Managers of petrochemical, refining, energy, offshore, pulp and paper and other services with in depth scorching processes and piping techniques are incessantly challenged with performing all the required coatings maintenance work solely in periods of outages. Outages are required in order that course of gear could be correctly maintained and repaired including cleaning of pipelines and vessels, upkeep and substitute of pumps, motors and valves, maintenance coating operations, and different work that may solely be completed when the operations are shut down.
When coatings work has to be performed on areas where elevated temperatures are involved, many think that the power needs to be shut down. This will not be the case.
A question incessantly posed by facility managers is, “Can I do maintenance portray work while the plant is operating?” As described beneath, the reply is, “Yes you can, but there are safety and health points that should be considered”.
Dangers to personnel must be managed regardless of when or the place work is carried out.
Safety and well being concerns
There is a spread of safety and health hazards that have to be thought-about on every industrial upkeep portray venture, whether or not the coating materials is being utilized to hot steel or not. Some of those embrace correct material dealing with and storage, fall safety, control of fire and explosion hazards, and publicity to noise, heavy metals, solvents and other well being risks.
These risks must be properly evaluated and controlled on each industrial maintenance portray challenge, regardless of when or the place the work is performed. While current on any job, when making use of specialty coatings to sizzling surfaces, some security and well being points should obtain additional consideration.
Flammable and combustible liquids in many coatings (solvents) can vaporize and form flammable mixtures in the air, especially when atomized during spray software or heated. The degree of hazard is dependent upon the next:
The auto ignition temperature (AIT) of the coating material is the only most important issue when making use of coatings to hot operating equipment. 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 heat source 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 type an ignitable combination with the air, near the surface 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 had been introduced.
For vapours of flammable liquids, there’s a minimum concentration below which the spread of the flame does not happen when involved with a supply of ignition. This is the Lower Flammable Limit (LFL). There is a most concentration of vapour within 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 concentration of vapours can help combustion.
If safety procedures are adopted, outages will not be required whereas maintenance is performed.
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 should be assumed that the focus of vapours in the air could exceed the LFL (at least for a quick while after application). As with coating utility to ambient temperature metal, controls should be carried out.
While the LFL is more likely to be achieved over a shorter time frame throughout sizzling utility of coatings than coatings work performed at ambient conditions, the resulting hearth hazard exists in each purposes. เพรสเชอร์เกจคือ is, the hearth hazard and related controls must be considered for the application of any solvent-borne flammable coating system, regardless of the work surroundings. It should be acknowledged that the gas component of the fire tetrahedron will be present in each ‘hot’ and ‘ambient’ environments and fundamental steps must be taken to reduce unnecessary solvent vapours in the work area. In addition, as outlined later, attention should even be directed to eliminating the remaining element of the tetrahedron – the supply of ignition.
Controlling flammable vapours
The gasoline factor of a hearth may be decreased by implementing basic controls such as handling and storing flammable liquids in permitted, self-closing containers, maintaining 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 could additionally be substituted, followed by floor washing with fresh 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 must be used to verify that the focus of flammable vapours is beneath the LFL. Combustible gasoline indicators have to be calibrated in accordance with the manufacturer’s recommendations and must be accredited for use in flammable atmospheres. Operators of the tools have to be educated in proper tools operation.
Readings should be taken within the common work space and the neighborhood of the operator and in areas where there are potential sources of ignition. Typically, items are set to alarm at 10% of the LFL. If the alarm sounds, coatings application work should immediately cease until the focus of flammable vapours is controlled. The objective of setting the alarm under the LFL is to supply a safety factor that results in control measures being applied earlier than there’s an imminent hazard of fire or explosion.
Monitoring of the combustible vapour focus shall be essential because the effectiveness of natural ventilation could additionally be variable. If control of flammable vapours requires mechanical air flow, an occupational security or well being skilled or engineer with experience in industrial ventilation ought to be consulted.
At a minimum, mechanical ventilation methods should present adequate capability to regulate flammable vapours to under 10% of the LFL by both exhaust air flow to remove contaminants from the work space or by dilution air flow by way of introduction of recent air to dilute contaminants. As with combustible gas indicators, air flow tools should be accredited for secure use in flammable atmospheres. In addition, air flow equipment should be grounded and bonded.
Additional ventilation, if needed, must be steady during coatings application as concentrations could enhance as more surfaces are coated during the course of a work shift, and particularly on scorching surfaces where the speed of vaporization is larger.
Ventilation during coatings utility ought to be steady, especially when working on sizzling surfaces.
Sources of Ignition
When making use of coatings to hot surfaces, the first source of ignition that readily involves thoughts is the warmth from the surface being painted. The AIT of the coating materials is the one most essential issue when applying coatings to hot operating tools. 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 surface, without the presence of any open spark or flame.
The key to controlling this supply of ignition is to confirm the surfaces being coated are below the AIT of the coatings being utilized. While floor temperatures may be known/available in lots of facilities, all surface areas of the process/piping being painted and/or any gear adjacent to the gadgets being painted the place overspray might deposit ought to be measured for precise floor temperature. The outcomes must be compared to the AIT of the coating system.
While auto-ignition and open sources of ignition may be readily apparent, a extra refined however nonetheless crucial supply of ignition to control on any industrial painting venture involving flammable solvents involves the production of static electricity. Equipment related to the spray-painting operation, such as spray utility gear 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 happens when the sluggish generation of warmth from oxidation of natural chemical compounds similar to paint solvents is accelerated till the ignition temperature of the gasoline is reached.
This condition is reached when the material is packed loosely permitting a big surface space to be uncovered, there’s sufficient air circulating across the materials for oxidation to happen, but the pure ventilation out there is inadequate to carry the warmth away quick sufficient to forestall it from build up.
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