Managers of petrochemical, refining, power, offshore, pulp and paper and other facilities with extensive scorching processes and piping techniques are incessantly challenged with performing all the mandatory coatings upkeep work only during periods of outages. Outages are required in order that process gear may be correctly maintained and repaired together with cleansing of pipelines and vessels, upkeep and replacement of pumps, motors and valves, upkeep coating operations, and different work that can only be completed when the operations are shut down.
When coatings work must be carried out on areas the place elevated temperatures are concerned, many assume that the ability must be shut down. This is most likely not the case.
A question regularly posed by facility managers is, “Can I do upkeep painting work whereas the plant is operating?” As described under, the reply is, “Yes you’ll have the ability to, but there are safety and well being issues that should be considered”.
Dangers to personnel must be managed no matter when or where work is carried out.
Safety and well being considerations
There is a range of security and health hazards that must be considered on each industrial maintenance painting venture, whether the coating material is being utilized to sizzling metal or not. Some of those embody proper materials dealing with and storage, fall protection, management of fire and explosion hazards, and exposure to noise, heavy metals, solvents and different health dangers.
These dangers have to be properly evaluated and controlled on each industrial upkeep portray challenge, no matter when or the place the work is carried out. While current on any job, when making use of specialty coatings to hot surfaces, some security and health issues ought to receive additional consideration.
Flammable and flamable liquids in lots of coatings (solvents) can vaporize and type flammable mixtures within the air, especially when atomized throughout spray software or heated. The diploma of hazard depends on the next:
The auto ignition temperature (AIT) of the coating material is the single most important issue when applying coatings to sizzling working gear. AIT is outlined (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 combination will ignite from its personal warmth source or contact with a heated floor with out the presence of an open spark or flame.”
The idea of flash point as outlined by NFPA 30 is “the minimal temperature of a liquid at which sufficient vapour is given off to type an ignitable combination with the air, close to the surface of the liquid”. In other words, the flash point describes the temperature of the liquid that’s excessive sufficient to generate enough vapour to create a flame if a supply of ignition were launched.
For vapours of flammable liquids, there is a minimal concentration below which the spread of the flame does not occur when in touch with a supply of ignition. This is the Lower Flammable Limit (LFL). There is เพรสเชอร์เกจคือ of vapour in the air above which the unfold of the flame does not 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 security procedures are adopted, outages will not be required whereas upkeep is performed.
Implementing controls
Applying coatings to sizzling surfaces will increase the rate at which the solvents are driven off. When applying solvent borne coatings to sizzling surfaces it should be assumed that the focus of vapours in the air could 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 hot utility of coatings than coatings work performed at ambient conditions, the ensuing fireplace hazard exists in each applications. That is, the fireplace hazard and associated controls should be thought-about for the appliance of any solvent-borne flammable coating system, whatever the work environment. It have to be acknowledged that the gasoline part of the fireplace tetrahedron shall be present in both ‘hot’ and ‘ambient’ environments and basic steps must be taken to minimize unnecessary solvent vapours in the work space. In addition, as outlined later, attention must even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gasoline factor of a fireplace can be decreased by implementing basic controls such as dealing with and storing flammable liquids in accredited, self-closing containers, keeping the variety of flammable liquids containers within the work space and in storage areas to the minimal essential and inside allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, adopted by floor washing with contemporary water or steam cleansing and pH testing of the floor, or non-combustible solvents corresponding to 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gasoline indicators ought to be used to confirm that the focus of flammable vapours is under the LFL. Combustible gasoline indicators have to be calibrated in accordance with the manufacturer’s recommendations and should be accredited for use in flammable atmospheres. Operators of the tools have to be educated in proper tools operation.
Readings ought to be taken within the basic work area and the vicinity 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 utility work ought to instantly stop until the concentration of flammable vapours is controlled. The objective 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 fireside or explosion.
Monitoring of the flammable vapour concentration will be necessary as the effectiveness of natural ventilation could additionally be variable. If management of flammable vapours requires mechanical air flow, an occupational security or health skilled or engineer with expertise in industrial air flow should be consulted.
At a minimal, mechanical ventilation techniques should present adequate capability to control flammable vapours to beneath 10% of the LFL by both exhaust ventilation to remove contaminants from the work area or by dilution air flow via introduction of contemporary air to dilute contaminants. As with flamable fuel indicators, ventilation equipment must be permitted for secure use in flammable atmospheres. In addition, ventilation gear must be grounded and bonded.
Additional air flow, if needed, should be steady during coatings utility as concentrations could improve as extra surfaces are coated during the course of a piece shift, and especially on sizzling surfaces where the speed of vaporization is greater.
Ventilation during coatings utility must be steady, especially when working on sizzling surfaces.
Sources of Ignition
When applying coatings to sizzling surfaces, the first source of ignition that readily involves mind is the heat from the surface being painted. The AIT of the coating material is the single most essential issue when making use of coatings to scorching operating equipment. The AIT of a substance or mixture is the minimal temperature at which a vapour-air combination will ignite when involved 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 below the AIT of the coatings being utilized. While floor temperatures may be known/available in plenty of services, all floor areas of the process/piping being painted and/or any tools adjacent to the items being painted where overspray might deposit must be measured for actual surface temperature. The results should be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily obvious, a more subtle but nonetheless crucial source of ignition to control on any industrial painting venture involving flammable solvents entails the production of static electrical energy. Equipment related to the spray-painting operation, similar to spray utility tools and ventilation gear, can generate static electricity.
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 occurs when the gradual technology of warmth from oxidation of organic chemical substances corresponding to paint solvents is accelerated till the ignition temperature of the fuel is reached.
This condition is reached when the material is packed loosely permitting a big floor area to be exposed, there’s enough air circulating across the materials for oxidation to happen, however the natural ventilation obtainable is insufficient to hold the heat away quick enough to stop it from building up.
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