The document discusses Dow Chemical Co's Fire & Explosion Index (F&EI) which combines material properties and process hazards to assess risk. The F&EI is calculated by determining material and process factors then multiplying them. Material factors consider properties like flash point and reactivity. Process factors examine issues like exothermic reactions, enclosed spaces, toxic materials, dust explosions, corrosion and more. The F&EI is used along with estimates of potential loss to evaluate risk.

1. SAFETY INDICES:
➢ Dow Chemical Co (1994) – Introduced a numerical Fire &
Explosion Index (F&EI)
➢ F&EI combines material properties with the process.
➢ Larger the value of F&EI, more hazardous the process.

2. Meaning of F&EI
Value of F&EI Qualitative degree of hazard
1 - 60 Light
61 - 96 Moderate
97 - 127 Intermediate
128 - 158
Increasing
hazard
High
> 159 Severe

3. How to calculate F&EI ?
➢ Identify the steps/units that are most hazardous
F&EI should be estimated as early as possible in the life of a
project.

4. Calculate
material
factor
General
process
hazard
factor (F1)
Special
process
hazard
factor (F2)
Overall
process
unit hazard
F3 = (F1) (F2)
Process
Unit
Calculate
F&EI
F3 * material
factor
Estimate
area of
exposure
Estimate
replacement
value in
exposure area
Determine
base
MPPD
Estimate
actual
MPPD
Determine
MPDO
Determine
BI
Loss control
Credit factor
= C1 * C2 * C3
This will feed
into the actual
MPPD box
Credit
Factor

5. MATERIAL FACTOR (MF):
➢ Measure of the intrinsic rate of energy release from
burning / explosion or any other chemical reaction.
➢ MF combines the flash points and reactivity value and
number of reactions.

6. Typical values of MF
Substance Flash Point (oC) Heat of combustion MJ/kg MF
Acetaldehyde -39 24.4 24
Acetone -20 28.6 16
Acetylene gas 48.2 40
Ammonia gas 18.6 4
Benzene -11 40.2 16
Chlorine - 0 1
Cyclohexane -20 43.5 16
Ethyl alcohol 13 26.8 16
Hydrogen gas 120 21
Nitroglycerine - 18.2 40
Sulfur - 9.3 4
Toluene 40 31.3 16
Vinyl Chloride gas 18.6 21
Table 2:

7. GENERAL PROCESS HAZARDS:
1. Exothermic Chemical Reactions: Penalty ranges from 0.3
(mildly exothermic, hydrogenation) to 1.23 for a highly
sensitive exotherm (nitration).
2. Exothermic Processes: Penalty of 0.2 for reactors only and
0.4 if heat is supplied by the combustion of a fluid.
3. Materials handling & transfer: This accounts for handling,
storing, pumping, compression of raw materials and
products. It ranges from 0.25 to 1.05.

8. GENERAL PROCESS HAZARDS (Cont.):
4. Enclosed or Indoor process units: This arises from the poor
ventilation 0.25 to 0.90.
5. Exothermic Chemical Reactions: 0.20 to 0.35 Minimum
requirement is access from two sides.
6. Exothermic Chemical Reactions: 0.25 to 0.50 This is a
penalty for large spills of flammable material close to process
equipment such as storage tanks next to an exothermic
reactor, or poor drainage system.

9. SPECIAL PROCESS HAZARDS:
1. Toxic materials
• Post-accident operations become more difficult if toxic
materials are present.
• Factor is ‘0’ for non-toxic materials and 0.8 for a substance
which can cause death after short exposure.
2. Sub-atmospheric pressure : Air from outside can leak into the
equipment. For absolute pressure < 500 mmHg, apply a
factor of 0.5.

10. SPECIAL PROCESS HAZARDS (Cont.):
3. Operation in or near flammable range : Accounts for the
possibility of air mixing with the flammable material (in
storage tanks, equipment, etc.) : may lead to explosion.
• 0.5 for storage tanks
• 0.3 for process upsets or purge failure
• 0.8 for always in flammable range.
4. Dust explosion :
• Risk is mainly determined by the particle size; smaller is the
particles , greater is the risk !

11. SPECIAL PROCESS HAZARDS (Cont.):
• Penalty factors are 0.25 for > 175 µm to 2 for < 175 µm.
5. Relief pressure :
• Accounts for pressure on the rate of leakage (Q ∝ 𝞓𝑷) Q↑
as 𝞓𝑷 ↑
• Graphs are given in Dow’s guide.
6. Low temperature :
• Accounts for brittle fracture (Challenger shuttle)
• 0.2 to 0.3

12. SPECIAL PROCESS HAZARDS (Cont.):
7. Quantity of Flammable Material :
• Greater the quantity, greater would be the loss and risk.
• It can range from 0.1 to 3.0.
8. Corrosion & Erosion :
• Depends upon the choice of material of construction
(internally as well as externally).
• Stream corrosion cracking.
• 0.1 to 0.75

13. SPECIAL PROCESS HAZARDS (Cont.):
9. Leakage from joints and packing :
• Gaskets, pumps and other roto – machines.
• 0.1 for minor leaks to 1.5 for reverse leaks like sight
glances, bellows or expansion joints.
10. Fired heaters :
• Boilers /furnaces using combustion of fuel increase the
chances of ignition
• Need to consult graphs.

14. SPECIAL PROCESS HAZARDS (Cont.):
11. Hot oil Heat exchangers :
• Most of the heating oils : Flammables
• Working temperature > Flash point
• High risk of fire / explosion
• 0.1 to 1.15 factors are used
12. Rotating Equipment:
• Compressors, centrifuges, mixers
• Factor of 0.5 is used

15. ESTIMATION OF POTENTIAL LOSS:
➢ Damage factor 1. Material factor
2. Process unit hazard factor
➢ Estimate the area of exposure
➢ Estimate the replacement value of the equipment : base
MPPD (Maximum Probable Property Damage)
➢ MPPD = base MPPDX credit control factors
➢ Estimate MPDO : Maximum Probable Days Outage
➢ Business Interruption