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

Managers of petrochemical, refining, power, offshore, pulp and paper and other services with in depth sizzling processes and piping techniques are incessantly challenged with performing all the necessary coatings maintenance work only during periods of outages. Outages are required in order that course of tools could be correctly maintained and repaired together with cleaning of pipelines and vessels, maintenance and alternative of pumps, motors and valves, maintenance coating operations, and different work that may solely be accomplished when the operations are shut down.
When coatings work has to be performed on areas the place elevated temperatures are involved, many suppose that the power has to be shut down. This may not be the case.
A query frequently posed by facility managers is, “Can I do maintenance portray work while the plant is operating?” As described below, the answer is, “Yes you can, however there are security and health issues that have to be considered”.
Dangers to personnel must be managed regardless of when or the place work is carried out.
Safety and health concerns

There is a range of safety and well being hazards that should be considered on each industrial upkeep painting challenge, whether or not the coating materials is being utilized to scorching metal or not. Some of those embrace proper material dealing with and storage, fall protection, management of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and other well being risks.
These risks have to be correctly evaluated and controlled on each industrial upkeep painting challenge, no matter when or where the work is carried out. While current on any job, when applying specialty coatings to sizzling surfaces, some safety and well being points ought to obtain further consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, particularly when atomized throughout spray utility or heated. The diploma of hazard is determined by the following:
The auto ignition temperature (AIT) of the coating materials is the single most necessary concern when applying coatings to scorching operating equipment. 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 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 type an ignitable mixture with the air, near the floor of the liquid”. In different words, the flash point describes the temperature of the liquid that is excessive sufficient to generate enough vapour to create a flame if a supply of ignition had been introduced.
For vapours of flammable liquids, there’s a minimal concentration beneath which the unfold of the flame doesn’t occur when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus of vapour in the air above which the unfold of the flame doesn’t happen. 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 safety procedures are adopted, outages will not be required whereas maintenance is performed.
Implementing controls

Applying coatings to scorching surfaces will increase the rate at which the solvents are pushed off. When making use of solvent borne coatings to hot surfaces it should be assumed that the concentration of vapours in the air could exceed the LFL (at least for a brief time after application). As with coating software to ambient temperature metal, controls must be carried out.
While the LFL is likely to be achieved over a shorter time frame throughout scorching software of coatings than coatings work carried out at ambient situations, the ensuing hearth hazard exists in each functions. That is, the fireplace hazard and related controls must be thought of for the applying of any solvent-borne flammable coating system, regardless of the work surroundings. It must be acknowledged that the fuel part of the fire tetrahedron might be current in both ‘hot’ and ‘ambient’ environments and primary steps should be taken to minimize unnecessary solvent vapours within the work area. In addition, as outlined later, consideration must also be directed to eliminating the remaining factor of the tetrahedron – the supply of ignition.
Controlling flammable vapours

The fuel factor of a hearth can be decreased by implementing fundamental controls corresponding to handling and storing flammable liquids in approved, self-closing containers, maintaining the variety of flammable liquids containers within the work space and in storage areas to the minimum essential and within allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate may be substituted, followed by floor washing with fresh water or steam cleaning and pH testing of the floor, or non-combustible solvents corresponding to 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 below the LFL. Combustible gas indicators have to be calibrated in accordance with the manufacturer’s suggestions and should be approved to be used in flammable atmospheres. Operators of the tools should be skilled in correct equipment operation.
Readings should be taken within the common work space and the vicinity of the operator and in areas where there are potential sources of ignition. Typically, items are set to alarm at 10% of the LFL. If the alarm sounds, coatings software work should immediately stop till the concentration of flammable vapours is managed. The objective of setting the alarm below the LFL is to supply a security factor that results in management measures being implemented before there’s an imminent danger of fire or explosion.
Monitoring of the combustible vapour concentration will be needed as the effectiveness of natural air flow may be variable. If control of flammable vapours requires mechanical air flow, an occupational safety or well being skilled or engineer with experience in industrial air flow must be consulted.
At a minimum, mechanical air flow systems should present adequate capability to regulate flammable vapours to under 10% of the LFL by both exhaust air flow to remove contaminants from the work area or by dilution air flow via introduction of recent air to dilute contaminants. As with flamable fuel indicators, air flow equipment should be accredited for secure use in flammable atmospheres. In addition, ventilation tools must be grounded and bonded.
Additional air flow, if needed, must be continuous throughout coatings software as concentrations may improve as more surfaces are coated during the course of a work shift, and particularly on hot surfaces the place the rate of vaporization is higher.
Ventilation during coatings software ought to be steady, particularly when engaged on hot surfaces.
Sources of Ignition

When making use of coatings to hot surfaces, the primary supply of ignition that readily comes to thoughts is the heat from the floor being painted. The AIT of the coating material is the one most essential problem when making use of coatings to scorching working gear. The AIT of a substance or combination is the minimum temperature at which a vapour-air mixture will ignite when involved with a heated surface, without the presence of any open spark or flame.
pressure gauge วัด แรง ดัน น้ำ to controlling this supply of ignition is to verify the surfaces being coated are below the AIT of the coatings being utilized. While surface temperatures may be known/available in many amenities, all surface areas of the process/piping being painted and/or any tools adjacent to the objects being painted the place overspray might deposit should be measured for actual surface temperature. The outcomes ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily apparent, a more subtle but nonetheless important source of ignition to regulate on any industrial portray challenge involving flammable solvents involves the production of static electricity. Equipment related to the spray-painting operation, similar to spray utility tools and ventilation tools, 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 occurs when the sluggish technology of heat from oxidation of organic chemical compounds similar to paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This condition is reached when the fabric is packed loosely allowing a big surface area to be exposed, there could be sufficient air circulating across the material for oxidation to occur, but the natural ventilation available is insufficient to hold the heat away quick enough to stop it from build up.
For more information, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx

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