroleum & Natural Gas. These are the property of
Ministry of Petroleum & Natural Gas and shall not be reproduced or copied
or loaned or exhibited to others without written consent from OISD.

Though every effort has been made to assure the accuracy and reliability of
the data contained in these documents, OISD hereby expressly disclaims
any liability or responsibility for loss or damage resulting from their use.

These documents are intended to supplement rather than replace the

prevailing statutory requirements.

(ii)
 FOREWORD
Oil Industry in India is over 100 years old. As such variety of practices have been in vogue
because of collaboration / association with different foreign companies and governments.
Standardization in design philosophies and operating & maintenance practices at national
level was hardly in existence. This, coupled with feed back from some serious accidents that
occurred in the recent past in India and abroad, emphasised the need for the industry to
review the existing state-of-the-art in designing, operating and maintaining oil and gas
installations.

With this in view, Oil Industry Safety Directorate (OISD) was established in 1986 staffed
from within the industry in formulating and implementing a series of self regulatory measures
aimed at removing obsolescence, standardising and upgrading the existing standards to
ensure safer operations. Accordingly, OISD constituted number of functional committees
comprising experts nominated from the industry to draw up standards and guidelines on
various subjects.

The original document on "Layouts for Oil and Gas Installations" was published in
November 1988 and its first revision released in July 1995. In August 2000 it was amended
inline with the recommendations of the High Power Committee. The present document on
“Layouts for Oil and Gas Installation” is the second revision of this OISD Standard.

Attempts have been made to incorporate the latest technological changes, experience gained
after the implementation of standards and relevant updation in the various national and
international codes and practices.

It is hoped that the provision of this document, if implemented objectively, will go a long
way in improving the safety in oil and gas industry.

This document will be reviewed periodically for improvements based on the experience and
better understanding. Suggestions from industry members may be addressed to:

The Coordinator
Committee on Layouts for Oil and Gas Installation
Oil Industry Safety Directorate
7th Floor, New Delhi House
27, Barakhamba Road
New Delhi-110 001

(iii)
 COMMITTEES ON
LAYOUTS FOR OIL AND GAS INSTALLATIONS

First Edition – November 1988

Leader
Shri R P Bhatia Engineers India Limited, New Delhi
Members
Shri K K Arora Oil and Natural Gas Corporation Ltd., Bombay.
Shri S K Mukherjee Hindustan Petroleum Corporation Ltd.,(R) Bombay
Shri V K Raina Bharat Petroleum Corporation Ltd., (M), Bombay.
Shri K Ravi Kumar Madras Refineries Limited, Madras.
Member Coordinator
Shri B K Trehan Oil Industry Safety Directorate.

First Revision – July 1995

Leader
Shri R P Bhatia / Engineers India Limited, New Delhi
Shri M M Kapur
(Feb 95 – July 95)
Members
Shri S K Mukherjee Hindustan Petroleum Corporation Ltd.,(R) Bombay
Shri K K Arora Oil and Natural Gas Corporation Ltd., Bombay.
Shri V K Raina Bharat Petroleum Corporation Ltd., (M), Bombay.
Shri S Pandarinathan Madras Refineries Limited, Madras.
Member Coordinator
Shri B Sadhukhan / Oil Industry Safety Directorate.
Shri S N Mathur (April 95 – July95)

Amended Edition – August 2000

Amendments were carried out to this standard based on the recommendation of High Power
Committee set up in 1997 by the Ministry of Petroleum and Natural gas to review the
standard with respect to land requirement inline with national and international standards.

(iv)
 COMMITTEES ON
LAYOUTS FOR OIL AND GAS INSTALLATIONS

Second Revision – Month /Year

LEADER
Shri Vinay Kumar GAIL (India) Limited, New Delhi

MEMBERS
Shri Arvind Kumar, Engineers India Limited, New Delhi

Shri K.T.Lokhande, Department of Explosives, Nagpur

Shri H.S.P. Rao, BPCL, Mumbai Refinery, Mumbai

Shri Thomas Chacko, Kochi Refineries Limited, Kochi

Shri S.G.Palnitkar, HPCL Visakh Refinery, Visakhapatnam.

Shri D.K.Banerjee IOCL Pipelines Division, NOIDA

Shri M.D.Shah IOCL, Panipat Refinery, Panipat

Shri S.S.Maji, IOCL Refineries HQ, New Delhi

Shri Sunil Dewan, BPCL, NOIDA

Shri A.Buragohain, Oil India Limited, Duliajan

MEMBER-CO-ORDINATOR

S K Aggarwal Oil Industry Safety Directorate, New Delhi

In addition to the above, several other experts from the industry contributed in the
preparation, review and finalization of this document.

(v)
 INDEX

SECTION CONTENTS PAGE No.

1.0 Introduction

2.0 Scope

3.0 Definitions

4.0 Plant Layout Philosophy

5.0 Layout of Blocks/Facilities

6.0 Layout of Process Units

7.0 Layout of Storage Tanks

8.0 Layout of LPG Facilities

9.0 References

TABLES

T1. Separation distances between Blocks / Facilities

T2. Separation distances between equipment within Process unit

T3. Inter-distances between Storage Tanks and Offsite facilities

(Large installation)

T4. Separation distances between Storage Tanks and Offsite

facilities (Small Installations)

T5. Separation distances between Storage Tanks within a Dyke

T6. Separation distances for LPG Facilities

T7. Separation distances between LPG Storage Vessels and

Boundary / Property line / Group of Buildings not
associated with LPG facilities

(vi)
OISD-STD-118 1
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LAYOUTS FOR OIL AND GAS INSTALLATIONS

