Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
  • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
  • F01C21/10—Outer members for co-operation with rotary pistons; Casings
  • F01C21/104—Stators; Members defining the outer boundaries of the working chamber
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
  • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
  • F01C21/08—Rotary pistons

Definitions

• the invention relates to a rotary vane pump with an eccentrically mounted rotary piston, housing and side covers made of an iron material and a method for producing the pump.
• Rotary vane pumps essentially contain a cylindrical work chamber, a rotary piston which is mounted eccentrically in the work chamber and at least two slide valves which are mounted in the slots of the rotary piston and are pressed by centrifugal force against the housing delimiting the work chamber during operation of the pump.
• the slides slide in the slots of the rotary piston, on the housing wall and the side covers inserted into the housing and wear out during pump operation, the rate of wear of the slides being essentially determined by the nature of the sliding surfaces.
• combinations of certain materials have been proposed for the parts of the pump which are in frictional engagement, for example a housing made of sintered metal, cover and slide made of the same graphite-containing material (DE-GM 82 02 785).
• this solution is less suitable primarily because of the higher strength requirements and also for cost reasons. It is therefore preferable to use pumps whose housing and side cover are made of an iron material, eg gray cast iron.
• a major disadvantage of these materials is their insufficient corrosion resistance.
• pitting-like corrosion spots form on the rotary lobes, the housing wall and the side covers, the amount and intensity of which can be increased considerably by the action of corrosive substances such as sulfur dioxide.
• the corrosion points roughen the sliding surfaces to a greater or lesser extent, which increases the wear rate of the slide considerably.
• corrosion products can fill the narrow gap between the rotary lobe and side cover or between the slide and rotary lobe slots in such a way that the pump can no longer be started after long periods of inactivity. Measures to reduce the corrosive attack have so far not led to a generally satisfactory solution.
• Spraying the sliding surfaces with PTFE aerosols results only in exceptional cases in a significant reduction in the corrosion rate, chrome-plated or nickel-plated running surfaces or the use of stainless steels reduce the corrosion rate, but the wear rate of the slide valves, which consist essentially of graphite, remains with these material combinations, especially at high peripheral speeds comparatively large.
• the invention is therefore based on the object of providing a rotary vane pump which operates in a humid and corrosive atmosphere without corrosion-related damage and whose vanes have a low wear rate.
• the object is achieved with a rotary vane pump of the type mentioned at the beginning, the rotary lobe, housing wall and side cover of which are provided with a protective layer of magnetite on the sides facing the working area.
• Magnetite protective layers made of magnetite shield the coated pump parts against atmospheric substances and prevent damage to the sliding surfaces through the formation of corrosion products. At the same time, the magnetite layer has a favorable friction behavior, so that the wear on the slide is low even at high peripheral speeds.
• the thickness of the magnetite protective layer should preferably be at least 0.005 and at most 0.05 mm, since with smaller thicknesses a closed layer is not always achieved and the impact resistance decreases with thicker layers.
• Magnetite layers generally have residual porosity and are therefore not always impermeable to fluids. In these cases it is advantageous to use magnetite layers infiltrated with a synthetic resin. Suitable as infiltration agents are all synthetic resins that are resistant to the aggressive substances at the working temperature of the pump. Particularly suitable are acrylate resins that are easy to process with good chemical and thermal resistance.
• the protective layer made of magnetite on the rotary lobe, housing wall and side covers of the rotary vane pump these pump parts are exposed to an atmosphere containing water vapor at a temperature between 500 and 650 ° C.
• the atmospheric pressure is about 0.01 to 0.05 bar, the treatment time is about 2 hours.
• the pump parts are then cooled to room temperature outside the vacuum furnace.
• the bluish-black impact-resistant magnetite layer formed on the surface of the pump parts is essentially impermeable to fluids.
• the pump parts provided with a magnetite layer are immersed in the melt or solution of a synthetic resin and the pores of the magnetite layer are filled with the impregnating agent.
• the infiltration of the resin is advantageously carried out in a manner known per se at vermin dertem atmospheric pressure, if necessary the pressure is then increased.
• the pump parts are heated to at least 80 ° C. to harden the synthetic resin, the temperature and also the hardening time being essentially determined by the type of resin.
• Thermoplastic and thermosetting synthetic resins and resin solutions are used as infiltration agents, which are resistant to temperature and corrosion and whose viscosity should not exceed about 100 mPa ⁇ s during infiltration.
• Acrylate resins such as polymethacrylate or triethylene glycol dimethyl acrylate, are preferred because of their resistance and short curing times.
• the coating of the pump parts - rotary lobe, housing and side cover - with magnetite enables the use of ferrous materials, such as gray cast iron, nodular cast iron, cast steel, unalloyed and low-alloyed steels, which could not or only to a limited extent be used for this purpose due to the shortcomings described above.
• the protective layer made of magnetite shields the pump parts made of these materials against corrosive fluids, prevents disturbing damage to the parts during pump operation and, due to its favorable friction behavior, enables the slide wear rate to be reduced.
• Rotary piston, housing and side cover made of gray cast iron 6620, DIN 1691, were heated in an autoclave at a rate of about 500 K / h to 600 ° C, the pressure was reduced to 0.03 bar and the autoclave was rinsed with a total of about 24 kg of water vapor. After a residence time of 2 hours, the steam supply was interrupted, the autoclave was opened and cooled to room temperature under normal atmospheric conditions.
• the pump parts were covered with a firmly adhering black glossy magnetite layer, the thickness of which was approximately 0.008 mm. Some of the pump parts coated with magnetite were infiltrated with a polymethacrylate resin, the viscosity of which at 20 ° C. was about 15 mPa ