Managers of petrochemical, refining, power, offshore, pulp and paper and different services with in depth scorching processes and piping systems are regularly challenged with performing all the necessary coatings maintenance work only in periods of outages. Outages are required in order that course of equipment could be correctly maintained and repaired together with cleansing of pipelines and vessels, maintenance and substitute of pumps, motors and valves, upkeep coating operations, and other work that may only be accomplished when the operations are shut down.
When coatings work must be carried out on areas where elevated temperatures are concerned, many suppose that the ability must be shut down. ที่วัดแรงดัน will not be the case.
A query frequently posed by facility managers is, “Can I do maintenance painting work while the plant is operating?” As described beneath, the answer is, “Yes you can, however there are safety and health points that should be considered”.
Dangers to personnel should be managed regardless of when or where work is performed.
Safety and well being considerations
There is a variety of safety and well being hazards that must be considered on every industrial maintenance painting project, whether the coating materials is being utilized to scorching metal or not. Some of these embrace proper material handling and storage, fall protection, control of fire and explosion hazards, and publicity to noise, heavy metals, solvents and other health risks.
These dangers must be properly evaluated and controlled on each industrial maintenance painting venture, no matter when or where the work is performed. While present on any job, when applying specialty coatings to scorching surfaces, some safety and health issues should obtain further consideration.
Flammable and combustible liquids in lots of coatings (solvents) can vaporize and type flammable mixtures in the air, especially when atomized during spray software or heated. The degree of hazard is determined by the following:
The auto ignition temperature (AIT) of the coating material is the single most important problem when making use of 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 minimal temperature at which a flammable gas-air or vapour-air mixture will ignite from its own warmth source or contact with a heated surface with out the presence of an open spark or flame.”
The idea of flash point as outlined by NFPA 30 is “the minimal temperature of a liquid at which sufficient vapour is given off to type an ignitable combination with the air, near the floor of the liquid”. In other phrases, the flash point describes the temperature of the liquid that’s excessive sufficient to generate sufficient vapour to create a flame if a supply of ignition were introduced.
For vapours of flammable liquids, there is a minimal concentration below which the spread of the flame doesn’t occur when in touch with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a most focus of vapour within the air above which the spread 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 may not be required whereas maintenance is carried out.
Implementing controls
Applying coatings to sizzling surfaces increases the rate at which the solvents are pushed off. When applying solvent borne coatings to hot surfaces it should be assumed that the concentration of vapours in the air could exceed the LFL (at least for a quick time after application). As with coating utility to ambient temperature metal, controls must be applied.
While the LFL is more likely to be achieved over a shorter period of time during sizzling application of coatings than coatings work performed at ambient situations, the resulting fire hazard exists in each purposes. That is, the hearth hazard and associated controls have to be thought of for the applying of any solvent-borne flammable coating system, regardless of the work surroundings. It have to be acknowledged that the gasoline component of the hearth tetrahedron shall be present in each ‘hot’ and ‘ambient’ environments and primary steps should be taken to attenuate pointless solvent vapours in the work space. In addition, as outlined later, attention should even be directed to eliminating the remaining component of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gasoline factor of a fire could be lowered by implementing fundamental controls similar 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 such as tri-sodium phosphate could additionally be substituted, adopted by floor washing with fresh water or steam cleaning and pH testing of the floor, or non-combustible solvents similar to 1,1,1 trichloroethane) for pre-surface preparation solvent cleansing.
Combustible gasoline indicators ought to be used to verify that the focus of flammable vapours is below the LFL. Combustible gas indicators have to be calibrated in accordance with the manufacturer’s suggestions and should be permitted to be used in flammable atmospheres. Operators of the tools must be skilled in proper gear operation.
Readings must be taken within the basic work space and the neighborhood of the operator and in areas the place there are potential sources of ignition. Typically, models are set to alarm at 10% of the LFL. If the alarm sounds, coatings software work should instantly stop until the concentration of flammable vapours is managed. The function of setting the alarm under the LFL is to offer a safety issue that leads to management measures being applied earlier than there is an imminent hazard of fireplace or explosion.
Monitoring of the combustible vapour concentration might be essential as the effectiveness of natural air flow may be variable. If management of flammable vapours requires mechanical ventilation, an occupational security or health professional or engineer with expertise in industrial air flow must be consulted.
At a minimum, mechanical air flow methods ought to present enough capability to regulate flammable vapours to below 10% of the LFL by either exhaust ventilation to take away contaminants from the work space or by dilution ventilation through introduction of recent air to dilute contaminants. As with combustible gas indicators, ventilation gear should be accredited for protected use in flammable atmospheres. In addition, ventilation gear have to be grounded and bonded.
Additional air flow, if wanted, must be steady during coatings utility as concentrations could improve as more surfaces are coated through the course of a piece shift, and especially on hot surfaces where the rate of vaporization is greater.
Ventilation during coatings application must be continuous, particularly when engaged on sizzling surfaces.
Sources of Ignition
When making use of coatings to scorching surfaces, the primary supply of ignition that readily comes to thoughts is the heat from the floor being painted. The AIT of the coating material is the one most necessary problem when making use of coatings to hot working tools. The AIT of a substance or mixture is the minimum 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 under the AIT of the coatings being utilized. While floor temperatures could also be known/available in plenty of facilities, all floor areas of the process/piping being painted and/or any gear adjacent to the items being painted where overspray might deposit must be measured for actual floor temperature. The outcomes ought to be in comparison with the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily obvious, a more refined however nonetheless important supply of ignition to manage on any industrial painting venture involving flammable solvents entails the production of static electricity. Equipment associated with the spray-painting operation, such as spray software equipment and ventilation equipment, can generate static electricity.
In addition to external sources of ignition, spontaneous ignition can occur when rags or wastes soaked with paint solvents are left in open containers. Spontaneous ignition happens when the slow technology of heat from oxidation of organic chemicals such as paint solvents is accelerated until the ignition temperature of the gasoline is reached.
This condition is reached when the fabric is packed loosely permitting a big surface area to be uncovered, there may be enough air circulating across the materials for oxidation to occur, but the natural air flow obtainable is inadequate to hold the warmth away quick sufficient to prevent it from building up.
For more data, go to www.ppgpmc.com/Oil-Gas-Chemical.aspx
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