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

Managers of petrochemical, refining, energy, offshore, pulp and paper and other services with extensive hot processes and piping systems are incessantly challenged with performing all the required coatings upkeep work solely during times of outages. Outages are required so that course of tools could be properly maintained and repaired including cleansing of pipelines and vessels, upkeep and alternative of pumps, motors and valves, upkeep coating operations, and other work that can solely be completed when the operations are shut down.
When coatings work needs to be performed on areas where elevated temperatures are concerned, many think that the facility has to be shut down. This may not be the case.
A question regularly posed by facility managers is, “Can I do upkeep portray work whereas the plant is operating?” As described beneath, the answer is, “Yes you presumably can, however there are security and well being issues that must be considered”.
Dangers to personnel have to be managed regardless of when or where work is carried out.
Safety and health concerns

There is a variety of security and health hazards that must be thought of on each industrial upkeep portray challenge, whether or not the coating material is being utilized to hot metal or not. Some of those include correct materials dealing with and storage, fall safety, management of fireside and explosion hazards, and publicity to noise, heavy metals, solvents and other well being dangers.
These risks have to be properly evaluated and controlled on each industrial maintenance portray venture, regardless of when or the place the work is performed. While current on any job, when applying specialty coatings to scorching surfaces, some security and well being issues should receive further consideration.
Flammable and flamable liquids in plenty of coatings (solvents) can vaporize and form flammable mixtures in the air, particularly when atomized throughout spray software 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 hot working tools. AIT is defined (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 mixture will ignite from its personal heat source or contact with a heated surface with out the presence of an open spark or flame.”

The idea of flash point as outlined by NFPA 30 is “the minimal temperature of a liquid at which adequate vapour is given off to form 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 excessive enough to generate enough vapour to create a flame if a source of ignition had been introduced.
For vapours of flammable liquids, there’s a minimum concentration below which the spread of the flame does not happen when in contact with a source 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 does not occur. This is the Upper Flammable Limit (UFL). The flammable vary is between the LFL and the UFL, when the focus of vapours can assist combustion.
If safety procedures are followed, outages may not be required whereas maintenance is performed.
Implementing controls

Applying coatings to hot surfaces will increase the rate at which the solvents are driven off. When making use of solvent borne coatings to sizzling surfaces it must be assumed that the concentration of vapours within the air might exceed the LFL (at least for a quick time after application). As with coating software to ambient temperature steel, controls have to be implemented.
While the LFL is likely to be achieved over a shorter time frame throughout hot application of coatings than coatings work performed at ambient situations, the resulting hearth hazard exists in each applications. That is, the fire hazard and related controls should be thought-about for the applying of any solvent-borne flammable coating system, whatever the work environment. It should be recognized that the fuel component of the hearth tetrahedron shall be current in both ‘hot’ and ‘ambient’ environments and fundamental steps should be taken to minimize unnecessary solvent vapours within the work area. In addition, as outlined later, attention should even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours

The gasoline factor of a fire can be lowered by implementing fundamental controls corresponding to handling and storing flammable liquids in approved, self-closing containers, keeping the number of flammable liquids containers in the work space and in storage areas to the minimal essential and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate could also be substituted, followed by floor washing with contemporary 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 cleansing.
Combustible fuel indicators should be used to verify that the concentration of flammable vapours is under the LFL. Combustible fuel indicators should be calibrated in accordance with the manufacturer’s recommendations and must be permitted for use in flammable atmospheres. Operators of the tools have to be educated in proper equipment operation.
Readings must be taken within the basic work space 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 software work ought to instantly stop till the focus of flammable vapours is controlled. The function of setting the alarm beneath the LFL is to provide a security issue that results in management measures being implemented before there’s an imminent danger of fireplace or explosion.
Monitoring of the combustible vapour concentration might be necessary as the effectiveness of pure air flow may be variable. If control of flammable vapours requires mechanical ventilation, an occupational security or health professional or engineer with expertise in industrial ventilation should be consulted.
At a minimum, mechanical ventilation methods should provide adequate capability to manage flammable vapours to beneath 10% of the LFL by either exhaust ventilation to remove contaminants from the work area or by dilution ventilation via introduction of fresh air to dilute contaminants. As with combustible gasoline indicators, ventilation gear must be approved for protected use in flammable atmospheres. In addition, air flow equipment should be grounded and bonded.
pressure gauge วัด แรง ดัน น้ำ , if needed, must be continuous during coatings software as concentrations could enhance as extra surfaces are coated in the course of the course of a work shift, and especially on hot surfaces the place the speed of vaporization is greater.
Ventilation throughout coatings software must be continuous, particularly when working on sizzling surfaces.
Sources of Ignition

When making use of coatings to hot surfaces, the first source of ignition that readily involves mind is the warmth from the floor being painted. The AIT of the coating materials is the only most necessary issue when making use of coatings to hot operating equipment. The AIT of a substance or combination is the minimal temperature at which a vapour-air combination will ignite when involved with a heated floor, without 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 applied. While surface temperatures may be known/available in many services, all surface areas of the process/piping being painted and/or any tools adjoining to the objects being painted where overspray could deposit should be measured for actual surface temperature. The results ought to be in comparison with the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily apparent, a more delicate however nonetheless critical supply of ignition to control on any industrial painting challenge involving flammable solvents involves the production of static electrical energy. Equipment associated with the spray-painting operation, similar to spray application equipment and air flow equipment, can generate static electricity.
In addition to external sources of ignition, spontaneous ignition can occur when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition happens when the gradual era of heat from oxidation of natural chemical compounds such as paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This condition is reached when the fabric is packed loosely permitting a large surface area to be uncovered, there may be sufficient air circulating across the materials for oxidation to occur, however the pure ventilation obtainable is inadequate to hold the warmth away quick sufficient to prevent it from increase.
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