Step 4 of 5•12 minutes read
Safety Measures
Some of the safety measures that are mentioned in this lesson have already been briefly presented in the PTW lesson. Usually, there is a tick box on the permit that you have to either tick off or leave blank.
Whenever possible, a space such as a workshop where conditions are deemed safe should be designated for hot work. That safe area should always be the first-hand choice when hot work is to be performed.
Atmosphere Testing
Hot Work Inside Enclosed Spaces
It is not unusual to carry out hot work inside cargo tanks, cofferdams or other areas considered to be enclosed spaces. When preparing for such jobs, it is not only gas testing that is important; all other procedures connected to enclosed space entry must also be followed.
Staff should always remain alert to the possibility of leakage of hydrocarbon gas from adjacent spaces or from pipelines running through the tank - regardless of the precaution to test these tanks and spaces. Respiratory hazards from several sources could be present in an enclosed space. These could include one or more of the following:
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Hydrocarbon vapours, such as butane and propane.
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Toxic contaminants associated with organic vapours, such as aromatic hydrocarbons, benzene, toluene, and others.
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Toxic gases, such as benzene, hydrogen sulphide, and mercaptans.
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Oxygen deficiency caused by the presence of inert gas.
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Oxidation (rusting) of bare steel surfaces, or microbial activity, may cause oxygen deficiency.
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Solid remains from inert gas and particulates, such as those from asbestos, welding operations, and paint mists.
Flammable Gases and Vapours
During the carriage and after the discharge of hydrocarbons, the presence of hydrocarbon vapour should always be suspected in enclosed spaces for the following reasons:
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Cargo may have leaked into compartments, including pump rooms, cofferdams, permanent ballast tanks, and tanks adjacent to those carrying cargoes.
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Cargo rests may remain on the internal surfaces of tanks, even after cleaning and ventilating.
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Sludge and scale in a tank declared gas-free tank may give off further hydrocarbon vapour if disturbed or subjected to a rise in temperature.
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Residues may remain in cargo or ballast pipelines and pumps.
A gas detector can detect combustible gases and vapours. Use an instrument capable of providing accurate reading at low concentrations to judge whether the atmosphere is safe for entry.
The combustible gas indicator (sometimes called explosimeter) detects the amount of flammable gas or vapour in the air. An instrument capable of providing an accurate reading at low concentrations should be used to judge whether the atmosphere is safe for entry. Combustible gas detectors are calibrated on standard gas. When testing for other gases and vapours reference should be made to the calibration curves supplied with the instrument. Particular care is required if accumulations of hydrogen can be suspected.
In deciding whether the atmosphere is safe to work in, a “nil” reading on a suitably sensitive combustible gas indicator is desirable. Where the readings have been steady for some time, up to 1% of the lower flammable limit (LFL) may be accepted, e.g. for hydrocarbons in conjunction with an oxygen reading of at least 20% by volume.
Signs
Different Signs – Different Messages
Signs should be informative and posted on suitable locations onboard. For hot work, different signs are available. The most common ones are:
Back of Card 3
Safety Considerations
Photo by Jimmy Nilsson Masth on Unsplash.
The efficiency of the work light plays an important role with regards to safety. Depending on the structure of the work area, it might be necessary to add extra lighting to facilitate for the workers.
Note that only a maximum of 24 V is allowed in an enclosed space, regardless of the type of lighting you bring.
The purpose of a welding curtain or screen is to protect passers-by and nearby workers from the welding arc light. Where welding takes place and other people are likely to be close-by, there should preferably be something in place to prevent them from being affected by the light, like curtains or screens. The hot work area should be equipped with a welding curtain.
During hot work operations, the only persons allowed in the area of the work are the persons stated on the PTW and the Risk Assessment/Job Safety Analysis. All other persons should be kept away, and to achieve that, barriers are used.
The intention of barriers is to keep other people away from dangers, such as:
- Sparks and flames.
- Disabled or loose equipment in the area.
- Open hatch cover if hot work is performed inside an enclosed space.
- Moving machinery or material.
Barriers are preferably accompanied by signs and must be respected at all times.
Fire-Fighting Equipment
The importance of a fire watch cannot be emphasised enough. In order for the fire watch to carry out the work properly, sufficient tools must be available.
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Back of Card 3
Designated Hot Work Area
Whenever possible, a space such as a workshop where conditions are deemed safe should be designated for hot work. That safe area should always be the first choice when hot work is to be performed. Hot work carried out in the designated hot work area does not normally require a hot work permit, except when hot work is being performed on equipment that may have contained a flammable gas or liquid.
A Designated Hot Work Area Shall Be:
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Non-combustible, of a fire-resistant construction, essentially free of combustibles and flammables.
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Fitted with a working surface for soldering and brazing activities should be of a non-combustible material.
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Suitably segregated from adjacent areas.
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Equipped with fire extinguishers.
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Equipped with a heat detector rather than a smoke detector.
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Equipped with mechanical ventilation to control smoke and fumes.
By systematically working to prevent potential work hazards, a safer work environment is maintained for everyone. When mounting scaffoldings it is particularly important to plan ahead and thoroughly go about construction. This is to be able to choose a design suited for the type of work at hand, taking in mind a safe assembly process, and resulting in a reliable and safe work environment.