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

Managers of petrochemical, refining, energy, offshore, pulp and paper and different amenities with in depth hot processes and piping systems are incessantly challenged with performing all the mandatory coatings upkeep work only in periods of outages. Outages are required so that process equipment could be correctly maintained and repaired together with cleaning of pipelines and vessels, maintenance and substitute of pumps, motors and valves, upkeep coating operations, and other work that may solely 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 ability has to be shut down. This is most likely not the case.
A query incessantly posed by facility managers is, “Can I do maintenance painting work while the plant is operating?” As described beneath, the answer is, “Yes you can, but there are security and health points that must be considered”.
Dangers to personnel must be managed no matter when or the place work is carried out.
Safety and health concerns
There is a spread of security and health hazards that must be considered on every industrial upkeep portray project, whether or not the coating materials is being applied to scorching metal or not. Some of those include correct material handling and storage, fall protection, management of fireplace and explosion hazards, and publicity to noise, heavy metals, solvents and other well being risks.
These risks have to be correctly evaluated and managed on each industrial maintenance painting venture, regardless of when or the place the work is carried out. While current on any job, when applying specialty coatings to scorching surfaces, some safety and health points should receive further consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and kind flammable mixtures in the air, especially when atomized throughout spray software or heated. The diploma of hazard depends on the next:
The auto ignition temperature (AIT) of the coating material is the only most necessary concern when applying coatings to sizzling operating gear. 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 own warmth source or contact with a heated surface with out the presence of an open spark or flame.”
The concept of flash level as defined by NFPA 30 is “the minimum temperature of a liquid at which sufficient vapour is given off to form an ignitable mixture with the air, near the floor of the liquid”. In other phrases, the flash point describes the temperature of the liquid that’s excessive enough to generate enough vapour to create a flame if a supply of ignition have been launched.
For vapours of flammable liquids, there’s a minimal focus beneath which the unfold of the flame doesn’t happen when in contact with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum concentration of vapour within the air above which the spread of the flame doesn’t happen. 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 followed, outages will not be required whereas upkeep is performed.
Implementing controls
Applying coatings to sizzling surfaces increases the rate at which the solvents are driven off. When making use of solvent borne coatings to scorching surfaces it should be assumed that the concentration of vapours in the air could exceed the LFL (at least for a quick while after application). As with coating utility to ambient temperature steel, controls should be carried out.
While เกจวัดแรงดันแบบแห้ง is prone to be achieved over a shorter period of time during hot utility of coatings than coatings work carried out at ambient circumstances, the ensuing fire hazard exists in each functions. That is, the hearth hazard and related controls have to be considered for the applying of any solvent-borne flammable coating system, whatever 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 basic steps have to be taken to attenuate pointless solvent vapours within the work space. In addition, as outlined later, consideration should also 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 lowered by implementing primary controls such as dealing with and storing flammable liquids in accredited, self-closing containers, preserving the variety of flammable liquids containers within the work area and in storage areas to the minimal needed and inside allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could also be substituted, followed by surface washing with fresh water or steam cleansing and pH testing of the surface, or non-combustible solvents such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gasoline indicators ought to be used to confirm that the concentration of flammable vapours is under the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s suggestions and have to be approved for use in flammable atmospheres. Operators of the gear must be skilled in correct equipment operation.
Readings must be taken within the common work area and the neighborhood of the operator and in areas the place there are potential sources of ignition. Typically, units are set to alarm at 10% of the LFL. If the alarm sounds, coatings application work ought to instantly cease until the concentration of flammable vapours is controlled. The objective of setting the alarm beneath the LFL is to supply a security factor that results in control measures being applied earlier than there’s an imminent hazard of fire or explosion.
Monitoring of the flammable vapour concentration will be necessary as the effectiveness of pure ventilation could also be variable. If control of flammable vapours requires mechanical ventilation, an occupational safety or well being skilled or engineer with experience in industrial ventilation should be consulted.
At a minimum, mechanical air flow systems ought to provide adequate capacity to manage flammable vapours to beneath 10% of the LFL by both exhaust air flow to take away contaminants from the work space or by dilution air flow through introduction of contemporary air to dilute contaminants. As with combustible gasoline indicators, ventilation equipment have to be permitted for safe use in flammable atmospheres. In addition, ventilation tools must be grounded and bonded.
Additional ventilation, if needed, should be continuous throughout coatings application as concentrations might improve as more surfaces are coated in the course of the course of a work shift, and particularly on sizzling surfaces where the speed of vaporization is greater.
Ventilation during coatings software must be continuous, especially when engaged on scorching surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the first source of ignition that readily involves thoughts is the heat from the surface being painted. The AIT of the coating materials is the only most important problem when making use of coatings to sizzling working equipment. The AIT of a substance or mixture is the minimal temperature at which a vapour-air mixture will ignite when in contact with a heated floor, with out the presence of any open spark or flame.
The key to controlling this supply of ignition is to verify the surfaces being coated are under the AIT of the coatings being applied. While surface temperatures could also be known/available in many amenities, all surface areas of the process/piping being painted and/or any tools adjacent to the objects being painted the place overspray could deposit must be measured for precise floor temperature. The results ought to be in comparability with the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily apparent, a more refined however nonetheless crucial supply of ignition to regulate on any industrial painting venture involving flammable solvents entails the manufacturing of static electricity. Equipment associated with the spray-painting operation, such as spray utility gear and air flow tools, can generate static electrical energy.
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 era of warmth from oxidation of natural chemical compounds corresponding to paint solvents is accelerated till the ignition temperature of the fuel is reached.
This situation is reached when the material is packed loosely permitting a big floor area to be exposed, there could be enough air circulating around the materials for oxidation to occur, but the pure ventilation available is insufficient to hold the warmth away fast enough to forestall it from increase.
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