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

Managers of petrochemical, refining, power, offshore, pulp and paper and different services with in depth sizzling processes and piping systems are regularly challenged with performing all the required coatings upkeep work solely in periods of outages. Outages are required in order that course of equipment could be properly maintained and repaired including cleaning of pipelines and vessels, upkeep and substitute of pumps, motors and valves, maintenance coating operations, and other work that can solely be completed when the operations are shut down.
When coatings work has to be carried out on areas where elevated temperatures are concerned, many think that the facility must be shut down. This may 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 presumably can, however there are security and well being issues that should be considered”.
Dangers to personnel have to be managed regardless of when or the place work is performed.
Safety and well being considerations
There is a spread of security and well being hazards that have to be thought-about on every industrial upkeep portray project, whether the coating materials is being applied to hot metal or not. Some of those embrace correct material dealing with and storage, fall protection, control of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and other well being dangers.
These risks have to be properly evaluated and managed on every industrial upkeep painting project, regardless of when or where the work is performed. While current on any job, when making use of specialty coatings to scorching surfaces, some safety and well being issues should obtain further consideration.
Flammable and combustible liquids in plenty of coatings (solvents) can vaporize and kind flammable mixtures in the air, especially when atomized throughout spray application or heated. The degree of hazard is determined by the following:
The auto ignition temperature (AIT) of the coating materials is the single most important problem when applying coatings to sizzling operating gear. AIT is outlined (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 without 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 adequate vapour is given off to kind an ignitable mixture with the air, near the surface of the liquid”. In other phrases, the flash point describes the temperature of the liquid that’s excessive sufficient to generate sufficient vapour to create a flame if a supply of ignition have been launched.
For vapours of flammable liquids, there is a minimum concentration under which the unfold of the flame does not happen when in touch 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 does not happen. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the focus of vapours can support combustion.
If safety procedures are followed, outages is probably not required whereas maintenance is carried out.
Implementing controls
Applying coatings to scorching surfaces increases the rate at which the solvents are driven off. When applying solvent borne coatings to sizzling surfaces it have to be assumed that the concentration of vapours in the air may exceed the LFL (at least for a brief while after application). As with coating utility to ambient temperature metal, controls must be carried out.
While เกรดวัดแรงดัน is likely to be achieved over a shorter time period during scorching application of coatings than coatings work carried out at ambient circumstances, the ensuing fire hazard exists in both applications. That is, the fireplace hazard and related controls should be thought-about for the appliance of any solvent-borne flammable coating system, regardless of the work setting. It should be recognized that the gasoline element of the hearth tetrahedron might be present in each ‘hot’ and ‘ambient’ environments and primary steps must be taken to reduce unnecessary solvent vapours in the work area. In addition, as outlined later, attention must even be directed to eliminating the remaining element of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gas component of a hearth could be reduced by implementing primary controls such as dealing with and storing flammable liquids in approved, self-closing containers, maintaining the variety of flammable liquids containers in the work space and in storage areas to the minimum needed and within allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate may be substituted, followed by surface washing with fresh 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 gas indicators should be used to verify that the focus of flammable vapours is beneath the LFL. Combustible gas indicators should be calibrated in accordance with the manufacturer’s recommendations and have to be accredited for use in flammable atmospheres. Operators of the equipment should be trained in correct equipment operation.
Readings ought to be taken within the common work space and the vicinity 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 application work should immediately stop until the focus of flammable vapours is managed. The purpose of setting the alarm beneath the LFL is to offer a safety issue that results in control measures being carried out earlier than there is an imminent danger of fireplace or explosion.
Monitoring of the combustible vapour concentration will be essential as the effectiveness of natural ventilation may be variable. If control of flammable vapours requires mechanical ventilation, an occupational safety or health skilled or engineer with expertise in industrial air flow must be consulted.
At a minimal, mechanical air flow techniques should provide enough capacity to regulate flammable vapours to below 10% of the LFL by both exhaust air flow to take away contaminants from the work space or by dilution air flow by way of introduction of contemporary air to dilute contaminants. As with combustible gasoline indicators, ventilation equipment must be approved for safe use in flammable atmospheres. In addition, ventilation tools should be grounded and bonded.
Additional air flow, if needed, ought to be steady during coatings utility as concentrations could improve as more surfaces are coated through the course of a piece shift, and especially on hot surfaces the place the rate of vaporization is higher.
Ventilation throughout coatings software should be steady, especially when engaged on sizzling surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the primary supply of ignition that readily involves mind is the warmth from the surface being painted. The AIT of the coating material is the single most essential issue when making use of coatings to hot operating equipment. The AIT of a substance or mixture is the minimal temperature at which a vapour-air combination will ignite when involved with a heated floor, with out the presence of any open spark or flame.
The key to controlling this supply of ignition is to confirm the surfaces being coated are under the AIT of the coatings being applied. While surface temperatures could additionally be known/available in plenty of facilities, all floor areas of the process/piping being painted and/or any gear adjoining to the items being painted the place overspray might deposit should be measured for actual floor temperature. The results ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily apparent, a extra subtle however nonetheless crucial source of ignition to control on any industrial portray venture involving flammable solvents involves 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 เกจวัดแรงดันเบนซิน to external 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 gradual technology of heat from oxidation of organic chemicals such as paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This situation is reached when the material is packed loosely permitting a large surface space to be exposed, there is enough air circulating around the materials for oxidation to occur, however the pure air flow obtainable is inadequate to carry the warmth away fast enough to stop it from build up.
For more info, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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