GP 03-02-02 Foam Systems for Storage Tanks June 2012

Foam Systems for Storage Tanks

GP 03-02-02

Scope
[I] This Global Practice (GP) covers the design and installation of fire-fighting foam systems using high
or low back-pressure foam makers, for use with fixed roof tanks operating at approximately atmospheric
pressure (not exceeding 21/2 psig [17 kPag]) or with annular pontoon or double deck open-top floating
roof tanks. The systems also are applicable to tanks furnished with internal floating roofs or covers.

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Copyright 2012r
ExxonMobil Development Company and ExxonMobil Pipeline Company hereby license the use of ExxonMobil Engineering Practices System (EMEPS) Global Practices (GPs) for
use by any ExxonMobil division, subsidiary, or more-than-50%-owned affiliate. The GPs may be downloaded and modified as necessary for project and affiliate use. Written
permission from ExxonMobil Development Company or ExxonMobil Pipeline Company is not required. However, any modified GPs must be renumbered to a project-specific or
affiliate-specific number to distinguish them from the GPs on the EMEPS web site. ExxonMobil operated joint ventures may utilize GPs to create project-specific or location-specific
specifications. It is the responsibility of individual affiliate or joint venture to ensure that the use of GPs and their derivatives is limited to joint venture related business and not
disclosed or used outside the JV without appropriate EM management approval.
 GP 03-02-02 Foam Systems for Storage Tanks June 2012

Table of Contents

Table of Figures............................................................................................................. 3

1. Required References.............................................................................................4
1.1. Global Practices–ExxonMobil Engineering Practices....................................4
1.2. NFPA–National Fire Protection Association..................................................4
2. Materials................................................................................................................. 4

3. Design..................................................................................................................... 5

4. Additional Design and Installation Requirements for Fixed Roof Tanks..........8

5. Additional Design and Installation Requirements for Open-Top Floating Roof

Tanks.....................................................................................................................13

6. Inspection and Testing........................................................................................18

Record of Change........................................................................................................ 19

Attachment: Purpose Code Definitions.........................................................................22

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Table of Figures

Figure 1: Design and Installation of Foam Chambers Mounted on Tank Shell.....10

Figure 2: Design and Installation of Foam Chambers Mounted on Shell Extension

for Use with Internal Floating Roofs or Covers........................................11

Figure 3: Single Foam Outlet Station Layout of Foam Outlet Assembly and
Solution Piping (Schematic and Detailed)................................................14

Figure 4: Multiple Foam Outlet Locations Tanks over 75 ft Diameter Typical Layout of
Foam Outlets and Solution Piping (Schematic)............................................16

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 GP 03-02-02 Foam Systems for Storage Tanks June 2012

1. Required References
This Section lists the Practices, codes, standards, specifications, and publications that shall be used with
this document. Unless otherwise specified herein, use the latest edition.

1.1. Global Practices–ExxonMobil Engineering Practices

GP 09-07-01 Accessories for Atmospheric Storage Tanks

1.2. NFPA–National Fire Protection Association

NFPA 11 Standard for Low-, Medium-, and High Expansion Foam
NFPA 30 Flammable and Combustible Liquids Code

2. Materials
1) [*] [A] Piping for risers, laterals, and distribution systems shall be carbon steel, Sch. 40 minimum
wall thickness, galvanized or lined with a heat-cured epoxy or phenolic-epoxy system with a
minimum dry film thickness of 8 mils (200 m). The Owner's Engineer shall approve use of unlined
pipe.
2) [S] Foam chambers, outlet assemblies, and deflectors shall be carbon steel, galvanized or epoxy lined.
Foam dams shall be fabricated from carbon steel. Pipe carrying foam concentrate shall not be
galvanized.
3) [S] Foam backboards shall be the same material specification and grade as the shell plate to which
they are attached.
4) [S] Frangible diaphragms, incorporated in the seal chamber of foam chambers, shall be 14 oz (0.061
in. [1.5 mm]) thick common soda lime glass, scored to facilitate breakage under foam pressure.
5) [S] Screening, installed at the foam deflector or air entry ports of foam makers, shall be 2 x 2 mesh
with 0.46 in. (12 mm) nominal opening.

