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

Managers of petrochemical, refining, power, offshore, pulp and paper and other services with in depth hot processes and piping methods are regularly challenged with performing all the necessary coatings maintenance work only during times of outages. Outages are required in order that course of gear can be properly maintained and repaired together with cleansing of pipelines and vessels, upkeep and alternative 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 where elevated temperatures are involved, many assume that the facility has 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 below, เกจวัดแรงดันลมดิจิตอล is, “Yes you can, however there are security and well being points that must be considered”.
Dangers to personnel have to be managed no matter when or where work is performed.
Safety and health issues
There is a variety of safety and health hazards that must be considered on each industrial upkeep portray challenge, whether or not the coating material is being utilized to hot steel or not. Some of those include proper material dealing with and storage, fall safety, management of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other health dangers.
These risks should be properly evaluated and managed on every industrial upkeep portray challenge, no matter 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 health issues should receive extra consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and form flammable mixtures in the air, especially when atomized during spray software or heated. The degree of hazard is dependent upon the next:
The auto ignition temperature (AIT) of the coating material is the single most important problem when making use of 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 personal heat 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 minimum temperature of a liquid at which enough vapour is given off to type an ignitable mixture with the air, close to the floor of the liquid”. In different words, the flash point describes the temperature of the liquid that’s high 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 below which the spread of the flame does not happen when involved with a source of ignition. This is the Lower Flammable Limit (LFL). There is a most focus of vapour within the air above which the spread of the flame does not happen. This is the Upper Flammable Limit (UFL). The flammable range is between the LFL and the UFL, when the concentration of vapours can help combustion.
If safety procedures are followed, outages will not be required while maintenance is performed.
Implementing controls
Applying coatings to sizzling surfaces increases the speed at which the solvents are pushed off. When applying solvent borne coatings to scorching surfaces it have to be assumed that the concentration of vapours within the air may exceed the LFL (at least for a brief time after application). As with coating utility to ambient temperature steel, controls must be implemented.
While the LFL is prone to be achieved over a shorter time frame throughout sizzling application of coatings than coatings work performed at ambient situations, the resulting fireplace hazard exists in each purposes. That is, the hearth hazard and related controls must be considered for the application of any solvent-borne flammable coating system, regardless of the work surroundings. pressure gauge 4 นิ้ว must be recognized that the gasoline component of the hearth tetrahedron shall be current in both ‘hot’ and ‘ambient’ environments and basic steps must be taken to reduce unnecessary solvent vapours in the work area. In addition, as outlined later, attention must also be directed to eliminating the remaining component of the tetrahedron – the source of ignition.
Controlling flammable vapours
The fuel element of a fireplace can be decreased by implementing primary controls such as 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 needed and within allowable (regulatory) limits.
Alkaline detergents similar 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 such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators must be used to verify that the concentration of flammable vapours is below the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s recommendations and have to be accredited for use in flammable atmospheres. Operators of the tools have to be educated 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, models are set to alarm at 10% of the LFL. If the alarm sounds, coatings utility work should immediately stop until the concentration of flammable vapours is managed. The purpose of setting the alarm under the LFL is to offer a safety issue that leads to management measures being implemented before there is an imminent hazard of fire or explosion.
Monitoring of the flammable vapour focus will be necessary as the effectiveness of natural ventilation could also be variable. If control of flammable vapours requires mechanical air flow, an occupational security or health skilled or engineer with experience in industrial ventilation should be consulted.
At a minimal, mechanical air flow methods should present sufficient capacity to control flammable vapours to beneath 10% of the LFL by either exhaust ventilation to take away contaminants from the work area or by dilution ventilation via introduction of fresh air to dilute contaminants. As with flamable gasoline indicators, ventilation tools have to be approved for safe use in flammable atmospheres. In addition, air flow equipment should be grounded and bonded.
Additional ventilation, if needed, should be continuous throughout coatings application as concentrations could increase as extra surfaces are coated in the course of the course of a piece shift, and especially on sizzling surfaces the place the speed of vaporization is greater.
Ventilation throughout coatings software ought to be steady, particularly when engaged on sizzling surfaces.
Sources of Ignition
When making use of coatings to sizzling surfaces, the primary source of ignition that readily comes to thoughts is the warmth from the surface being painted. The AIT of the coating material is the one most necessary problem when applying coatings to hot operating tools. The AIT of a substance or combination is the minimal temperature at which a vapour-air mixture will ignite when in touch with a heated surface, with out the presence of any open spark or flame.
The key to controlling this source of ignition is to confirm the surfaces being coated are beneath the AIT of the coatings being utilized. While floor temperatures may be known/available in lots of services, all surface areas of the process/piping being painted and/or any tools adjoining to the objects being painted where overspray might deposit must be measured for precise floor temperature. The outcomes 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 but nonetheless crucial source of ignition to control 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 gear and air flow tools, can generate static electrical energy.
In addition to exterior sources of ignition, spontaneous ignition can happen when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition happens when the slow generation of heat from oxidation of natural chemical compounds similar to 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 surface space to be exposed, there’s sufficient air circulating across the material for oxidation to happen, however the natural air flow out there is inadequate to carry the warmth away fast sufficient to forestall it from build up.
For extra information, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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