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

Managers of petrochemical, refining, power, offshore, pulp and paper and different services with intensive scorching processes and piping techniques are regularly challenged with performing all the mandatory coatings maintenance work solely in periods of outages. Outages are required so that process gear may be properly maintained and repaired together with cleaning of pipelines and vessels, upkeep and substitute of pumps, motors and valves, upkeep coating operations, and different work that may only be achieved when the operations are shut down.
When coatings work needs to be carried out on areas the place elevated temperatures are involved, many assume that the ability has to be shut down. This is in all probability not the case.
A query regularly posed by facility managers is, “Can I do upkeep painting work whereas the plant is operating?” As described below, the reply is, “Yes you can, however there are safety and health issues that should be considered”.
Dangers to personnel must be managed regardless of when or the place work is performed.
Safety and well being issues

There is a range of safety and health hazards that must be considered on each industrial maintenance painting project, whether or not the coating material is being applied to hot steel or not. Some of those embody proper materials dealing with and storage, fall protection, management of fireplace and explosion hazards, and publicity to noise, heavy metals, solvents and different health dangers.
These dangers have to be correctly evaluated and controlled on every industrial upkeep painting venture, no matter when or where the work is carried out. While current on any job, when applying specialty coatings to sizzling surfaces, some security and health points should receive extra consideration.
Flammable and flamable liquids in lots of coatings (solvents) can vaporize and form flammable mixtures within the air, especially when atomized during spray application or heated. The degree of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating material is the single most necessary issue when making use of coatings to sizzling operating equipment. 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 personal heat supply or contact with a heated surface without the presence of an open spark or flame.”

The idea of flash point as defined by NFPA 30 is “the minimal temperature of a liquid at which adequate vapour is given off to kind 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 is high sufficient to generate enough vapour to create a flame if a source of ignition had been launched.
For vapours of flammable liquids, there is a minimal focus beneath which the unfold of the flame doesn’t happen when involved 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 spread 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 may not be required whereas upkeep is performed.
Implementing controls

Applying coatings to scorching surfaces will increase the speed at which the solvents are pushed off. When applying solvent borne coatings to sizzling surfaces it must be assumed that the concentration of vapours in the air could exceed the LFL (at least for a brief while after application). As with coating software to ambient temperature steel, controls must be carried out.
While the LFL is prone to be achieved over a shorter time period during scorching application of coatings than coatings work performed at ambient circumstances, the resulting fire hazard exists in both purposes. That is, the fire hazard and related controls have to be thought-about for the applying of any solvent-borne flammable coating system, whatever the work setting. It have to be recognized that the fuel element of the fireplace tetrahedron might be current in both ‘hot’ and ‘ambient’ environments and basic steps have to be taken to reduce unnecessary solvent vapours in the work space. 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 could be lowered by implementing fundamental controls corresponding to handling and storing flammable liquids in accredited, self-closing containers, maintaining the number of flammable liquids containers in the work area and in storage areas to the minimal essential and inside allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could also be substituted, adopted by surface washing with contemporary water or steam cleansing and pH testing of the floor, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gas indicators ought to be used to confirm that the focus of flammable vapours is below the LFL. Combustible gas indicators must be calibrated in accordance with the manufacturer’s suggestions and should be approved for use in flammable atmospheres. Operators of the equipment must be educated in correct equipment operation.
Readings must be taken within the general work area 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 application work ought to immediately cease until the concentration of flammable vapours is controlled. The objective of setting the alarm below the LFL is to provide a safety issue that leads to control measures being carried out before there might be an imminent danger of fireplace or explosion.
Monitoring of the combustible vapour focus will be needed as the effectiveness of natural air flow could also be variable. If management of flammable vapours requires mechanical ventilation, an occupational security or well being skilled or engineer with experience in industrial ventilation ought to be consulted.
At a minimum, mechanical ventilation techniques should provide enough capacity to control flammable vapours to beneath 10% of the LFL by either exhaust air flow to remove contaminants from the work area or by dilution air flow by way of introduction of contemporary air to dilute contaminants. As with combustible gas indicators, air flow tools have to be approved for protected use in flammable atmospheres. In addition, air flow tools must be grounded and bonded.
Additional ventilation, if needed, must be continuous throughout coatings utility as concentrations could improve as extra surfaces are coated in the course of the course of a piece shift, and particularly on hot surfaces where the speed of vaporization is larger.
Ventilation during coatings application should be steady, particularly when working on hot surfaces.
Sources of Ignition

When applying coatings to hot surfaces, the primary source of ignition that readily comes to thoughts is the heat from the surface being painted. The AIT of the coating materials is the one most important problem when making use of coatings to scorching 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 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 below the AIT of the coatings being utilized. While floor temperatures could also be known/available in many facilities, all floor areas of the process/piping being painted and/or any equipment adjoining to the items being painted where overspray might deposit must be measured for actual surface temperature. The results must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily obvious, a more delicate but nonetheless critical source of ignition to manage on any industrial portray project involving flammable solvents includes the production of static electricity. Equipment related to the spray-painting operation, such as spray software tools and air flow gear, can generate static electrical energy.
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 gradual generation of warmth from oxidation of organic chemicals such as paint solvents is accelerated till the ignition temperature of the gas is reached.
digital pressure gauge is reached when the fabric is packed loosely permitting a big floor area to be uncovered, there might be enough air circulating around the material for oxidation to happen, but the natural ventilation obtainable is insufficient to carry the warmth away fast sufficient to forestall it from building up.
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