Managers of petrochemical, refining, energy, offshore, pulp and paper and different services with extensive hot processes and piping systems are regularly challenged with performing all the mandatory coatings maintenance work only during times of outages. Outages are required in order that process tools could be properly maintained and repaired together with cleansing of pipelines and vessels, upkeep and substitute of pumps, motors and valves, upkeep coating operations, and different work that may solely be completed when the operations are shut down.
When coatings work must be carried out on areas where elevated temperatures are concerned, many suppose that the ability needs to be shut down. This will not be the case.
A query regularly posed by facility managers is, “Can I do upkeep painting work whereas the plant is operating?” As described beneath, the reply is, “Yes you possibly can, but there are security and well being issues that should be considered”.
Dangers to personnel must be managed no matter when or where work is performed.
Safety and health issues
There is a spread of security and health hazards that have to be considered on each industrial maintenance portray project, whether the coating material is being applied to sizzling metal or not. Some of these include proper materials dealing with and storage, fall protection, management of fireplace and explosion hazards, and publicity to noise, heavy metals, solvents and other health risks.
These dangers must be correctly evaluated and controlled on every industrial maintenance painting project, no matter when or the place the work is performed. While present on any job, when making use of specialty coatings to sizzling surfaces, some safety and health issues should obtain extra consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and form flammable mixtures in the air, especially when atomized throughout spray software or heated. The diploma of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating material is the single most necessary issue when applying coatings to scorching working tools. 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 mixture will ignite from its personal heat supply or contact with a heated floor with out the presence of an open spark or flame.”
The concept of flash point as defined by NFPA 30 is “the minimum temperature of a liquid at which enough vapour is given off to type an ignitable combination with the air, near the floor of the liquid”. In other phrases, 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 have been introduced.
For vapours of flammable liquids, there is a minimal focus beneath which the unfold of the flame doesn’t occur when involved with a supply 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 security procedures are followed, outages may not be required while upkeep is performed.
Implementing controls
Applying coatings to sizzling surfaces will increase the speed at which the solvents are driven off. When making use of solvent borne coatings to scorching surfaces it must be assumed that the focus of vapours within the air could exceed the LFL (at least for a brief while after application). As with coating utility to ambient temperature steel, controls have to be carried out.
While the LFL is more doubtless to be achieved over a shorter time frame during hot utility of coatings than coatings work performed at ambient conditions, the ensuing fireplace hazard exists in both applications. That is, the fire hazard and related controls should be thought of for the application of any solvent-borne flammable coating system, regardless of the work environment. It have to be acknowledged that the gas element of the hearth tetrahedron might be current in both ‘hot’ and ‘ambient’ environments and basic steps have to be taken to reduce unnecessary 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 gasoline factor of a fire may be decreased by implementing fundamental controls similar to handling and storing flammable liquids in approved, self-closing containers, maintaining the number of flammable liquids containers in the work space and in storage areas to the minimum essential and inside allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, followed by surface washing with recent water or steam cleaning 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 should be used to verify that the concentration of flammable vapours is below the LFL. Combustible gas indicators have to be calibrated in accordance with the manufacturer’s recommendations and have to be approved for use in flammable atmospheres. Operators of the tools should be trained in correct tools operation.
Readings must 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 utility work should instantly cease till the focus of flammable vapours is controlled. เกจวัดแรงอัดกระบอกสูบ of setting the alarm under the LFL is to offer a security factor that results in control measures being carried out before there might be an imminent hazard of fireplace or explosion.
Monitoring of the combustible vapour focus might be needed because the effectiveness of natural ventilation may be variable. If management of flammable vapours requires mechanical ventilation, an occupational security or health skilled or engineer with expertise in industrial ventilation ought to be consulted.
At a minimum, mechanical air flow methods should provide enough capacity to manage flammable vapours to under 10% of the LFL by either exhaust air flow to take away contaminants from the work area or by dilution air flow through introduction of fresh air to dilute contaminants. As with flamable gasoline indicators, air flow gear should be accredited for secure use in flammable atmospheres. In addition, air flow equipment should be grounded and bonded.
Additional air flow, if needed, should be steady throughout coatings application as concentrations could improve as more surfaces are coated in the course of the course of a piece shift, and particularly on hot surfaces the place the rate of vaporization is higher.
Ventilation during coatings application should be continuous, especially when working on sizzling surfaces.
Sources of Ignition
When applying coatings to scorching surfaces, the first supply of ignition that readily comes to mind is the warmth from the surface being painted. The AIT of the coating materials is the one most essential issue when making use of coatings to sizzling working tools. 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 verify the surfaces being coated are beneath the AIT of the coatings being applied. While floor temperatures could additionally be known/available in many services, all surface areas of the process/piping being painted and/or any gear adjoining to the objects being painted where overspray may deposit should be measured for actual 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 additionally be readily obvious, a more delicate however nonetheless important supply of ignition to control on any industrial portray project involving flammable solvents entails the production of static electricity. Equipment related to the spray-painting operation, corresponding to spray utility 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 happens when the gradual generation of warmth from oxidation of organic chemicals corresponding to paint solvents is accelerated until the ignition temperature of the gasoline is reached.
This situation is reached when the fabric is packed loosely permitting a large floor area to be uncovered, there may be enough air circulating across the materials for oxidation to happen, but the pure air flow available is inadequate to carry the heat away fast enough to forestall it from build up.
For extra data, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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