Managers of petrochemical, refining, power, offshore, pulp and paper and different facilities with extensive hot processes and piping systems are frequently challenged with performing all the required coatings maintenance work solely during periods of outages. Outages are required in order that course of gear could be properly maintained and repaired including cleansing of pipelines and vessels, maintenance and replacement of pumps, motors and valves, upkeep coating operations, and other work that may solely be achieved when the operations are shut down.
When coatings work has to be performed on areas where elevated temperatures are involved, many assume that the ability needs to be shut down. This may not be the case.
A query frequently posed by facility managers is, “Can I do upkeep painting work while the plant is operating?” As described below, the reply is, “Yes you can, however there are safety 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 range of security and well being hazards that must be thought of on every industrial upkeep painting venture, whether or not the coating material is being applied to scorching metal or not. Some of those embody proper material dealing with and storage, fall safety, control of fire and explosion hazards, and exposure to noise, heavy metals, solvents and different health risks.
These risks must be correctly evaluated and controlled on each industrial upkeep painting venture, regardless of when or the place the work is carried out. While present on any job, when making use of specialty coatings to scorching surfaces, some security and health issues should receive extra consideration.
Flammable and combustible liquids in lots of coatings (solvents) can vaporize and form flammable mixtures within the air, especially when atomized during spray application or heated. The degree of hazard is determined by the next:
The auto ignition temperature (AIT) of the coating material is the only most important problem 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 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 concept of flash point as outlined by NFPA 30 is “the minimum temperature of a liquid at which adequate vapour is given off to kind an ignitable mixture with the air, near the floor of the liquid”. In different phrases, the flash point describes the temperature of the liquid that is excessive enough to generate enough vapour to create a flame if a source of ignition were launched.
For pressure gauge ราคา ถูก of flammable liquids, there is a minimum 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 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 help combustion.
If safety procedures are followed, outages will not be required whereas upkeep is performed.
Implementing controls
Applying coatings to hot surfaces increases the rate at which the solvents are pushed off. When applying solvent borne coatings to scorching surfaces it have to be assumed that the concentration of vapours within the air may exceed the LFL (at least for a quick time after application). As with coating utility to ambient temperature steel, controls have to be applied.
While the LFL is likely to be achieved over a shorter time frame during sizzling utility of coatings than coatings work carried out at ambient situations, the resulting fire hazard exists in each functions. That is, the fireplace hazard and related controls should be considered for the application of any solvent-borne flammable coating system, regardless of the work setting. It have to be acknowledged that the gasoline part of the fire tetrahedron shall be current in both ‘hot’ and ‘ambient’ environments and primary steps should be taken to reduce pointless solvent vapours within the work space. In addition, as outlined later, consideration must also be directed to eliminating the remaining component of the tetrahedron – the source of ignition.
Controlling flammable vapours
The fuel factor of a fire could be decreased by implementing basic controls corresponding to dealing with and storing flammable liquids in accredited, self-closing containers, preserving the number of flammable liquids containers in the work space and in storage areas to the minimal necessary and inside allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, followed by floor 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 gas indicators must be used to confirm that the concentration of flammable vapours is below the LFL. Combustible gas indicators have to be calibrated in accordance with the manufacturer’s suggestions and must be permitted for use in flammable atmospheres. Operators of the gear must be educated in proper equipment operation.
Readings should be taken within the general work area 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 utility work should immediately stop till the concentration of flammable vapours is controlled. The purpose of setting the alarm below the LFL is to offer a safety issue that leads to control measures being implemented before there is an imminent danger of fire or explosion.
Monitoring of the flammable vapour concentration shall be necessary as the effectiveness of pure ventilation may be variable. If management of flammable vapours requires mechanical ventilation, an occupational safety or health skilled or engineer with expertise in industrial ventilation should be consulted.
At a minimum, mechanical ventilation systems ought to present sufficient capability to control flammable vapours to under 10% of the LFL by both exhaust air flow to remove contaminants from the work space or by dilution ventilation via introduction of fresh air to dilute contaminants. As with combustible fuel indicators, ventilation tools must be permitted for protected use in flammable atmospheres. In addition, air flow tools must be grounded and bonded.
Additional air flow, if wanted, ought to be steady throughout coatings software as concentrations could increase as more surfaces are coated in the course of the course of a piece shift, and particularly on scorching surfaces the place the rate of vaporization is larger.
Ventilation throughout coatings software ought to be continuous, especially when engaged on sizzling surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the primary source of ignition that readily comes to thoughts is the heat from the surface being painted. The AIT of the coating material is the one most important problem when making use of coatings to sizzling working gear. The AIT of a substance or combination is the minimal temperature at which a vapour-air mixture will ignite when in touch with a heated surface, 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 beneath the AIT of the coatings being applied. While surface temperatures could additionally be known/available in many amenities, all surface areas of the process/piping being painted and/or any gear adjoining to the items being painted where overspray may deposit must be measured for precise floor temperature. The results ought to be in comparison with the AIT of the coating system.
While auto-ignition and open sources of ignition could also be readily obvious, a extra delicate however nonetheless crucial source of ignition to manage on any industrial portray venture involving flammable solvents includes the production of static electrical energy. Equipment associated with the spray-painting operation, corresponding to spray application equipment and air flow 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 natural chemical compounds similar to paint solvents is accelerated till the ignition temperature of the fuel is reached.
This situation is reached when the fabric is packed loosely allowing a large surface space to be uncovered, there is sufficient air circulating across the material for oxidation to occur, but the pure ventilation obtainable is insufficient to hold the heat away fast enough to prevent it from building up.
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