Defining Offsite Facilities for Process Plants

Contributors (In alphabetical order):
Jadeep Coudhary, Anita R. LegvoldJames O. Pennock


Some have asked questions such as: "What is Balance of Plant?"; "What is Offsites?" What is OSBL?" and "What needs to be considered when a project includes Offsites." 
The term Offsites is a general term and does not mean the same for every project or every plant. A project may include extensive tankage for feed storage along with tankage for in-process product, intermediate product, run-down tankage, slops and finished product tankage. Another project may include none of this because they already exist. The point here is just because you are told that the project includes "Offsites" you need to ask a lot of questions to determine exactly what they mean and what will be required.
The purpose of this document is to aid in answering this type of question. This document will not tell you how to design the Offsites or design any of the individual sub-items or equipment found on this list. That design guidance should properly be left up to you, your supervisors and your management. I do however intend to start a listing of major elements along with some minor key issues that should be considered. 
I invite others to submit their own thoughts and comments to add to and improve this list.


Section Subject

1 Definitions -- Offsite vs. Onsite 
2 Codes, Standards, and Practices 
3 Site Issues 
4 Terrain, Grading, Roads, & Drainage 
5 Tankage 
6 Flares 
7 Piperacks & Sleepers 
8 Pipelines 
9 Loading / Unloading Racks (Truck, Rail, Barge, and Ship) 
10 Cooling Water Supply Systems 
11 Hazardous Chemicals 
12 Waste Treatment Facilities 
13 Electrical 
14 Buildings & Auxiliaries 
15 Fire Protection & Safety 
16 LPG Bottling Facilities
17 Solids Storage & Disposal

1, Definitions

Offsite -- In a process plant (Refinery, Chemical, Petrochemical, Power, etc.), any supporting facility that is not a direct part of the primary or secondary process reaction train or utility block. Offsites are also called OSBL.

Onsite - Any single or collection of inter-related and inter-connected process equipment that performs an integrated process function. Typically any Onsite Unit could be made to function independently of another Onsite Unit. Onsite Units are also called ISBL.

Utility Block - A single or multiple grouping of facilities that generate the support services required by the Onsite Process units to function. This normally includes: Steam Generation, Plant Air, Instrument Air, Decimalized Water, Plant Water, etc.

Balance of Plant - This is another term for Offsites and/or anything else other than the Onsite Units or the Utility Block.

Battery Limit -- Line used on a plot plan to determine the outside limit of a unit. The Battery Limit line is usually established early in the project and documented on all discipline documents such as Plot Plans, Site Plans, Drawing Indexes, etc... (1)

Property Line -- A Property Line is the recorded boundary of a plot of land. (2) Defines the separation between what is recognized legally as Owner's land and non-Owner's or other land.

On Property -- All land and or water inside the Property line shown on the property map or deed.

Off Property - Off property is any land (or water) outside of the Property line shown on the property map or deed.

Right of Way (ROW) -- Any land (On Property or Off Property) set aside and designated for a specific use or purpose. A Right-of-Way within a piece of property may also be designated for use by someone other than the property owner.

Setback or Setback Line -- A line established by law, deed restriction, or custom, fixing the minimum distance from the property line of the exterior face of buildings, walls and any other construction form; s street, road, or highway right-of-way line (3). Setback is a clear area normally at the boundary of a piece of property with conditions and restrictions for building or use.

Easements -- A vested or acquired right to use land other than as a tenant, for a specific purpose; such right being held by someone other than the owner who holds the title to the land (2). An easement is typically a strip of land within which overhead power lines or underground pipes are run.

(1) -- Lamit, Louis Gary, 1981 Prentice-Hall
(2) -- Construction Dictionary

2, Codes, Standards, & Practices

ANSI (American National Standards Institute)
API (American Petroleum Institute) 
ASME (American Society of Mechanical Engineers) 
ASTM - American Society of Testing Materials
AWS (American Welding Society)-- 
AWWA (American Water Works Association)
CFR (Code of Federal Regulations)
Division of Weights & Measures -- 
DOT (Department of Transportation)
FAR (Federal Accounting Regulations) 
IRI (Insurance Regulators Institute) 
Local Permits (Country, State, City, etc.)
MSS (Manufacturing Standards Society) -- 
NACE (National Association of Corrosion Engineers)-- 
NFPA (National Fire Protection Association) 
OIA (Oil Insurers Association) 
PFI (Pipe Fabrication Institute) 
USCG (United States Coast Guard) Regulations

3, Site Issues 

Brownfield (Revamp Existing)
Climate (Wind Rose)
Feed stock type, source and method of delivery
Future growth
Grass Roots or Greenfield (New construction)
Impact across the fence
Power requirements and source
Products, Primary, Secondary and by-products
Seismic zone
SHE (Safety, Health and Environmental) 
Utilities requirements

