Managers of petrochemical, refining, power, offshore, pulp and paper and different amenities with in depth sizzling processes and piping systems are incessantly challenged with performing all the necessary coatings maintenance work only during times of outages. Outages are required so that course of tools can be correctly maintained and repaired together with cleansing of pipelines and vessels, maintenance and alternative of pumps, motors and valves, maintenance coating operations, and different work that can only be accomplished when the operations are shut down.
When coatings work needs to be performed on areas where elevated temperatures are concerned, many think that the power needs to be shut down. This may not be the case.
A query regularly posed by facility managers is, “Can I do maintenance portray work whereas the plant is operating?” As described under, the reply is, “Yes you presumably can, but there are safety and health points that should be considered”.
Dangers to personnel have to be managed regardless of when or where work is carried out.
Safety and health concerns
There is a spread of security and health hazards that should be considered on each industrial maintenance portray challenge, whether the coating material is being applied to sizzling steel or not. Some of those include correct materials dealing with and storage, fall protection, control of fireside and explosion hazards, and exposure to noise, heavy metals, solvents and other health dangers.
These risks must be properly evaluated and managed on every industrial maintenance portray project, regardless of when or the place the work is performed. While เกจวัดแรงดันออกซิเจน on any job, when making use of specialty coatings to scorching surfaces, some security and well being issues should obtain additional consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, especially when atomized throughout spray software or heated. The degree of hazard is dependent upon the next:
The auto ignition temperature (AIT) of the coating material is the one most important concern when applying coatings to sizzling operating 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 combination will ignite from its personal heat source or contact with a heated floor without the presence of an open spark or flame.”
The idea of flash level as outlined by NFPA 30 is “the minimal temperature of a liquid at which adequate vapour is given off to type 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’s high sufficient to generate sufficient vapour to create a flame if a source of ignition had been launched.
For vapours of flammable liquids, there’s a minimum concentration beneath which the spread of the flame does not occur when in contact with a supply 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 range is between the LFL and the UFL, when the concentration of vapours can assist combustion.
If security procedures are followed, outages is in all probability not required whereas upkeep is carried out.
Implementing controls
Applying coatings to sizzling surfaces will increase the speed at which the solvents are driven off. When applying solvent borne coatings to hot surfaces it have to be assumed that the concentration of vapours within the air could exceed the LFL (at least for a quick time after application). As with coating software to ambient temperature steel, controls should be applied.
While the LFL is likely to be achieved over a shorter time period throughout sizzling application of coatings than coatings work carried out at ambient conditions, the resulting hearth hazard exists in both functions. That is, the hearth hazard and related controls should be thought of for the applying of any solvent-borne flammable coating system, regardless of the work environment. It must be recognized that the gas element of the hearth tetrahedron shall be present in each ‘hot’ and ‘ambient’ environments and basic steps must be taken to reduce unnecessary solvent vapours within the work area. In addition, as outlined later, attention should even be directed to eliminating the remaining factor of the tetrahedron – the source of ignition.
Controlling flammable vapours
The gasoline element of a fire could be decreased by implementing fundamental controls similar to dealing with and storing flammable liquids in approved, self-closing containers, keeping the number of flammable liquids containers in the work area and in storage areas to the minimal needed and inside allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate could additionally be substituted, adopted by surface washing with contemporary 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 fuel indicators ought to be used to verify that the concentration of flammable vapours is under the LFL. Combustible gas indicators have to be calibrated in accordance with the manufacturer’s recommendations and have to be permitted to be used in flammable atmospheres. Operators of the equipment must be educated in correct gear operation.
Readings should be taken in the general 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 should immediately cease until the focus of flammable vapours is managed. The objective of setting the alarm under the LFL is to offer a safety issue that ends in control measures being applied earlier than there might be an imminent danger of fire or explosion.
Monitoring of the combustible vapour concentration shall be necessary because the effectiveness of pure air flow could additionally be variable. If management of flammable vapours requires mechanical air flow, an occupational safety or well being professional or engineer with expertise in industrial air flow should be consulted.
At a minimal, mechanical ventilation methods ought to present adequate capacity to regulate flammable vapours to under 10% of the LFL by both exhaust air flow to take away contaminants from the work space or by dilution ventilation by way of introduction of fresh air to dilute contaminants. As with flamable fuel indicators, ventilation gear have to be accredited for safe use in flammable atmospheres. In addition, air flow gear have to be grounded and bonded.
Additional air flow, if wanted, must be steady during coatings application as concentrations may enhance as more surfaces are coated in the course of the course of a work shift, and particularly on sizzling surfaces the place the speed of vaporization is larger.
Ventilation throughout coatings application must be steady, especially when working on hot surfaces.
Sources of Ignition
When making use of coatings to scorching surfaces, the primary supply of ignition that readily involves mind is the warmth from the surface being painted. The AIT of the coating materials is the only most necessary problem when making use of coatings to hot operating gear. The AIT of a substance or combination is the minimal temperature at which a vapour-air mixture will ignite when in contact with a heated floor, without 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 may be known/available in many services, all surface areas of the process/piping being painted and/or any gear adjoining to the items being painted the place overspray could deposit should 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 extra refined however nonetheless important supply of ignition to regulate on any industrial painting challenge involving flammable solvents includes the manufacturing of static electricity. Equipment related to the spray-painting operation, similar to spray software gear and ventilation gear, can generate static electricity.
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 occurs when the gradual generation of heat from oxidation of natural chemical substances similar to paint solvents is accelerated till the ignition temperature of the gas is reached.
This situation is reached when the material is packed loosely permitting a large floor area to be uncovered, there’s enough air circulating around the materials for oxidation to occur, but the pure ventilation out there is inadequate to carry the heat away quick enough to forestall it from build up.
For extra data, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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