CONFINED SPACE ENTRY

Helen Verstraelen

CONFINED SPACE DEFINITION

Is large enough and so configured that an employee can enter bodily and perform work;

Has limited or restricted means of entry or exit; Is not designed for continuous human

occupancy. 2 categories:

With open top with a dept that will restrict the natural movement of air

Enclosed spaces with very limited openings for entry

EXAMPLES

Cargo tanks Manholes Chain lockers Fuel tanks Ballast tanks Double bottoms Void spaces

IG plant Pipes Trenches Pump rooms Sewage tanks Cable trunks …

POTENTIAL HAZARDS

Flammable atmosphere Asphyxiating atmosphere Toxic atmosphere Irritant atmosphere Mechanical hazards Communication problems Entry and exit problems Thermal effects Noise and vibrations Physical hazards

FLAMMABLE ATMOSPHERE

Arise from enriched O2 atmospheres Vaporization of flammable liquids Chemical reactions Concentration of chemical dust

Flammable gasses are often heavier than air and will seek lower levels

Gasses lighter than air will rise and develop a flammable concentration if trapped above the opening

Byproducts of work can generate explosive conditions Welding Combustible dust during cargo operations ( grain,

fertilizers, chemicals…)

ASPHYXIATING ATMOSPHERE

Normal 20.9% O2 in air

Decreased O2 % can cause: 17%: increased breathing volume and higher heartbeat 14-16%: increased breathing volume, accelerated

heartbeat, poor muscular coordination, rapid fatigue, intermittent respiration

6-10%: nausea, vomiting, inability to perform, unconsciousness

<6%: spasmatic breathing, convulsive movements, death within minutes

ASPHYXIATING ATMOSPHERE

Reduced O2 level can be the result of: Consumption of air

Combustion of flammable substances: welding, heating, cutting, …

Bacterial action: fermentation Chemical reactions: rust formation Rate of consumption influenced by number of people and

the amount of their physical activity working in the space

Displacement of air Gasses as Nitrogen or CO2 are used to displace air or

combustible gases and will result in an asphyxiating atmosphere

TOXIC ATMOSPHERE

Toxic atmosphere can be caused by: Manufacturing process The product stored: ex. removing decomposed organic

material from a tank can liberate toxic substances, such as H2S

The operation performed in the confined space: ex. Welding

During cargo operation a mechanical or human error may also produce toxic gases

CO is a hazardous gas that may build up in an space after incomplete combustion of organic materials (wood, coal, gas, oil..) or microbial decomposition of organic matter. Dangerous at 200ppm, fatal at 1000ppm. Can not be tested with a combustible gas indicator, must be tested specifically

TOXIC ATMOSPHERE

Limit values: TLV (Threshold limit value): concentration for a

healthy person 8 hours a day during his whole working life.

TLV – STEL (Short term limit value): 15 minutes time weighted average, max 4 times a day, min 60 minutes between 2 periods

TLV ceiling: may never be passed

MECHANICAL DANGERS

Each piece of mechanical or electrical equipment should be manually isolated before entry into a CS to prevent inadvertent activation

The space should be completely isolated to prevent vapor leaks, flashbacks, …

Closing of valves is not sufficient. Physically disconnection or blanking is necessary. Testing of the blanked or disconnected lines in needed when re-entering gases may re-contaminate the space

Other areas of concern are steam valves, pressure lines and chemical transfer pipes

COMMUNICATION PROBLEMS

Communication between the in- and outside of the CS is very important

When visual monitoring of the worker is not possible because of the design of the CS or the location of the entry hatch, a voice or alarm-activated explosion proof type of communication system will be necessary

Suitable illumination of an approved type is needed to provide sufficient visibility for the job

ENTRY AND EXIT

The physical limitations of the entry and exit of a CS are directly related to the hazard of the CS

Precautions for safe entry and exit should be taken and standby equipment should be ready for rescue

Consider the following Type of CF and access to the entrance Number and size of openings Barriers in the space Time required for exiting in case of fire or vapor incursion Time required to rescue injured persons

THERMAL EFFECTS

When the body temperature increases above 38,5°C, workers are less efficient, and are prone to heat exhaustion, heat cramps or heat stroke

Special precautions must be taken in cold environments to prevent frostbite, or hypothermia

Protective clothing for both hot or cold environment will add additional bulk to the worker and must be considered in allowing for movement in the CS and exit time

NOICE AND VIBRATION

Workers in CS are exposed to higher sound levels as the sound reverberates on the walls, thus increasing the risk of hearing damage (temporarily or permanent)

Even when it is not intense enough to cause hearing problems, it may still interrupt communication with the standby person at the exit

Whole body vibration may affect multiple body parts and organs

Segmental vibration, appears to be more localized in creating injury to the fingers and hands when using tools as pneumatic hammers or rotary grinders or…

ENTRY

The act by which a person intentionally passes through an opening into a permit required confined space.

Any part of the body passing through the opening is considered entry.

ENTRANT - SUPERVISOR

Entrant: The crewmember(s) who will physically enter the confined space to perform the work.

Supervisor: The officer responsible for coordinating the entry into the confined space. He is also directly responsible.

ATTENDANT

The crewmember who remains outside the confined space and monitors the entrant(s); guards the space against unauthorized entry; warns the entrants of any unusual conditions; and summons the rescue personnel if needed.

