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

Managers of petrochemical, refining, power, offshore, pulp and paper and different services with in depth sizzling processes and piping techniques are incessantly challenged with performing all the necessary coatings maintenance work only during periods of outages. Outages are required so that process tools may be correctly maintained and repaired including cleansing of pipelines and vessels, upkeep and alternative of pumps, motors and valves, maintenance coating operations, and other work that may solely be achieved when the operations are shut down.
When coatings work must be performed on areas where elevated temperatures are involved, many suppose that the ability must be shut down. This will not be the case.
A question regularly posed by facility managers is, “Can I do maintenance painting work while the plant is operating?” As described below, the answer is, “Yes you can, but there are safety and well being issues that have to be considered”.
Dangers to personnel should be managed regardless of when or the place work is carried out.
Safety and well being concerns

There is a spread of safety and health hazards that must be considered on every industrial upkeep painting project, whether the coating material is being utilized to sizzling steel or not. Some of those include proper materials dealing with and storage, fall safety, management of fire and explosion hazards, and publicity to noise, heavy metals, solvents and other well being risks.
pressure gauge have to be properly evaluated and controlled on each industrial upkeep painting venture, no matter when or where the work is carried out. While present on any job, when making use of specialty coatings to hot surfaces, some security and health issues should obtain further consideration.
Flammable and combustible liquids in plenty of coatings (solvents) can vaporize and kind flammable mixtures within the air, especially when atomized throughout spray software or heated. The diploma of hazard is determined by the next:
The auto ignition temperature (AIT) of the coating materials is the single most important issue when applying coatings to sizzling operating equipment. AIT is defined (by the National Safety Council publication Accident Prevention Manual For Business and Industry: Engineering & Technology) as “…the minimal temperature at which a flammable gas-air or vapour-air mixture will ignite from its personal heat source or contact with a heated floor without the presence of an open spark or flame.”

The idea of flash point as outlined by NFPA 30 is “the minimum temperature of a liquid at which adequate vapour is given off to type an ignitable combination with the air, near the surface of the liquid”. In different words, the flash point describes the temperature of the liquid that is high sufficient to generate sufficient vapour to create a flame if a supply of ignition have been launched.
For vapours of flammable liquids, there’s a minimal focus below which the unfold of the flame does not occur when in touch with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a maximum concentration of vapour in the air above which the unfold 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 focus of vapours can support combustion.
If safety procedures are adopted, outages is most likely not required whereas maintenance is performed.
Implementing controls

Applying coatings to sizzling surfaces will increase the rate at which the solvents are driven off. When making use of solvent borne coatings to sizzling surfaces it have to be assumed that the concentration of vapours within the air might exceed the LFL (at least for a quick time after application). As with coating software to ambient temperature steel, controls have to be carried out.
While the LFL is prone to be achieved over a shorter time period throughout sizzling application of coatings than coatings work performed at ambient circumstances, the resulting fireplace hazard exists in each functions. That is, the fireplace hazard and associated controls have to be thought-about for the application of any solvent-borne flammable coating system, regardless of the work setting. It must be recognized that the fuel component of the fire tetrahedron will be present in both ‘hot’ and ‘ambient’ environments and fundamental steps should be taken to minimize unnecessary solvent vapours in the work area. In addition, as outlined later, consideration must also be directed to eliminating the remaining element of the tetrahedron – the source of ignition.
Controlling flammable vapours

The gas factor of a fire could be lowered by implementing basic controls such as handling and storing flammable liquids in accredited, self-closing containers, preserving the number of flammable liquids containers in the work space and in storage areas to the minimal needed and within allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate may be substituted, followed by surface washing with contemporary water or steam cleansing and pH testing of the surface, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gas indicators ought to be used to verify that the focus of flammable vapours is beneath the LFL. Combustible fuel indicators should be calibrated in accordance with the manufacturer’s recommendations and have to be permitted to be used in flammable atmospheres. Operators of the tools must be trained in proper tools operation.
Readings must be taken in the basic work area and the vicinity of the operator and in areas the place there are potential sources of ignition. Typically, models are set to alarm at 10% of the LFL. If the alarm sounds, coatings software work ought to instantly stop until the concentration of flammable vapours is managed. The function of setting the alarm beneath the LFL is to offer a security issue that results in management measures being carried out before there might be an imminent danger of fireside or explosion.
Monitoring of the flammable vapour concentration might be needed because the effectiveness of pure air flow may be variable. If management of flammable vapours requires mechanical air flow, an occupational security or health skilled or engineer with expertise in industrial air flow should be consulted.
At a minimal, mechanical ventilation techniques should provide enough capacity to control flammable vapours to under 10% of the LFL by both exhaust ventilation to remove contaminants from the work space or by dilution ventilation via introduction of recent air to dilute contaminants. As with combustible fuel indicators, air flow gear must be permitted for safe use in flammable atmospheres. In addition, ventilation gear should be grounded and bonded.
Additional ventilation, if needed, ought to be steady throughout coatings software as concentrations may increase as extra surfaces are coated through the course of a work shift, and particularly on hot surfaces where the speed of vaporization is larger.
Ventilation during coatings utility should be continuous, especially when engaged on sizzling surfaces.
Sources of Ignition

When applying coatings to scorching surfaces, the primary source of ignition that readily comes to thoughts is the heat from the surface being painted. The AIT of the coating material is the one most important issue when applying coatings to sizzling operating gear. The AIT of a substance or combination is the minimal temperature at which a vapour-air mixture will ignite when in contact with a heated surface, without the presence of any open spark or flame.
The key to controlling this source of ignition is to confirm the surfaces being coated are beneath the AIT of the coatings being applied. While floor temperatures could also be known/available in many amenities, all floor areas of the process/piping being painted and/or any tools adjacent to the items being painted where overspray could deposit ought to be measured for precise floor temperature. The outcomes ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily obvious, a more delicate however nonetheless critical supply of ignition to manage on any industrial portray challenge involving flammable solvents entails the manufacturing of static electrical energy. Equipment associated with the spray-painting operation, similar to spray utility equipment and air flow tools, can generate static electrical energy.
In addition to exterior sources of ignition, spontaneous ignition can occur when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition occurs when the gradual generation of heat from oxidation of organic chemical substances corresponding to paint solvents is accelerated until the ignition temperature of the gasoline is reached.
This situation is reached when the material is packed loosely permitting a big floor space to be uncovered, there may be enough air circulating across the material for oxidation to happen, but the pure air flow obtainable is insufficient to carry the heat away fast enough to prevent it from build up.
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