Hot Work

The sources of heat most commonly involved in hot work processes and covered by the recommendations include:

* gas/electric welding and cutting apparatus
* blowlamps/blowtorches
* bitumen/tar boilers
* grinding wheels and cutting discs
* brazing and soldering

A suggested Hot Work Permit is included in the document and has been designed taking into account recent experience from fires caused by hot work.

Serious fires frequently occur during maintenance and construction operations, where work is proceeding on either machinery/plant or the fabric of buildings. Most of these are the result of carelessness and ineffective supervision during operations requiring the use of open flames or the local application of heat. In order to prevent such an event a formal risk assessment should always be carried out whenever any hot work is contemplated.

Hot work activities may ignite adjacent or unseen material, heat may be conducted away from the working area by metal components and sparks or hot metal may travel a long distance while retaining the potential to ignite combustible materials. Frequent training should be given to all relevant personnel to make them aware of these and other dangers associated with hot work. In addition to controlling those hot work operations carried out by their own staff, supervisors should also be made aware that it is vital to control the hot work operations of contractors and sub-contractors.

Welding and other hot work processes, carried out on plant, tanks or vessels which contain or have contained flammable or other dangerous materials, constitute a very serious fire hazard and should not be carried out unless the relevant safety precautions have been observed

RECOMMENDATIONS
1) Permit to Work
Experience has shown that a satisfactory standard of care and supervision is far more likely to be achieved where a formalised written permit to work system is in force, under a suitably experienced supervisor with the authority to ensure compliance with the procedures.

 

Consequently these recommendations comprise overall advice together with a Hot Work Permit, on the reverse side of which is a check list of the more obvious precautions. The permit and check list may be freely copied.

2) General precautions
Hot work should only be authorised where a safer method of work is not available. For example pipe jointing may be possible without soldered fittings and hot work avoided when external surfaces are being prepared for painting.

Hot work should only be carried out by trained personnel.Wherever possible items to be the subject of hot work should be removed to a safe area designated for that purpose.

In sprinklered premises hot work should not be carried out when the water supply to the sprinkler is shut off. Adequate precautions should be taken to prevent accidental discharge.
When hot work is being undertaken in premises fitted with an automatic fire detection system, only the zone where the work is being carried out should be isolated. The zone should be reinstated as soon as the task has been completed.

A trained person, not directly involved with the work, should provide a continuous fire watch during and after each period of work (see section 4 ‘Following completion of Hot Work’), to detect and extinguish any incipient burning in the work area and in all adjoining areas to which sparks and heat may spread. These could include the floors below and above, and areas on the other sides of walls from where the work is being carried out.

Before any attempt is made to start the proposed hot work, a formal risk assessment should be carried out and the results recorded, to assess the possible consequences of the operation. The following questions should be considered, together with specific questions according to the actual conditions:

Is it necessary for hot work to be conducted at all?
Would it be feasible to transfer the workplace to a safer area (such as a workshop), or perhaps employ a bolted solution rather than the use of hot work?


If the hot work were to run out of control and fire should result,
a) who or what is at risk within the room?
b) could fire spread out of the room?
c) if the fire were to spread further, what other occupancies could be involved?

Is there a back-up for any mechanical or electrical equipment, computer systems and data which could be damaged by fire?

Are there any personnel who need to use the area at the same time as the hot work is being done? Can alternative arrangements be made?

Could the work lead to the Company’s security being compromised?

The following sections should be useful as a guide.

3.2 Clearance and protection of work area
Before work commences, an area within 10 metres of the hot work process should be cleared of combustible materials and flammable liquids, and all elements of combustible construction and surface finishes protected, as should any openings, holes or gaps in walls, floors and ceilings through which sparks could pass. The distance may need to be more than 10 metres in some circumstances, especially where overhead work is to be undertaken.

Where combustible materials within 10 metres cannot be removed, they should be completely protected. Flammable liquids should always be removed from the area.

Protection, except where mentioned otherwise, should be by the use of non-combustible or purpose-made blankets, drapes or screens. The most commonly available blankets or drapes are those incorporating woven glass fibres.

Combustible floors in the designated areas should be covered with overlapping sheets of non-combustible material or wetted and liberally covered with sand. Particular care should be taken to ensure that any gaps in the flooring are adequately covered.

Floors should be swept clean.

Good ventilation should be provided in all areas where hot work is to be carried out, as procedures may produce copious volumes of smoke and fumes.

Hot work should never be carried out in an area containing a hazardous atmosphere, such as flammable vapours or combustible dust. Where a hazardous atmosphere is suspected, air samples should be taken and work only commenced when the atmosphere has been certified to be non-hazardous. If there is a risk that the hazardous atmosphere may recur, further testing of the atmosphere will be necessary.

Flammable solvents should not be used to clean surfaces immediately before work commences.

3.3 Prevention of fire spread outside the work area
Before carrying out work on one side of a wall or partition an examination should be made of the area on the other side to ensure that any combustible materials are not in danger of ignition by direct or conducted heat. Heat may be readily conducted where walls are metal or metal items such as beams, bolts or pipes penetrate to the other side.

3.4 Composite panels
Where hot work is to be undertaken on composite building panels or similar constructions the type of insulating or other materials behind metal or other non-combustible surfaces should be assessed. If combustible materials are identified or suspected, alternative methods should always be employed. If in doubt, one should always assume that composite panels have a combustible core. Cold stores in particular usually incorporate large amounts of combustible insulating materials in both wall and ceiling panels.

3.5 Voids
An inspection should be carried out for voids above, below or around the work area, such as false ceilings, cable ducts or other cavities, which may be able to transmit flames or smoke from one area to another.

3.6 Multiple occupancy buildings
Liaison should be established in multiple occupancy buildings before work commences to enable contractors or others to be effectively controlled and access made available to areas adjacent to where work is to be undertaken.

 

3.7 Fire precautions
At least two approved extinguishers of a suitable type (see references 4 and 5) or a hydraulic hose reel should be provided at the place where the hot work is to take place and made ready for immediate use in the event of an outbreak of fire. One or more of the personnel directly involved with the work and the person undertaking the fire watch should be trained in the use of this equipment. In general, it is preferable that fires involving flammable gases should only be controlled and not extinguished until such a time as the gas supply can be shut off.

All personnel involved with the hot work should be familiar with the means of escape from the premises and the method of raising the fire alarm and summoning the brigade.

3.8 Security of equipment
The carrying out of hot work may mean that items within the area and others removed from it are more exposed to theft than in a normal running organisation. It is essential to ensure that areas are available for accommodating any displaced items, including computers and data.

4. Following completion of hot work
4.1 Clearance of area
When work is complete, paint strippings, hot stub ends of welding rods and other hot waste materials should be removed and disposed of safetly.

All equipment, including gas cylinders, should be removed to a secure area at the end of the working period or when the task is completed, if this is sooner. Where bitumen/tar boilers are involved, only the gas cylinders need to be removed.

4.2 Fire watch
The fire watch should continue for a least 30 minutes after work is completed, with further checks at regular intervals, up to 60 minutes after completion – see Section 2, ‘General precautions’.

5. Equipment used for hot work - precautions
5.1 Gas welding and cutting apparatus
Gas welding and cutting procedures should only be carried out by trained personnel.
Equipment and hoses should be in good condition, set up in accordance with the manufacturer’s instructions.

Gas cylinders should always be adequately supported, preferably by mounting on purpose-built trolleys.

5.2 Electric welding and cutting apparatus
The cable connecting any electric welding apparatus to the source of electrical supply should be as short as possible.

Care should be taken to ensure that all wiring is of suitable design and construction to carry the heavy currents required and that all connections are correctly made so that they cannot give rise to overheating or sparking.

