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

Managers of petrochemical, refining, power, offshore, pulp and paper and different services with extensive scorching processes and piping methods are incessantly challenged with performing all the necessary coatings upkeep work only in periods of outages. Outages are required so that course of gear may be correctly maintained and repaired including cleansing of pipelines and vessels, upkeep and replacement of pumps, motors and valves, upkeep coating operations, and other work that may only be achieved when the operations are shut down.
When coatings work has to be performed on areas where elevated temperatures are concerned, many think that the ability has to be shut down. This will not be the case.
A question incessantly posed by facility managers is, “Can I do maintenance portray work whereas the plant is operating?” As described below, the reply is, “Yes you can, but there are security and well being points that must be considered”.
Dangers to personnel should be managed regardless of when or the place work is carried out.
Safety and well being issues
There is a variety of security and health hazards that must be thought of on every industrial maintenance painting project, whether the coating material is being utilized to sizzling steel or not. Some of these include proper material dealing with and storage, fall protection, control of fireside and explosion hazards, and publicity to noise, heavy metals, solvents and different well being risks.
These dangers should be properly evaluated and managed on each industrial upkeep painting venture, no matter when or where the work is performed. While present on any job, when making use of specialty coatings to sizzling surfaces, some safety and well being issues should receive additional consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and kind flammable mixtures in the air, particularly when atomized throughout spray application or heated. The degree of hazard is decided by the next:
The auto ignition temperature (AIT) of the coating materials is the only most important 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 combination will ignite from its personal heat source or contact with a heated surface with out the presence of an open spark or flame.”
The idea of flash point as outlined by NFPA 30 is “the minimum temperature of a liquid at which sufficient vapour is given off to kind an ignitable combination with the air, close to the floor of the liquid”. In เกจวัดแรงดันน้ำ , the flash level 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 introduced.
For vapours of flammable liquids, there is a minimum concentration under which the spread of the flame doesn’t occur when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus of vapour in 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 followed, outages may not be required whereas maintenance is performed.
Implementing controls
Applying coatings to sizzling surfaces will increase the rate at which the solvents are driven off. When applying solvent borne coatings to scorching surfaces it have to be assumed that the concentration of vapours in the air might exceed the LFL (at least for a short while after application). As with coating application to ambient temperature metal, controls have to be carried out.
While the LFL is likely to be achieved over a shorter time frame during scorching software of coatings than coatings work carried out at ambient situations, the resulting fire hazard exists in both purposes. That is, the hearth hazard and associated controls have to be thought-about for the applying of any solvent-borne flammable coating system, whatever the work surroundings. It have to be acknowledged that the gasoline component of the fire tetrahedron will be current in each ‘hot’ and ‘ambient’ environments and basic steps have to be taken to reduce unnecessary solvent vapours within the work area. In addition, as outlined later, consideration must also be directed to eliminating the remaining component of the tetrahedron – the source of ignition.
Controlling flammable vapours
The gasoline factor of a fireplace may be reduced by implementing primary controls such as handling and storing flammable liquids in accredited, self-closing containers, maintaining the variety of flammable liquids containers in the work space and in storage areas to the minimum essential and within allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could additionally be substituted, followed by floor washing with contemporary 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 cleaning.
Combustible fuel indicators ought to be used to verify that the concentration of flammable vapours is beneath the LFL. Combustible gasoline indicators must be calibrated in accordance with the manufacturer’s suggestions and must be accredited to be used in flammable atmospheres. Operators of the tools must be educated in correct equipment operation.
Readings should be taken within the general work space 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 utility work should immediately stop till the concentration of flammable vapours is controlled. The purpose of setting the alarm below the LFL is to offer a safety factor that leads to control measures being applied earlier than there’s an imminent danger of fireplace or explosion.
Monitoring of the flammable vapour concentration will be necessary as the effectiveness of natural ventilation could additionally be variable. If management of flammable vapours requires mechanical ventilation, an occupational security or health skilled or engineer with expertise in industrial ventilation should be consulted.
At a minimum, mechanical air flow methods ought to present sufficient capacity to control flammable vapours to beneath 10% of the LFL by both exhaust ventilation to take away contaminants from the work area or by dilution ventilation via introduction of fresh air to dilute contaminants. As with flamable fuel indicators, ventilation equipment have to be accredited for secure use in flammable atmospheres. In addition, air flow gear should be grounded and bonded.
Additional ventilation, if wanted, must be steady during coatings application as concentrations may increase as extra surfaces are coated during the course of a work shift, and particularly on scorching surfaces the place the speed of vaporization is higher.
Ventilation during coatings utility ought to be steady, especially when engaged on scorching surfaces.
Sources of Ignition
When applying coatings to sizzling surfaces, the primary source of ignition that readily involves thoughts is the warmth from the floor being painted. The AIT of the coating materials is the one most essential concern when applying coatings to sizzling working gear. The AIT of a substance or combination is the minimum temperature at which a vapour-air mixture will ignite when involved with a heated surface, with out the presence of any open spark or flame.
The key to controlling this source of ignition is to verify the surfaces being coated are beneath 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 the place overspray may deposit should be measured for precise surface temperature. The outcomes should be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily apparent, a more delicate however nonetheless crucial source of ignition to manage on any industrial portray venture involving flammable solvents includes the manufacturing of static electricity. Equipment associated with the spray-painting operation, similar to spray software equipment and air flow tools, can generate static electrical energy.
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 occurs when the slow generation of warmth from oxidation of natural chemicals such as paint solvents is accelerated until the ignition temperature of the fuel is reached.
This situation is reached when the fabric is packed loosely permitting a big floor space to be uncovered, there is enough air circulating around the materials for oxidation to occur, but the pure air flow obtainable is inadequate to carry the heat away fast enough to prevent it from build up.
For more info, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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