Managers of petrochemical, refining, energy, offshore, pulp and paper and other amenities with extensive sizzling processes and piping techniques are frequently challenged with performing all the necessary coatings maintenance work only in periods of outages. Outages are required in order that process gear could be correctly maintained and repaired together with cleaning of pipelines and vessels, maintenance and substitute of pumps, motors and valves, maintenance coating operations, and other work that can solely be achieved when the operations are shut down.
When coatings work has to be carried out on areas the place elevated temperatures are involved, many think that the facility has to be shut down. This will not be the case.
A question regularly posed by facility managers is, “Can I do maintenance portray work whereas the plant is operating?” As described beneath, the reply is, “Yes you presumably can, but there are security and health issues that should be considered”.
Dangers to personnel should be managed no matter when or the place work is carried out.
Safety and well being considerations
There is a spread of security and health hazards that have to be considered on each industrial upkeep painting challenge, whether or not the coating materials is being applied to scorching metal or not. Some of these include proper materials handling and storage, fall protection, control of fireside and explosion hazards, and publicity to noise, heavy metals, solvents and other well being dangers.
These dangers have to be correctly evaluated and managed on every industrial upkeep painting challenge, no matter when or where the work is performed. While present on any job, when applying specialty coatings to hot surfaces, some security and health points ought to obtain further consideration.
Flammable and flamable liquids in plenty of coatings (solvents) can vaporize and form flammable mixtures in the air, particularly when atomized throughout spray utility or heated. The diploma of hazard is dependent upon the following:
The auto ignition temperature (AIT) of the coating materials is the one most important issue when applying coatings to sizzling operating gear. AIT is outlined (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 heat supply or contact with a heated surface without the presence of an open spark or flame.”
The idea of flash point as outlined by NFPA 30 is “the minimum temperature of a liquid at which adequate vapour is given off to type an ignitable combination with the air, close to the floor of the liquid”. In different phrases, the flash level describes the temperature of the liquid that is excessive enough to generate enough vapour to create a flame if a supply of ignition were introduced.
For vapours of flammable liquids, there is a minimum concentration under which the unfold of the flame doesn’t happen when in touch with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a most concentration of vapour in the air above which the unfold of the flame doesn’t happen. This is the Upper Flammable Limit (UFL). The flammable vary is between the LFL and the UFL, when the concentration of vapours can assist combustion.
If safety procedures are followed, outages may not be required while maintenance is performed.
Implementing controls
Applying coatings to scorching surfaces increases the rate at which the solvents are driven off. When making use of solvent borne coatings to sizzling surfaces it must be assumed that the concentration of vapours within the air might exceed the LFL (at least for a brief time after application). As with coating utility to ambient temperature steel, controls have to be implemented.
While the LFL is prone to be achieved over a shorter time period during scorching application of coatings than coatings work performed at ambient circumstances, the resulting fire hazard exists in both purposes. That is, the fire hazard and associated controls should be considered for the application of any solvent-borne flammable coating system, regardless of the work setting. It have to be recognized that the fuel part of the hearth tetrahedron shall be present in each ‘hot’ and ‘ambient’ environments and basic steps have to be taken to reduce pointless solvent vapours in the work area. In addition, as outlined later, attention should also be directed to eliminating the remaining element of the tetrahedron – the source of ignition.
Controlling เกจวัดแรงดันสูญญากาศ of a hearth can be lowered by implementing fundamental controls corresponding to dealing with and storing flammable liquids in permitted, self-closing containers, keeping the number of flammable liquids containers within the work area and in storage areas to the minimal essential and within allowable (regulatory) limits.
Alkaline detergents corresponding to tri-sodium phosphate could also be substituted, followed by surface washing with recent 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 cleansing.
Combustible gas indicators should be used to confirm that the focus of flammable vapours is below the LFL. Combustible fuel indicators must be calibrated in accordance with the manufacturer’s recommendations and have to be approved to be used in flammable atmospheres. Operators of the gear have to be skilled in proper equipment operation.
Readings should be taken within the common work space and the neighborhood 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 immediately stop till the concentration of flammable vapours is managed. The function of setting the alarm under the LFL is to offer a security factor that results in management measures being carried out earlier than there might be an imminent hazard of fire or explosion.
Monitoring of the flammable vapour focus might be essential because the effectiveness of natural ventilation may be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or health skilled or engineer with experience in industrial air flow ought to be consulted.
At a minimal, mechanical air flow techniques ought to present sufficient capacity to control flammable vapours to below 10% of the LFL by either exhaust air flow to remove contaminants from the work space or by dilution air flow through introduction of contemporary air to dilute contaminants. As with flamable gasoline indicators, ventilation gear must be permitted for secure use in flammable atmospheres. In addition, air flow gear have to be grounded and bonded.
Additional air flow, if wanted, should be continuous throughout coatings utility as concentrations might enhance as more surfaces are coated during the course of a work shift, and particularly on hot surfaces the place the speed of vaporization is higher.
Ventilation throughout coatings utility should be steady, especially when engaged on scorching surfaces.
Sources of Ignition
When applying coatings to sizzling surfaces, the first supply of ignition that readily involves mind is the warmth from the surface being painted. The AIT of the coating materials is the single most essential issue when making use of coatings to sizzling working gear. The AIT of a substance or mixture is the minimal temperature at which a vapour-air mixture will ignite when involved with a heated floor, with out 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 gear adjacent to the items being painted where overspray may deposit ought to be measured for actual surface temperature. The results must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily obvious, a more refined but nonetheless critical supply of ignition to manage on any industrial portray challenge involving flammable solvents involves the manufacturing of static electricity. Equipment related to the spray-painting operation, similar to spray software gear and ventilation tools, can generate static electricity.
In addition to external sources of ignition, spontaneous ignition can happen when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition occurs when the sluggish era of warmth from oxidation of natural chemicals corresponding to paint solvents is accelerated until the ignition temperature of the gasoline is reached.
This condition is reached when the material is packed loosely allowing a large floor area to be exposed, there might be sufficient air circulating around the materials for oxidation to happen, but the natural air flow obtainable is insufficient to carry the heat away fast enough to stop it from increase.
For more data, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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