Operators should be made aware of the importance of three connections (welding lead, welding return and welding safety earth) for every welding circuit.

5.3 Blowlamps and blowtorches
LPG blowlamps/blowtorches should be extinguished and allowed to cool before changing cylinders. Paraffin or petrol blow lamps should only be filled and lit in the open and should not be refilled when hot.

Blowlamps/blowtorches should be lit as short a time as possible before work commences and extinguished immediately the work ceases.

Lighting up should only be carried out in accordance with the manufacturers instructions. Blowlamps/blowtorches should not be left unattended when alight.

Electrically-powered hot air blowers are a particular source of danger as no flame is apparent. When using these appliances the same safety measures should be observed as when undertaking other forms of hot work. Before each period of use the electrical cable to the blower should be inspected to ensure that it has not been damaged by heat or abrasion.

5.4 Bitumen/tar boilers
Bitumen/tar boilers, lead heaters and similar equipment should only be taken onto roofs in exceptional circumstances, when a non-combustible heat insulating base must be provided to prevent heat igniting the roof.

The equipment must always be supervised by an experienced operator and be sited on a firm and level surface where spilled material can easily be controlled.

Gas cylinders must be at least 3 metres from the burner. Gas hoses should be in good condition and properly fitted. Cylinders not in use should be stored away from the working area.
The bitumen level and its temperature should be monitored and the lid should normally be kept on the boiler.

The burner should be turned off before transporting the boiler on a lorry or trailer.

5.5 Grinding wheels and cutting discs
The correct grade of wheel or disc should be used for the task in hand.
Before each period of use, the wheel/disc should be checked to ensure that it is securely fastened and in good condition.

6. Contracted work
Prior to entering into a contractual arrangement with contractors, advice should be obtained from an insurer or insurance adviser because the adequacy of a contractor’s insurance arrangements may vary considerably.

Contractors should be made aware of the specific site hazards and the fire safety procedures to be adopted, including the hot work permit system. A written undertaking to observe the precautions should be obtained from the contractors prior to the commencement of the work.

7. Procedure for Hot Work Permits
7.1 Issuing authority
The person nominated to authorise hot work, normally the company fire or safety officer, must have experience or training in the problems associated with hot work and be of suitable status to ensure compliance with the procedures.

Before work starts a hot work permit should be obtained from the authorised person. A suggested format for a permit is included in this document. This should be used on every occasion that hot work of any type is undertaken within or upon the fabric of established buildings or any structures or plant in the open. This procedure should also apply to construction sites once fitting out has commenced, and to all buildings which are being refurbished.

 

7.2 Limitations to issue of permit
A hot work permit should not be issued without considering the significance of any other permits to work in the vicinity, or adjacent manufacturing processes which may involved the use of flammable liquids or gases.

A hot work permit should be issued for a specific task that is to be undertaken in a clearly identified area. Hot work permits should not be issued for protracted periods. Separate hot work permits should be issued for work which extends from morning to afternoon periods.

7.3 Checklist
Before completing the first part of the hot work permit, the person responsible for issuing the permit for the work should complete the checklist, in conjunction with the person responsible for carrying out the work, to indicate that fire protection measures are adequate, suitable precautions have been taken and the equipment to be used is safe.

7.4 Additional conditions

If the person authorised to issue the hot work permit is not satisfied with the arrangements, further measures may be requested, and any additional conditions should be entered in the space provided. The earliest time at which a final fire-check should be made will also be specified. This will normally be at least one hour after the time of expiry of the hot work permit, when work must be complete. If trained personnel will not be available to make this check ( for example in the case of a permit issued late in the day) work must not be commenced.

7.5 Retention of the permit
The hot work permit should be completed in duplicate, with the top copy being handed to the person responsible for carrying out the work. The second copy should be retained by the issuer who may wish to inspect the site of the work or instigate spot checks to ensure that conditions have been made and that work is complete before the hot work permit expires.

The completed form should be returned to the issuer and retained for future reference.