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

Managers of petrochemical, refining, energy, offshore, pulp and paper and different amenities with in depth scorching processes and piping methods are frequently challenged with performing all the mandatory coatings maintenance work solely during periods of outages. Outages are required in order that course of tools may be correctly maintained and repaired including cleaning of pipelines and vessels, maintenance and replacement 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 performed on areas the place elevated temperatures are involved, many suppose that the ability needs to be shut down. เกจ์วัดแรงดันน้ำ may 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 beneath, the answer is, “Yes you’ll be able to, but there are safety and well being points that have to 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 security and well being hazards that should be thought-about on every industrial maintenance portray venture, whether the coating materials is being applied to sizzling metal or not. Some of these embrace correct materials handling and storage, fall safety, control of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and different health risks.
These dangers must be correctly evaluated and managed on every industrial maintenance painting project, regardless of when or the place the work is performed. While present on any job, when applying specialty coatings to sizzling surfaces, some security and health issues should receive extra consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and form flammable mixtures within the air, particularly 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 only most necessary concern when applying coatings to hot working 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 own warmth source or contact with a heated surface 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 sufficient vapour is given off to kind an ignitable mixture with the air, close to the floor of the liquid”. In other phrases, the flash level describes the temperature of the liquid that is high 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 minimal focus below which the spread 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 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 may not be required whereas upkeep is performed.
Implementing controls
Applying coatings to hot surfaces increases the speed at which the solvents are pushed off. When applying solvent borne coatings to sizzling surfaces it should be assumed that the concentration of vapours within the air could exceed the LFL (at least for a brief while after application). As with coating application to ambient temperature steel, controls have to be applied.
While the LFL is more likely to be achieved over a shorter time period throughout hot software of coatings than coatings work performed at ambient conditions, the resulting fireplace hazard exists in each purposes. That is, the fire hazard and related controls should be thought-about for the application of any solvent-borne flammable coating system, regardless of the work surroundings. It have to be recognized that the fuel element of the hearth tetrahedron might be current in both ‘hot’ and ‘ambient’ environments and basic steps have to be taken to reduce unnecessary solvent vapours within the work area. In addition, as outlined later, attention must also be directed to eliminating the remaining element of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gas factor of a fireplace can be lowered by implementing basic controls corresponding to dealing with and storing flammable liquids in accredited, self-closing containers, keeping the variety of flammable liquids containers within the work space and in storage areas to the minimal needed and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate may be substituted, adopted by floor washing with recent water or steam cleansing and pH testing of the floor, or non-combustible solvents such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gas indicators ought to be used to confirm that the focus of flammable vapours is beneath the LFL. Combustible gas indicators should be calibrated in accordance with the manufacturer’s suggestions and have to be permitted to be used in flammable atmospheres. หลักการทํางานของpressuregauge of the gear should be skilled in correct tools operation.
Readings must be taken in the general work space and the neighborhood of the operator and in areas the place 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 instantly stop till the concentration of flammable vapours is managed. The function of setting the alarm beneath the LFL is to offer a security factor that leads to management measures being applied earlier than there may be an imminent danger of fireplace or explosion.
Monitoring of the flammable vapour concentration will be essential because the effectiveness of natural ventilation could also 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 must be consulted.
At a minimum, mechanical ventilation techniques ought to present sufficient capability to manage flammable vapours to under 10% of the LFL by both exhaust ventilation to remove contaminants from the work area or by dilution air flow via introduction of contemporary air to dilute contaminants. As with flamable gasoline indicators, ventilation tools must be approved for secure use in flammable atmospheres. In addition, air flow gear have to be grounded and bonded.
Additional air flow, if wanted, ought to be steady during coatings application as concentrations may improve as more surfaces are coated through the course of a work shift, and particularly on hot surfaces the place the speed of vaporization is higher.
Ventilation throughout coatings application must be continuous, particularly when working on hot surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the primary source of ignition that readily involves mind is the heat from the surface being painted. The AIT of the coating materials is the only most essential problem when making use of coatings to sizzling working tools. The AIT of a substance or combination is the minimum temperature at which a vapour-air mixture will ignite when in contact with a heated surface, with out the presence of any open spark or flame.
The key to controlling this source of ignition is to confirm the surfaces being coated are beneath the AIT of the coatings being utilized. While floor temperatures may be known/available in many facilities, all floor areas of the process/piping being painted and/or any gear adjoining to the objects being painted the place overspray might deposit must be measured for precise surface temperature. The outcomes ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily obvious, a extra delicate but nonetheless critical supply of ignition to manage on any industrial portray project involving flammable solvents includes the production of static electrical energy. Equipment related to the spray-painting operation, corresponding to spray application equipment and ventilation gear, can generate static electrical energy.
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 slow technology of heat from oxidation of organic chemicals such as paint solvents is accelerated until the ignition temperature of the gas is reached.
This condition is reached when the material is packed loosely permitting a large floor area to be uncovered, there’s sufficient air circulating around the material for oxidation to happen, however the natural ventilation available is insufficient to carry the warmth away fast enough to stop it from increase.
For more data, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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