Managers of petrochemical, refining, energy, offshore, pulp and paper and other services with extensive hot processes and piping methods are incessantly challenged with performing all the mandatory coatings upkeep work only in periods of outages. Outages are required so that course of tools can be correctly maintained and repaired including cleaning of pipelines and vessels, maintenance and alternative of pumps, motors and valves, maintenance coating operations, and different work that can only be achieved when the operations are shut down.
When coatings work must be carried out on areas where elevated temperatures are involved, many suppose that the power must 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’ll find a way to, however there are safety and health issues that have to be considered”.
Dangers to personnel should be managed no matter when or the place work is performed.
Safety and well being issues
There is a variety of security and well being hazards that must be thought-about on each industrial upkeep painting project, whether or not the coating material is being applied to scorching metal or not. Some of these embrace correct materials handling and storage, fall protection, control of fire and explosion hazards, and exposure to noise, heavy metals, solvents and different health risks.
These dangers should be properly evaluated and managed on each industrial maintenance portray challenge, no matter when or where the work is performed. While present on any job, when applying specialty coatings to scorching surfaces, some security and health issues should receive extra consideration.
Flammable and flamable liquids in lots of coatings (solvents) can vaporize and type flammable mixtures in the air, particularly 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 necessary issue when applying coatings to scorching operating gear. AIT is defined (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 combination will ignite from its own warmth supply 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 adequate vapour is given off to type an ignitable mixture 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 minimal focus under which the spread of the flame doesn’t happen when involved with a source of ignition. This is the Lower Flammable Limit (LFL). There is a maximum concentration of vapour in the air above which the unfold 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 is most likely not required while maintenance is carried out.
Implementing controls
Applying coatings to scorching surfaces will increase the speed at which the solvents are pushed off. When making use of solvent borne coatings to scorching surfaces it should be assumed that the concentration of vapours in the air could exceed the LFL (at least for a brief while after application). As with coating software to ambient temperature steel, controls have to be implemented.
While the LFL is prone to be achieved over a shorter period of time throughout scorching utility of coatings than coatings work carried out at ambient situations, the resulting fireplace hazard exists in each applications. That is, the fireplace hazard and associated controls have to be thought-about for the appliance of any solvent-borne flammable coating system, regardless of the work environment. It have to be recognized that the fuel part of the fire tetrahedron shall be present in both ‘hot’ and ‘ambient’ environments and primary steps should be taken to reduce unnecessary solvent vapours within the work area. In addition, as outlined later, attention must even be directed to eliminating the remaining element of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gasoline component of a fireplace can be lowered by implementing basic controls such as handling and storing flammable liquids in accredited, self-closing containers, keeping the variety of flammable liquids containers within the work space and in storage areas to the minimum essential and within allowable (regulatory) limits.
Alkaline detergents similar to tri-sodium phosphate may be substituted, adopted by surface washing with recent water or steam cleaning and pH testing of the surface, or non-combustible solvents such as 1,1,1 trichloroethane) for pre-surface preparation solvent cleaning.
Combustible gas indicators must be used to confirm that the concentration of flammable vapours is below the LFL. Combustible gasoline indicators must be calibrated in accordance with the manufacturer’s suggestions and should be accredited to be used in flammable atmospheres. Operators of the equipment must be skilled in correct gear operation.
Readings should be taken in the general work space and the neighborhood of the operator and in areas where there are potential sources of ignition. Typically, models are set to alarm at 10% of the LFL. If เกจวัดแรงดันอากาศ , coatings software work ought to instantly stop till the focus of flammable vapours is controlled. The function of setting the alarm beneath the LFL is to offer a security 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 essential as the effectiveness of natural air flow may be variable. If control of flammable vapours requires mechanical air flow, an occupational safety or well being professional or engineer with experience in industrial air flow must be consulted.
At a minimum, mechanical air flow systems should present sufficient capability to manage flammable vapours to below 10% of the LFL by both exhaust ventilation to take away contaminants from the work area or by dilution air flow by way of introduction of recent air to dilute contaminants. As with flamable fuel indicators, air flow gear must be approved for protected use in flammable atmospheres. In addition, air flow gear should be grounded and bonded.
Additional ventilation, if wanted, ought to be continuous throughout coatings application as concentrations could increase as more surfaces are coated during the course of a piece shift, and especially on hot surfaces where the rate of vaporization is larger.
Ventilation during coatings software should be steady, particularly when engaged on sizzling surfaces.
Sources of Ignition
When making use of coatings to hot 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 important problem when making use of coatings to scorching working equipment. The AIT of a substance or mixture is the minimal temperature at which a vapour-air combination will ignite when in contact 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 under the AIT of the coatings being utilized. While surface temperatures may be known/available in many amenities, all floor areas of the process/piping being painted and/or any tools adjacent to the items being painted where overspray could deposit should be measured for precise surface temperature. The results must be in comparison with the AIT of the coating system.
While auto-ignition and open sources of ignition could additionally be readily apparent, a more delicate however nonetheless important source of ignition to regulate on any industrial portray venture involving flammable solvents includes the manufacturing of static electrical energy. Equipment related to the spray-painting operation, such as spray application tools and air flow 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 gradual era of heat from oxidation of natural chemical substances such as paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This situation is reached when the material is packed loosely permitting a big floor area to be uncovered, there’s sufficient air circulating around the materials for oxidation to happen, but the natural air flow out there is inadequate to carry the heat away fast enough to prevent it from building up.
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