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Principles of fire and explosion protection

Faculty of Chemical EngineeringUniversiti Teknologi MARA

Dr Syed Shatir A. Syed-Hassan

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Principles of fire protection

The protection of petroleum facilities follows the same overall philosophy that would be applied to any building or installation.

Basic requirements: Personnel evacuation Containment Isolation Suppression

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General Philosophy

The fire and explosion protection engineering design philosophy can be defined by the following objectives:

i. Prevent the immediate exposure of individuals to fire and explosion hazards.No facility should be designed such that an employee or the public could be immediately harmed if they were to be exposed to the operation.

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General Philosophy

ii. Provide inherently safe facilities. Inherently design safety features at facilities provides for

adequate spacing, arrangement and segregation of equipment from high hazard to low hazard.

• The least hazardous process systems should be used for obtaining the desired product or production objectives.

• Protective systems are provided to minimize the effects that may occur from a catastrophic incident.

iii. Meet the prescriptive and objective requirements of governmental laws and regulations.

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General Philosophy

iv. Achieve a level of fire and explosion risk that is acceptable to the employees, the general public, the petroleum and related industries, the local and national government, and the company itself.

v. Protect the economic interest of the company for both short and long range impacts.

vi. Comply with a corporation's policies, standards and guidelines.

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Layers of Protection

Most facilities are designed around layers of protection commonly referred to as Independent Layers of Protection (ILP).

A protection layer qualifies as an ILP when one of the following conditions are met the protection provided reduces the risk of a serious event

by 100 times the protective function is provided with a high degree of

availability it has the following characteristics - specificity,

independence, dependability, and auditability

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Layers of Protection

ALARMS

SIS

RELIEF

CONTAINMENT

EMERGENCY RESPONSE

BPCS

• BPCS - Basic process control

• Alarms - draw attention

• SIS - Safety interlock system to stop/start equipment (ESD)

• Relief - Prevent excessive pressure

• Containment - Prevent materials from reaching, workers, community or environment

• Emergency Response - evacuation, fire fighting, health care, etc.

AUTOMATION

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Layers of protection

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Segregation, Separation and Arrangement Segregation is the grouping of similar

hydrocarbon processes into the same major area.

The segregated high hazard areas can also be separated as far as necessary from other areas of the facility and the public.

The major facility segregation categories are process, storage, loading, flaring, utilities and administrative.

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Segregation, Separation and Arrangement The primary design consideration should be the

protection of employees and the general public from the effects of an explosion or fire.

The ideal situation for offshore facility is to locate the accommodation on a separate installation jacket that is spaced as far as practical from the production processes and the process platform oil or gas pipeline risers.

Arrangement means the orientation and assemblage of the equipment in a facility.

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Control of Ignition Source

A common ignition source is sparks resulting from static charge buildup and sudden discharge.

Static charge buildup is a result of physically separating a poor conductor from a good conductor or another poor conductor.

Examples of static charge build up: Walking across a rug Removing a sweater Combing hair

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Control of Ignition Source

The major generators of static electricity at hydrocarbon facilities are: Flowing liquids or gases containing impurities or

particulates Sprayed liquids Liquid mixing or blending operations Moving machinery Personnel

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Control of Ignition Source Static electricity can be overcome

or controlled by several basic approaches such as bonding and grounding.

Bonding tries to achieve a common electrical potential on all equipment so that a charge does not have the opportunity to accumulate.

Grounding is the process of electrically connecting one or more conducting objects to a ground potential.

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Control and Instrumentation Process control maintains

variables at set points, which are fixed at some desired values

Without adequate and reliable process controls, an unexpected process occurrence cannot be monitored, controlled and eliminated.

Alarm has an annunciator and visual indication. Require analysis by a person - A plant operator must decide.

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Emergency Shutdown System

An Emergency Shutdown (ESD) system is a method to rapidly cease the operation of the process and isolate it from incoming or going connections or flows to reduce the likelihood of an unwanted event from occurring, continuing, or escalating.

Facilities that do not have the capability to immediately provide an emergency shutdown should be considered high risks. Similarly, if the reliability of an ESD system is very poor.

ESD systems are designed so that several mechanisms can initiate a facility shutdown

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Methods of Fire Suppression The objectives of fire suppression systems: i) to

provide cooling; ii) to control fire (prevent it from spreading); ii) to provide extinguishment of the fire incident.

Some methods of fire suppression Portable Fire Extinguishers Sprinkler System Water Deluge System Water Spray System Water Flooding Steam Smothering Water Curtains

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Portable Fire Extinguishers

The most common method of extinguishing hydrocarbon fires in the incipient stage.

Portable extinguishers are classified by expected application on a specific type of fire (i.e., A, B, C, or D) and the expected area of suppression.

The four types of fires are grouped according to the type of material that is burning

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Portable Fire Extinguishers

Class A fires include those in which ordinary combustibles such as wood, cloth, and paper are burning.

CIass B fires are those in which flammable liquids, oils, and grease are burning.

Class C fires are those involving live electrical equipment.

Class D fires involve combustible metals such as magnesium, potassium, and sodium

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Portable Fire Extinguishers

Extinguishers for Class A FiresClass A fire extinguishers are usually water

based. Water provides a heat-absorbing (cooling) effect on the burning material to extinguish the fire.

Pressurized water extinguishers use air under pressure to expel the water.

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Portable Fire Extinguishers

Extinguishers for Class B Fires• Class B fires are put out by excluding air, by

slowing down the release of flammable vapors, or by interrupting the chain reaction of the combustion. • Three types of extinguishing agents: carbon

dioxide, dry chemical, and foamwater.

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Portable Fire Extinguishers

Extinguishers for Class C Fires• The extinguishing agent in a class C fire extinguisher

must be electrically non-conductive.• Both carbon dioxide and dry chemicals can be used in

electrical fires.

Extinguishers for Class D Fires• A heat-absorbing extinguishing medium is needed for

fires in combustible metals. • Also, the extinguishing medium must not react with

the burning metal.

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Sprinkler Systems

Commonly provided to indoor occupancies, such as warehouses, offices, etc.

Considered essentially 100% effective for fire suppression if properly maintained and the hazard has not changed since the original design.

Activated by the heat of the fire melting a tension loaded cap at the sprinkler head.

Cap melts or falls away releasing water from the pipe distribution network. Thus they do not activate until a fire condition is absolutely real.

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Water Deluge System

Should generally be activated by automatic means. Activation by manual means defeats the objective of installing a deluge system.

Most systems provided at petroleum facilities are typically activated by a heat detection.

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Water Flooding

Water flooding is the principle to inject water into the interior of a storage tank for the purposes of preventing flammable or combustible liquids from being released from a leakage point or to extinguish a fire.

The principle involves fill a vessel or tank so that the lighter density hydrocarbon fluids float on the water and only water is released from the container.

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Steam Smothering

Typically limited to fires that might occur as a result of a tube leak in a furnace or heater.

The steam is most effective in smothering fires when they are located in relatively small confined areas.

Steam extinguishes fire by the exclusion of free air and the reduction of available oxygen content to the immediate area, similar to other gaseous suppression agents

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Summary• Layers of protection (6 layers)• Segregation, separation and arrangement• Control of ignition point• Control and instrumentation

• Alarms• Blinking light (visual indicator)

• Emergency shutdown system• Fire suppression methods

• Fire extinguisher• Sprinkler• Water deluge system• Water flooding• Steam smothering

• Evacuation, fire fighting, health care etc.