4, Terrain, Grading, Roads, Ditches & Drainage

- Level vs. Sloping

Geotechnical influences
- Type of soil
- Angle of repose
- Grading
- Contours
- Grubbing (Tree and shrub removal)
- Rough Grading
- Finished Grading

- Primary
- Secondary
- Type and purpose of traffic
- Right hand or left hand drive
- Traffic pattern, potential for congestion
- Pipeway or Sleeper Crossings (Overhead Vs Ramp & Culvert)

Rail Spurs (see Loading and Unloading for additional criteria)
- Number
- Location
- Capacity (number of rail cars)
- Elevation
- Roadbed & Ballast Details
- Vertical and Horizontal Clearance requirements
- Standards and jurisdiction of Rail company (Right of Way)

Drainage systems
- Storm
- Oily Water
- Chemical
- Sanitary Sewage
- Contaminated
- Other

- Depth
- Width
- Slope

- Location, Size, Type
- Invert Elevation

Basins & Ponds
- In ground or On ground
- Lined vs. Unlined (or Rip Rap)
- Skimmers & Aerators
- Overflows & Runoff
- Fenced or Unfenced
- Access

Stiles, Stairs, Catwalks, and Platforms
- Existing or new
- Material if existing
- Material if new
- Location & Elevation
- Access
- Valve extension stem requirements

5, Tankage

Types & Purpose
- Atmospheric vs. Pressurized
- Cone Roof
- Floating Roof
- Bullets
- Spheres
- Spheroids
- Other (Used tank cars as storage)

Tank Construction
- Single Wall vs. Double Wall
- Metallic vs. nonmetallic
- Unlined vs. Lined
- Insulated, Jacketed, Heated, Cooled,

Commodity Grouping & Spacing Criteria
- Commodity (Compatible vs. non compatible)
- Single Tank
- Multiple Tank Group -- Same Size
- Multiple Tank Group -- Different Sizes

Spill Containment
- Containment Criteria
- Earthen Berm (Dike)
- Wall (Concrete)
- Topography
- Combination

Tank Supports and Foundations
- Foundation Types
- Foundation Details
- Sloping Bottoms
- Settlement

Tank Auxiliary Equipment
- Heaters & Coolers
- Internal Coil Type
- Internal Bayonet Type
- External Type
- Mixers
- Motor Driven Mechanical Types
- Jet Types
- Support requirements
- Removal methods and clearance

Fire or ignition suppression
- Snuffing steam to V/PRV (Vacuum & Pressure Relief Valve) Tail Pipes
- Water Spray Systems (Deluge Systems)

Tank Nozzles & Appurtenance
- Primary Inlet & Outlet Connections (Single vs. Multiple)
- Vent Connections (Closed, Open, Flame Arresters)
- Drain Connections (Closed, Winterized, Non-winterized)
- Instrument Connections (Flow, Level, Pressure, and Temperature)
- -- Level Controller & Gage
- -- Float & Target Board
- -- Automatic (Tape Type) Tank Gage
- -- Gage Hatch
- -- Pressure Taps
- -- Thermowells
- -- Radar type Level Instruments
- -- Sonar
- Heating Coil Connections (Inlet/Outlet)
- Mixer Mounting Nozzles 
- Manholes
- Internal Nozzles
- -- Internal Piping
- -- Swing Lines (Winch, Clearance, Accessibility)
- -- Internal Pipe Supports
- -- Internal Floating Roof Supports
- Orientation & Elevation
- Size & Rating
- Projection
- Recommendations
- -- Avoid weld seams

Ladders, Stairs, and Platforms
- Orientation
- Primary access - entrance and exit
- Roof traffic Vs Formal Platform
- Safety - Tank Edge Handrail

- Types
- Location
- Sumps
- Piping Elements

Product Piping
- Differential Settlement
- Location of First Support
- Natural Anchors (Dike Sleeves)
- Slops Collection System

Hot Oil Systems
- Asphalt Tankage & Distribution

Utilities Piping
- Condensate
- Instrument Air
- Nitrogen
- Plant Water
- Plant Air
- Potable Water
- Steam
- Glycol
- Ammonia
- Cooling Water
- Chilled Water
- Tracing Fluids (Low Temp. or High Temp.)

