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

Managers of petrochemical, refining, energy, offshore, pulp and paper and other facilities with in depth sizzling processes and piping systems are frequently challenged with performing all the mandatory coatings maintenance work solely during periods of outages. Outages are required so that process gear can be correctly maintained and repaired including cleaning of pipelines and vessels, upkeep and substitute of pumps, motors and valves, upkeep coating operations, and different work that may only be completed when the operations are shut down.
When digital pressure gauge needs to be carried out on areas the place elevated temperatures are concerned, many think that the facility must be shut down. This is probably not the case.
A question frequently posed by facility managers is, “Can I do maintenance portray work while the plant is operating?” As described beneath, the reply is, “Yes you can, however there are safety and health points that should be considered”.
Dangers to personnel should be managed no matter when or where work is carried out.
Safety and health considerations

There is a spread of security and well being hazards that should be considered on every industrial maintenance painting challenge, whether or not the coating materials is being utilized to hot steel or not. Some of those embody correct material handling and storage, fall safety, control of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and other health risks.
These dangers should be correctly evaluated and managed on every industrial upkeep painting challenge, regardless of when or where the work is performed. While present on any job, when applying specialty coatings to scorching surfaces, some safety and well being points should receive extra consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and kind flammable mixtures in the air, especially when atomized during spray software or heated. The degree of hazard depends on the next:
The auto ignition temperature (AIT) of the coating materials is the only most essential problem when applying coatings to scorching operating equipment. AIT is outlined (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 supply or contact with a heated floor without the presence of an open spark or flame.”

The concept 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 mixture with the air, close to the floor of the liquid”. In different phrases, the flash level describes the temperature of the liquid that’s excessive sufficient to generate enough vapour to create a flame if a source of ignition had been launched.
For vapours of flammable liquids, there’s a minimal concentration under 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 spread 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 help combustion.
If safety procedures are adopted, outages may not be required whereas maintenance is performed.
Implementing controls

Applying coatings to sizzling surfaces will increase the speed 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 might exceed the LFL (at least for a brief time after application). As with coating application to ambient temperature metal, controls have to be implemented.
While the LFL is prone to be achieved over a shorter time period throughout hot utility of coatings than coatings work carried out at ambient situations, the ensuing fire hazard exists in both functions. That is, the fireplace hazard and related controls must be considered for the appliance of any solvent-borne flammable coating system, regardless of the work surroundings. It must be recognized that the fuel part of the fire tetrahedron shall be present in both ‘hot’ and ‘ambient’ environments and basic steps should be taken to attenuate pointless solvent vapours within the work area. In addition, as outlined later, attention must even be directed to eliminating the remaining factor of the tetrahedron – the supply of ignition.
Controlling flammable vapours

The fuel component of a fire can be decreased by implementing primary controls similar to handling and storing flammable liquids in approved, self-closing containers, preserving the number of flammable liquids containers in the work area and in storage areas to the minimum essential and within allowable (regulatory) limits.
Alkaline detergents similar 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 gas indicators ought to be used to verify that the concentration of flammable vapours is below the LFL. Combustible gasoline indicators must be calibrated in accordance with the manufacturer’s suggestions and must be permitted for use in flammable atmospheres. Operators of the tools must be skilled in proper tools operation.
Readings ought to be taken within the basic work space and the vicinity 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 software work ought to instantly stop till the concentration of flammable vapours is managed. The objective of setting the alarm below the LFL is to provide a security factor that leads to control measures being implemented earlier than there is an imminent danger of fireplace or explosion.
Monitoring of the combustible vapour focus will be necessary because the effectiveness of natural ventilation could also be variable. If control of flammable vapours requires mechanical air flow, an occupational safety or health skilled or engineer with expertise in industrial air flow must be consulted.
At a minimal, mechanical air flow methods should provide enough capability to regulate flammable vapours to under 10% of the LFL by either exhaust ventilation to take away contaminants from the work area or by dilution air flow via introduction of fresh air to dilute contaminants. As with flamable fuel indicators, ventilation tools must be accredited for safe use in flammable atmospheres. In addition, air flow gear must be grounded and bonded.
Additional ventilation, if needed, should be continuous throughout coatings utility as concentrations may improve as extra surfaces are coated in the course of the course of a piece shift, and especially on scorching surfaces where the rate of vaporization is higher.
Ventilation during coatings application must be steady, particularly when engaged on sizzling surfaces.
Sources of Ignition

When making use of coatings to sizzling surfaces, the primary source of ignition that readily involves mind is the heat from the surface being painted. The AIT of the coating material is the single most necessary issue when applying coatings to hot operating gear. 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, without the presence of any open spark or flame.
The key to controlling this source of ignition is to verify the surfaces being coated are under the AIT of the coatings being utilized. While surface temperatures may be known/available in many services, all surface areas of the process/piping being painted and/or any gear adjacent to the items being painted where overspray might deposit ought to be measured for precise surface temperature. The results must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily apparent, a extra subtle however nonetheless critical supply of ignition to manage on any industrial portray challenge involving flammable solvents includes the production of static electrical energy. Equipment related to the spray-painting operation, such as spray software 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 gradual generation of heat from oxidation of organic chemicals such as paint solvents is accelerated until the ignition temperature of the gasoline is reached.
This situation is reached when the material is packed loosely allowing a big surface space to be exposed, there may be enough air circulating across the materials for oxidation to occur, however the pure ventilation obtainable is inadequate to hold the warmth away quick sufficient to stop it from building up.
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