Managers of petrochemical, refining, power, offshore, pulp and paper and other amenities with in depth sizzling processes and piping techniques are regularly challenged with performing all the mandatory coatings upkeep work solely in periods of outages. Outages are required in order that process tools may be properly maintained and repaired together with cleansing of pipelines and vessels, upkeep and substitute of pumps, motors and valves, maintenance coating operations, and other work that can solely be accomplished when the operations are shut down.
When coatings work needs to be carried out on areas the place elevated temperatures are involved, many assume that the ability has to be shut down. This will not be the case.
A question frequently posed by facility managers is, “Can I do maintenance portray work whereas the plant is operating?” As described below, the answer is, “Yes you can, but there are security and health points that should be considered”.
Dangers to personnel should be managed no matter when or the place work is performed.
Safety and well being issues
There is a variety of safety and well being hazards that should be thought of on each industrial upkeep painting challenge, whether or not the coating materials is being applied to hot steel or not. Some of these embrace proper materials dealing with and storage, fall protection, management of fireplace and explosion hazards, and publicity to noise, heavy metals, solvents and other well being risks.
These risks must be properly evaluated and controlled on every industrial upkeep portray project, no matter when or the place the work is carried out. While current on any job, when making use of specialty coatings to sizzling surfaces, some security and well being points should obtain extra consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and kind flammable mixtures within the air, especially when atomized throughout spray utility or heated. The degree of hazard is dependent upon the next:
The auto ignition temperature (AIT) of the coating materials is the one most essential issue when applying coatings to sizzling working 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 combination will ignite from its own heat supply or contact with a heated floor with out the presence of an open spark or flame.”
The idea of flash point as defined by NFPA 30 is “the minimal temperature of a liquid at which adequate vapour is given off to type an ignitable combination with the air, close to the floor of the liquid”. In different phrases, the flash point describes the temperature of the liquid that’s high enough to generate sufficient vapour to create a flame if a supply of ignition were launched.
For vapours of flammable liquids, there’s a minimal focus under which the unfold of the flame doesn’t occur when involved with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum concentration of vapour in the air above which the spread of the flame doesn’t occur. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the concentration of vapours can support combustion.
If security procedures are adopted, outages is probably not required whereas upkeep is carried out.
Implementing controls
Applying coatings to hot surfaces will increase the speed at which the solvents are pushed off. When applying solvent borne coatings to scorching surfaces it have to be assumed that the focus of vapours within the air could exceed the LFL (at least for a short time after application). As with เกจวัดแรงดันแก๊สlpgรถยนต์ to ambient temperature steel, controls should be carried out.
While the LFL is more doubtless to be achieved over a shorter period of time throughout hot utility of coatings than coatings work carried out at ambient situations, the ensuing fire hazard exists in each applications. That is, the fire hazard and related controls must be considered for the appliance of any solvent-borne flammable coating system, whatever the work surroundings. It must be recognized that the gasoline component of the hearth tetrahedron might be current in both ‘hot’ and ‘ambient’ environments and fundamental steps have to be taken to reduce unnecessary 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 source of ignition.
Controlling flammable vapours
The gas factor of a fireplace can be reduced by implementing fundamental controls corresponding to dealing with and storing flammable liquids in accredited, self-closing containers, maintaining the number of flammable liquids containers within the work area and in storage areas to the minimum needed and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate may be substituted, adopted by floor washing with contemporary water or steam cleaning and pH testing of the floor, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gas indicators should be used to confirm that the concentration of flammable vapours is beneath the LFL. Combustible gasoline indicators should be calibrated in accordance with the manufacturer’s suggestions and must be accredited to be used in flammable atmospheres. Operators of the gear should be educated in correct equipment operation.
Readings should be taken in the basic work space 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 utility work should immediately cease until the focus of flammable vapours is controlled. The purpose of setting the alarm under the LFL is to offer a safety factor that results in control measures being implemented before there’s an imminent danger of fire or explosion.
Monitoring of the flammable vapour focus might be needed because the effectiveness of natural air flow may be variable. If control of flammable vapours requires mechanical air flow, an occupational security or well being skilled or engineer with experience in industrial air flow ought to be consulted.
At a minimum, mechanical ventilation techniques should present sufficient capability to control flammable vapours to below 10% of the LFL by either exhaust ventilation to remove contaminants from the work area or by dilution ventilation via introduction of recent air to dilute contaminants. As with combustible fuel indicators, air flow tools must be approved for secure use in flammable atmospheres. In addition, ventilation equipment should be grounded and bonded.
Additional ventilation, if wanted, must be continuous during coatings software as concentrations might improve as more surfaces are coated through the course of a piece shift, and especially on sizzling surfaces the place the speed of vaporization is higher.
Ventilation throughout coatings utility should be steady, particularly when working on sizzling surfaces.
Sources of Ignition
When applying coatings to sizzling surfaces, the primary source of ignition that readily comes to thoughts is the warmth from the surface being painted. The AIT of the coating material is the single most necessary problem when applying coatings to scorching 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 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 beneath the AIT of the coatings being utilized. While surface temperatures may be known/available in plenty of services, all floor areas of the process/piping being painted and/or any gear adjacent to the items being painted where overspray could deposit must be measured for precise surface temperature. The outcomes must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily obvious, a extra subtle however nonetheless critical supply of ignition to regulate on any industrial portray challenge involving flammable solvents entails the manufacturing of static electrical energy. Equipment associated with the spray-painting operation, such as spray utility equipment and ventilation gear, can generate static electricity.
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 sluggish generation of warmth from oxidation of natural chemical substances similar to paint solvents is accelerated till 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 sufficient air circulating around the material for oxidation to occur, however the pure air flow out there is insufficient to hold the heat away quick enough to prevent it from build up.
For extra information, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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