1.0 INTRODUCTION 3.0 DEFINITIONS
Hydrocarbon processing and handling a) Block
plants are inherently hazardous. Today's Facilities operated / used in integrated
trend of large and complex plants way and surrounded by roads. For
present substantial risk potential. At example process unit, boiler house,
times plants are modified to operate at group of tanks located in a dyke, group
higher capacities or efficiencies of pressurized storage tanks, loading
necessitating larger storage requirements gantries, flare etc.
than contemplated earlier. For these
reasons, initial site analysis for the C4 and Lighter ends
proposed new construction or addition Hydrocarbons or a mixture of
should be done carefully while Hydrocarbons containing four or less
considering the space allocation to the than four carbon atoms. Examples are
various facilities. Butane, Propane, Propylene etc. LPG, a
The hydrocarbon industry over the years mixture of propane and butane also fall
learnt lessons from fires and explosions under the same category.
throughout the world and has been up- c) Crude Oil Gathering Station:
dating plant safety norms including
inter-distances between facilities and Crude oil gathering station / Group
their relative locations. The minimum gathering station is a production
distances recommended many years ago installation used for gathering, treating
need review in the context of today's or storing crude oil and includes central
environment in the industry. tank farm, oil collecting station, gas
compressor station and well head
It is not intended that requirement of this installation.
standard should be applied rigidly to d) Facility
existing premises where, for a variety of
reasons, it may not be practicable to This refers to any building, structure,
comply with. installation, equipment, pipeline, or
other physical feature used in petroleum
refining, storage, transportation and
2.0 SCOPE distribution.
This document lays down minimum e) Fire station
requirements of layouts within the plant
boundary for petroleum refineries, Oil / A building housing facilities of parking
Gas production and processing plants, fire tenders and keeping other ready to
LPG facilities, Pipeline installations / use fire-fighting equipment for meeting
terminals, Lube oil installations and plant emergencies, fire control room
other Petroleum storage installations with required communication
such as Crude oil gathering stations, facilities/mimic panel.
Marketing depots and terminals, f) Fire Water pump house
Aviation storage & fuelling stations,
Tank farm for storage of crude / A building housing fire water pumps,
products. jockey pumps, communication and
alarm system, instrumentation and the
The requirement of green belt / buffer required operating & supporting
zone beyond the plant boundary is personnel.
outside the scope of this standard. Such
provisions should be considered based g) Flash Point
on local environmental / security "Flash point" of any petroleum liquid is
requirements. the lowest temperature at which the
liquid yields vapour in sufficient
concentration to form an ignitable
mixture with air and gives a momentary
"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 2
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flash on application of a small pilot
flame under specified conditions of test
as per IS: 1448 (Part-I).
h) Gas Processing Plant k) LPG Facilities

Gas processing plant is a facility where LPG facility is one where liquefied
natural gas is received and processed to petroleum gas (LPG) is stored,
separate gas, LPG, condensate etc. received / despatched by rail / road /
pipeline and / or filled in cylinders.
i) General Classification Of Petroleum
Products l) Lube Oil Installations
The facilities for receipt, storage and
Petroleum products are classified blending of base oils & additives into
according to their closed cup FLASH finished Lube products. It includes lube-
POINTS as given below: blending plants, grease manufacturing
plants.
— Class-A Petroleum: Liquids which
have flash point below 23oC. m) May
— Class-B Petroleum: Liquids which Indicates provisions that are optional.
have flash point of 23 oC and above
but below 65 oC. n) Oil / Gas Production Plant

— Class-C Petroleum: Liquids Oil / Gas production plant is a plant

which have flash point of 65 oC and where oil and/or gas is collected,
above but below 93 oC. stabilized and despatched for further
processing. Drilling activities and
— Excluded Petroleum: Liquids facilities upstream of the Christmas Tree
which have flash point of 93 oC and of a well are not covered under this
above. definition.
Liquefied gases including LPG do not o) Pipeline Installations
fall under this classification but form
separate category. Pipeline Installations are the facilities on
cross-country pipelines and include
Note: In the following cases, above sectionalizing valve station, pig
classification does not apply and special launching / receiving station,
precautions should be taken as required: intermediate pumping station /
compressor station, tap-off station,
(i) Where ambient temperatures or the dispatch and receiving facilities with or
handling temperatures are higher without storage.
than the flash point of the product.
p) Petroleum Refinery
(ii) Where product handled is artificially
heated to a temperature above its Petroleum Refinery is a plant where
flash point. crude oil is received and processed into
intermediates and finished products.
j) Hazardous Area
q) Process Unit
An area will be deemed to be hazardous
where; A unit having integrated sequence of
operation, physical and chemical, and
(i) Petroleum having flash point below may involve preparation, separation,
65 deg.C or any flammable gas or purification, or change in state, energy
vapor in a concentration capable of content or composition.
ignition is likely to be present.
r) Protection for exposure
(ii) Petroleum or any flammable liquid
having flash point above 65 deg.C is This refers to fire protection for
likely to be refined, blended or structures on property adjacent to liquid
stored at above its flash point. storage.
For classification and extent of s) Service building
hazardous area, refer "The Petroleum
Rules - 2002". A building housing facilities for
inspection / maintenance / other