3. Design
1) [S] Lateral terminal connection:
a) Laterals shall terminate outside the dike and on the roadside of all pipelines and drainage ditches.
b) The terminal connections shall be located in relation to fire hydrants such that the total length of
hose from the hydrant to fire truck does not exceed 25 ft (7.5 m), and the distance from the fire
truck to foam lateral terminals does not exceed 50 ft (15 m). The terminal connections shall be

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located in at least one vessel diameter or 100 ft (30 m), but in no case less than 50 ft (15 m) from
the tank being protected, with a block valve, a check valve, and a 21/2 NPS (65 mm) hose
connection fitted with a pressure tight cap and a vent valve.
c) Terminal connections shall be from 2 ft to 4 ft (600 mm to 1200 mm) above grade and shall be
protected against collision. Where systems are located within 3 ft (1 m) of roadways or
accessways, in areas of high vehicular traffic, the systems shall be protected by concrete-filled
guards. Guards shall be NPS 4 (100 mm) Sch. 40 pipe, filed with concrete, and set in concrete
foundation.
d) A sign shall be installed at each lateral termination point to identify the tank served.
2) [S] Fire hose coupling type at terminal connections and at foam outlet stations shall be specified. In
some locations, the plant fire departments will provide the actual fire hose couplings.
3) [S] Coupling thread type shall be suitable for use with Owner's fire-fighting equipment. Couplings
shall be provided with dust caps or plugs.
4) [S] For tanks requiring multiple laterals, up to two laterals can be brought to a single location 4 ft
(1200 mm) apart. However, not more than two laterals from any one tank shall be brought to the
same location.
5) [S] The lateral terminals shall be located on the side of the tank lot that most directly faces the
prevailing wind, if any, consistent with good access.
6) [S] The terminal connections on foam makers shall be as follows:
a) Laterals to single foam outlets up to 250 gpm (0.95 m3/min) capacity shall terminate in one NPS
21/2 (65 mm) size mating hose coupling.
b) Laterals to single foam outlets greater than 250 gpm (0.95 m3/min) capacity or to multiple foam
outlets shall terminate in one NPS 21/2 (65 mm) size mating hose coupling for every 250 gpm
(0.95 m3/min) of lateral capacity or part thereof.
7) [S] The riser pipe size from the foam maker to the foam chamber shall be determined by hydraulic
calculation, but shall not be smaller than the foam chamber inlet flange size.
8) [S] Riser supports shall be 1/2 in. (12 mm) thick plate, 12 in. (300 mm) length, with the width
depending on riser dimension, but selected to maintain the riser a minimum of 4 in. (100 mm) clear
from the tank shell. Installation shall be as follows:
a) Each support shall be located on about 8 ft (2.4 m) centers and placed perpendicular to the tank
shell and centered on the riser pipe.
b) The edges of the plate shall be continuously welded on all sides to both tank shell and pipe with
1
/4 in. (6 mm) fillet welds to support the shell in event of a fire.
9) [S] Foam lateral size shall be determined by hydraulic calculation, but shall not be less than NPS 2 1/2
(65 mm) size. Laterals shall be installed as follows:
a) Slope continuously toward the termination point outside the dike. If this is impractical, a
(normally closed) NPS 3/4 (20 mm) drain valve shall be provided at the low point.
b) Not run through the dike area of any other tank, group of tanks, or paired tanks. However, piping
within a group of tanks may cross intermediate toe walls within that group.
c) Maintain a minimum elevation of 1 ft (300 mm) above finished grade.
10) [S] The ratio of the strainer's open basket area to its inlet pipe area shall be at least 10:1. The net
open area of the strainer shall be at least four times the area of the suction piping.
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11) [S] Underground carbon steel piping, and portions of aboveground carbon steel piping, that pass
through a dike or pipe sleeve shall be protected against external corrosion using a Single Coat-Single
Wrap or Double Coat-Double Wrap protective coating system.
12) [S] Permanent connections between the fire water system and any process system shall be prohibited.

