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

Managers of petrochemical, refining, power, offshore, pulp and paper and different amenities with in depth sizzling processes and piping techniques are regularly challenged with performing all the mandatory coatings maintenance work solely in periods of outages. Outages are required in order that course of equipment could be correctly maintained and repaired including cleansing of pipelines and vessels, maintenance and replacement of pumps, motors and valves, maintenance coating operations, and different work that may solely 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 will not be the case.
A query regularly posed by facility managers is, “Can I do upkeep portray work while the plant is operating?” As described below, the reply is, “Yes you can, but there are security 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 considerations
There is a spread of safety and health hazards that have to be considered on every industrial upkeep painting venture, whether or not the coating material is being utilized to hot metal or not. Some of these embody correct material handling and storage, fall safety, control of fireplace and explosion hazards, and exposure to noise, heavy metals, solvents and different well being risks.
These dangers have to be correctly evaluated and managed on each industrial upkeep painting venture, regardless of when or where the work is performed. While current on any job, when applying specialty coatings to sizzling surfaces, some security and well being issues ought to obtain extra consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, especially when atomized during spray utility or heated. The degree of hazard is decided by the next:
The auto ignition temperature (AIT) of the coating materials is the single most necessary issue when applying coatings to scorching operating 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 personal heat supply or contact with a heated surface with out the presence of an open spark or flame.”
The concept of flash level as outlined 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 surface of the liquid”. In other words, the flash point describes the temperature of the liquid that is high sufficient to generate sufficient vapour to create a flame if a supply of ignition were launched.
For vapours of flammable liquids, there’s a minimal concentration below which the spread of the flame doesn’t happen when involved with a source of ignition. This is the Lower Flammable Limit (LFL). There is a most 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 concentration of vapours can support combustion.
If safety procedures are followed, outages may not be required while upkeep is performed.
Implementing controls
Applying coatings to hot surfaces increases the speed at which the solvents are driven off. When applying solvent borne coatings to scorching surfaces it must be assumed that the focus of vapours within the air may exceed the LFL (at least for a short time after application). As with coating utility to ambient temperature metal, controls must be applied.
While the LFL is likely to be achieved over a shorter period of time throughout sizzling utility of coatings than coatings work carried out at ambient situations, the ensuing hearth hazard exists in both purposes. That is, the fire hazard and related controls have to be thought of for the applying of any solvent-borne flammable coating system, whatever the work surroundings. It must be acknowledged that the gasoline element of the fireplace tetrahedron shall be current in both ‘hot’ and ‘ambient’ environments and fundamental steps must be taken to attenuate pointless solvent vapours within the work space. 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 factor of a fireplace may be lowered by implementing primary controls corresponding to dealing with and storing flammable liquids in approved, 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 similar to tri-sodium phosphate may be substituted, followed by surface washing with fresh water or steam cleaning and pH testing of the surface, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators ought to be used to verify that the concentration of flammable vapours is under the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s suggestions and have to be accredited to be used in flammable atmospheres. Operators of the equipment have to be educated in correct gear operation.
Readings ought to be taken in the basic work area and the vicinity of the operator and in areas the place there are potential sources of ignition. Typically, units are set to alarm at 10% of the LFL. If the alarm sounds, coatings software work should instantly cease till the concentration of flammable vapours is managed. The function of setting the alarm under the LFL is to provide a security factor that results in control measures being implemented before there is an imminent danger of fireplace or explosion.
Monitoring of the flammable vapour focus will be essential because the effectiveness of natural air flow may be variable. If management of flammable vapours requires mechanical air flow, an occupational safety or health professional or engineer with expertise in industrial air flow ought to be consulted.
At a minimum, mechanical air flow methods should provide enough capability to regulate flammable vapours to under 10% of the LFL by both exhaust ventilation to remove contaminants from the work space or by dilution air flow by way of introduction of contemporary air to dilute contaminants. As with flamable fuel indicators, ventilation tools have to be approved for secure use in flammable atmospheres. In addition, air flow tools should be grounded and bonded.
Additional air flow, if needed, should be continuous during coatings utility as concentrations could enhance as extra surfaces are coated during the course of a work shift, and particularly on hot surfaces where the rate of vaporization is greater.
Ventilation throughout coatings software should be continuous, especially when working on hot surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the first supply of ignition that readily involves mind is the heat from the floor being painted. เพรสเชอร์เกจnuovafima of the coating materials is the only most important concern when making use of coatings to scorching working equipment. The AIT of a substance or mixture is the minimum temperature at which a vapour-air combination will ignite when in contact with a heated surface, without the presence of any open spark or flame.
The key to controlling this supply of ignition is to confirm the surfaces being coated are beneath the AIT of the coatings being utilized. While surface temperatures may be known/available in lots of services, all surface areas of the process/piping being painted and/or any equipment adjacent to the objects being painted the place overspray might deposit ought to 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 obvious, a extra delicate however nonetheless important source of ignition to manage on any industrial portray venture involving flammable solvents includes the manufacturing of static electricity. Equipment associated with the spray-painting operation, similar to spray application gear and air flow equipment, 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 sluggish era of heat from oxidation of natural chemical substances such as paint solvents is accelerated until the ignition temperature of the fuel is reached.
This condition is reached when the fabric is packed loosely permitting a big floor space to be uncovered, there’s sufficient air circulating across the materials for oxidation to happen, but the pure ventilation obtainable is inadequate to hold the warmth away quick enough to stop it from build up.
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