CONFINED SPACE PERMIT

A Permit-Required Confined Space is confined space that has one or more of the following characteristics:

Contains or has the potential to contain a hazardous atmosphere;

Contains a material that has the potential for engulfing an entrant;

Has an internal configuration such that an entrant could become trapped or asphyxiated; or

Contains any other serious safety or health hazard.

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CONFINED SPACE ENTRY PROCEDURE

Isolate the space Ventilate/Inert the space Conduct tailboard Complete permit Test the atmosphere Enter the space

ISOLATE THE SPACE FROM ALL HAZARDS

Close Valves Double block & bleed, or blank flange

Empty the Space Depressurize, vent & drain

Lockout/Tagout Equipment Electrical sources Rotating/reciprocating parts Hazardous materials

Clean residue from the space

VENTILATE / INERT THE SPACE

Use mechanical ventilation Fans or air horns

Ventilate at the rate of at least four (4) volumes per hour Larger spaces require more ventilation

Make sure air supply is not contaminated Ventilation air supply must be from

fresh air uncontaminated with flammables, toxins, etc.

Inertion is needed when explosive gasses are present

TAILBORD BREEFING

Entire crew must attend Attendants, entrants, entry supervisor

Review hazards of entry and work Review PPE Review procedure for contacting rescue

verify rescue available

Complete permit

COMPLETE ENTRY FORM

Permit must be correctly and completely filled out prior to entry.

Permit must be activated by Entry Supervisor’s signature to be valid.

No entry is allowed without a valid permit. Permits are valid for up to 12 hours. When work is completed, permit and

tailboard form should be returned to safety. Cancelled permits must be kept on file

TEST THE ATMOSPHERE

IN THIS ORDER: Check for Oxygen Content:

At least 19.5% and less than 23.5% Check for Combustibles:

Less than 10% of the LEL Check for Toxic Gasses:

Most commonly carbon monoxide (PEL <35 ppm)

or any other hazardous materials as determined by the use of the space.

OXYGEN / FLAMMBABILITY TEST

Oxygen: Electrochemical principle. See Toxicity test

with CO

Flammability: Wheatstone bridge or IR: see “gas fires” for

principles

TOXICITY TEST (CO example)

TOXICITY TEST (CO example)

Electrochemical sensors detect gases by measuring the electric that is generated by chemical reactions (oxidation/reduction). The chemical reaction in the case of CO gas generation is :

CO + H2O -> CO2 + 2H+ + 2e-

(Detection principle), carbon monoxide is oxidized on the detection electrode, and hydrogen ions are generated. On the counter electrode, hydrogen ions (equal to the hydrogen ions on the detection electrode) react with oxygen from the air and generate water. The electricity generated by this reaction chain is proportional to gas concentration, thus the gas concentration can be determined by monitoring the generated electricity.

TOXICITY TEST

Tubes with absorbent material:

Airborne chemicals are trapped onto the surface of the absorbent.

Decolourisation takes place Gas specific 1 time use. Momentum

measurement!!!

IMPORTANT NOTICE

Any time a limit is exceeded, no matter what the reason, all personnel shall immediately exit the space, and no others shall enter until atmospheric conditions are returned to safe levels.

THERE ARE NO EXCEPTIONS TO THIS!THERE ARE NO EXCEPTIONS TO THIS!

WHEN PERFORM ATMOSPHERE TESTING

Prior to every entry when the space is vacant;

After a 10 minute ventilation period (if ventilation is necessary);

At least hourly for permit-required confined spaces.

More frequently, if conditions or suspicions warrant.

Always test theAlways test theair at various levels air at various levels to be sure that theto be sure that theentire space is safe.entire space is safe.

Good AirGood Air

Poor AirPoor Air

Deadly AirDeadly Air

Good air near Good air near the opening the opening does NOT mean does NOT mean there is good air there is good air at the bottom!at the bottom!

ENTER THE SPACE

An attendant shall be posted near the entrance for the duration of the work. He shall be in constant communication with the entrants while the job is in progress.

All entrants shall sign the sign in log when entering the space and sign out when exiting.

The attendant shall maintain the permit and sign in log for the duration of the work.

JOB FINISHED

Remove all personnel, tools, and debris from the space. Sign off the log.

Close the space. Cancel the permit. Review the job with the host employer

(hazards, problems, other employers, etc.)

ATTENDANT RESPONSIBILITIES

To monitor entrants during the job and during entry & exit to help insure their safety. The attendant may not abandon his post for any reason while

personnel are in the space unless relieved by another qualified attendant.

To monitor atmospheric conditions in the space prior to and during entry.

To control access to the confined space. To summon emergency assistance as needed. To assess hazards in and around the space, and take

action on the same. To keep records of confined space work, such as air test

results, personnel entry/exit, etc.

ENTRANT RESPONSIBILITIES

To assure that the space has been adequately ventilated, isolated, emptied, or otherwise made safe for entry.

To immediately exit a space, without question, upon word of the attendant, no matter what the reason.

To follow all safety rules and procedures that apply to the job.

To be familiar with the work to be performed and the procedures that apply to the job.

To use the appropriate PPE whenever necessary.

SUPERVISOR RESPONSIBILITIES

To assure adequate protection is provided to the entrants by verifying adequate lockout/tagout and that all hazards are securely isolated.

To support the attendant’s authority in controlling access to a confined space.

To verify that all personnel have exited prior to closing the space.

To assure that all personnel involved are aware of the hazards associated with the space.

To assure that rescue services are available prior to entry.