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

Managers of petrochemical, refining, power, offshore, pulp and paper and other amenities with intensive sizzling processes and piping systems are incessantly challenged with performing all the required coatings upkeep work only in periods of outages. Outages are required in order that course of tools may be correctly maintained and repaired including cleaning of pipelines and vessels, maintenance and substitute of pumps, motors and valves, maintenance coating operations, and other work that may only be achieved when the operations are shut down.
When coatings work must be performed on areas the place elevated temperatures are concerned, many assume that the facility needs to be shut down. This may not be the case.
A question incessantly posed by facility managers is, “Can I do maintenance portray work while the plant is operating?” As described under, the answer is, “Yes you possibly can, however there are security and health points that have to be considered”.
Dangers to personnel must be managed regardless of when or the place work is performed.
Safety and well being issues
There is a spread of safety and well being hazards that must be considered on each industrial upkeep portray project, whether or not the coating materials is being applied to sizzling metal or not. Some of those embody correct material dealing with and storage, fall protection, control of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other health dangers.
These dangers have to be properly evaluated and controlled on each industrial maintenance portray venture, regardless of when or where the work is performed. While current on any job, when making use of specialty coatings to sizzling surfaces, some safety and well being issues ought to receive extra consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and form flammable mixtures within the air, particularly when atomized throughout spray utility or heated. The degree of hazard is determined by the next:
The auto ignition temperature (AIT) of the coating materials is the single most important problem when making use of 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 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 defined by NFPA 30 is “the minimal temperature of a liquid at which sufficient vapour is given off to type an ignitable mixture with the air, close to the surface of the liquid”. In other phrases, the flash level describes the temperature of the liquid that’s high sufficient to generate enough vapour to create a flame if a source of ignition were launched.
For vapours of flammable liquids, there is a minimal concentration beneath which the unfold of the flame doesn’t occur when in contact with a source of ignition. This is the Lower Flammable Limit (LFL). There is a most focus 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 assist combustion.
If safety procedures are adopted, outages will not be required while upkeep is carried out.
Implementing controls
Applying coatings to sizzling surfaces increases the speed at which the solvents are driven off. When applying solvent borne coatings to hot surfaces it should be assumed that the concentration of vapours within the air could exceed the LFL (at least for a quick time after application). As with coating application to ambient temperature metal, controls should be carried out.
While the LFL is more doubtless to be achieved over a shorter time frame during hot utility of coatings than coatings work performed at ambient situations, the resulting fireplace hazard exists in both applications. That is, the fireplace hazard and associated controls must be thought of for the appliance of any solvent-borne flammable coating system, regardless of the work environment. It have to be recognized that the gasoline part of the fire tetrahedron might be current in each ‘hot’ and ‘ambient’ environments and basic steps should be taken to minimize unnecessary solvent vapours within the work space. In addition, as outlined later, consideration must even be directed to eliminating the remaining element of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The fuel component of a fireplace could be lowered by implementing basic controls corresponding to handling and storing flammable liquids in approved, self-closing containers, keeping the number of flammable liquids containers in the work space and in storage areas to the minimal essential and within allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, followed by floor washing with fresh water or steam cleansing and pH testing of the floor, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible fuel indicators ought to be used to confirm that the concentration of flammable vapours is below the LFL. Combustible fuel indicators should be calibrated in accordance with the manufacturer’s suggestions and have to be accredited to be used in flammable atmospheres. Operators of the equipment must be trained in proper gear operation.
Readings must be taken in the general work area 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 application work should immediately cease until the concentration of flammable vapours is managed. The objective of setting the alarm beneath the LFL is to supply a security issue that results in control measures being applied before there is an imminent danger of fireside or explosion.
Monitoring of the combustible vapour concentration will be essential because the effectiveness of natural air flow could also be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or well being skilled or engineer with experience in industrial air flow should be consulted.
At เกจวัดไนโตรเจนราคา , mechanical ventilation techniques ought to present adequate capability to control flammable vapours to beneath 10% of the LFL by either exhaust ventilation to remove contaminants from the work space or by dilution ventilation via introduction of contemporary air to dilute contaminants. As with combustible gasoline indicators, air flow equipment must be permitted for protected use in flammable atmospheres. In addition, air flow tools have to be grounded and bonded.
Additional ventilation, if needed, ought to be continuous throughout coatings software as concentrations may improve as extra surfaces are coated during the course of a piece shift, and particularly on sizzling surfaces where the speed of vaporization is larger.
Ventilation during coatings software should be steady, especially when working on sizzling surfaces.
Sources of Ignition
When making use of coatings to scorching surfaces, the first supply of ignition that readily involves mind is the heat from the surface being painted. The AIT of the coating material is the only most essential problem when making use of coatings to sizzling 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 surface, without the presence of any open spark or flame.
The key to controlling this source of ignition is to confirm the surfaces being coated are below the AIT of the coatings being utilized. While floor temperatures may be known/available in lots of amenities, all floor areas of the process/piping being painted and/or any gear adjoining to the objects being painted where overspray might deposit ought to be measured for actual surface temperature. The results should be in comparison with the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily obvious, a more delicate however nonetheless critical source of ignition to regulate on any industrial portray challenge involving flammable solvents includes the manufacturing of static electricity. Equipment related to the spray-painting operation, corresponding to spray utility tools and air flow gear, can generate static electrical energy.
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 slow generation of heat from oxidation of organic chemicals corresponding to paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This condition is reached when the fabric is packed loosely allowing a big floor space to be uncovered, there’s sufficient air circulating across the materials for oxidation to happen, however the pure ventilation obtainable is inadequate to hold the heat away quick sufficient to forestall it from build up.
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