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

Managers of petrochemical, refining, power, offshore, pulp and paper and different facilities with intensive sizzling processes and piping techniques are incessantly challenged with performing all the necessary coatings upkeep work solely in periods of outages. Outages are required in order that course of equipment could be properly maintained and repaired together with cleansing of pipelines and vessels, upkeep and alternative 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 must be performed on areas where elevated temperatures are concerned, many assume that the facility must be shut down. This will not be the case.
A question frequently posed by facility managers is, “Can I do maintenance portray work while the plant is operating?” As described beneath, the reply is, “Yes you’ll be able to, however there are safety and health issues that must be considered”.
Dangers to personnel must be managed regardless of when or where work is carried out.
Safety and well being considerations
There is a variety of safety and health hazards that have to be thought-about on each industrial maintenance painting venture, whether or not the coating materials is being applied to hot metal or not. Some of these embody correct material dealing with and storage, fall protection, control of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other well being dangers.
These dangers have to be properly evaluated and controlled on every industrial maintenance painting venture, no matter when or the place the work is performed. While present on any job, when making use of specialty coatings to scorching surfaces, some safety and well being points should obtain additional consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and kind flammable mixtures in the air, particularly when atomized during spray software or heated. The diploma of hazard is decided by the next:
The auto ignition temperature (AIT) of the coating materials is the one most important problem when making use of coatings to scorching operating equipment. 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 mixture will ignite from its personal heat source or contact with a heated floor 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 enough vapour is given off to form an ignitable combination with the air, close to the floor of the liquid”. In other words, the flash level describes the temperature of the liquid that is excessive sufficient to generate sufficient vapour to create a flame if a supply of ignition had been launched.
For vapours of flammable liquids, there’s a minimal focus under which the unfold of the flame does not occur when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is a most focus of vapour in the air above which the unfold of the flame does not happen. 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 adopted, outages is most likely not required whereas maintenance is performed.
Implementing ราคาเกจวัดแรงดันน้ำ
Applying coatings to hot surfaces will increase the rate at which the solvents are driven off. When making use of solvent borne coatings to hot surfaces it have to be assumed that the concentration of vapours within the air may exceed the LFL (at least for a short time after application). As with coating utility to ambient temperature steel, controls have to be implemented.
While the LFL is more likely to be achieved over a shorter period of time throughout sizzling application of coatings than coatings work carried out at ambient circumstances, the resulting fire hazard exists in each applications. That is, the fire hazard and related controls should be considered for the appliance of any solvent-borne flammable coating system, whatever the work setting. It must be recognized that the gasoline part of the fire tetrahedron might be present in both ‘hot’ and ‘ambient’ environments and basic steps should be taken to attenuate pointless solvent vapours within the work space. In addition, as outlined later, attention should even be directed to eliminating the remaining component of the tetrahedron – the source of ignition.
Controlling flammable vapours
The fuel element of a fire can be reduced by implementing primary controls such as dealing with and storing flammable liquids in accredited, self-closing containers, preserving the variety of flammable liquids containers in the work area and in storage areas to the minimal necessary and inside allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could also be substituted, followed by surface washing with contemporary water or steam cleansing and pH testing of the surface, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gasoline indicators must be used to verify that the focus of flammable vapours is under the LFL. Combustible fuel indicators have to be calibrated in accordance with the manufacturer’s suggestions and must be permitted to be used in flammable atmospheres. Operators of the tools should be educated in proper tools operation.
Readings ought to be taken within the basic work area and the vicinity 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 ought to immediately cease until the focus of flammable vapours is managed. The objective of setting the alarm beneath the LFL is to offer a safety issue that ends in control measures being applied before there is an imminent danger of fireside or explosion.
Monitoring of the combustible vapour focus will be essential as the effectiveness of pure ventilation could additionally be variable. If control of flammable vapours requires mechanical air flow, an occupational safety or health professional or engineer with expertise in industrial air flow should be consulted.
At a minimal, mechanical ventilation systems should present adequate capability to manage flammable vapours to beneath 10% of the LFL by both exhaust ventilation to take away contaminants from the work space or by dilution air flow by way of introduction of recent air to dilute contaminants. As with flamable gas indicators, ventilation tools should be approved for safe use in flammable atmospheres. In addition, ventilation equipment have to be grounded and bonded.
Additional air flow, if needed, should be continuous during coatings software as concentrations might enhance as more surfaces are coated in the course of the course of a work shift, and particularly on sizzling surfaces the place the speed of vaporization is higher.
Ventilation during coatings software ought to be steady, especially when working on hot 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 essential problem when making use of coatings to sizzling operating tools. The AIT of a substance or mixture is the minimum temperature at which a vapour-air mixture will ignite when in contact with a heated floor, with out the presence of any open spark or flame.
The key to controlling this supply of ignition is to verify the surfaces being coated are under the AIT of the coatings being utilized. While floor temperatures could also be known/available in many facilities, all floor areas of the process/piping being painted and/or any equipment adjacent to the gadgets being painted where overspray could deposit should be measured for precise floor 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 more refined however nonetheless critical source of ignition to control on any industrial portray challenge involving flammable solvents entails the production of static electrical energy. Equipment related to the spray-painting operation, corresponding to spray utility equipment and air flow 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 gradual technology of heat from oxidation of organic chemical substances such as paint solvents is accelerated until the ignition temperature of the fuel is reached.
This situation is reached when the fabric is packed loosely allowing a big surface area to be uncovered, there is sufficient air circulating across the material for oxidation to occur, but the natural air flow out there is insufficient to hold the warmth away fast enough to prevent it from build up.
For extra information, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
Share

Leave a Comment