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

Managers of petrochemical, refining, power, offshore, pulp and paper and other amenities with in depth scorching processes and piping techniques are incessantly challenged with performing all the mandatory coatings upkeep work solely during periods of outages. Outages are required in order that process gear may be correctly maintained and repaired including cleaning of pipelines and vessels, upkeep and replacement of pumps, motors and valves, maintenance coating operations, and different work that may only be accomplished when the operations are shut down.
When coatings work must be carried out on areas the place elevated temperatures are involved, many think that the facility needs 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 below, the answer is, “Yes you possibly can, however there are safety and health issues that have to be considered”.
pressure gauge ยี่ห้อ tk to personnel have to be managed no matter when or where work is carried out.
Safety and well being considerations
There is a range of security and well being hazards that must be thought-about on each industrial maintenance painting project, whether or not the coating materials is being utilized to scorching steel or not. Some of those embody correct material dealing with and storage, fall protection, control of fireside and explosion hazards, and publicity to noise, heavy metals, solvents and different health risks.
These dangers must be properly evaluated and managed on every industrial upkeep painting project, regardless of when or where the work is carried out. While current on any job, when applying specialty coatings to hot surfaces, some security and health points ought to receive additional consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and form flammable mixtures in the air, especially when atomized during spray utility or heated. The diploma of hazard is dependent upon the next:
The auto ignition temperature (AIT) of the coating material is the single most important issue when making use of coatings to scorching 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 warmth source or contact with a heated surface without the presence of an open spark or flame.”
The idea of flash level as outlined by NFPA 30 is “the minimal temperature of a liquid at which adequate vapour is given off to form 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 enough to generate enough vapour to create a flame if a source of ignition have been launched.
For vapours of flammable liquids, there is a minimal focus beneath which the spread of the flame does not occur when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus of vapour within the air above which the spread of the flame does not happen. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the concentration of vapours can help combustion.
If safety procedures are adopted, outages may not be required whereas upkeep is carried out.
Implementing controls
Applying coatings to sizzling surfaces will increase the speed at which the solvents are pushed off. When applying solvent borne coatings to sizzling 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 utility to ambient temperature metal, controls must be carried out.
While the LFL is likely to be achieved over a shorter time frame during scorching utility of coatings than coatings work carried out at ambient conditions, the ensuing hearth hazard exists in each purposes. That is, the fireplace hazard and related controls have to be considered for the applying of any solvent-borne flammable coating system, whatever the work surroundings. It must be acknowledged that the gas part of the fire tetrahedron will be current in both ‘hot’ and ‘ambient’ environments and basic steps should be taken to minimize unnecessary solvent vapours in the work space. In addition, as outlined later, consideration should also be directed to eliminating the remaining factor of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gas factor of a hearth could 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 such as tri-sodium phosphate could additionally be substituted, adopted by floor washing with recent water or steam cleaning and pH testing of the floor, 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 below the LFL. Combustible gas indicators should be calibrated in accordance with the manufacturer’s suggestions and should be permitted for use in flammable atmospheres. Operators of the gear must be skilled in correct equipment operation.
Readings should be taken within the general work area and the vicinity 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 software work should instantly cease till the concentration of flammable vapours is controlled. The purpose of setting the alarm beneath the LFL is to supply a safety factor that ends in management measures being carried out before there is an imminent danger of fire or explosion.
Monitoring of the flammable vapour concentration might be essential because the effectiveness of natural air flow could additionally be variable. If management of flammable vapours requires mechanical air flow, an occupational safety or health skilled or engineer with experience in industrial air flow ought to be consulted.
At a minimal, mechanical ventilation methods ought to provide sufficient capacity to manage flammable vapours to below 10% of the LFL by either exhaust ventilation to take away contaminants from the work space or by dilution air flow via introduction of recent air to dilute contaminants. As with flamable fuel indicators, ventilation equipment have to be approved for safe use in flammable atmospheres. In addition, air flow equipment have to be grounded and bonded.
Additional air flow, if needed, must be continuous during coatings software as concentrations may increase as extra surfaces are coated during the course of a piece shift, and particularly on hot surfaces where the speed of vaporization is higher.
Ventilation during coatings software must be continuous, particularly when engaged on sizzling surfaces.
Sources of Ignition
When applying coatings to scorching surfaces, the primary supply of ignition that readily involves mind is the warmth from the surface being painted. The AIT of the coating material is the single most necessary issue when making use of coatings to hot working 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, 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 beneath the AIT of the coatings being applied. While floor temperatures could also be known/available in many services, all surface areas of the process/piping being painted and/or any tools adjoining to the gadgets being painted where overspray may deposit must be measured for actual surface temperature. ส่วนประกอบpressuregauge should be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily apparent, a more subtle 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 utility gear and ventilation equipment, can generate static electricity.
In addition to external 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 sluggish generation of heat from oxidation of organic chemical substances corresponding to paint solvents is accelerated till the ignition temperature of the fuel is reached.
This condition is reached when the fabric is packed loosely allowing a large surface area to be uncovered, there’s enough air circulating across the material for oxidation to happen, but the pure ventilation out there is insufficient to hold the heat away fast sufficient to stop it from building up.
For more info, go to

Leave a Comment