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

Managers of petrochemical, refining, energy, offshore, pulp and paper and different services with intensive hot processes and piping techniques are regularly challenged with performing all the mandatory coatings upkeep work only during times of outages. Outages are required in order that course of tools could be properly maintained and repaired including cleansing of pipelines and vessels, maintenance and replacement of pumps, motors and valves, maintenance coating operations, and other work that may solely be achieved when the operations are shut down.
When coatings work has to be performed on areas where elevated temperatures are involved, many assume that the ability must be shut down. This is in all probability not the case.
A question frequently posed by facility managers is, “Can I do upkeep portray work whereas the plant is operating?” As described under, the reply is, “Yes you’ll find a way to, however 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 performed.
เพรสเชอร์เกจลม and health issues
There is a range of safety and well being hazards that should be thought-about on every industrial upkeep painting venture, whether or not the coating material is being utilized to scorching metal or not. Some of those include correct material handling and storage, fall safety, management of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other well being dangers.
These dangers should be properly evaluated and controlled on each industrial maintenance portray project, no matter when or where the work is carried out. While present on any job, when applying specialty coatings to sizzling surfaces, some security and well being issues should obtain further consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and kind flammable mixtures in the air, especially when atomized throughout spray software or heated. The diploma of hazard is dependent upon the next:
The auto ignition temperature (AIT) of the coating material is the only most necessary issue when applying coatings to scorching working equipment. 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 minimal temperature of a liquid at which sufficient vapour is given off to kind an ignitable combination with the air, near the floor of the liquid”. In other words, the flash point describes the temperature of the liquid that’s high sufficient to generate enough vapour to create a flame if a supply of ignition were launched.
For vapours of flammable liquids, there’s a minimal focus under which the spread of the flame does not occur when in contact with a source of ignition. This is the Lower Flammable Limit (LFL). There is a most focus of vapour within the air above which the spread of the flame doesn’t 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 will not be required while maintenance is performed.
Implementing controls
Applying coatings to sizzling surfaces increases the rate at which the solvents are driven off. When applying solvent borne coatings to sizzling surfaces it must 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 metal, controls must be carried out.
While the LFL is prone to be achieved over a shorter period of time during hot software of coatings than coatings work carried out at ambient situations, the ensuing fireplace hazard exists in each applications. That is, the fireplace hazard and associated controls must be thought of for the application of any solvent-borne flammable coating system, regardless of the work surroundings. It should be acknowledged that the fuel component of the fireplace tetrahedron shall be current in each ‘hot’ and ‘ambient’ environments and primary steps should 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 source of ignition.
Controlling flammable vapours
The gasoline element of a hearth could be reduced by implementing basic controls such as dealing with and storing flammable liquids in approved, self-closing containers, keeping the variety of flammable liquids containers within the work space and in storage areas to the minimal essential and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate could additionally be substituted, followed by floor washing with recent water or steam cleaning and pH testing of the floor, or non-combustible solvents such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gas indicators ought to be used to verify that the focus of flammable vapours is under the LFL. Combustible gas indicators must be calibrated in accordance with the manufacturer’s recommendations and have to be permitted for use in flammable atmospheres. Operators of the gear have to be trained in correct equipment 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, models are set to alarm at 10% of the LFL. If the alarm sounds, coatings utility work ought to instantly stop until the focus of flammable vapours is controlled. The purpose of setting the alarm below the LFL is to offer a safety factor that ends in management measures being implemented before there’s an imminent danger of fireside or explosion.
Monitoring of the combustible vapour focus will be essential because the effectiveness of pure air flow could also be variable. If control of flammable vapours requires mechanical air flow, an occupational safety or well being skilled or engineer with expertise in industrial ventilation must be consulted.
At a minimum, mechanical ventilation systems ought to present adequate capacity to manage flammable vapours to below 10% of the LFL by either exhaust air flow to remove contaminants from the work area or by dilution air flow by way of introduction of contemporary air to dilute contaminants. As with flamable gas indicators, air flow tools should be approved for secure use in flammable atmospheres. In addition, ventilation tools have to be grounded and bonded.
Additional air flow, if needed, ought to be continuous during coatings utility as concentrations may enhance as extra surfaces are coated through the course of a piece shift, and especially on scorching surfaces the place the rate of vaporization is higher.
Ventilation during coatings software must be steady, particularly when engaged on scorching surfaces.
Sources of Ignition
When making use of coatings to scorching surfaces, the primary source of ignition that readily comes to thoughts is the warmth from the floor being painted. The AIT of the coating materials is the one most essential concern when making use of coatings to scorching working equipment. The AIT of a substance or combination is the minimal temperature at which a vapour-air mixture will ignite when in touch with a heated floor, 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 under the AIT of the coatings being utilized. While floor temperatures could additionally be known/available in lots of facilities, all floor areas of the process/piping being painted and/or any tools adjacent to the gadgets being painted where overspray could deposit should be measured for actual floor temperature. The results must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily apparent, a more refined but nonetheless important source of ignition to control on any industrial painting challenge involving flammable solvents entails the production of static electrical energy. Equipment related to the spray-painting operation, corresponding to spray application gear and air flow gear, can generate static electrical energy.
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 warmth from oxidation of organic chemical compounds corresponding to paint solvents is accelerated till the ignition temperature of the gas is reached.
This situation is reached when the material is packed loosely allowing a large floor area to be exposed, there’s enough air circulating around the material for oxidation to occur, but the pure ventilation available is inadequate to carry the warmth away quick sufficient to prevent it from build up.
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