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

Managers of petrochemical, refining, power, offshore, pulp and paper and different services with intensive hot processes and piping techniques are incessantly challenged with performing all the necessary coatings maintenance work only during times of outages. Outages are required in order that course of gear may be properly maintained and repaired together with cleaning of pipelines and vessels, upkeep and alternative of pumps, motors and valves, maintenance coating operations, and different work that may only be completed when the operations are shut down.
When coatings work has to be performed on areas the place elevated temperatures are involved, many assume that the facility must be shut down. This will not be the case.
A query frequently posed by facility managers is, “Can I do upkeep portray work while the plant is operating?” As described under, the reply is, “Yes you’ll find a way to, but there are security and health points that must be considered”.
Dangers to personnel have to be managed no matter when or the place work is performed.
Safety and health considerations

There is a spread of safety and well being hazards that should be thought of on every industrial maintenance painting venture, whether the coating materials is being utilized to scorching metal or not. Some of these include proper material dealing with and storage, fall safety, management of fire and explosion hazards, and publicity to noise, heavy metals, solvents and other health risks.
These risks must be properly evaluated and controlled on each industrial upkeep portray venture, regardless of when or where the work is carried out. While current on any job, when making use of specialty coatings to scorching surfaces, some security and well being issues should obtain further consideration.
Flammable and combustible liquids in plenty of coatings (solvents) can vaporize and type flammable mixtures within the air, especially when atomized throughout spray application 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 hot operating 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 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 adequate vapour is given off to kind an ignitable mixture with the air, near the surface of the liquid”. In different words, the flash point describes the temperature of the liquid that is high sufficient to generate sufficient vapour to create a flame if a source of ignition were introduced.
For vapours of flammable liquids, there’s a minimum focus below which the unfold of the flame doesn’t happen when in contact with a source 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 vary is between the LFL and the UFL, when the focus of vapours can support combustion.
If safety procedures are followed, outages will not be required whereas maintenance is carried out.
Implementing controls

Applying coatings to scorching surfaces increases the speed at which the solvents are pushed off. When making use of solvent borne coatings to sizzling surfaces it have to be assumed that the concentration of vapours in the air could exceed the LFL (at least for a quick while after application). As with coating utility to ambient temperature metal, controls must be implemented.
While the LFL is likely to be achieved over a shorter time period throughout sizzling application of coatings than coatings work carried out at ambient situations, the resulting fire hazard exists in both functions. That is, the hearth hazard and related controls should be thought of for the application of any solvent-borne flammable coating system, whatever the work surroundings. It have to be acknowledged that the fuel element of the fireplace tetrahedron shall be current in each ‘hot’ and ‘ambient’ environments and primary steps should be taken to minimize pointless solvent vapours in the work space. In addition, as outlined later, attention must even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours

The gas component of a fireplace could be decreased by implementing fundamental controls corresponding to dealing with and storing flammable liquids in approved, self-closing containers, keeping the number of flammable liquids containers in the work area and in storage areas to the minimum necessary and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate may be substituted, adopted by surface washing with recent water or steam cleansing and pH testing of the surface, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators must be used to verify that the focus of flammable vapours is beneath the LFL. Combustible gasoline indicators should be calibrated in accordance with the manufacturer’s suggestions and should be accredited for use in flammable atmospheres. Operators of the equipment have to be trained in correct gear operation.
Readings should be taken in the general work area and the vicinity of the operator and in areas where 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 cease till the concentration of flammable vapours is controlled. The objective of setting the alarm under the LFL is to supply a security factor that results in control measures being implemented before there could be an imminent hazard of fireside or explosion.
Monitoring of the combustible vapour focus will be essential as the effectiveness of natural ventilation may be variable. If control of flammable vapours requires mechanical air flow, an occupational security or well being professional or engineer with experience in industrial air flow should be consulted.
At a minimum, mechanical air flow methods should present enough capability to manage flammable vapours to under 10% of the LFL by both exhaust ventilation to take away contaminants from the work area or by dilution ventilation through introduction of fresh air to dilute contaminants. As with flamable gasoline indicators, ventilation tools must be accredited for protected use in flammable atmospheres. In addition, ventilation gear should be grounded and bonded.
Additional ventilation, if needed, ought to be steady throughout coatings software as concentrations might enhance as more surfaces are coated during the course of a piece shift, and particularly on hot surfaces the place the speed of vaporization is greater.
Ventilation during coatings utility must be steady, particularly when working on scorching surfaces.
Sources of Ignition

When applying coatings to scorching surfaces, the primary source of ignition that readily comes to mind is the heat from the floor being painted. digital pressure gauge of the coating material is the single most necessary issue when making use of coatings to hot working 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 confirm the surfaces being coated are below the AIT of the coatings being applied. While surface temperatures may be known/available in many amenities, all surface areas of the process/piping being painted and/or any equipment adjacent to the objects being painted the place overspray could deposit ought to 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 could also be readily obvious, a extra refined however nonetheless important supply of ignition to regulate on any industrial painting venture involving flammable solvents includes the production of static electrical energy. Equipment related to the spray-painting operation, similar to spray application 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 happens when the slow generation of warmth from oxidation of organic chemical compounds such as paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This condition is reached when the material is packed loosely allowing a big surface space to be exposed, there is sufficient air circulating around the material for oxidation to happen, however the natural ventilation obtainable is inadequate to hold the heat away quick sufficient to forestall it from build up.
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