"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 3
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supporting services which are directly d) Pedestrian pathways should be
required for operation of the plant e.g. provided / marked alongside the primary
warehouse, workshop etc. traffic roads.
e) Alternative access shall be provided for
each facility so that it can be approached
t) Shall for fire fighting in the event of blockage
Indicates provisions that are mandatory. on one route.
u) Should f) Road widths, gradient and
turning radii at road junctions
Indicates provisions that are shall be designed to facilitate
recommended but not mandatory. movement of the largest fire-
Implementation of these provisions shall fighting vehicle in the event of
be made based upon consideration of the emergency.
followings, as appropriate: (a) risk /
benefit analysis, (b) company standards, g) Rail spur shall be located close
(c) company experience, and (d) to the periphery of the plant to
company philosophy. minimise road/pipe crossings
and blockage of roads during
v) Stabling Line shunting.
It is an additional railway line / spur h) Layout of the facilities shall be
reserved for additional rake / stabling. made to minimise truck traffic
w) Storage / filling shed ingress in the plant.
Facility for storage and filling of packed i) Two road approaches from the
(non-bulk) petroleum product. highway / major road should be
provided, one for employees and
x) Tank height other for product / material
Tank height is the height from tank movement. Both these
bottom to top kerb angle for cone roof approaches should be available
tanks. For floating roof tanks, it is the for receipt of assistance in
height from tank bottom to top of tank emergency.
shell. j) Presence of ignition source shall
y) Tank vehicle loading / unloading always be contemplated beyond
the boundary wall of the
Facility for loading / unloading of installation.
petroleum product to / from tank wagon
or tank truck. k) Orientation of flares, furnaces &
heaters, dusty operations (e.g.
4.0 PLANT LAYOUT PHILOSOPHY sulphur handling etc) and
Following philosophy should be adopted cooling towers should be
in layout of an installation; decided based on prevailing
wind direction to avoid travel of
a) Block layout should be adopted as far as hydrocarbon vapour over
possible. Plant layout arrangement sources of ignition.
should follow the general route of raw
material to process unit(s) with tankages l) Erection methods shall be
interposed as required followed by studied for all types of
storage & despatch facilities. The entire equipment / structures. Towers,
area should be sub-divided into blocks. reactors, fired equipment etc
should be located in such an
b) All process units and dyked enclosures area so to facilitate erection.
of storage tanks shall be planned in
separate blocks with roads all around for m) Maintenance requirements for each type
access and safety. of equipment shall be identified and
considered.
c) Primary traffic roads in the installation
should be outside hazardous areas. n) For construction activities, area should
Roads separating the blocks shall act as be earmarked.
firebreaks.

"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 4
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o) Future expansion should be assessed and (b) Process unit(s), tank farm, loading
space provision be made accordingly. gantry, solid storage, utilities, Effluent
Treatment Plant (ETP) and approach
roads should be located on high ground
5.0. LAYOUT OF BLOCKS / to avoid flooding.
FACILITIES (c) In case process units are operated in an
To prepare a layout, information should integrated way and shutdowns are taken
be collected on the following aspects, as simultaneously, then it may be
applicable; considered as a single block.
- Process units, utility requirements, (d) Control room should be located in a
storage tanks, LPG storage vessels non-hazardous area upwind of process
and other pressurized storage vessels plants / hydrocarbon storage and
handling facilities. It shall not be located
- Product receipt / despatch and mode on a lower level than surrounding plants
of transport (rail, road and pipeline) and tank farms. There shall be no
- Warehouses, storage areas for solid structure that would fall on the control
products such as petroleum coke, room in case of a blast. For details, refer
petroleum wax, sulfur, bitumen / OISD-STD-163.
asphalt etc and other open storage (e) Utility block(s) should preferably be
areas like scrap yards and dumping located adjacent to unit blocks.
ground
(f) Power generation facilities which also
- Chemical / Toxic chemicals storage, supply steam for process requirement
hazardous waste storage / disposal. should be located near the process unit
- Flares block. When external power grid is
interconnected with plant power
- Service buildings, fire station and fire generation facilities, either the power
training ground plant should be located at the side of the
- Site topography including elevation, boundary wall or the external power
slope, and drainage transmission lines should be taken
underground upto interconnection grid.
- Meteorological data,
(g) Overhead power transmission lines shall
- Bathymetric data (high tide level, not pass over the installation including
surge wave height etc.) for the parking areas. Horizontal clearance
installations in coastal areas. shall be in line with the Indian
- Seismic data Electricity Rules.
- Highest flood level in the area, water (h) High Tension (HT) sub-station(s) should
table, natural streams/ canals be located close to major load centers.
- Approach roads to main plant areas (i) Low Tension (LT) sub-station should be
located at load centers in such a way that
- Aviation considerations the distance between distribution
- Risk to and from adjacent facilities transformer and farthest motor is
minimum.
- Environmental considerations
(j) Cooling Towers should be located
- Statutory obligations downwind of process equipment and
substation so that fog developed will not
cause corrosion or obstruct vision or
5.1 General consideration for the layout short-circuiting.
of blocks / facilities (k) Storage tanks should be grouped
While locating the various facilities / according to product classification. In
blocks, the following should be undulating areas, storage tanks should
considered: be located at lower elevations
(a) Layout of Blocks / facilities should be in (l) Truck loading / unloading facilities
sequential order of process flow. should be located close to product
movement gate and should be oriented
"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 5
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to provide one-way traffic pattern for located at minimum distance of 60
entrance and exit. meters from any hydrocarbon source.
Rail loading facilities should be located (t) Fire station, firewater storage &
along the periphery of the installation. firewater pump house shall be located at
a safe place away from hazardous areas.
(m) Sulphur recovery unit and sulphur Fire station should be upwind of process
loading area should be located close to units and hydrocarbon storage area with
product movement gate and away from straight approach to process units / other
process units, hazardous and populated critical areas.
areas.
(u) Location of firewater pumps &
Equipment drawing air (e.g. air tanks shall be inline with OISD-STD-
compressors, air blower, FD fan etc) 116, OISD-STD-117 & OISD-STD-144
should be located away from Sulfur as the case may be.
recovery unit / Sulfur handling facility.
Minimum separation distance of 50
meters is recommended between sulfur
storage / handling and any facility or
boundary wall. 5.2 Separation distances;

(n) Petroleum coke storage and handling Minimum separation distances between
facilities should be located as far as various blocks / facilities described
possible away from process units, air above shall be as per Table-1. The table
separation plants, populated and shall be read in conjunction with the
hazardous areas. notes specified with the table.

