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

Managers of petrochemical, refining, energy, offshore, pulp and paper and different services with extensive sizzling processes and piping methods are regularly challenged with performing all the mandatory coatings upkeep work only during times of outages. Outages are required so that process tools may be properly maintained and repaired including cleansing of pipelines and vessels, upkeep and alternative of pumps, motors and valves, maintenance coating operations, and different work that can solely be achieved when the operations are shut down.
When coatings work needs to be carried out on areas the place elevated temperatures are involved, many suppose that the ability must be shut down. This may not be the case.
A query incessantly posed by facility managers is, “Can I do upkeep painting work whereas the plant is operating?” As described below, the answer is, “Yes you’ll find a way to, but there are safety and health issues that should be considered”.
Dangers to personnel have to be managed no matter when or where work is carried out.
Safety and health considerations
There is a spread of safety and well being hazards that have to be thought-about on every industrial maintenance painting venture, whether or not the coating materials is being utilized to scorching metal or not. Some of these embrace proper material handling and storage, fall safety, control of fire and explosion hazards, and publicity to noise, heavy metals, solvents and other well being risks.
These dangers have to be correctly evaluated and managed on every industrial maintenance portray venture, regardless of when or the place the work is performed. While current on any job, when making use of specialty coatings to hot surfaces, some safety and well being points should receive extra consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and form flammable mixtures within the air, particularly when atomized during spray application or heated. The degree of hazard depends on the next:
The auto ignition temperature (AIT) of the coating material is the single most important issue when making use of coatings to scorching working 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 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 point as defined by NFPA 30 is “the minimal temperature of a liquid at which sufficient vapour is given off to type an ignitable combination with the air, near the floor of the liquid”. In เครื่องมือใช้วัดความดัน , the flash level describes the temperature of the liquid that is excessive enough to generate enough vapour to create a flame if a supply of ignition were launched.
For vapours of flammable liquids, there is a minimal concentration below which the unfold of the flame does not occur when in contact with a source of ignition. This is the Lower Flammable Limit (LFL). There is a most concentration of vapour within the air above which the unfold of the flame does not occur. This is the Upper Flammable Limit (UFL). The flammable vary is between the LFL and the UFL, when the focus of vapours can support combustion.
If security procedures are followed, outages is most likely not required whereas upkeep is performed.
Implementing controls
Applying coatings to hot surfaces will increase the speed at which the solvents are pushed off. When applying solvent borne coatings to sizzling surfaces it must be assumed that the focus of vapours in the air may exceed the LFL (at least for a quick time after application). As with coating application to ambient temperature metal, controls must be implemented.
While the LFL is more probably to be achieved over a shorter time frame during hot software of coatings than coatings work performed at ambient situations, the ensuing hearth hazard exists in each functions. That is, the fire hazard and associated controls have to be considered for the application of any solvent-borne flammable coating system, whatever the work environment. It should be recognized that the gas part of the fire tetrahedron might be present in each ‘hot’ and ‘ambient’ environments and primary steps have to be taken to minimize unnecessary solvent vapours in the work area. In addition, as outlined later, consideration should even be directed to eliminating the remaining factor of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The fuel factor of a fireplace may be decreased by implementing fundamental controls such as dealing with and storing flammable liquids in accredited, self-closing containers, maintaining the number of flammable liquids containers in the work area and in storage areas to the minimum needed and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate could also be substituted, followed by surface washing with recent water or steam cleaning and pH testing of the floor, 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 below the LFL. Combustible fuel indicators have to be calibrated in accordance with the manufacturer’s recommendations and should be accredited for use in flammable atmospheres. Operators of the equipment should be educated in proper tools operation.
Readings should be taken in the basic work space 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 utility work ought to immediately cease until the focus of flammable vapours is controlled. The objective of setting the alarm below the LFL is to provide a security factor that leads to management measures being carried out before there could be an imminent danger of fireplace or explosion.
Monitoring of the combustible vapour concentration might be necessary because the effectiveness of pure air flow could additionally be variable. If control of flammable vapours requires mechanical ventilation, an occupational safety or health professional or engineer with expertise in industrial ventilation must be consulted.
At a minimal, mechanical ventilation methods should present enough capability to regulate flammable vapours to beneath 10% of the LFL by both exhaust air flow to remove contaminants from the work space or by dilution air flow by way of introduction of fresh air to dilute contaminants. As with flamable fuel indicators, air flow tools must be permitted for safe use in flammable atmospheres. In addition, ventilation gear must be grounded and bonded.
Additional ventilation, if wanted, should be steady during coatings utility as concentrations may enhance as more surfaces are coated during the course of a piece shift, and particularly on sizzling surfaces where the rate of vaporization is greater.
Ventilation during coatings utility must be continuous, especially when working on hot surfaces.
Sources of Ignition
When applying coatings to hot surfaces, the primary source of ignition that readily involves mind is the heat from the floor being painted. The AIT of the coating material is the only most important issue when making use of coatings to scorching working tools. The AIT of a substance or combination is the minimal temperature at which a vapour-air combination will ignite when in touch with a heated floor, with out the presence of any open spark or flame.
The key to controlling this source of ignition is to confirm the surfaces being coated are under the AIT of the coatings being applied. While floor temperatures could also be known/available in many facilities, all floor areas of the process/piping being painted and/or any tools adjacent to the gadgets being painted where overspray could deposit should be measured for precise surface temperature. เกจวัดแก๊สlpg ought to be in comparability with the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily obvious, a more refined however nonetheless critical source of ignition to manage on any industrial portray project involving flammable solvents involves the manufacturing of static electrical energy. Equipment related to the spray-painting operation, similar to spray utility gear and air flow gear, can generate static electricity.
In addition to external 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 sluggish era of heat from oxidation of organic chemical substances such as paint solvents is accelerated until the ignition temperature of the fuel is reached.
This situation is reached when the material is packed loosely allowing a large surface space to be exposed, there’s enough air circulating around the materials for oxidation to occur, however the pure air flow available is insufficient to carry the warmth away quick sufficient to stop it from building up.
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