Dike Penetrations (Piping)
- Sleeves (U/G Protection & Grounding)
- Double Containment
- Casings

Operations Issues
- "Roll Over"
- "Boil Over"

Maintenance Issues
- Access (Mobile Equipment)
- Cleaning and Repair
- Housekeeping Pads (Spillage control)
- Utility Station Location & Access
- CIP (Clean in place)
- Wash Stations & Spray Wands

6, Flare, Incinerator, and Thermal Oxidizer

- Location Criteria
- Prevailing Wind (Wind Rose)
- Flare Header
- System Study

Flare KO Drums 
- Horizontal
- Vertical/Stack base integrated 
- Support
- Pump out

Flare Number and Types
- Number of Flare Stacks
- Ground Flare
- Elevated -- Free Standing
- Elevated -- Derrick Supported 
- Elevated -- Cable Guided

Flare Accessories
- Flame Arrester

Flare Stack Utilities
- Fuel Gas
- Pilot Gas
- Igniter Line
- Atomizing Steam
- Flame Arrester Drain

- Location Criteria
- Prevailing Wind (Wind Rose)
- Collection System

Incinerator Utilities
- Fuel Gas
- Pilot Gas
- Igniter Line
- Atomizing Steam

Thermal Oxidizers
- Location Criteria
- Prevailing Wind (Wind Rose)
- Collection System

Thermal Oxidizer Utilities
- Fuel Gas
- Pilot Gas
- Igniter Line
- Atomizing Steam

7, Piperacks and Sleepers

Support Types
- Elevated (Overhead) Racks
- Sleeper Racks
- Bridges

Materials of construction
- Steel
- Concrete
- Combination

Overhead Racks
- Height 
- Number of levels
- Current Space Requirements
- Future Space Requirements
- Operating Temperature induced expansion
- Solar induced expansion
- Maximum Spans
- Minimum Line Sizes
- Piping Loops
- Shoes, Anchors, & Guides

Pipe Sleepers
- Height
- Changes in Direction (Flat Turn vs. Elevated)
- Current Space Requirements
- Future Space Requirements
- Operating Temperature induced expansion
- Solar induced expansion
- Maximum Spans
- Minimum Line Sizes
- Piping Loops
- Shoes, Anchors, & Guides

Pipe Bridges
- Number
- Location
- Height
- Span

Auxiliary Piping Services & Systems
- Utility Systems
- Steam Tracing
- Jacketed Piping
- Internal Cleaning requirements for piping systems 
- Future (space allowance)

Miscellaneous Piping Details
- Process Vents & Drains
- Hydrotest Vents & Drains
- Size, location, and access
- Cleaning connections (Maintenance)
- Slip Lining

8, Pipelines

Types and Purpose
- Cross Country
- Inter Plant
- Intra Plant

Accounting Meters
- Meter Provers 
- "Bonded Zone"
- Fencing and Security

Pig Launchers & Pig Catchers (Receivers)
- Package System
- Vendor or Third Party Sub contracted
- Stick build

Pipe Line Pigging Criteria
- Minimum bend radius

Slug Catchers
- Types

Special Valving Considerations 
- Types
- Support

Special Instrumentation 
- Pig Signals (Pig Sig)

9, Loading / Unloading Racks (Truck, Rail, Barge, and Ship)

Product Data
- Liquid Products
- Gas Products
- Dry Products
- Non-flammable Liquid Chemical Products
- Flammable Liquid Hydrocarbon Products
- Liquefied Petroleum Gas (LPG) Products

Shipping method
- Truck
- Rail
- Barge
- Ship

Loading & Unloading Method 
- Loading Arms or Loading Hoses
- Top Loading 
- Bottom Loading (Truck & Rail only)
- Vapor recovery criteria

Shipping Plan
- Number of shipments
- Frequency of shipments
- Loading time
- Unloading time

Loading Rack Size & Location Criteria
- NFPA Criteria
- Size of Carrier (Truck, Rail Car, Barge/Ship)
- Minimum distance between loading "Spots"
- Outline of structure
- Loading Arm Type
- Loading Arm reach
- Loading Arm rest position
- Height and reach of swing-down platforms
- Access & clearance for Operators
- Stair and Ladder access and egress

Barge & Ship only
- Fixed or Floating Dock
- Tide & Current Data
- Maximum "Swing" envelope (Vessel empty at high tide vs. vessel full at low tide)

- Meters
- Grounding Lugs
- Spill containment
- Shelters
- Piping

Utility Requirements
- Utility Steam
- Plant Water
- Plant Air
- Breathing Air
- Nitrogen (for blanketing)

Safety & Fire Protection
- Monitors
- Hydrants
- Deluge Systems
- Fire Blankets
- Fire Extinguishers
- ESD (Emergency Shut Down) System
- Foam Systems

10, Cooling Water Supply Systems

- Once through system
- Closed loop Cooling Tower system
- Atmospheric (Flooded) System

Water Source
- Municipal Water Supply (City, County, etc.)
- River Intake
- Ocean Intake
- Lake
- Wells
- Surge Pond

Water Intake & Outfall Structures
- River
- Oceans & Bays

Tower Types
- Forced Draft
- Induced Draft
- Natural Draft

Prevailing Wind 
- Direction (primary and secondary)
- Timing (Spring, Summer, Fall, and Winter?)
- Force
- Duration