(o) Separate collection system should be 6.0 LAYOUT OF PROCESS UNITS

provided for different types of waste Equipment in process unit can be
generated in the process plant such as arranged in many ways. Safety,
oily water, caustic, acid effluents, fecal economy, operability, and ease of
etc. Effluent Treatment Plant should be maintenance should be considered in
located minimum one block away from locating each item within the unit.
process unit area, down wind of process Adequate spacing between equipment
units and important areas considering will help in minimizing the spread of
odour & emission of volatile organic fire. Consideration should be given to
compound. This should be closer to access for fire fighting.
disposal point by the side of the
boundary and at lower grade to facilitate
gravity flow of effluent. 6.1 General Considerations for the layout
(p) Flare should be located upwind of of Process Equipment
process units and the area around flare (a) Process flow sequence and operating
should be paved. For more details procedures should be thoroughly
OISD-STD-106 on "Process Design and understood so that equipment
Operating Philosophies on Relief and arrangement in the plot plan is
Disposal systems" shall be referred. functional. Equipment should be
(q) Main pipe racks / pipe track shall arranged in logistic process sequence for
not be routed through process units. optimum piping runs and operational
Provide overhead clearance for vehicles and maintenance ease. Spacing between
over roadways and railroads. equipment shall be adequate for
undertaking maintenance jobs.
(r) Roads should be provided in a
symmetric manner to serve all process (b) The unit pipe rack should be kept in the
areas requiring access for the operation, centre, thereby splitting the unit into two
maintenance and fire fighting. These or more areas of equipment. Pumps may
roads should encircle the process blocks/ be arranged in two rows close to and on
process units. either side of the pipe rack. Heat
Exchangers and vessels should be
(s) Smoking booths should not be grouped together forming outer rows on
provided in the hydrocarbon industry. both sides of the rack.
However if required, these shall be
"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 6
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(c) Heat exchangers should be located (k) The local control panel for soot blower
perpendicular to the pipe rack on the control and flue gas analyzer only
outer row to facilitate pulling of tube should be located on and near the
bundles with mobile crane or by other process heater. The rest of controls
means. Shell and tube heat exchanger should be taken to control room.
should have a longitudinal clearance of
at least one-meter plus the length of (l) Gas compressors should be located down
removable bundles. wind from heaters so that leaked gases
will not drift towards the heater. Gas
(d) Air fin coolers should be installed above compressors should have roofing and
the pipe rack / technological structures / open from sides to avoid accumulation
independent structure. Pumps handling of heavier vapours/gases on the floor of
hydrocarbons
o above the temperature of compressor house. Compressor house
230 C or C4 and Lighters should not be should be located near the battery limits
installed underneath the air fin coolers. to facilitate ease in maintenance and
operation. Drop out area should be
(e) Vessels having large liquid hold-up should provided for maintenance.
be installed at lower heights and
preferably at grade. Adequate drainage (m) No other tankage except day tanks /
should be provided around such vessels. process chemicals shall be provided
Where process requirement dictates their within battery limits of any process unit.
installation above grade, these should be
located in open area. (n) Process chemicals storage tanks should be
provided with kerb wall of minimum
(f) Towers / columns should be located along 300-mm height. Hydrocarbons day tanks
the pipe rack towards open areas for shall be provided with dyke in line
unobstructed erection as well as section 7.0 of this standard.
maintenance of internals at grade. Tall
towers requiring frequent operating (o) Cold boxes should be located on grade or
attention at upper levels may be located on separate elevated structures.
at one place so that common connecting Adequate space should be provided
platform can be provided. around cold boxes for ease of operation
and maintenance.
(g) Thermo-siphon reboilers should preferably
be placed close to their associated (p) Flare knock out drum for the process units
towers. should be located at battery limit of the
unit.
(h) Vessels, column, Reactors with internals
and / or containing catalysts, chemicals (q) Blow down facilities / buried drum should
etc should have a drop-out area for be located at one corner of the plant
removing / installing the internals and / farthest from furnace or any fired
or for loading / unloading of catalysts equipment and on the lee-ward side of
and chemicals. the unit.

(i) Heaters should be located up wind at one Vent from Blow down facility shall be
corner of the unit. Space should be minimum 6m above the highest
provided for removal and cleaning of equipment falling with in radius of 15 m
heater tubes besides approach for crane. from the vent stack.
Areas around the heaters shall be graded (r) Operators cabin may be provided in the
for guiding spills away from process process unit. The cabin should be
equipment. Forced Draft fans shall be located upwind side of the unit in non-
located away from process equipment hazardous area and away from draining /
from where they are likely to suck sampling facilities. The cabin should be
hydrocarbon vapors. for minimum occupancy of the shift
(j) No trenches or pits which might hold operators of the respective facilities
flammables should extend under the only.
furnace and connections with (s) Stairways should be provided for the main
underground drain system should be access.
sealed over an area 15 meters from the
furnace walls. (t) Minimum headroom under vessels, pipes,
cable racks, etc should be 2.1 meters.

