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Chapter XFire Fighting System

Learning Objectives

After identification of all possible HAZARD in the plant, system for fire fighting is important

feature of this system is that this system should work in any emergency situation. There

should be approach to this system if any thing goes wrong. So preparation of layout of fire

fighting system becomes important.

Contents

10.1 Introduction

10.2 Ignition Sources

10.3 What is Fire?

10.4 Flash Point

10.5 Chemical Explosion

10.6 Mechanical Explosion

10.8 Fire Protection Facilities

10.9 Types of Fire Protection Facilities

10.9.1 Internal Appliances

10.10 Fire Water Supply

10.11 Pumps

10.12 Capacity for Hydrant System

10.13 Fixed Foam System

Summing Up

Self-assessments

10.1 Introduction

We will learn in this chapter in which way a system should be designed and

executed through to get the best performance of system even in emergency.

A) Chemicals present a very substantial hazard due to fires and explosions.The three most common chemical plant accidents are.

1. Fire

2. Toxic release

3. Explosions

B) The essential elements for combustion are

1. Fuel

2. Oxidiser

3. Ignition-source

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C) Fuels, oxidisers, ignition source in chemical industry.

Fuels :-

Liquids : Gasolene, Acetone, Ether, Pentane etc.

Solids : Plastics, Wood, Dust, Fibers,

Gases : Acetylene, Propane, Hydrogen.

Oxidiser

Gases : O2, F

2, Cl

2

Liquids : HNO3/H2O2/ Some acids.Solids : Metal Peroxides/ NH

4NO

2

10.2 Ignition Sources

Sparks, Flame, Static Electricity, Heat.

10.3 What is Fire?

It is a chemical reaction in which a substance combines with an oxidant and

releases energy, part of the energy releases is used to sub stain the reaction

10.4 Flash Point

It is the lowest temperature at which it gives off enough vapour to form an

ignitable mixture with air. The flash point generally increases with increase

in pressure.

10.5 Chemical Explosion

It is a rapid expansion of gases resulting in a rapidly moving pressure or

shock wave. The expansion can be mechanical in sudden exposure of a

pressure vessel or it can be a result of a rapid chemical reaction.

AIR

UEL

AIR

UEL

IGNITION

SOURCE

IGNITION

SOURCE

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10.6 Mechanical Explosion

It is due to the sudden failure of a vessel containing high-pressure gas.

Designs to Prevent Fires and Explosions

1) Inerting- process of adding inert gas to a combustible mixture to reducethe concentration of oxygen below the limit- n2 gas is generally used.

2) Curbing of production of static electricity

3) Prevent sparks.

4) Explosion proof electrical equipments.

5) Ventilation open air plant.

6) Sprinkler system.

10.8 Fire Protection Facilities

Compliance of the tariff advisory committee rules or OISED i.e. that is Oil

Industry Safety Directorate (established in 1986) . Rules will not only obtainappropriate discount is the fire insurance premium but will also instill that

feeling of security in the minds of staff. Direct loss from fire and the resultant

wastage is always serious but indirect loss of business is much more serious.

10.9 Types of Fire Protection Facilities

1) Internal appliances

2) Mechanically driven fire engines and trailer pumps

3) A well designed and laid hydrant system.

10.9.1 Internal Appliances

Generally consist of hand appliances and hose reels

A) Hand appliances buckets and extinguishers.

B) List of approves manufactures.

C) These are essentially first-aid equipments only meant for attacking small

fires in their initial stages and are not intended to deal with large outbreaks

of fires.

D) It is recommended that extinguishers installed in any one building or

single occupancy be similar in shape and appearance as far as possible

E) Boards

1) Nature of contacts of a building2) Process carried out

3) Types of fires which may occur.

Class of fire Suitable appliances

Fire in ordinary combustibles (wood, Chemical extinguishers of soda

fibres, paper etc.). /acid.Gas/expelled water types

and water buckets.

Fires in flammable liquids, paints, grease, Chemical extinguishers of

solvents. foam/carbon dioxides and dry

powder types and sand buckets.

Fire air gaseous substances under Chemical extinguishers ofpressure. carbon dioxide and dry powder

type.

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Fires in reactive chemicals, active metals. Special types of dry power

extinguishers and sand

buckets.

Fires in electrical equipments. Chemical of carbon dioxide and

sand buckets.Extinguishers

10.10 Fire Water Supply

1) It shall be stores in underground lines reservoir or above ground steel,

concrete or masonry.

2) Effective capacity

above the level of the foot valve seat in case of negative suction.

3) Reservoirs of above 2,25000 lit capacity as calculated for 2 hrs/3hrs/4hrs

aggregate pumping capacity shall be in the compartments to facilitate

cleaning and repairs.

10.11 Pumps

1) Pumps shall be exclusively used for fire-fighting purpose.

2) Pumps shall be direct couples belt driven pumps are not accepted.

3) Part of pumps like impeller, shaft sleeve, wearing rings shall be of non-

corrosive metal preferably of brass or bronze.

4) Pump capacity would depend on whether tapping for water spray or

foam protection for tanks is taken from the hydrant service.

