Managers of petrochemical, refining, energy, offshore, pulp and paper and other amenities with intensive scorching processes and piping systems are frequently challenged with performing all the required coatings upkeep work only during times of outages. Outages are required so that course of equipment can be correctly maintained and repaired including cleaning of pipelines and vessels, maintenance and replacement of pumps, motors and valves, upkeep coating operations, and different work that can only be achieved when the operations are shut down.
When coatings work has to be performed on areas where elevated temperatures are concerned, many suppose that the ability has to be shut down. This may not be the case.
A question incessantly posed by facility managers is, “Can I do upkeep painting work whereas the plant is operating?” As described beneath, the reply is, “Yes you can, but there are safety and health issues that should be considered”.
Dangers to personnel should be managed regardless of when or where work is carried out.
Safety and well being concerns
There is a range of security and well being hazards that should be thought of on every industrial upkeep portray venture, whether or not the coating material is being applied to scorching metal or not. Some of those embody correct materials handling and storage, fall safety, management of fireside and explosion hazards, and publicity to noise, heavy metals, solvents and other health dangers.
These dangers should be properly evaluated and controlled on each industrial upkeep portray challenge, regardless of when or where the work is carried out. While present on any job, when applying specialty coatings to sizzling surfaces, some security and health issues should obtain further consideration.
Flammable and flamable liquids in many coatings (solvents) can vaporize and type flammable mixtures in the air, particularly when atomized throughout spray software or heated. The degree of hazard depends on the following:
The auto ignition temperature (AIT) of the coating materials is the one most essential concern when applying coatings to scorching working equipment. 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 personal warmth source or contact with a heated surface with out the presence of an open spark or flame.”
The idea of flash level as defined by NFPA 30 is “the minimum temperature of a liquid at which sufficient vapour is given off to form an ignitable combination with the air, near the floor of the liquid”. In different phrases, the flash level describes the temperature of the liquid that’s high enough to generate enough vapour to create a flame if a source of ignition have been launched.
For vapours of flammable liquids, there’s a minimal focus below which the spread of the flame doesn’t occur when in contact 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 does not occur. This is the Upper Flammable Limit (UFL). The flammable vary is between the LFL and the UFL, when the focus of vapours can assist combustion.
If security procedures are followed, outages will not be required while maintenance is carried out.
Implementing controls
Applying coatings to scorching surfaces will increase the rate at which the solvents are driven off. When applying solvent borne coatings to scorching surfaces it have to be assumed that the concentration of vapours within the air might exceed the LFL (at least for a quick time after application). As with coating utility to ambient temperature metal, controls have to be carried out.
While the LFL is prone to be achieved over a shorter period of time during scorching software of coatings than coatings work carried out at ambient conditions, the resulting hearth hazard exists in each functions. That is, the hearth hazard and associated controls must be thought-about for the application of any solvent-borne flammable coating system, regardless of the work surroundings. It have to be acknowledged that the fuel element of the fireplace tetrahedron might be current in both ‘hot’ and ‘ambient’ environments and basic steps must be taken to reduce unnecessary solvent vapours within the work space. In เกจวัดแรงดันน้ำ4หุน , as outlined later, consideration should even be directed to eliminating the remaining component of the tetrahedron – the source of ignition.
Controlling flammable vapours
The fuel component of a fire could be lowered by implementing fundamental controls similar to handling and storing flammable liquids in approved, self-closing containers, keeping the number of flammable liquids containers in the work space and in storage areas to the minimum necessary and inside allowable (regulatory) limits.
Alkaline detergents such as tri-sodium phosphate could also be substituted, followed by surface washing with contemporary water or steam cleaning and pH testing of the floor, or non-combustible solvents such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gasoline indicators ought to be used to confirm that the concentration of flammable vapours is beneath the LFL. Combustible gas indicators must be calibrated in accordance with the manufacturer’s suggestions and have to be approved for use in flammable atmospheres. Operators of the tools have to be trained in proper equipment operation.
Readings must be taken in the general work space and the vicinity 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 utility work should instantly cease until the concentration of flammable vapours is managed. The purpose of setting the alarm under the LFL is to offer a safety issue that results in management measures being carried out before there’s an imminent danger of fireside or explosion.
Monitoring of the flammable vapour concentration will be necessary because the effectiveness of natural ventilation could also be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or well being professional or engineer with expertise in industrial air flow ought to be consulted.
At a minimal, mechanical air flow techniques should present sufficient capacity to regulate flammable vapours to below 10% of the LFL by both exhaust air flow to remove contaminants from the work area or by dilution air flow via introduction of contemporary air to dilute contaminants. As with flamable gasoline indicators, air flow gear should be approved for protected use in flammable atmospheres. In addition, ventilation gear should be grounded and bonded.
Additional ventilation, if needed, ought to be steady during coatings software as concentrations could enhance as more surfaces are coated through the course of a piece shift, and particularly on sizzling surfaces where the speed of vaporization is higher.
Ventilation throughout coatings software should be continuous, particularly when working on scorching surfaces.
Sources of Ignition
When applying coatings to hot surfaces, the primary source of ignition that readily involves mind is the heat from the floor being painted. The AIT of the coating material is the single most essential problem when making use of coatings to scorching working tools. The AIT of a substance or mixture is the minimum temperature at which a vapour-air mixture will ignite when in touch with a heated surface, 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 under the AIT of the coatings being utilized. While floor temperatures may be known/available in many services, all surface areas of the process/piping being painted and/or any tools adjacent to the objects being painted where overspray might deposit ought to be measured for actual floor temperature. The outcomes ought to be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily obvious, a extra refined however nonetheless critical supply of ignition to regulate on any industrial portray challenge involving flammable solvents includes the manufacturing of static electricity. Equipment associated with the spray-painting operation, similar to spray software tools and air flow 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 happens when the slow era of heat from oxidation of organic chemical compounds similar to paint solvents is accelerated till the ignition temperature of the fuel is reached.
This situation is reached when the material is packed loosely permitting a large surface area to be exposed, there’s enough air circulating across the material for oxidation to happen, however the natural air flow obtainable is inadequate to hold the heat away quick sufficient to forestall it from build up.
For more information, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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