"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 7
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(u) Equipment should be spaced to permit use (c) The height of tank enclosure dyke
of mobile equipment and power tools or (including free board) shall be at least
servicing and maintaining equipment 1.0 m and shall not be more than 2.0 m
during turn around periods. above average inside grade level. The
dyke wall made up of earth, concrete or
solid masonry shall be designed to
6.2 Equipment spacing with in process withstand the hydrostatic load. Earthen
units; dyke wall shall have not less than 0.6-
meter wide flat section on top for
Minimum separation distances between stability of the dyke wall.
various equipment within process units
are given in Table-2. The distances (d) For excluded petroleum, the capacity of
recommended should be followed to the the dyked enclosure should be based on
extent feasible. Equipment spacing spill containment and not for
within the process unit may be varied to containment on tank rupture. The
meet the requirements specified by minimum height of dyke wall in case of
Licensors or of the Engineering excluded petroleum shall be 600 mm.
Consultants. However, the distances (e) Separation distances between the nearest
specified in notes to Table-2 shall be tanks located in separate dykes shall not
met. be less than the diameter of the larger of
7.0 LAYOUT OF STORAGE TANKS the two tanks or 30 meters, whichever is
more.
7.1 General considerations
(f) Process equipment should not be located
7.1.1 Dyked Enclosures; inside the dyke. Pump stations and
(a) Petroleum storage tanks shall be located in piping manifold should be located
dyked enclosures with roads all around outside dyke areas by the side of roads.
the enclosure. Aggregate capacity of (g) Tanks located overhead shall meet
tanks located in one dyked enclosure safety distances and shall also have
shall not exceed following values: dyked enclosure of RCC construction
• 60,000 cum. for a group of fixed roof and provided with efficient drainage
tanks. system for the dyke enclosure.
• 120,000 cum. for a group of floating 7.1.2 Grouping;
roof tanks (a) Grouping of petroleum products for
Fixed cum floating roof tanks shall be storage shall be based on the product
treated as fixed roof tanks. However in classification. Class-A and / or Class-B
case these tanks are provided with petroleum may be stored in the same-
windows opening on the shell and these dyked enclosure. Class-C petroleum
windows will not get blocked in any should preferably be stored in separate
case, then these may be considered as enclosure. However, where Class-C
floating roof tanks. petroleum is stored in a common dyke
along with Class-A and/or Class-B
If a group of tanks contains both fixed petroleum, all safety stipulations
and floating roof tanks, then it shall be applicable for Class-A and/ or Class-B
treated as a group of fixed roof tanks for respectively shall apply.
the purpose of above limits.
(b) Excluded petroleum shall be stored in a
(b) Dyked enclosure shall be able to contain separate dyked enclosure and shall not
the complete contents of the largest tank be stored along with Class-A, Class-B or
in the dyke in case of any emergency. Class-C petroleum.
Enclosure capacity shall be calculated
after deducting the volume of tanks (c) Tanks shall be arranged in maximum
(other than the largest tank) and the tank two rows so that each tank is
pads within the dyke upto the height of approachable from the road surrounding
the enclosure. A free board of 200 mm the enclosure. This stipulation need not
above the calculated liquid level shall be be applied to tanks storing excluded
considered for fixing the height of the petroleum class.
dyke.

"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 8
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Tanks having 50,000 cum capacity and for Class-A and Class-B petroleum
above shall be laid in single row. products is more than 5000 cum or the
diameter of Class-A or Class-B product
7.1.3 Fire walls; tank is more than 9 meters.
(a) In a dyked enclosure where more than (b) For smaller installation, minimum
one tank is located, firewalls of separation distances shall be as specified
minimum height 600mm shall be in Table-5. This table is applicable
provided to prevent spills from one tank where total storage capacity of Class-A
endangering any other tank in the same & Class-B is less than 5000 cum and
enclosure. diameter of any tank storing Class-A
(b) A group of small tanks each not and Class-B petroleum product does not
exceeding 9 meters in diameter and exceed 9 meters. Table-5 shall also be
in all not exceeding 5,000 cum in applicable for the installation storing
capacity shall be treated as one tank only Class-C petroleum.
for the provision of firewall. (c) Excluded petroleum should be treated as
(c) For excluded petroleum product Class-C petroleum for the purpose of
storage, firewall of height not less than separation distances and Table – 5 shall
300 mm shall be provided by limiting be applicable for their separation
the number of tanks to 10 or the capacity distances.
of group of tanks to 5,000 cum 8.0 LAYOUT OF LPG FACILITIES
whichever is lower.
8.1 General Considerations:
7.1.4 General;
8.1.1 LPG Storage;
(a) The tank height shall not exceed one and
half times the diameter of the tank or 20 The requirements given below are
m whichever is less. For the installations applicable to above ground LPG storage
covered under Oil Mines Regulation, the facilities. For mounded LPG storage,
maximum height of the tank, dyke refer OISD-STD-150.
requirements etc. shall be as per Oil
Mines Regulations (a) Vessels shall be arranged into groups
each having a maximum of six vessels.
(b) Piping from / to any tank located in a Capacity of each group shall be limited
dyked enclosure should not pass through to 15000 cum. Each group shall be
any other dyked enclosure. Piping provided with a curb wall.
connected to tanks should run directly to
outside of dyke to the extent possible to (b) Any vessel in one group shall be
minimise piping within the enclosures. separated from a vessel in another group
by a minimum distance of 30 meters.
(c) The minimum distance between a tank
shell and the inside toe of the dyke wall (c) Spheres and bullets shall be treated as
shall not be less than half the height of separate groups with 30 meters
the tank. separation distance between two groups.

(d) There shall be access on all four sides of (d) Longitudinal axes of horizontal vessels
each dyke area and roads should be (Bullets) should not point towards other
linked to minimize the effect if one road vessels, vital process equipments and
is cut off during the fire. control room.
(e) Storage vessels should be located down
wind of process units, important
7.2 Separation Distances between tanks / buildings and facilities.
offsites facilities;
(f) LPG storage vessels shall not be located
The following stipulations shall apply within the same dykes where other
for the separation distances for above liquid hydrocarbons are stored.
ground tanks storing petroleum:
(g) Storage vessels shall be laid out in
(a) For larger installation, minimum single row both in case of the spheres
separation distances shall be as specified and bullets. Storage vessels shall not be
in Table- 3 and Table-4. The tables are stacked one above the other.
applicable where total storage capacity
"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 9
----------------------------------------------------------------------------------------------------------------------------
-----------
(h) Spillage collection shallow sump shall Full rake loading / unloading is shall be
be located at a distance where the flames done on two separate rail gantries
from sump fire will not impinge on the having a minimum distance of 50m.
vessel. This distance shall not be less
than the diameter of the nearest vessel or 8.2 Separation distances for LPG
15 meters whichever is higher. The facilities;
capacity of the collection sump shall be Minimum separation distances for above
as per OISD-STD–144. ground LPG facilities shall be as given
(i) Curb wall around the storage tank shall in Table-6 & Table-7. For other details
have a minimum height of 30cm. refer OISD-STD-144.
However it shall not exceed 60cm at For mounded LPG storage, refer OISD-
shallow sump position, as otherwise STD-150.
evaporation of spilled LPG may get
affected.
8.1.2 LPG bottling facility;
(a) LPG bottling facilities should be located
at a safe distance from other facilities
with minimum ingress to trucking traffic
and downwind to storage.
(b) There shall not be any deep ditches in
the surrounding area to avoid LPG
settling.
(c) Stacking areas for empty and filled
cylinders should be located separately.
Cylinders shall be stacked vertically.
Filling machines and testing facilities
shall be organized in sequential manner
distinctly in a separate area.
(d) Filled LPG cylinders shall not be stored
in the vicinity of cylinders containing
other gases or hazardous substances.
(e) Trucking traffic shall be smooth to avoid
blocking/ obstruction for loading and
unloading of cylinders.