4. Additional Design and Installation Requirements for

Fixed Roof Tanks
1) [S] The provision of fixed fire protection for tanks containing non-water-soluble flammable liquids,
with closed-cup flash point that is either under 100°F (38°C), or at 100°F (38°C) and above if such
stocks are heated to a temperature above or within 15F (8C) of their flash point, shall be as follows:
a) A surface application type fire-fighting foam system utilizing fixed discharge outlets for use on
fixed roof tanks shall be designed in accordance with NFPA 11.
b) The number of foam chambers (and deflectors) installed shall be as shown in Table 1.

Table 1: Foam Chambers Required

Nominal Tank Diameter Number of Foam
ft m Chambers per Tank

< 20 <6 0
20 to 80 6 to 24 1
> 80 to 110 > 24 to 33 2
> 110 to 130 > 33 to 40 3
> 130 to 150 > 40 to 46 4
> 150 to 170 > 46 to 52 5
> 170 to 190 > 52 to 58 6

c) Tanks with a fixed roof and no internal floating cover or roof shall be designed such that the foam
chambers shall be shell mounted per Figure 1.
d) Tanks with a fixed roof and an internal floating cover or roof shall be designed such that the foam
chamber shall be tank-shell mounted per Table 1, provided the deflector does not interfere with
the specified upper travel limit of the internal floating cover or roof. Shell extension mounted per
Figure 2 is permitted for retrofits.
e) Exception 1: Fixed roof tanks shall meet the requirements for open-top floating roof tanks, per
Section 5, when the construction meets both the following conditions:
i) Provided with an internal floating roof that is either a pontoon-type floating roof or double
deck design floating roof.
ii) The fixed roof is aluminum, fiberglass, or other lightweight geodesic dome or external cone
roof.
f) Exception 2: The tank is provided with a SHE Critical nitrogen blanketing system.
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Figure 1: Design and Installation of Foam Chambers Mounted on Tank Shell

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Figure 2: Design and Installation of Foam Chambers Mounted on Shell

Extension for Use with Internal Floating Roofs or Covers

2) [S] Water-soluble flammable liquids: the Owner's Engineer and the plant Fire Chief shall specify the
need for foam chambers and the applicable details of design and installation.
3) [S] When multiple foam chambers are required, they shall be equally spaced around the tank.

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4) [S] Foam makers shall be provided and installed as follows:

a) [A] Foam makers with a capacity of 500 gpm at 150 psig (1.89 m3/min at 1034 kPag) inlet
pressure, and that are a Company-approved equal to National Foam Type PHB 50 SS, shall be
used. The foam maker shall be located in the riser piping such that the aspirator opening is 5 ft
(1500 mm) above finished grade.
b) [A] For locations requiring low back-pressure foam systems, National Foam Type MCS-33,
MCS-55, or Company-approved equivalent shall be used. These foam makers shall be located
under the foam chamber at the top of the tank.
c) The foam maker air entry ports shall be provided with screens per Section 2, Item (5). Screens
can be obtained from: National Foam Systems, Inc., 150 Gordon Drive, Lionville, PA 19353.
5) [S] Piping layout: Each foam chamber shall be equipped with its own riser, foam maker, and lateral.
Pipe risers and foam makers shall be installed directly below the foam chambers. A flanged spool
piece shall be installed upstream of the foam maker (near finished grade) to permit periodic flushing
of the lateral.
6) [S] Lateral pipe size: Laterals shall be sized such that the maximum pressure drop between the end of
the lateral and foam maker does not exceed 35 psig (240 kPag).
7) [S] Foam chambers on internal floating roof tanks shall not be located above ventilation openings on
the shell.
8) [*] [A] [C] Non water-soluble combustible liquids: When approved by the Owner's Engineer and the
plant Fire Chief, a semi-fixed subsurface foam injection system designed per NFPA 11 may be
considered to satisfy local regulatory requirements for tanks that satisfy both of the following
conditions are satisfied:
a) The tank is a fixed roof tank without an internal floating cover.
b) The tank stores a non-polar liquid having a closed-cup flash point of 100°F (38°C) or higher at a
temperature lower than its closed-cup flash point minus 15°F (8°C).

