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

Managers of petrochemical, refining, energy, offshore, pulp and paper and different amenities with intensive scorching processes and piping techniques are frequently challenged with performing all the required coatings upkeep work only during times of outages. Outages are required so that course of gear can be correctly maintained and repaired including cleansing of pipelines and vessels, maintenance and replacement of pumps, motors and valves, upkeep coating operations, and different work that may solely be achieved when the operations are shut down.
When coatings work has to be carried out on areas the place elevated temperatures are concerned, many think that the facility needs to be shut down. This will not be the case.
pressure gauge weksler ราคา posed by facility managers is, “Can I do maintenance portray work while the plant is operating?” As described below, the reply is, “Yes you possibly can, however there are safety and well being issues that have to be considered”.
Dangers to personnel must be managed regardless of when or where work is carried out.
Safety and well being issues
There is a range of safety and well being hazards that must be thought-about on every industrial upkeep painting project, whether the coating materials is being applied to hot metal or not. Some of these embrace correct materials dealing with and storage, fall safety, management of fire and explosion hazards, and exposure to noise, heavy metals, solvents and other health risks.
These dangers have to be properly evaluated and managed on every industrial upkeep portray venture, regardless of when or the place the work is carried out. While present on any job, when applying specialty coatings to hot surfaces, some security and health points should obtain additional consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and form flammable mixtures within the air, especially when atomized throughout spray software or heated. The diploma of hazard depends on the next:
The auto ignition temperature (AIT) of the coating materials is the one most important concern when applying 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 minimum temperature at which a flammable gas-air or vapour-air combination will ignite from its own heat source or contact with a heated surface with out the presence of an open spark or flame.”
The idea of flash point as defined by NFPA 30 is “the minimum 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 words, the flash level describes the temperature of the liquid that is excessive enough to generate sufficient vapour to create a flame if a source of ignition had been introduced.
For vapours of flammable liquids, there’s a minimum concentration beneath which the spread of the flame does not occur when in touch with a supply 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 occur. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the concentration of vapours can assist combustion.
If security procedures are followed, outages will not be required while upkeep is carried out.
Implementing controls
Applying coatings to sizzling surfaces increases the speed at which the solvents are pushed off. When applying solvent borne coatings to sizzling surfaces it have to be assumed that the focus of vapours in the air may exceed the LFL (at least for a quick while after application). As with coating utility to ambient temperature metal, controls should be applied.
While the LFL is prone to be achieved over a shorter period of time during sizzling application of coatings than coatings work performed at ambient conditions, the resulting fireplace hazard exists in both purposes. That is, the hearth hazard and associated controls have to be thought-about for the applying of any solvent-borne flammable coating system, regardless of the work surroundings. It should be acknowledged that the gasoline part of the fire tetrahedron will be present in both ‘hot’ and ‘ambient’ environments and fundamental steps have to be taken to attenuate pointless solvent vapours within the work area. In addition, as outlined later, consideration should also be directed to eliminating the remaining element of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gas element of a hearth can be reduced by implementing fundamental controls such as dealing with and storing flammable liquids in accredited, self-closing containers, keeping the number of flammable liquids containers within the work space and in storage areas to the minimal necessary and inside allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could additionally be substituted, followed by floor washing with recent water or steam cleansing and pH testing of the floor, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible fuel indicators must be used to confirm that the focus of flammable vapours is below the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s suggestions and should be approved to be used in flammable atmospheres. Operators of the equipment should be educated in correct equipment operation.
Readings ought to 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, items are set to alarm at 10% of the LFL. If the alarm sounds, coatings software work ought to instantly cease until the concentration of flammable vapours is controlled. The objective of setting the alarm beneath the LFL is to supply a security factor that ends in control measures being implemented earlier than there might be an imminent danger of fireplace or explosion.
Monitoring of the combustible vapour focus shall be necessary as the effectiveness of natural air flow may be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or health skilled or engineer with experience in industrial ventilation must be consulted.
At a minimum, mechanical ventilation systems ought to present adequate capability to manage flammable vapours to beneath 10% of the LFL by both exhaust air flow to take away contaminants from the work area or by dilution ventilation via introduction of fresh air to dilute contaminants. As with flamable fuel indicators, air flow tools have to be accredited for protected use in flammable atmospheres. In addition, air flow tools must be grounded and bonded.
Additional ventilation, if wanted, must be continuous during coatings software as concentrations might enhance as more surfaces are coated through the course of a piece shift, and especially on scorching surfaces the place the rate of vaporization is larger.
Ventilation throughout coatings utility must be continuous, especially when engaged on scorching surfaces.
Sources of Ignition
When making use of coatings to scorching surfaces, the first supply of ignition that readily involves thoughts is the warmth from the floor being painted. The AIT of the coating material is the only most essential problem when making use of coatings to scorching operating tools. The AIT of a substance or mixture is the minimum temperature at which a vapour-air mixture will ignite when in touch with a heated surface, without the presence of any open spark or flame.
The key to controlling this supply of ignition is to verify the surfaces being coated are below the AIT of the coatings being utilized. While floor temperatures may be known/available in lots of services, all surface areas of the process/piping being painted and/or any gear adjacent to the gadgets being painted where overspray may deposit should be measured for actual surface temperature. The results ought to be in comparability with the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily apparent, a extra subtle however nonetheless critical source of ignition to manage on any industrial portray project involving flammable solvents involves the production of static electrical energy. Equipment related to the spray-painting operation, similar to spray application tools and air flow gear, 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 sluggish era of heat from oxidation of organic chemical compounds similar to paint solvents is accelerated until the ignition temperature of the fuel is reached.
This situation is reached when the material is packed loosely permitting a large floor area to be uncovered, there’s enough air circulating across the material for oxidation to happen, but the pure ventilation available is insufficient to carry the heat away fast sufficient to stop it from build up.
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