8.1.3 Bulk handling facilities;

(a) LPG truck loading/unloading gantry
shall be located in a separate block and
shall not be grouped with other
petroleum products.
Maximum number of LPG tank truck
bays shall be restricted to 8 in one
group. The bay should be designed in
such a way that the driver's cabin will be
facing the exit direction and shall have
no obstruction.
(b) LPG rail loading/unloading gantry
shall be located on a separate rail spur
and shall not be grouped with other
petroleum products.
(c) Rail loading/unloading of LPG should
be restricted to a maximum of half rake.
"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
OISD-STD-118 10
----------------------------------------------------------------------------------------------------------------------------
-----------
9.0 REFERENCES:
1. The Petroleum
Rules - 2002.

2. The Static and

Mobile Pressure Vessels (Unfired) Rules,
1981

3. Oil Mines Safety

Regulations - 1984

4. OISD-STD-106
on Process Design and Operating
Philosophies on Relief and Disposal
System.

5. OISD-STD-116
on Fire protection Facilities for
Petroleum Refineries / Process Plants

6. OISD-STD –117
on Fire protection facilities for Petroleum
depots and terminals

7. OISD-STD- 144
on LPG bottling plant and layouts.

8. API Standard
2610–Design, construction, operation,
maintenance and inspection of Terminal
and Tank facilities.

9. API
Recommended Practices 2001– Fire
protection in Refineries.

10. Loss Prevention

in process Industries by Frank P Lees.

11. NFPA 30,

flammable and Combustible Liquid
Code.

"OISD hereby expressly disclaims any liability or responsibility for loss or damage
resulting from use of the OISD Standards/ Guidelines/ Recommended Practices."
 SEPARATION DISTANCES BETWEEN BLOCKS/FACILITIES TABLE – 1
Sr no From / To 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 Process Units
Note-1 Note-3 30 30 30 60 90 45 45 60 45 30 60 60 30 90

2 Process Control Room

(Note –2) Note-3 x Note-4 Note-5 30 60 90 45 45 30 Note-3 x 30 15 30 30

3 Storage Tanks Class-A

30 Note-4 Note-6 Note-6 Note-6 30 90 30 30 60 (90) 30 T3 60 30 50

4 Storage Tank Class-B

30 Note -5 Note-6 Note-6 Note-6 30 90 30 30 60 (90) 30 T3 30 30 50

5 Storage Tank Class-C

30 30 Note-6 Note-6 Note-6 30 90 30 30 60 (90) 30 T3 30 30 50

6 Pressurised Storage:
LPG/ C4 & Lighter / H2 60 60 30 30 30 T7 90 30 T6 90 (90) 30 T7 45 30 60

7 Flare
(Note-7) 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90

8 Bulk Loading POL

(Rail /Road) 45 45 30 30 30 30 90 Note-8 Note-9 60 30 Note-10 T3 60 30 50

9 Bulk Loading LPG

(Rail /Road) 45 45 30 30 30 T6 90 Note-9 T6 90 (90) T6 T6 60 30 50

10 Fire Station /
First Aid Center 60 30 60 60 60 90 90 60 90 x 30 30 12 12 30 90

11 Boiler house / Process

Unit Heaters (Note-11) 45 Note-3 (90) (90) (90) (90) 90 30 (90) 30 x 15 50 30 30 Note-
Rail Spur 12
12
30 x 30 30 30 30 90 Note-10 T6 30 15 x 30 6 15 50
13 Boundary wall around
installation 60 30 T3 T3 T3 T7 90 T3 T6 12 50 30 x 6 30 50

14 Service buildings
60 15 60 30 30 45 90 60 60 12 30 6 6 x 30 50
15 Cooling tower,
30 30 30 30 30 30 90 30 30 30 30 15 30 30 x 15
16 API Separators / Oil
sludge pit 90 30 50 50 50 60 90 50 50 90 Note-12 50 50 50 15 x

General Notes to Table-1 ;

