Managers of petrochemical, refining, power, offshore, pulp and paper and other amenities with intensive hot processes and piping techniques are frequently challenged with performing all the mandatory coatings upkeep work solely during periods of outages. Outages are required in order that process tools may be correctly maintained and repaired including cleaning of pipelines and vessels, maintenance and alternative of pumps, motors and valves, upkeep coating operations, and other work that can solely be accomplished when the operations are shut down.
When coatings work must be carried out on areas the place elevated temperatures are involved, many think that the facility needs to be shut down. This will not be the case.
A query incessantly posed by facility managers is, “Can I do upkeep painting work whereas the plant is operating?” As described under, the reply is, “Yes you possibly can, however there are safety and health issues that should be considered”.
Dangers to personnel must be managed no matter when or where work is carried out.
Safety and health concerns
There is a spread of security and well being hazards that must be considered on each industrial maintenance portray challenge, whether or not the coating material is being applied to hot steel or not. Some of those include correct material handling and storage, fall protection, management of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other well being risks.
These risks have to be correctly evaluated and controlled on every industrial upkeep painting venture, 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 points should receive additional consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, especially when atomized during spray application or heated. The diploma of hazard depends on the next:
The auto ignition temperature (AIT) of the coating material is the one most essential problem when applying coatings to hot operating tools. AIT is outlined (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 source or contact with a heated floor with out the presence of an open spark or flame.”
The idea of flash level as outlined 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, close to the surface of the liquid”. In different words, the flash level describes the temperature of the liquid that’s excessive sufficient to generate enough vapour to create a flame if a source of ignition had been launched.
For vapours of flammable liquids, there is a minimum focus beneath which the unfold of the flame doesn’t happen when in contact with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a most concentration of vapour within the air above which the unfold of the flame doesn’t occur. This is the Upper Flammable Limit (UFL). The flammable vary is between the LFL and the UFL, when the concentration of vapours can support combustion.
If safety procedures are followed, outages may not be required whereas upkeep is performed.
Implementing controls
Applying coatings to hot surfaces will increase the rate at which the solvents are pushed off. When making use of solvent borne coatings to hot surfaces it have to be assumed that the focus of vapours within the air might exceed the LFL (at least for a quick while after application). As with coating application to ambient temperature steel, controls must be carried out.
While the LFL is likely to be achieved over a shorter time period during hot utility of coatings than coatings work performed at ambient conditions, the resulting fire hazard exists in both applications. That is, the fireplace hazard and related controls have to be considered for the appliance of any solvent-borne flammable coating system, regardless of the work environment. It should be acknowledged that the fuel part of the hearth tetrahedron might be current in each ‘hot’ and ‘ambient’ environments and fundamental steps should be taken to attenuate unnecessary solvent vapours in the work space. 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 gasoline element of a fireplace may be decreased by implementing fundamental controls corresponding to dealing with 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 minimum needed and within allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate could additionally be substituted, adopted by floor washing with recent 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 cleansing.
Combustible gasoline indicators ought to be used to confirm that the focus of flammable vapours is beneath the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s recommendations and must be approved for use in flammable atmospheres. Operators of the equipment must be trained in proper tools operation.
Readings must be taken in the common work area and the neighborhood of the operator and in areas where there are potential sources of ignition. Typically, units are set to alarm at 10% of the LFL. If the alarm sounds, coatings software work ought to immediately stop till the focus of flammable vapours is managed. The purpose of setting the alarm beneath the LFL is to provide a safety factor that ends in control measures being carried out before there might be an imminent hazard of fireside or explosion.
Monitoring of the flammable vapour concentration might be needed because the effectiveness of natural air flow could additionally be variable. If management of flammable vapours requires mechanical air flow, an occupational security or health skilled or engineer with expertise in industrial ventilation should be consulted.
At a minimal, mechanical air flow systems should provide adequate capacity to regulate flammable vapours to under 10% of the LFL by both exhaust air flow to remove contaminants from the work area or by dilution ventilation via introduction of fresh air to dilute contaminants. As with combustible gasoline indicators, air flow tools should be approved for safe use in flammable atmospheres. In addition, ventilation gear must be grounded and bonded.
Additional air flow, if wanted, ought to be continuous throughout coatings utility as concentrations might improve as extra surfaces are coated during the course of a piece shift, and especially on scorching surfaces the place the speed of vaporization is greater.
Ventilation throughout coatings application ought to be continuous, particularly when working on sizzling surfaces.
Sources of Ignition
When applying coatings to scorching surfaces, the first source of ignition that readily comes to thoughts is the heat from the floor being painted. The AIT of the coating materials is the one most necessary issue when making use of coatings to scorching working gear. The AIT of a substance or combination is the minimum temperature at which a vapour-air combination will ignite when in contact with a heated floor, 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 applied. While surface temperatures may be known/available in many services, all floor areas of the process/piping being painted and/or any gear adjoining to the objects being painted where overspray might deposit must 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 could also be readily apparent, a extra refined but nonetheless important supply of ignition to manage on any industrial painting 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 equipment, can generate static electricity.
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 era of heat from oxidation of organic chemical substances similar to paint solvents is accelerated until the ignition temperature of the gasoline is reached.
เพรสเชอร์เกจวัดแรงดันน้ำ is reached when the fabric is packed loosely permitting a large surface space to be uncovered, there’s enough air circulating across the material for oxidation to occur, but the pure ventilation available is inadequate to carry the heat away fast enough to forestall it from increase.
For extra data, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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