Managers of petrochemical, refining, energy, offshore, pulp and paper and different facilities with extensive hot processes and piping techniques are frequently challenged with performing all the mandatory coatings upkeep work only during times of outages. Outages are required in order that course of gear can be correctly maintained and repaired including cleansing of pipelines and vessels, maintenance and alternative of pumps, motors and valves, upkeep coating operations, and different work that can solely be completed when the operations are shut down.
When coatings work needs to be carried out on areas the place elevated temperatures are involved, many think that the ability 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 answer is, “Yes you’ll find a way to, however there are safety and health issues that should be considered”.
Dangers to personnel have to be managed regardless of when or where work is carried out.
Safety and well being issues
There is a variety of safety and well being hazards that must be thought-about on each industrial upkeep painting challenge, whether or not the coating materials is being utilized to hot metal or not. Some of those embody correct materials handling and storage, fall protection, management of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other health dangers.
These dangers should be properly evaluated and managed 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 receive further consideration.
Flammable and combustible liquids in lots of coatings (solvents) can vaporize and type flammable mixtures in the air, particularly when atomized throughout 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 important issue when applying coatings to hot 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 mixture will ignite from its own warmth supply or contact with a heated surface 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 enough vapour is given off to form an ignitable combination with the air, close to the floor of the liquid”. In different words, the flash level describes the temperature of the liquid that’s high enough to generate sufficient vapour to create a flame if a supply of ignition have been launched.
For vapours of flammable liquids, there is a minimal concentration under which the unfold of the flame doesn’t happen when in contact with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum focus 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 adopted, outages may not be required whereas maintenance is carried out.
Applying coatings to hot surfaces will increase the speed at which the solvents are pushed off. When making use of solvent borne coatings to sizzling surfaces it must be assumed that the concentration of vapours in the air may exceed the LFL (at least for a brief time after application). As with coating utility to ambient temperature metal, controls have to be implemented.
While the LFL is more probably to be achieved over a shorter period of time during sizzling software 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 application of any solvent-borne flammable coating system, whatever the work environment. It have to be recognized that the gasoline element of the fire tetrahedron shall be present in both ‘hot’ and ‘ambient’ environments and fundamental steps have to be taken to minimize unnecessary solvent vapours within the work area. In addition, as outlined later, attention should also be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The fuel element of a fire could be decreased by implementing basic controls corresponding to dealing with and storing flammable liquids in approved, self-closing containers, preserving the variety of flammable liquids containers within the work area and in storage areas to the minimum essential and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate could also be substituted, adopted by surface washing with fresh water or steam cleansing and pH testing of the surface, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gasoline indicators should be used to confirm that the focus of flammable vapours is under the LFL. Combustible gas indicators must be calibrated in accordance with the manufacturer’s suggestions and must be accredited to be used in flammable atmospheres. Operators of the tools must be educated in correct tools operation.
Readings should be taken in the basic work space and the neighborhood of the operator and in areas where there are potential sources of ignition. Typically, units are set to alarm at 10% of the LFL. If the alarm sounds, coatings application work ought to immediately stop until the concentration of flammable vapours is controlled. The function of setting the alarm beneath the LFL is to offer a security issue that leads to control measures being implemented earlier than there’s an imminent hazard of fireside or explosion.
Monitoring of the combustible 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 security or well being skilled or engineer with experience in industrial air flow ought to be consulted.
At a minimal, mechanical air flow techniques ought to provide sufficient capacity to regulate flammable vapours to under 10% of the LFL by either exhaust ventilation to take away contaminants from the work space or by dilution ventilation via introduction of recent air to dilute contaminants. As with combustible gasoline indicators, ventilation tools have to be accredited for secure use in flammable atmospheres. In addition, ventilation equipment must be grounded and bonded.
Additional air flow, if wanted, must be steady throughout coatings software as concentrations might improve as extra surfaces are coated during the course of a work shift, and particularly on scorching surfaces the place the rate of vaporization is higher.
Ventilation throughout coatings application should be continuous, particularly when working on scorching surfaces.
เกจวัดแรงดันลมคือ of Ignition
When making use of coatings to hot surfaces, the primary supply of ignition that readily comes to thoughts is the warmth from the surface being painted. The AIT of the coating materials is the only most important issue when applying coatings to scorching operating tools. The AIT of a substance or mixture is the minimal 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 confirm the surfaces being coated are under the AIT of the coatings being applied. While floor temperatures could additionally be known/available in many facilities, all surface areas of the process/piping being painted and/or any tools adjoining to the objects being painted the place overspray might deposit ought to be measured for precise surface temperature. The outcomes ought to be in comparability with the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily obvious, a extra delicate however nonetheless crucial source of ignition to manage on any industrial portray challenge involving flammable solvents entails the manufacturing of static electrical energy. Equipment associated with the spray-painting operation, such as spray software equipment and ventilation tools, 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 slow era of warmth from oxidation of natural chemical substances such as paint solvents is accelerated until the ignition temperature of the gas is reached.
This condition is reached when the material is packed loosely allowing a large floor area to be uncovered, there is enough air circulating around the materials for oxidation to occur, but the natural ventilation obtainable is inadequate to hold the heat away fast enough to stop it from increase.
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