Technical Notes
PAINTING FACILITYNOTES, REQUIREMENTS, INFORMATION, ETC.Construction, Function: The majority of painting facilities suitable for use with both solvent-based and water-based consist of: an insulated cabin into which air enters via the ceiling filter (during painting this is fresh air heated to approx. 20°C ; during drying it is recirculated air heated to e.g. 100°C with a low percentage of fresh air [approx. 10%]). The fresh air is drawn in above the roof through the intake air duct and after passing the prefilter, it is fed to the ceiling filter by a radial fan. The intake air flows vertically through the cabin (from top to bottom) with as little turbulence as possible towards the extraction duct. This is located centrally in the longitudinal direction under the metal grating and is fitted with a paint mist separator. The waste air is filtered of paint mist and fed by fan either through the waste air duct into the open air (during spraying) or through the recirculation duct (during drying) and back into the intake air duct (recirculation mode). Complex technical systems are used to ensure that the intake air is uniformly distributed as it passes through the ceiling filter and the cabin. The soiling of the filter is indicated via a differential pressure gauge. A slight positive pressure in the cabin prevents dirt particles from entering.
With the use of additional heat exchangers (heat reclamation) the waste air can be made to heat the incoming fresh air. This saves energy and ensures the correct spraying temperature of approx. +20°C to +23°C in especially cold regions with low ambient temperatures. Project planning requires exact information on the type of hall roof construction. Openings in roofs and their subsequent sealing off must be carried out by local specialist companies. The intake air is heated via an oil or gas burner or in special cases with warm water or electricity with indirect production of warn air via a special warm-air heater. It is advisable to install the heating units with heat exchanger, burner and fans in a walled-off machine room (fire prevention, noise reduction). The relevant local legislation must be observed. The machine room may be located on either the left or right side, behind or above the painting booth.
Short-lift platforms can be installed to prevent flat spots on tires and to achieve better working positions for painting jobs on the lower part of the vehicle
The Extraction dust should be installed in a foundation pan under the paint mist separator (floor filter). In order to keep construction costs low, the foundation design should be as simple as possible. Foundation plans are supplied by the manufacturer. It may be necessary to concrete in a metal foundation frame (consult the manufacturer). If the desired foundation option is not feasible, (e. g. in workshops with cellars), above-floor pedestal systems are also available on the market. In this case, the vehicle is driven onto the cabin floor, which is approx. 300mm above the level of the workshop floor, on ramps (approx. 2m long). The waste air system of pedestal facilities has its disadvantages. Pedestal systems should therefore only be considered in exceptional circumstances.
The choice of painting facility is largely determined by..
The facility should be installed and assembled by the manufacturer or supplier if possible. He will then takes it into commission, draw up delivery and inspection protocols and provide detailed instruction for the user. You should only consider erecting the facility yourself under exceptional circumstances, in which case particularly close contact with the manufacturer and specific training by the manufacturer are essential. Installing the facility yourself will usually limit your entitlement to warranty services. Construction, Function (continued): Points to be noted are those listed in the quotation under the heading of "services to be rendered by the purchaser" such as:
The capacity figures refer to the proper use of solvent based and water based paints. Water-based paint is applied in two spraying operations, with the second immediately following the first (wet on wet). The water in the paint must then evaporate as thoroughly as possible before the clear lacquer is applied (this can be recognized by a mat surface without water patches). The water evaporates more slowly than the solvent in conventional paints. The airing time for water-based paints can be shortened e.g. by...
Practical comparisons of the entire application process for the two different types of paint have shown only negligible time differences. And differences in the facility occupancy time per vehicle and in the total time spent by the vehicle in the painting facility are insignificant. Solvent-based 2-component base paints are not applied wet on wet, and after spraying it should be left to air to for approx. 5 minutes before drying (otherwise there is risk of bubbling). Finishing-painting of cabin walls: Various manufacturers (e.g. Blowtherm, Garmat, Saico, USI) supply the cabin elements ready painted inside and outside. The majority of manufacturers, however, supply the parts or galvanized only. In such cases, the purchaser must apply the top coats of paint. Interior paintwork must be resistant to solvents. Light pastel shades are preferable (these may be contrasted effectively by decorative paint work on the outside areas). Clean the parts from grease with combination thinners. Then paint with a primer filler (drying time approx. 12 hours at 20°C.
MB Minimum Requirements: The list below includes important MB minimum requirements for PC painting facilities (suitable for solvent-based amd water based paints). They are taken from the brochure "Requirements for Painting Systems for MB PCs/CVs" (note PC = Passengers Cars; CV = Commercial Vehicles). This brochure can be obtained by request through the MBUSA Standard Service Equipment Program (Technical Information Department) Montvale , NJ.
The utility value, serviceability, paintwork quality operator satisfaction etc. depend heavily on constant maintenance of the painting facility. Filters in particular should be carefully replaced at the recommended intervals or when the differential pressure limits (for example) are reached. Cleanliness in the painting booth is of vital importance. Naturally, this also applies for...
Testing of compressed air-quality: Stricter standards are set for the purity of compressed air used for paint spray guns. These requirements are met by special compressed-air maintenance units, which are installed in the painting booth. A test kit available from SATA can be used to assess the degree of contamination of the compressed air by filtering out and examining any residues. Miscellaneous notes: The deliberate positive pressure in the painting booth is intended to prevent dirt particles from entering. Incorrect pressures in the booth are noticeable e.g. by the way the door opens. Trails of dirt at the edges of the ceiling filters or prefilters indicate that the air supply is unfiltered. Maintenance schedule: (see checklist/maintenance schedule in Quality Assurance section). This is intended as a rough guide and assumes a normal level of use of the painting booth. Adjustments for real circumstances are unavoidable. In addition, the manufacturer's specific maintenance instructions must be observed and taken into account in the maintenance schedule. Painting Requirements:Checking the air flow in the booth: This can be done using the flow tester (e.g. Draeger tubes). Clearly visible white smoke is produced when the air from the puff ball passes through the test tube. This makes the movement of the air in the booth visible and the air flow can be assessed by visual inspection. The smoke must flow evenly along the bodywork from top to bottom and be drawn off via the floor filter without turbulence. If turbulence is apparent, this indicates that the intake air is not emerging evenly from the ceiling filters. If the ceiling filters are in order, a readjustment of the air distribution via the ceiling filter (plenum) must be performed by the manufacturer. If the smoke is not drawn towards the floor filter, then soiled floor filters can be assumed.
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