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

Managers of petrochemical, refining, power, offshore, pulp and paper and other facilities with intensive hot processes and piping methods are regularly challenged with performing all the mandatory coatings maintenance work only in periods of outages. Outages are required in order that course of tools could be correctly maintained and repaired including cleansing of pipelines and vessels, maintenance and replacement of pumps, motors and valves, maintenance coating operations, and different work that may solely be achieved when the operations are shut down.
When coatings work must be carried out on areas the place elevated temperatures are involved, many suppose that the facility must be shut down. This will not be the case.
A query regularly posed by facility managers is, “Can I do upkeep portray work while the plant is operating?” As described under, the answer is, “Yes you’ll find a way to, but there are security and health issues that have to be considered”.
Dangers to personnel should be managed regardless of when or the place work is carried out.
Safety and well being issues
There is a variety of safety and well being hazards that must be thought of on each industrial maintenance portray project, whether the coating materials is being utilized to hot metal or not. Some of those embody proper materials handling and storage, fall safety, management of fireplace and explosion hazards, and publicity to noise, heavy metals, solvents and other well being dangers.
These dangers must be properly evaluated and managed on every industrial maintenance painting challenge, regardless of when or where the work is performed. While current on any job, when making use of specialty coatings to scorching surfaces, some security and well being issues should receive extra consideration.
Flammable and combustible liquids in lots of coatings (solvents) can vaporize and form flammable mixtures within the air, particularly when atomized throughout spray application or heated. The diploma of hazard depends on the following:
The auto ignition temperature (AIT) of the coating materials is the one most necessary problem when making use of coatings to sizzling working tools. 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 mixture will ignite from its personal warmth source or contact with a heated surface without the presence of an open spark or flame.”
The concept of flash level as outlined by NFPA 30 is “the minimum temperature of a liquid at which adequate vapour is given off to type an ignitable combination with the air, near the floor of the liquid”. In other phrases, the flash point describes the temperature of the liquid that’s high sufficient to generate enough vapour to create a flame if a source of ignition have been introduced.
For vapours of flammable liquids, there’s a minimal focus below which the unfold of the flame doesn’t happen when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is เกจ์วัดแก๊สหุงต้ม of vapour within the air above which the unfold of the flame does not occur. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the concentration of vapours can support combustion.
If security procedures are followed, outages will not be required whereas maintenance is carried out.
Implementing controls
Applying coatings to scorching surfaces will increase the speed at which the solvents are pushed off. When making use of solvent borne coatings to sizzling surfaces it must be assumed that the concentration of vapours in the air could exceed the LFL (at least for a quick time after application). As with coating application to ambient temperature steel, controls should be implemented.
While the LFL is more likely to be achieved over a shorter time frame during scorching utility of coatings than coatings work carried out at ambient situations, the ensuing fireplace hazard exists in each purposes. That is, the fire hazard and associated controls have to be considered for the applying of any solvent-borne flammable coating system, whatever the work environment. It must be recognized that the gas part of the fireplace tetrahedron might be present in both ‘hot’ and ‘ambient’ environments and fundamental steps must be taken to reduce pointless solvent vapours within the work space. In addition, as outlined later, consideration should also be directed to eliminating the remaining factor of the tetrahedron – the source of ignition.
Controlling flammable vapours
The gasoline factor of a hearth can be decreased by implementing basic controls similar to dealing with and storing flammable liquids in approved, self-closing containers, preserving the number of flammable liquids containers in the work area and in storage areas to the minimal needed and within allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate could also be substituted, followed by surface washing with contemporary water or steam cleaning and pH testing of the floor, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gas indicators must be used to confirm that the focus of flammable vapours is under the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s suggestions and have to be accredited for use in flammable atmospheres. Operators of the equipment should be trained in correct tools operation.
Readings should be taken within the basic work space and the neighborhood 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 utility work ought to immediately stop till the focus of flammable vapours is controlled. The function of setting the alarm below the LFL is to supply a security factor that results in management measures being carried out earlier than there’s an imminent danger of fireside or explosion.
Monitoring of the flammable vapour concentration shall be essential as the effectiveness of pure ventilation could additionally be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or well being professional or engineer with expertise in industrial air flow should be consulted.
At a minimum, mechanical air flow techniques ought to provide sufficient capability to regulate flammable vapours to beneath 10% of the LFL by either exhaust ventilation to remove contaminants from the work space or by dilution air flow by way of introduction of contemporary air to dilute contaminants. As with pressure gauge nuova fima ราคา , air flow gear have to be permitted for protected use in flammable atmospheres. In addition, air flow gear must be grounded and bonded.
Additional ventilation, if needed, should be continuous throughout coatings application as concentrations might enhance as more surfaces are coated during the course of a piece shift, and especially on hot surfaces where the rate of vaporization is greater.
Ventilation throughout coatings utility ought to be continuous, especially when working on scorching 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 only most necessary issue when applying coatings to hot operating 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 source of ignition is to verify the surfaces being coated are below the AIT of the coatings being applied. While floor temperatures could additionally be known/available in plenty of facilities, all surface areas of the process/piping being painted and/or any equipment adjoining to the items being painted where overspray might deposit should be measured for actual floor temperature. The outcomes ought to be in comparability with the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily apparent, a more refined however nonetheless important supply of ignition to manage on any industrial painting project involving flammable solvents includes the production of static electricity. Equipment associated with the spray-painting operation, similar to spray utility equipment 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 occurs when the gradual technology of heat from oxidation of organic chemicals such as paint solvents is accelerated till 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 exposed, there may be enough air circulating around the materials for oxidation to occur, however the natural air flow obtainable is insufficient to carry the warmth away quick sufficient to stop it from building up.
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