5. Additional Design and Installation Requirements for

Open-Top Floating Roof Tanks
1) [S] Foam dams shall be installed on all floating roof tanks. A fire-fighting foam system using fixed
foam discharge outlets in accordance with NFPA 11 shall be provided in all open-top floating roof
tanks that store crude oils, or that store low-flash stocks with the following:
a) Closed-cup flash point under 100°F (38°C), or
b) Closed-cup flash point of 100°F (38°C) and above if such stocks are heated to a temperature
above or within 15°F (8°C) of their flash point.
2) [S] For open-top floating roof tanks up to 75 ft (22.5 m) diameter, a single foam outlet station shall be
located by the top platform per Figure 3.

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Figure 3: Single Foam Outlet Station Layout of Foam Outlet Assembly and
Solution Piping (Schematic and Detailed)

3) [S] For open-top floating roof tanks larger than 75 ft (22.5 m) diameter, one foam station shall be
installed for each 80 ft (24 m), and fraction thereof, of tank circumference, equally spaced around the
circumference per Figure 4.

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Figure 4: Multiple Foam Outlet Locations Tanks over 75 ft Diameter Typical

Layout of Foam Outlets and Solution Piping (Schematic)

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4) [S] [A] The foam outlet assembly, consisting of a foam maker, foam deflector, and mounting
assembly, shall be National Foam Systems, Inc., Type MBS-9SA/MCS-9FR or Company-approved
equivalent. The foam maker shall be furnished with an orifice diameter of 0.65 in. (16.5 mm). The
foam maker air entry ports and the foam deflector shall be provided with a bird screen per Section 2,
Item (5). See Section 4, Item (4c) for address of National Foam Systems.
5) [S] A single foam riser shall be used to deliver foam solution to the foam outlets. When multiple
foam outlets are installed, the distribution piping to individual outlets shall be located on top of the
wind girder to be accessible for inspection.
6) [S] The foam system including the lateral, riser, and distribution piping shall be sized to deliver 60
gpm (0.23 m3/min) foam solution to each foam maker inlet at a pressure of 60 psig (414 kPag), based
on a foam proportioning truck discharge pressure of 100 psig (700 kPag).
7) [S] Foam backboards and foam dams shall be designed for wind pressure. (Design wind velocity
shall be specified by the Owner's Engineer.) Foam dam bracing shall be on the outside of the dam,
away from the foam, so as not to impede the flow of foam. The foam dam shall extend completely
around the roof, and, except for drain slots per Figure 3, shall be continuously seal welded to the roof
for the full length of the dam.
8) [S] Foam backboards mounting and minimum dimensions shall comply with the following:
a) Foam backboards shall be mounted flush with the inside diameter (ID) of the shell.
b) The backboard shall be minimum height, but sufficient to have the foam deflector clear the
maximum travel of the roof seal weather shield and other protruding parts at the uppermost
position of the roof.
c) [A] The width of the backboard shall be 10 ft (3000 mm) minimum, unless otherwise dictated by
unusual wind conditions or experience at the plant location. The Owner's Engineer shall approve
deviation from this minimum width.
9) [S] Guard railings per GP 09-07-01 shall be installed on wind girders of open-top floating roof tanks,
completely around the tank, when one or more foam outlet stations are installed.

6. Inspection and Testing

1) [S] [A] Acceptance tests: Foam systems covered by this GP shall be tested in accordance with NFPA
11 requirements, and with the approval of the Owner's Representative and the plant Fire Chief, by
generating foam into the storage tank prior to the tank being placed in service. The following are
minimum testing requirements:
a) During the test, the foam proportioning truck discharge pressure shall be sufficient to obtain the
desired pressure at each foam maker inlet.
b) The test shall demonstrate that the installed system is capable of covering the area to be protected,
as specified below:
i) Fixed roof tanks: Complete coverage of the bottom of the tank shall be achieved in not more
than 15 minutes of foam application.
ii) Open-top floating roof tanks with single foam outlet system: Coverage shall extend over
approximately 40 linear ft (12 m) of seal area on both sides of the foam station within 10
minutes of application time.

