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 scorching processes and piping techniques are frequently challenged with performing all the mandatory coatings maintenance work only during periods of outages. Outages are required in order that course of tools could be correctly maintained and repaired including cleansing of pipelines and vessels, maintenance and alternative of pumps, motors and valves, maintenance coating operations, and other work that may solely be accomplished when the operations are shut down.
When coatings work needs to be carried out on areas the place elevated temperatures are concerned, many suppose that the facility must be shut down. This will not be the case.
A question frequently posed by facility managers is, “Can I do upkeep portray work whereas the plant is operating?” As described beneath, the reply is, “Yes you probably can, but there are safety and health points that should be considered”.
Dangers to personnel must be managed no matter when or the place work is performed.
เกจวัดแรงดันถังลม and health considerations
There is a variety of security and well being hazards that have to be considered on every industrial maintenance painting venture, whether the coating materials is being applied to sizzling metal or not. Some of these embrace correct materials dealing with and storage, fall safety, control of fire and explosion hazards, and exposure to noise, heavy metals, solvents and other well being dangers.
These risks should be correctly evaluated and managed on each industrial maintenance portray project, regardless of when or the place the work is carried out. While current on any job, when making use of specialty coatings to sizzling surfaces, some safety and health issues should obtain additional consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and kind flammable mixtures within the air, especially when atomized during spray software or heated. The diploma of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating materials is the single most necessary concern when applying coatings to scorching operating 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 mixture will ignite from its own heat source or contact with a heated surface 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 type an ignitable mixture with the air, close to the floor of the liquid”. In different phrases, the flash point describes the temperature of the liquid that is excessive sufficient to generate enough vapour to create a flame if a source of ignition have been launched.
For vapours of flammable liquids, there’s a minimum focus beneath which the unfold of the flame does not happen when in touch with a source 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 may not be required whereas maintenance is carried out.
Implementing controls
Applying coatings to scorching surfaces increases the rate at which the solvents are driven off. When applying solvent borne coatings to scorching surfaces it should be assumed that the focus of vapours within the air could exceed the LFL (at least for a short time after application). As with coating software to ambient temperature metal, controls must be carried out.
While the LFL is likely to be achieved over a shorter time period throughout scorching application of coatings than coatings work performed at ambient conditions, the resulting hearth hazard exists in both functions. That is, the fire hazard and associated controls should be thought-about for the application of any solvent-borne flammable coating system, regardless of the work surroundings. It must be recognized that the fuel part of the fire tetrahedron will be present in both ‘hot’ and ‘ambient’ environments and basic steps should be taken to attenuate pointless solvent vapours in the work space. In addition, as outlined later, attention must even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gas factor of a fireplace may be reduced by implementing fundamental controls similar to handling and storing flammable liquids in permitted, self-closing containers, preserving the variety of flammable liquids containers in the work space and in storage areas to the minimum needed and inside allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could also be substituted, adopted by surface washing with fresh 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 gasoline indicators should be used to confirm that the concentration of flammable vapours is beneath the LFL. Combustible gasoline indicators must be calibrated in accordance with the manufacturer’s suggestions and should be permitted for use in flammable atmospheres. Operators of the equipment must be trained in correct equipment operation.
Readings should be taken in the common work space and the neighborhood of the operator and in areas the place there are potential sources of ignition. Typically, items are set to alarm at 10% of the LFL. If the alarm sounds, coatings application work should immediately stop till the focus of flammable vapours is controlled. The objective of setting the alarm below the LFL is to supply a safety factor that leads to control measures being applied before there is an imminent danger of fire or explosion.
Monitoring of the flammable vapour concentration will be needed because the effectiveness of pure ventilation may be variable. If control of flammable vapours requires mechanical air flow, an occupational safety or health professional or engineer with expertise in industrial air flow should be consulted.
At a minimum, mechanical air flow techniques ought to present adequate capability to manage flammable vapours to below 10% of the LFL by either exhaust air flow to remove contaminants from the work space or by dilution air flow via introduction of contemporary air to dilute contaminants. As with combustible fuel indicators, ventilation equipment must be permitted for protected use in flammable atmospheres. In addition, ventilation gear should be grounded and bonded.
Additional ventilation, if needed, must be steady during coatings software as concentrations may improve as extra surfaces are coated in the course of the course of a work shift, and especially on scorching surfaces the place the rate of vaporization is larger.
Ventilation throughout coatings utility should be steady, especially when working on hot surfaces.
Sources of Ignition
When applying coatings to scorching surfaces, the first supply of ignition that readily involves thoughts is the warmth from the surface being painted. เกจวัดแรง of the coating material is the only most necessary problem when applying coatings to hot operating gear. The AIT of a substance or combination is the minimal temperature at which a vapour-air mixture will ignite when involved with a heated floor, without the presence of any open spark or flame.
The key to controlling this supply of ignition is to verify the surfaces being coated are below the AIT of the coatings being applied. While surface temperatures may be known/available in plenty of amenities, all floor areas of the process/piping being painted and/or any gear adjoining to the items being painted where overspray may deposit must be measured for actual floor temperature. The results ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily apparent, a more refined however nonetheless crucial source of ignition to control on any industrial portray project involving flammable solvents includes the production of static electricity. Equipment related to the spray-painting operation, similar to spray application tools and air flow equipment, 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 slow era of heat from oxidation of natural chemical substances similar to paint solvents is accelerated till the ignition temperature of the gas is reached.
This condition is reached when the fabric is packed loosely allowing a big surface space to be exposed, there’s sufficient air circulating across the materials for oxidation to occur, however the pure air flow available is insufficient to hold the warmth away quick enough to stop it from build up.
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