Considerations for the appliance of high-temperature coatings – Part 1

Managers of petrochemical, refining, power, offshore, pulp and paper and different amenities with intensive scorching processes and piping techniques are incessantly challenged with performing all the mandatory coatings maintenance work solely during periods of outages. Outages are required so that course of tools can be properly maintained and repaired together with cleansing of pipelines and vessels, maintenance and alternative of pumps, motors and valves, upkeep coating operations, and different work that can only be completed when the operations are shut down.
When coatings work needs to be performed on areas the place elevated temperatures are involved, many think that the facility must be shut down. This is most likely not the case.
A query regularly posed by facility managers is, “Can I do upkeep painting work while the plant is operating?” As described below, the reply is, “Yes you possibly can, however there are safety and health issues that should be considered”.
Dangers to personnel have to be managed no matter when or where work is performed.
Safety and health issues

There is a variety of security and health hazards that should be thought of on each industrial maintenance portray venture, whether or not the coating material is being applied to hot steel or not. Some of these embrace proper material handling and storage, fall protection, control of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and different well being dangers.
These risks should be properly evaluated and managed on every industrial maintenance portray venture, no matter when or where the work is carried out. While current on any job, when making use of specialty coatings to sizzling surfaces, some security and well being points should obtain further consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and form flammable mixtures in the air, especially when atomized throughout spray application or heated. The degree of hazard depends on the next:
The auto ignition temperature (AIT) of the coating materials is the one most important problem when making use of coatings to sizzling working gear. AIT is defined (by the National Safety Council publication Accident Prevention Manual For Business and Industry: Engineering & Technology) as “…the minimum temperature at which a flammable gas-air or vapour-air combination will ignite from its personal warmth source or contact with a heated floor without the presence of an open spark or flame.”

The idea of flash level as defined by NFPA 30 is “the minimal temperature of a liquid at which enough vapour is given off to form an ignitable combination with the air, close to the surface of the liquid”. In different words, the flash level describes the temperature of the liquid that is high enough to generate sufficient vapour to create a flame if a supply of ignition were introduced.
For vapours of flammable liquids, there is a minimal focus under which the unfold of the flame does not occur when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus of vapour within the air above which the spread of the flame does not occur. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the concentration of vapours can help combustion.
If safety procedures are adopted, outages is in all probability not required while upkeep is performed.
Implementing controls

Applying coatings to sizzling surfaces will increase the speed at which the solvents are driven off. When making use of solvent borne coatings to sizzling surfaces it must be assumed that the focus of vapours within the air could exceed the LFL (at least for a quick while after application). As with coating software to ambient temperature steel, controls must be applied.
While the LFL is likely to be achieved over a shorter time frame throughout scorching utility of coatings than coatings work performed at ambient circumstances, the ensuing fire hazard exists in each applications. That is, the hearth hazard and related controls should be thought of for the application of any solvent-borne flammable coating system, whatever the work surroundings. It must be acknowledged that the gasoline component of the fireplace tetrahedron might be current in each ‘hot’ and ‘ambient’ environments and primary steps must be taken to reduce unnecessary solvent vapours within the work area. In addition, as outlined later, consideration should even be directed to eliminating the remaining element of the tetrahedron – the source of ignition.
Controlling flammable vapours

The fuel element of a fire can be reduced by implementing fundamental controls corresponding to handling and storing flammable liquids in permitted, self-closing containers, preserving the variety of flammable liquids containers in the work area and in storage areas to the minimum necessary and inside allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, followed by floor washing with recent water or steam cleansing and pH testing of the surface, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible fuel indicators should be used to verify that the focus of flammable vapours is below the LFL. Combustible fuel indicators should be calibrated in accordance with the manufacturer’s suggestions and have to be approved for use in flammable atmospheres. Operators of the gear should be trained in correct gear operation.
Readings must be taken in the general work area and the neighborhood of the operator and in areas where there are potential sources of ignition. Typically, models are set to alarm at 10% of the LFL. If the alarm sounds, coatings application work ought to instantly stop until the concentration of flammable vapours is controlled. The objective of setting the alarm beneath the LFL is to supply a security factor that leads to management measures being implemented before there’s an imminent danger of fireside or explosion.
Monitoring of the combustible vapour concentration shall be needed as the effectiveness of natural air flow could additionally be variable. If management of flammable vapours requires mechanical air flow, an occupational safety or health skilled or engineer with expertise in industrial air flow should be consulted.
At a minimal, mechanical ventilation methods should present enough capability to regulate flammable vapours to below 10% of the LFL by either exhaust ventilation to take away contaminants from the work space or by dilution air flow via introduction of fresh air to dilute contaminants. As with flamable gasoline indicators, air flow gear should be accredited for secure use in flammable atmospheres. In addition, ventilation equipment must be grounded and bonded.
digital pressure gauge , if needed, should be continuous during coatings software as concentrations may increase as extra surfaces are coated in the course of the course of a work shift, and especially on hot surfaces the place the speed of vaporization is higher.
Ventilation during coatings application ought to be continuous, especially when working on hot surfaces.
Sources of Ignition

When applying coatings to hot surfaces, the first source of ignition that readily involves mind is the heat from the floor being painted. The AIT of the coating materials is the only most essential concern when making use of coatings to hot operating equipment. The AIT of a substance or combination is the minimum temperature at which a vapour-air combination will ignite when involved with a heated floor, with out the presence of any open spark or flame.
The key to controlling this supply of ignition is to confirm the surfaces being coated are below the AIT of the coatings being utilized. While surface temperatures may be known/available in many amenities, all floor areas of the process/piping being painted and/or any tools adjacent to the objects being painted where overspray could deposit ought to be measured for actual floor temperature. The results ought to be compared to the AIT of the coating system.
While digital pressure gauge -ignition and open sources of ignition may be readily apparent, a more subtle but nonetheless important supply of ignition to regulate on any industrial painting project involving flammable solvents includes the manufacturing of static electricity. เพรสเชอร์เกจ associated with the spray-painting operation, corresponding to spray application gear and air flow tools, can generate static electricity.
In addition to exterior sources of ignition, spontaneous ignition can happen when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition happens when the slow technology of heat from oxidation of organic chemicals similar to paint solvents is accelerated until the ignition temperature of the fuel is reached.
This condition is reached when the material is packed loosely allowing a large floor area to be exposed, there is sufficient air circulating across the material for oxidation to occur, however the natural air flow obtainable is inadequate to hold the heat away fast enough to stop it from build up.
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