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
a) All distances are in meters. “T” indicates the table number to be referred. “x” means any distance suitable for constructional or
operational convenience.
b) All distances shall be measured between the nearest points on the perimeter of each facility except (i) In case of tank vehicle loading /
unloading area where the distance shall be from the center of nearest bay. (ii) The distances given in the brackets ( ) are from the shell of
the Heater / Boiler / Furnace / Still.
Specific notes to Table-1:
Note-1: This shall be 36 meters considering the 6-meter wide road passing through the center. The edge of the road shall not be less than 15 meters away from the edge of
the unit.
Note-2: Type of construction shall be as per OISD-STD-163.
Note-3: Process control room to Process units / boiler house / heaters the minimum separation distance shall be 30 m. For a control room attached to single process unit
or a boiler or a heater, the minimum separation distance shall be 16 m. For Gas processing plants, it shall be minimum 30 meters irrespective of whether it is for
one or more units.
Note-4: Shall be 60 m for non-blast construction and 30 m for blast resistant construction.
Note-5: Shall be 45 m for non-blast construction and 30 m for blast resistant construction.
Note-6: Separation distances between the nearest tanks located in two dykes shall be equivalent to the diameter of the larger tank or 30 m, whichever is more. For
distances within a dyke, it shall be as per Table-3 and Table-4
Note-7 The distances specified are for the elevated flare. For ground flare, these distances shall be 150 m. For Exploration & Production installations, this shall be in
line with Oil Mines Regulations
Note-8 Separation distance between Tank truck gantry and wagon gantry shall be 50m.
Note-9 The separation distance shall be 50 m. However for LPG tank truck bulk loading to POL tank truck bulk loading it shall be 30 m.
Note-10 Separation distance between tank truck gantry and rail spur shall be 50 m.
Note-11: Boiler house or heater of a process unit is to be treated as a separate identity only for the consideration of surrounding blocks / facilities. However, heater of a
process unit remains an integral part of the process unit to which it is attached and in that case the inter equipment distances should be inline with Table –2.
Note-12: Centralized / common API separators, Corrugated Plate Interceptor (CPI), open oil separators shall be categorized under the same risk and shall be located at a
distance of 90 meters from heaters / boilers. However, if these are covered from the top and provided with adequate venting to safe location, the minimum
separation distance shall be 30 meter.
SEPARATION DISTANCES BETWEEN EQUIPMENT WITHIN PROCESS UNIT TABLE-2

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
 Sr no From / To
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 Fired Heater / Any fired x 15 15 15 22 15 15 20 15 15 15 x 18 6 30 15
equipment
2 Reactors 15 2 2 6 8 7 15 7 7 4 3 15 5 3 15 3
3 Distillation column 15 2 3 4 7 5 15 5 5 2 3 15 3 3 15 3
4 Accumulators – 15 6 4 2 8 5 15 4 4 2 3 15 3 3 15 3
Hydrocarbons
5 Compressors - 22 8 7 8 3 7 15 7 7 7 7 15 4 3 20 7
Hydrocarbons
6 Hot oil pump 15 7 5 5 7 1 7 1 1 2 2 15 3 x 15 x
7 Fuel Oil / HCs day tank 15 15 15 15 15 7 T-5 15 15 15 15 15 15 x 15 15
8 Pumps for class- A & all 20 7 5 4 7 1 15 1 1 2 2 15 3 x 15 x
above Auto-ignition temp
9 Pumps - for all other 15 7 5 4 7 1 15 1 1 2 2 15 3 x 15 x
Hydrocarbons
10 Heat Exchangers 15 4 2 2 7 2 15 2 2 2 2 15 2 2 15 x
11 Air fin coolers for 15 3 3 3 7 2 15 2 2 2 x 15 2 x 15 2
Hydrocarbons
12 Fired heater Local control x 15 15 15 15 15 15 15 15 15 15 x 10 x 15 5
panel
13 Pressure vessels / Drums of 18 5 3 3 4 3 15 3 3 2 2 10 2 3 15 2
Hydrocarbons
14 Main Pipe rack 6 3 3 3 3 x x x x 2 x x 3 x 15 x
15 Blow down facility – 30 15 15 15 20 15 15 15 15 15 15 15 15 15 x 15
Drum, pump, vent stack
16 Structural main – 15 3 3 3 7 x 15 x x x 2 5 2 x 15 x
Technological platforms

General notes to Table –2:

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
a) All distances are face-to-face clear minimum distances in meters.

b) “x” indicates suitable distance as per good engineering practices to meet construction, operational and maintenance requirements.

c) Distances specified in Table-2 are the minimum recommended distances that the industry should adhere. These could be suitably
modified as required to suit space constraints and relevant engineering practices except the followings.

(i) Blow down facility (open pit type) / oil catcher shall be located at a distance not less than 30 m from fired heater / any fired
equipment. If the blow down drum is located underground / oil catcher is cover with vent to safe location, the minimum
separation distance shall be 15m.

(ii) Fuel Oil day tank shall be located at a distance of not less than 15m from equipment except those facilities such as heat
exchanger, pump connected directly with the Fuel Oil system.

d) Firewater hydrant / monitors shall be minimum 15 m away from the equipment that is to be protected.

e) Water spray deluge valve shall be minimum 15 m from equipment handling hydrocarbon.

f) Fuel gas knock out drum shall be located at a minimum separation distance of 15 m from the heater.

g) Separation distances specified in other OISD standards or elsewhere in this standard (other than Table –2) shall be followed as
recommended.

SEPARATION DISTANCES BETWEEN TANK / OFFSITE FACILITIES - (For large installations) TABLE - 3

Tanks / Facility 1 2 3 4 5 6 7 8 9
"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
1 Storage Tank for Petroleum Class A / T4 T4 15 15 15 15 8 15 0.5 D
Class B.
Min 20 m
2 Storage Tank for Petroleum Class C T4 x 15 x 8 x x x 0.5 D
Min 20 m
3 Storage / Filling Shed for petroleum 15 15 x 8 15 15 8 15 15
Class A or class B
4 Storage / Filling Shed for Petroleum 15 x 8 x 8 x x x 10
Class C
5 Tank vehicle loading / Unloading for 15 15 15 8 x x 8 15 20
petroleum class A or class B
6 Tank Vehicle loading / unloading for 15 x 15 x x x x x 10
Class C
7 Flame proof Electric Motor 8 x 8 x 8 x x 8 x

