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

Managers of petrochemical, refining, power, offshore, pulp and paper and different facilities with in depth sizzling processes and piping systems are incessantly challenged with performing all the required coatings upkeep work only during periods of outages. Outages are required in order that course of tools could be correctly maintained and repaired together with cleansing of pipelines and vessels, maintenance and substitute of pumps, motors and valves, upkeep coating operations, and other work that can solely be accomplished when the operations are shut down.
When coatings work has to be carried out on areas the place elevated temperatures are involved, many suppose that the power has to be shut down. This will not be the case.
A question regularly posed by facility managers is, “Can I do upkeep painting work while the plant is operating?” As described under, the reply is, “Yes you can, however there are security and well being points that should be considered”.
Dangers to personnel have to be managed no matter when or where work is carried out.
Safety and health concerns

There is a variety of security and well being hazards that must be considered on every industrial maintenance portray challenge, whether the coating material is being applied to sizzling metal or not. Some of these embrace proper material dealing with and storage, fall protection, management of fire and explosion hazards, and exposure to noise, heavy metals, solvents and different health dangers.
These dangers must be correctly evaluated and controlled on every industrial upkeep portray challenge, regardless of when or the place the work is carried out. While present on any job, when making use of specialty coatings to hot surfaces, some security and health issues should receive further consideration.
Flammable and flamable liquids in lots of coatings (solvents) can vaporize and form flammable mixtures in the air, particularly when atomized during spray utility or heated. The degree of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating materials is the single most essential concern when applying coatings to scorching working gear. AIT is defined (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 heat supply or contact with a heated floor with out the presence of an open spark or flame.”

The concept of flash level as defined by NFPA 30 is “the minimum temperature of a liquid at which sufficient vapour is given off to type an ignitable combination with the air, near the floor of the liquid”. In different words, the flash point describes the temperature of the liquid that’s excessive enough to generate sufficient vapour to create a flame if a supply of ignition were launched.
For vapours of flammable liquids, there is a minimum focus below which the unfold of the flame doesn’t happen when in touch with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus of vapour within the air above which the spread 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 focus of vapours can help combustion.
If security procedures are followed, outages may not be required whereas maintenance is carried out.
Implementing controls

Applying coatings to hot 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 focus of vapours in the air could exceed the LFL (at least for a quick time after application). As with coating software to ambient temperature metal, controls should be carried out.
While the LFL is prone to be achieved over a shorter time period during sizzling application of coatings than coatings work carried out at ambient circumstances, the ensuing fireplace hazard exists in each applications. That is, the hearth hazard and related controls must be considered for the appliance of any solvent-borne flammable coating system, whatever the work environment. It must be recognized that the gasoline component of the fire tetrahedron shall be current in both ‘hot’ and ‘ambient’ environments and basic steps should be taken to reduce pointless solvent vapours in the work area. In addition, as outlined later, consideration must even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours

The fuel element of a fireplace may be decreased by implementing basic controls corresponding to handling and storing flammable liquids in accredited, self-closing containers, keeping the variety of flammable liquids containers in the work area and in storage areas to the minimum essential and within allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, followed by surface 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 cleaning.
Combustible gas indicators ought to be used to confirm that the concentration of flammable vapours is under the LFL. Combustible fuel indicators should be calibrated in accordance with the manufacturer’s suggestions and must be accredited for use in flammable atmospheres. Operators of the gear must be educated in proper gear operation.
Readings ought to be taken within the common work space and the neighborhood of the operator and in areas the place there are potential sources of ignition. Typically, models are set to alarm at 10% of the LFL. If the alarm sounds, coatings application work ought to instantly cease till the concentration of flammable vapours is controlled. The objective of setting the alarm beneath the LFL is to supply a safety issue that results in management measures being applied before there is an imminent danger of fire or explosion.
Monitoring of the combustible vapour concentration will be essential because the effectiveness of natural air flow may be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or health professional or engineer with experience in industrial ventilation ought to be consulted.
At a minimal, mechanical air flow systems should present adequate capability to control flammable vapours to under 10% of the LFL by either exhaust air flow to take away contaminants from the work area or by dilution air flow through introduction of contemporary air to dilute contaminants. As with combustible gasoline indicators, air flow gear must be approved for protected use in flammable atmospheres. In addition, air flow tools should be grounded and bonded.
Additional ventilation, if wanted, ought to be continuous during coatings application as concentrations may improve as more surfaces are coated through the course of a work shift, and particularly on hot surfaces where the rate of vaporization is greater.
Ventilation during coatings software must be continuous, especially when engaged on sizzling surfaces.
Sources of Ignition

When applying coatings to hot surfaces, the first source of ignition that readily comes to mind is the warmth from the surface being painted. pressure gauge แบบ น้ำมัน of the coating material is the one most important issue when making use of coatings to hot operating equipment. The AIT of a substance or mixture is the minimum temperature at which a vapour-air mixture will ignite when involved with a heated surface, with out 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 applied. While floor temperatures may be known/available in many facilities, all floor areas of the process/piping being painted and/or any gear adjacent to the gadgets being painted the place overspray may deposit must be measured for actual floor temperature. The results ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily apparent, a extra delicate however nonetheless crucial supply of ignition to regulate on any industrial painting challenge involving flammable solvents involves the production of static electricity. Equipment associated with the spray-painting operation, similar to spray software equipment and air flow tools, can generate static electrical energy.
In addition to external sources of ignition, spontaneous ignition can happen 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 chemicals such as 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 space to be exposed, there’s 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 building up.
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