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iii) Open-top floating roof tanks with multiple foam outlet system: Coverage of the complete
seal area shall be achieved within 10 minutes of application time.
2) [S] New and/or retrofitted foam systems shall be tested in accordance with NFPA 11 requirements
and the minimum testing requirements outlined above as part of the acceptance procedures.

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Record of Change
Version 1.0.0 Date: 01/02
Location Action Description
Initial Publish.

Version 2.0.0 Date: 08/03

General General technical and editorial revisions.
Section 3 Addition Rationale for fire hose couplings to reflect plant consistency.
Section 3 Addition Rationale to reflect that terminals for laterals do not have to be exactly
upwind.
Section 4, Item Modification Clarified that this applies to all internal floating roof tanks except those
1 provided with a double or pontoon roof and the roof is a geodesic dome.
Sections 4 and Modification Rationale for firefighting practice for internal floating roof tanks.
5

Version 2.0.0 Date: 11/03

Global Practice version number and format updated to comply with new
process; however, original publish date remains, and no content was
modified.

Version 3.0.0 Date: 12/04

Section 1.1 Addition Added reference to GP 09-07-01.
Section 1.2 Modification Changed National Fire Prevention Association to National Fire
Protection Association. Added NFPA 30.
Section 2, Item Modification Added "Pipe carrying foam concentrate shall not be galvanized."
(2)
Section 2, Item Modification Modified Rationale to include debris accumulation as a reason for
(5) installing screening.
Section 3, Item Modification Added "Connections should be located at least a distance of one tank
(1b) diameter from the tank but in no case less than 50 ft (15 m)
Section 3, Item Modification Modified Rationale to state "The maximum distance for hose connections
(1b) from the hydrants and foam system to the fire trucks are established to"
be consistent with fire truck hoses.
Section 3, Item Modification Modified Rationale to add "Collision protection may be provided by
(1c) installing guards where systems are located within 3 ft (1 m) of roadways
or accessways in areas of high vehicular traffic. Guards shall be NPS 4
(100 mm) Sch. 40 pipe, filled with concrete and set in a concrete
foundation"

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Section 3, Item Modification Modified Rationale to include preventing a spill fire "at one tank" from
(8b) damaging the foam laterals of other tanks.
Section 3, Item Modification Modified Rationale to specify "safely" hooking up hoses to laterals.
(8c)
Section 3, Item Addition Added requirement that "The ratio of the strainer's open basket area to its
9 pipe area shall be at least 10:1. The net open area of the strainer shall be
at least four times the area of the suction piping."
Section 3, Item Modification Changed from 3.9. Modified to read "Underground carbon steel piping
(10) and portions of above ground carbon steel piping that pass through a dike
or pipe sleeve shall be protected against external corrosion using a Single
Coat Single Wrap or Double Coat Double Wrap protective coating
system."
Section 3, Item Modification Changed from 3.9. Modified Rationale to include "These portions can
(10) experience severe corrosion if not protected as described."
Section 3, Item Addition Added, "Permanent connections between the fire water system and any
(11) process system shall be prohibited" to prevent contamination of fire
water with process fluids.
Section 4, Item Modification Consolidated criteria for specifying fixed fire protection by incorporating
(1) information from former 5.10 and added provision to exclude internal
floating roof tanks with nitrogen blanketing from requiring foam systems
unless required by local codes. The nitrogen system should be "safety
critical."
Section 4, Item Modification Modified Rationale to note that foam concentrates for alcohol type fires
(2) "are often alcohol type specific."
Section 4, Item Modification Modified Rationale to include use of screens to prevent debris from
(4c) plugging the system.
Section 5, Item Modification Relocated the Note in Section 5, Item (2) to the Section 5, Item (2)
(2) Rationale.
Section 5, Item Modification Added a reference to GP 09-07-01 for guard railings.
(9)
Section 5, Item Deleted Deleted Section 5, Item (10). See Section 4, Item (1).
(10)
Section 6, Item Modification Added the plant Fire Chief's approval to acceptance testing.
(1)
Section 6, Item Modification Clarified the test requirements for foam systems.
(1a)
Section 6, Item Modification Modified Rationale to specify that these are the minimum requirements.
(1b)
General Modification Added references to NFPA 11 and NFPA 30 in Rationale. Removed
Pipelines from GP.