8 Non flame proof electric Motor 15 x 15 x 15 x 8 x x

9 Boundary wall 0.5 D 0.5 D 15 10 20 10 x x x

Min 20 m Min 20 m

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
 SEPARATION DISTANCES BETWEEN STORAGE TANKS WITHIN A DYKE TABLE– 4

Item Between floating Roof Tanks Between fixed Roof Tanks Class A Between Class C Petroleum Storage
Class A & B &B tanks
1 All tanks with Diameter upto 50 meters (D+d) / 4 (D+d) / 4 (D+d) / 6
Min 10 m Min 10 m Min 6 m
2 Tanks with Diameter exceeding 50 meters. (D+d) / 4 (D+d) / 3 (D+d) / 4

General notes to Table – 3 & 4

a) All distances are in meters.
b) “x” indicates suitable distance as per good engineering practices to meet construction, operational and maintenance requirements
c) D & d stands for diameter of larger and smaller tanks.
d) In Table – 3 all distances shall be measured between the nearest points on the perimeter of each facility except in the case of tank
vehicle loading/unloading area where the distance shall be measured from the center of each bay.

e) In Table –4, Distances given are shell to shell in the same dyke.

f)For different combination of storage tanks, the stringent of the applicable formulae shall be considered for minimum separation
distance.

g) The distance of storage tanks from boundary wall is applicable for;

(i) Floating roof tanks having protection for exposure

(ii) Tanks with weak roof-to-shell joint having approved foam or inerting system and the tank diameter not exceeding 50 meters

h) For the facilities not covered in Table- 3, refer Table-1.

SEPARATION DISTANCES BETWEEN TANKS/OFFSITE FACILITIES - (For small installations) TABLE – 5
"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
 1 2 3 4 5 6 7 8 9 10 11 12 13
0.5D /
1 Storage Tank Class A 0.5D 0.5D 9 9 9 15 15 15 3 15 15 15
6.0
0.5D 0.5D / D D
2 Storage Tank Class B 0.5D 9 0.5D 0.5D 9 4.5 4.5 3 4.5
6.0 Min 4.5 Min 4.5
0.5D / 0.5D / 0.5D 0.5D
3 Storage Tank Class C x 9 0.5D x 9 4.5 x x x
6.0 6.0 Min 3.0 Min 3.0
Storage / Filling shed for
4 9 9 9 x 4.5 6 9 9 9 3 9 9 9
petroleum Class -A
Storage / Filling shed for
5 9 0.5D 0.5D 4.5 x 1.5 9 4.5 4.5 1.5 4.5 4.5 4.5
petroleum Class -B
Storage / Filling shed for
6 9 0.5D x 6 1.5 x 9 4.5 x x x 3 3
petroleum Class -C
Tank vehicle Loading /
7 15 9 9 9 9 9 x 9 9 3 9 9 9
unloading Class - A
Tank vehicle Loading /
8 15 4.5 4.5 9 4.5 4.5 9 x 4.5 1.5 4.5 4.5 4.5
unloading Class - B
Tank vehicle Loading /
9 15 4.5 x 9 4.5 x 9 4.5 x x x 3 3
unloading Class - C
Flame proof Electric
10 3 3 x 3 1.5 x 3 1.5 x x 3 x x
motors
Non Flame proof Electric
11 15 4.5 x 9 4.5 x 9 4.5 x 3 x x x
motors
Office building, stores, D 0.5 D
12 15 9 4.5 3 9 4.5 3 x x x x
amenities Min 4.5 Min 3.0
D 0.5D
13 Boundary wall 15 9 4.5 3 9 4.5 3 x x x x
Min 4.5 Min 3.0

General notes to Table –5:

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
a) All distances are in meter and the table specifies the minimum requirement.

b) “x” indicates suitable distance as per good engineering practices to meet construction, operational and maintenance requirements

c) “D” indicates the diameter of the larger tank.

d) Distances given for the tanks are shell to shell in the same dyke.

e) Where alternate distances are specified (like 0.5 D / 6.0), the minimum thereof shall be used.

f) All distances shall be measured between the nearest points on the perimeter of each facility except in case of tank vehicle loading
/unloading area where the distance shall be from the center of each bay.

g) Pig launcher/receiver at liquid hydrocarbon handling pipeline installations should be located at least 5 m from boundary.

SEPARATION DISTANCES FOR LPG FACILITIES TABLE - 6

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
 Sr no. FROM / TO 1 2 3 4 5 6 7 8

1 LPG Storage vessels Note-1 T7 30 30 50 30 15 60

2 Boundary wall / group of buildings not T7 x 30 30 50 30 30 x

associated with LPG plant
3 Shed for filling and storage of LPG, Cold 30 30 15 30 50 30 15 60
repair shed, Cylinder evacuation facilities
4 Tank Truck Loading / unloading gantry 30 30 30 30 50 50 30 60

5 Tank wagon gantry 50 50 50 50 50 50 30 60

6 Rail spur 30 30 30 50 50 50 30 60

7 Pump house / Compressor house (LPG) 15 30 15 30 30 30 x 60

8 Fire Water pump house 60 x 60 60 60 60 60 x

TABLE– 7

SEPARATION DISTANCES BETWEEN LPG STORAGE VESSELS AND BOUNDARY WALL / GROUP OF BUILDINGS NOT
ASSOCIATED WITH LPG FACILITIES
"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."
 Capacity of Each vessel in Cum of water
10 - 20 21 - 40 41 - 350 351 - 450 451-750 751 - 3800
Distance in meters
15 20 30 40 60 90

General Notes to Table-6 & Table-7;

a) Table-6 is applicable for total storage of above 100 Tonnes.

b) All distances are in meters

c) “x “indicates suitable distance as per good engineering practices to meet construction, operational and maintenance requirements

d) T7 indicates Table –7;

e) Distance of stabling line shall be as per Railway Standards.

Specific Notes to Table- 6;

Note–1: The distance shall be 2 meters or 1/4 of the sum of the diameters of the adjacent vessels or half the diameter of the larger of the
two adjacent vessels in the same group whichever is greater.

"OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from use of the OISD Standards/
Guidelines/ Recommended Practices."