Managers of petrochemical, refining, power, offshore, pulp and paper and different amenities with in depth hot processes and piping techniques are frequently challenged with performing all the required coatings maintenance work only during times of outages. Outages are required so that course of equipment can be properly maintained and repaired including cleansing of pipelines and vessels, upkeep and replacement of pumps, motors and valves, maintenance coating operations, and different work that may solely be achieved when the operations are shut down.
When coatings work must be performed on areas where elevated temperatures are involved, many suppose that the ability has to be shut down. This is probably not the case.
A query frequently 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 issues that should be considered”.
Dangers to personnel have to be managed no matter when or where work is performed.
Safety and well being considerations
There is a variety of safety and health hazards that should be thought-about on each industrial upkeep painting challenge, whether the coating material is being applied to sizzling steel or not. Some of those embrace proper materials handling and storage, fall safety, management of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other health risks.
These dangers must be properly evaluated and managed on each industrial maintenance portray project, no matter when or the place the work is performed. While present on any job, when making use of specialty coatings to sizzling surfaces, some security and well being issues ought to obtain extra consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, particularly when atomized throughout spray utility or heated. The degree of hazard depends on the following:
The auto ignition temperature (AIT) of the coating material is the only most important problem when applying coatings to sizzling operating equipment. AIT is defined (by the National Safety Council publication Accident Prevention Manual For Business and Industry: Engineering & Technology) as “…the minimum temperature at which a flammable gas-air or vapour-air mixture will ignite from its personal heat source or contact with a heated surface without the presence of an open spark or flame.”
The idea of flash level as defined by NFPA 30 is “the minimal temperature of a liquid at which sufficient vapour is given off to form an ignitable mixture with the air, near the floor of the liquid”. In different phrases, the flash level describes the temperature of the liquid that’s high enough to generate sufficient vapour to create a flame if a supply of ignition have been introduced.
For vapours of flammable liquids, there’s a minimum concentration under which the unfold of the flame doesn’t happen when involved with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus of vapour within the air above which the unfold of the flame doesn’t happen. 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 while upkeep is performed.
Implementing controls
Applying coatings to hot surfaces will increase the rate at which the solvents are pushed off. When applying solvent borne coatings to scorching surfaces it must be assumed that the concentration of vapours in the air may exceed the LFL (at least for a short while after application). As with coating application to ambient temperature metal, controls should be implemented.
While the LFL is likely to be achieved over a shorter time period throughout sizzling application of coatings than coatings work carried out at ambient circumstances, the resulting fire hazard exists in both applications. That is, the fireplace hazard and related controls should be thought of for the application of any solvent-borne flammable coating system, whatever the work setting. It should be acknowledged that the gasoline component of the fireplace tetrahedron shall be present in both ‘hot’ and ‘ambient’ environments and fundamental steps should be taken to reduce pointless solvent vapours in the work space. In addition, as outlined later, attention should even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gasoline component of a fire may be reduced by implementing basic controls corresponding to handling and storing flammable liquids in approved, 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 contemporary water or steam cleansing and pH testing of the surface, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators should be used to confirm that the concentration of flammable vapours is below the LFL. Combustible gasoline indicators must be calibrated in accordance with the manufacturer’s suggestions and should be permitted to be used in flammable atmospheres. Operators of the equipment must be skilled in proper tools 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 ราคาเกจวัดแรงดัน , coatings utility work should instantly cease till the focus of flammable vapours is managed. The objective of setting the alarm below the LFL is to offer a security factor that ends in control measures being applied earlier than there may be an imminent danger of fireside or explosion.
Monitoring of the combustible vapour focus shall be needed because the effectiveness of pure air flow could also be variable. If control of flammable vapours requires mechanical ventilation, an occupational security or well being skilled or engineer with expertise in industrial ventilation should be consulted.
At a minimum, mechanical air flow systems ought to present adequate capability to regulate 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 recent air to dilute contaminants. As with combustible gasoline indicators, ventilation gear should be accredited for secure use in flammable atmospheres. In addition, air flow gear should be grounded and bonded.
Additional ventilation, if wanted, should be continuous throughout coatings software as concentrations may increase as extra surfaces are coated in the course of the course of a work shift, and especially on hot surfaces the place the speed of vaporization is larger.
Ventilation during coatings utility must be steady, especially when engaged on sizzling surfaces.
Sources of Ignition
When applying coatings to sizzling surfaces, the first supply of ignition that readily involves mind is the heat from the floor being painted. The AIT of the coating materials is the single most important concern when applying coatings to scorching working equipment. 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, 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 gear adjacent to the objects being painted where overspray might deposit should be measured for precise floor temperature. The outcomes should be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily obvious, a more subtle however nonetheless important source of ignition to regulate on any industrial painting challenge involving flammable solvents entails the production of static electricity. Equipment related to the spray-painting operation, corresponding to spray software equipment and ventilation equipment, can generate static electricity.
In addition to exterior 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 warmth from oxidation of organic chemical compounds similar to 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 large surface area to be uncovered, there is enough air circulating across the material for oxidation to occur, but the pure ventilation obtainable is insufficient to hold the heat away fast enough to stop it from increase.
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