Version 3.1.0 Date: 06/12

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General Modification Updated purpose codes and rationales throughout GP.

Section 3, Modification Specified "outside the dike."
Item (1a)
Section 3, Modification Updated connection distance from tank.
Item (1b)
Section 3, Modification Relocated collision protection specification from rationale to Item (1c).
Item (1c)
Section 3, Modification Added "inlet" to piping area to clarify the ratio of strainer's open basket
Item (10) area to inlet piping area.
Section 4, Modification Combined the original Items (1), (1a), and (1b) into a paragraph for
Item (1) consistency and clarification.
Section 4, Modification Reword for clarification.
Item (1a)
Table 1 Modification Added the number of foam chambers per tank for tanks with nominal
tank diameter above 46 m to 52 m and above 52 m to 58 m.
Section 6, Modification Changed, "in the presence and to the satisfaction" to "with the approval."
Item (1)
Added word "testing" to requirements.
Section 6, Addition Added item.
Item (2)
All Global Modifications To standardize the format of the Global Practices and to meet other
Practices requirements, the following changes have been implemented:
"For ExxonMobil Use Only" has been replaced with "For Company Use
Only."
A copyright waiver has been added in the first page Footer.
The definition of asterisks in the Scope has been deleted. The asterisk is
now defined in the Purpose Code attachment and is used within brackets
as other Purpose Codes.
Multiple paragraphs within a Section have been numbered.
The standard text for Required References has been modified.
The standard text for Additional Requirements has been modified.
The [S] Purpose Code has been modified.
The following Purpose Codes have been added:
[*] for additional information or decision required of Owner's
Engineer.
[A] for approval requirements before beginning work or finalizing
design.

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Attachment: Purpose Code Definitions

Code Description
* Assigned to paragraphs that require the Owner's Engineer to provide additional information or
make a decision.
A Assigned to paragraphs that require approval from the Owner's Engineer before the work may
proceed or the design is finalized.
C Assigned to paragraphs whose primary purpose is reduced costs. Reduced cost in this context
refers to initial investment cost and does not include life cycle cost considerations. Life cycle
cost considerations are captured under reliability, maintainability, or operability purpose codes.
E Assigned to paragraphs whose primary purpose is driven by environmental considerations.
Environmental considerations typically include specifications intended to protect against
emissions/leakage to the air, water, and/or soil. Deviations from the specifications contained
in such paragraphs require formal review and approval according to local environmental
policy.
I Assigned to paragraphs that provide only clarifying information, such as Scope statements,
definitions of terms, etc.
M Assigned to paragraphs whose primary purpose is to provide for maintainability of equipment
or systems. Maintainability provisions are those that facilitate the performance of maintenance
on equipment/systems either during downtimes or during onstream operations.
O Assigned to paragraphs whose primary purpose is to assure operability of equipment or
systems. Operability is the ability of the equipment/system to perform satisfactorily even
though conditions are off-design, such as during start-ups, process swings, subcomponent
malfunction, etc.
R Assigned to paragraphs whose primary purpose is to improve or assure the reliability of
equipment or systems. Reliability is a measure of the ability of equipment/systems to operate
without malfunction or failure between planned maintenance interventions.
S Assigned to paragraphs containing specifications/guidance where the primary purpose is the
avoidance of incidents impacting personnel safety, process safety, and the public in general
and/or involving responses to emergency situations. Any deviation from the specifications
contained in such designated paragraphs requires formal review and approval according to
local safety policy.
Personnel Safety: Refers to the prevention of incident-related personnel injuries or illness,
e.g., burns, cuts, abrasions, inhalation of or exposure to dangerous
substances, etc., that could result in medical treatment, restricted work,
lost-time incidents, or fatalities.
Process Safety: Refers to the prevention and control of process releases, fires, and/or
explosions that could result in damage to equipment, process disruption,
or personnel injury or illness.

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