Managers of petrochemical, refining, power, offshore, pulp and paper and different facilities with intensive scorching processes and piping techniques are regularly challenged with performing all the required coatings maintenance work only in periods of outages. Outages are required in order that process equipment could be properly maintained and repaired including cleansing of pipelines and vessels, upkeep and alternative of pumps, motors and valves, upkeep coating operations, and other work that may solely be completed when the operations are shut down.
When coatings work has to be performed on areas the place elevated temperatures are concerned, many assume that the power has to be shut down. This will not be the case.
A query incessantly posed by facility managers is, “Can I do upkeep portray work while the plant is operating?” As described below, the answer is, “Yes you can, however there are safety and health points that should be considered”.
Dangers to personnel must be managed regardless of when or the place work is carried out.
Safety and health concerns
There is a spread of security and health hazards that must be considered on each industrial upkeep portray challenge, whether the coating materials is being applied to hot metal or not. Some of these embrace proper materials handling and storage, fall safety, management of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and different health risks.
These risks should be correctly evaluated and managed on every industrial maintenance portray venture, regardless of when or where the work is performed. While current on any job, when applying specialty coatings to sizzling surfaces, some safety and well being points should obtain further consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and kind flammable mixtures in the air, particularly when atomized during spray utility or heated. The degree of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating material is the one most essential concern when applying coatings to scorching operating tools. 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 own warmth supply or contact with a heated floor with out 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 enough vapour is given off to form an ignitable combination with the air, close to the floor of the liquid”. In other phrases, the flash level describes the temperature of the liquid that is excessive sufficient to generate enough vapour to create a flame if a supply of ignition have been introduced.
For vapours of flammable liquids, there’s a minimum focus under which the unfold of the flame doesn’t happen when in contact 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 concentration of vapours can help combustion.
If safety procedures are adopted, outages may not be required while maintenance is carried out.
Implementing controls
Applying coatings to sizzling surfaces will increase the speed at which the solvents are driven off. When applying solvent borne coatings to scorching surfaces it must be assumed that the focus of vapours within the air could exceed the LFL (at least for a short while after application). As with coating utility to ambient temperature steel, controls have to be implemented.
While the LFL is prone to be achieved over a shorter time frame during sizzling utility of coatings than coatings work carried out at ambient situations, the resulting fire hazard exists in each functions. That is, the fireplace hazard and related controls must be thought of for the application of any solvent-borne flammable coating system, whatever the work surroundings. It should be recognized that the gas element of the hearth tetrahedron shall be present in each ‘hot’ and ‘ambient’ environments and basic steps have to be taken to attenuate pointless solvent vapours in the work area. In addition, as outlined later, consideration should even be directed to eliminating the remaining component of the tetrahedron – the source of ignition.
Controlling flammable vapours
The gasoline factor of a fireplace can be decreased by implementing primary controls similar to dealing with and storing flammable liquids in accredited, self-closing containers, keeping the variety of flammable liquids containers within the work area and in storage areas to the minimal necessary and within allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate may be substituted, followed 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 cleaning.
Combustible fuel indicators should be used to verify that the focus of flammable vapours is under the LFL. Combustible fuel indicators should be calibrated in accordance with the manufacturer’s recommendations and must be accredited for use in flammable atmospheres. Operators of the gear must be educated in correct gear operation.
Readings ought to be taken in the common work space and the vicinity of the operator and in areas the place 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 stop until the focus of flammable vapours is managed. The function of setting the alarm under the LFL is to offer a security factor that leads to management measures being carried out before there might be an imminent danger of fireplace or explosion.
เกจวัดแรงดันถังแก๊ส of the flammable vapour focus will be essential as the effectiveness of natural air flow may be variable. If management of flammable vapours requires mechanical air flow, an occupational safety or health skilled or engineer with experience in industrial ventilation should be consulted.
At a minimum, mechanical air flow systems should provide enough capacity to control flammable vapours to beneath 10% of the LFL by either exhaust ventilation to take away contaminants from the work area or by dilution air flow through introduction of recent air to dilute contaminants. As with combustible fuel indicators, ventilation equipment must be permitted for protected use in flammable atmospheres. In addition, air flow tools should be grounded and bonded.
Additional ventilation, if wanted, must be continuous throughout coatings utility as concentrations may improve as extra surfaces are coated during the course of a work shift, and especially on sizzling surfaces where the speed of vaporization is larger.
Ventilation during coatings software must be steady, particularly when engaged on sizzling surfaces.
Sources of Ignition
When making use of coatings to sizzling surfaces, the first supply of ignition that readily involves mind is the heat from the surface being painted. The AIT of the coating materials is the single most necessary problem when applying coatings to hot working tools. The AIT of a substance or mixture is the minimal temperature at which a vapour-air combination will ignite when in contact with a heated surface, without the presence of any open spark or flame.
The key to controlling this supply of ignition is to verify the surfaces being coated are beneath the AIT of the coatings being applied. While floor temperatures could additionally be known/available in many services, all surface areas of the process/piping being painted and/or any gear adjoining to the items being painted the place overspray could deposit should be measured for actual surface temperature. The results ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily obvious, a more delicate however nonetheless important supply of ignition to control on any industrial portray venture involving flammable solvents includes the manufacturing of static electrical energy. Equipment associated with the spray-painting operation, corresponding to spray utility tools and ventilation tools, can generate static electrical energy.
In addition to exterior sources of ignition, spontaneous ignition can occur when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition happens when the slow technology of warmth from oxidation of organic chemical substances corresponding to paint solvents is accelerated until the ignition temperature of the gas is reached.
This condition is reached when the fabric is packed loosely permitting a big surface area to be uncovered, there could be enough air circulating around the materials for oxidation to happen, however the natural ventilation out there is inadequate to carry the warmth away fast sufficient to stop it from increase.
For extra info, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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