Basin Design
- In-ground
- Under-ground
- Strainers and Filters
- Fixed Screens
- Rotating Screens

Pump Types & Location
- Vertical 
- Horizontal (same level next to basin)
- Horizontal (elevated above basin)

- Stand alone
- Manned

- Portable crane
- Built-in lifting facilities

Cooling Water Supply and Return Piping
- Material
- Location (Above ground or below ground)

Water Treatment Chemical piping 
- Stainless Steel
- Alloys

Cathotic Protection
- Type
- Pipe Riser Location
- Insulating Flange Sets

11, Hazardous Chemicals Handling and Storage

Commodities List

MSDS (Material Safety Data Sheet)

Unloading Facilities




- Safety Shower/Eye Wash

Winterized (Tempered water system)

12, Waste Treatment Facilities

- Storm Water
- Oily Water
- Chemical
- Sanitary
- Contaminated

Collection Locations

Collection and transfer methods
- Gravity (only) to Treatment
- Gravity to Sump & Pump to Treatment

Types of Treatment

13, Electrical & Instrumentation

Equipment Types
- Instrument Rack/Cabinets
- Junction Boxes
- Load Centers
- Substations
- Switch and Starter Racks
- Transformers

Aboveground Distribution
- Cable Trays
- Conduit Racks
- Light Standards
- Power Poles
- Push Button Stations
- Telephone Poles
- Transmission Towers

Underground Distribution
- Direct Bury Cable
- Duct Banks (Concrete encasement)
- Electrical Manholes
- Electrical Pull Boxes

Clearance criteria Electrical to:
- Process Equipment
- Piping
- Structures
- Pipe Racks
- Roads
- Rail Facilities

14, Buildings & Auxiliaries

Buildings and purpose
- Administration - 
- Cafeteria -- 
- Change House (Locker Room) -- 
- Chemical Storage -- 
- Control (House) Center -- 
- Fire House -- 
- First Aid -- 
- Gate or Guard Houses -- 
- House of Worship (Mosque) -- 
- Laboratory (Product QC) -- 
- Machine Shop -- 
- Maintenance -- 
- Safety Center & Training -- 
- Warehouse --

- Parking Lots
- Truck Loading/Unloading Docks

Utility Services 
- Chemical Waste -- 
- Chilled Water -- 
- Comfort Steam & Condensate -- 
- Contaminated Waste
- Hot & Cold Water
- Lab Gas -- 
- Potable Water -- 
- Sanitary Waste -- 
- Storm Water -- 

Piping Materials

15, Fire Protection & Safety

Fire Protection & Safety Plan
- Basic Safety Plan
- Contingency Plan

Fire Water System
- Fire Water Source
- Fire Water Storage
- Fire Water Pumps
- Fire Water Loop (Mains and Laterals)
- Fire Hydrants and Monitors
- Foam Chambers (Number and Orientation)
- Foam Stations (Number and Orientation)
- Fire Protection Manifolds (Pumper Connections)
- Fire Hose Carts

Materials of Construction
- Carbon Steel w/ external coating
- Carbon Steel w/ Internal Lining & external coating
- Ductile Iron
- FRP Piping
- Cement Lining
- Nonmetallic Linings
- Thrust Blocks & Anchors

Fire Training Area
- Location 
- Facilities

Fire Equipment

16, Product packaging

LPG Bottling Facility
- Type, 
- Open, sheltered, enclosed
- Empty bottle receiving
- Filling
- Full bottle storage
- Bottle shipping
- Truck scales (weighbridge)

Lube Oil packaging facility
- Type
- Sheltered
- Enclosed
- Size

Shipping method
- Truck
- Rail

17, Solids Storage & Disposal

- Sulphur
- Coke
- Treated waste

- Dry
- Semi-dry

- Open
- Sheltered


- On property
- Off property

Shipping method
- Truck
- Rail
- Barge
- Other


About the Author

jaydeep chaudhary

{cb:Jaydeep R. Chaudhary is a piping designer with 4+ years of experience with oil & gas projects working with Hyundai Heavy Industries, Seoul South Korea.}

About the Author


{cb:Anita R. Legvold is a Piping Design Engineer with more than 35 years experience covering process plant engineering, design, and field activities. She is now semi-retired and lives in Florida, USA.}

About the Author


{cb:James O. Pennock has more than forty-five years in the process plant design profession. He has been involved in both home office and job site assignments on refinery, chemical, petrochemical, power and other projects. His experience ranges from entry level designer to engineering manager. Much of this was with Fluor. He is also the author of the book "Piping Engineering Leadership for Process Plant Projects." He is now retired, living in Florida, USA and does only occasional consulting work.

Mr. Pennock can be contacted via E-Mail at This email address is being protected from spambots. You need JavaScript enabled to view it..}

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