10.12 Capacity for Hydrant System

Hydrant Pump capacity Del. Pr. @rated

cap.1) light hazard 20 96 5.6 kg/cm2

21-55 137 7

56-100 171 7

Exceeding 171 +47 per every 8.8

100 125 hy

2) ordinary hazards 20 137 7

21-55 171 7

56-100 273 7

Exceeding 273+76 per every 8.8

100 125 hydrant or

part there of butnot greater than 1092

3) high hazard(a) 20 171 7

21-55 273 8.8

56-100 &10 8.8

Exceeding 410 +410 for ever y 10.5

100 150 hydrant

4) high hazard(b) 20 171x2 7

21-55 273x2 7/8.8

56-100 410x2 7/8.8

Exceeding + ever y additional 8.8/10.5

100 200 hydrant Exceeding 616 pumps

500

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Are acceptable

Number of hydrants equivalent

Double hydrant 2 hydrants

Monitors 63MM 3

75 MM 4

100 MM- 6

Where storage tanks containing flammable liquids are protected by MVWS-

medium vel. Water spray system tapped from hose hydrant system, the water

requirement of the spray system shall be calculated for tanks located in

common dyke which have the rate of10 lit/min/sq.mt. Of the tank shell surface

area.

+

Loaded for supplementary hose streams

Largest tank in a Sykes has diameter

UPTO 10M 1700 LIT/MIN

11-20 2250 LIT/MIN

21 AND ABOVE 4500 LIT/MIN

If total of MVWS = hose stream > hydrant this pumping capacity covers.

10.13 Fixed Foam System

Water requirements shall be considered for the largest protected tank at the

rate of 5 lit/min sq. mt. of liquid surface area.

Where sphere/bullets containing LPG are protected by MVWS the water

requirement shall be calculated for upto 3 spheres/bullets having largest

aggregate surface area located within r +15 of each other at the rate of 10 lit/min/ Sq. Mit.

Jockey pump: High hazards (b) capacity to be 180 LPM pumps shall be capable

of furnishing not less than 150%of rated capacity @ head not less than 65% of

the rated head.

Suction velocity

High hazard (b) pump shall be 30 mt. Clear of all equipments containing

hydrocarbons

Mains

1) Is 1239 up to 6" ERW

is 3589 for 8" and above size ERW

2) Supported @ 3.5. Internals

3) 10% radiography

4) 6mt. Away from face of building and open storage area for light and

ordinary hazards and 15m in case of high hazards.

5) Mains shall be in rings.

6) The mains shall not traverse ground that is under the control of the

owner.

7) The velocity at any point should not exceed 3 mt/ sec.8) Gate valves confirming to is 780 p.n.1.6 and is 2906 pn 1.6 will be used.

9) The hole system may be stress analyzed.

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Hydrants/fixed monitors

1) Connection for any purpose other than fire fighting are not permitted

from hydrants.

2) All hydrants outlets shall be 1 m above ground level.

3) Stand post shall be 80 mm for single headed and 100 mm for double

headed.4) 100 mm stand post for monitors 63 and 75 mm size and 150 mm for 100

mm monitor and painted fire red

5) Distance between two hydrants

Light hazards 60 mt.

Ordinary hazards 45 mt.

High hazards 30 mt.

6) Hydrants/monitors shall not be installed with in dyked enclosures not

can the main line pass through it.

Summing Up

For the fire fighting system, there are certain guidelines fixed by the statutory

body. These guidelines are to be followed and the piping engineer has to

identify the Hazardous Areas and take corrective action. This is again a

network to be laid along with the rest of the piping of the plant and care has

to be taken during the preparation of the plant layout. Head and quantity

balancing is again important for the fire fighting system.

Self-assessment

1. Capacity of the hydrant system depends upon the Hazard class.

( True / false)

2. Highest pumping capacity is required for_______________.

3. All hydrant outlet shall be above the ground level.

4. For ordinary hazards distance between two hydrant is

.

5. No stress analysis is required for fire fighting system since they are

working on water. ( True/false)

6. For the light hard, distance between two hydrant will be .

7. For fire fighting system valve used are .

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Answers to Self-assessments

Chapter IV

Cooling Water System

1. (i) Induced draft (ii) Force draft

2. False

3. Head and quantity

4. Downward direction

5. Gate valve and Globe valve

Chapter V

Piping for Steam Distribution

1. True

2. True3. False

4. 25 - 53 metre/sec.

Chapter VII

Tower

1. True

2. (i) Feed line (ii) Draw line

3. True

4. 1) Removal of exterior item 2) Interior Components

5. True6. True

7. Evenly spaced

Chapter VIII

Traced and Jacketed Piping

1. True

2. True

3. Product line and the tracer

4. True

5. Temperature difference between the tracer and the product is low

6. Clipped or wired

7. Avoid electrolytic corrosion

Chapter IX

Design Consideration for Tank Farm

1. Chief Controller of Explosive

2. - < 230C

3. 25 m3

4. Class A, Class B, Class C

5. 1. Petroleum Act 1934, 2. Petroleum Rule 1976

6. Static and Mobile Pressure Vessel Rule

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Answers to Self-assessments

Chapter X

Fire Fighting System

1. True

2. High Hard (b)

3. One meter

4. 45 metre5. False

6. 60 metre

7. gate valve