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

Managers of petrochemical, refining, power, offshore, pulp and paper and other amenities with intensive sizzling processes and piping methods are regularly challenged with performing all the required coatings upkeep work only during periods of outages. Outages are required in order that process tools can be properly maintained and repaired including cleaning of pipelines and vessels, upkeep and alternative of pumps, motors and valves, upkeep coating operations, and different work that can only be accomplished when the operations are shut down.
When coatings work needs to be performed on areas the place elevated temperatures are concerned, many suppose that the ability needs to be shut down. This may 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 beneath, the reply is, “Yes you can, however there are safety and well being issues that must be considered”.
Dangers to personnel should be managed regardless of when or the place work is carried out.
Safety and health issues
There is a spread of safety and health hazards that should be thought-about on every industrial upkeep portray project, whether the coating material is being applied to sizzling steel or not. Some of these include proper material handling and storage, fall protection, management of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and other health risks.
These risks must be properly evaluated and controlled on every industrial upkeep portray venture, regardless of when or the place the work is carried out. While present on any job, when applying specialty coatings to sizzling surfaces, some safety and well being issues should obtain additional consideration.
Flammable and combustible liquids in plenty of coatings (solvents) can vaporize and type flammable mixtures within the air, especially when atomized during spray software or heated. The degree of hazard is decided by the next:
The auto ignition temperature (AIT) of the coating material is the one most necessary issue when making use of coatings to scorching 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 own heat source or contact with a heated floor 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 sufficient vapour is given off to kind an ignitable combination with the air, close to the floor of the liquid”. In other words, the flash point describes the temperature of the liquid that is excessive enough to generate sufficient vapour to create a flame if a supply of ignition had been introduced.
For vapours of flammable liquids, there is a minimum concentration beneath 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 concentration of vapour in the air above which the spread of the flame doesn’t occur. This is the Upper Flammable Limit (UFL). The flammable vary 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 applying solvent borne coatings to sizzling surfaces it must be assumed that the focus of vapours within the air may exceed the LFL (at least for a brief time after application). As with coating application to ambient temperature metal, controls should be applied.
While the LFL is likely to be achieved over a shorter time period during scorching software of coatings than coatings work performed at ambient circumstances, the ensuing fireplace hazard exists in each applications. digital pressure gauge ราคา is, the fireplace hazard and associated controls have to be thought of for the application of any solvent-borne flammable coating system, whatever the work setting. It must be recognized that the gas component of the fire tetrahedron will be present in each ‘hot’ and ‘ambient’ environments and fundamental steps must be taken to minimize pointless solvent vapours in the work space. In addition, as outlined later, consideration must even be directed to eliminating the remaining factor of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The fuel factor of a fireplace can be lowered by implementing basic controls similar to dealing with 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 inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate could additionally be substituted, followed by floor washing with recent water or steam cleansing and pH testing of the floor, or non-combustible solvents such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators must be used to confirm that the focus of flammable vapours is beneath the LFL. Combustible gas indicators must be calibrated in accordance with the manufacturer’s recommendations and should be approved to be used in flammable atmospheres. Operators of the equipment must be skilled in proper gear operation.
Readings should be taken within the general 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 application work should instantly cease till the focus of flammable vapours is controlled. The purpose of setting the alarm below the LFL is to provide a security issue that ends in control measures being implemented earlier than there is an imminent hazard of fireplace or explosion.
Monitoring of the combustible vapour concentration will be necessary because the effectiveness of natural ventilation may be variable. If management of flammable vapours requires mechanical air flow, an occupational safety or well being professional or engineer with experience in industrial air flow ought to be consulted.
At a minimum, mechanical ventilation techniques ought to present sufficient capability to control flammable vapours to under 10% of the LFL by both exhaust air flow to take away contaminants from the work space or by dilution ventilation by way of introduction of fresh air to dilute contaminants. As with combustible fuel indicators, air flow equipment should be accredited for safe use in flammable atmospheres. In addition, air flow gear have to be grounded and bonded.
Additional ventilation, if wanted, should be continuous during coatings application as concentrations could improve as extra surfaces are coated in the course of the course of a piece shift, and especially on hot surfaces where the speed of vaporization is greater.
Ventilation during coatings application ought to be steady, especially when engaged on scorching surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the primary source of ignition that readily involves thoughts is the heat from the floor being painted. The AIT of the coating materials is the single most necessary issue when applying coatings to scorching operating equipment. The AIT of a substance or mixture is the minimal temperature at which a vapour-air mixture will ignite when involved with a heated floor, 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 beneath the AIT of the coatings being utilized. While floor temperatures could also be known/available in plenty of amenities, all floor areas of the process/piping being painted and/or any gear adjoining to the items being painted where overspray might deposit should be measured for precise 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 obvious, a extra delicate but nonetheless critical supply of ignition to regulate on any industrial portray challenge involving flammable solvents entails the production of static electrical energy. Equipment related to the spray-painting operation, such as spray application equipment and air flow equipment, 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 gradual generation of heat from oxidation of organic chemical substances such as paint solvents is accelerated until the ignition temperature of the gasoline is reached.
This condition is reached when the material is packed loosely allowing a big surface area to be uncovered, there is sufficient air circulating around the materials for oxidation to happen, but the natural air flow out there is insufficient to hold the heat away fast sufficient to forestall it from increase.
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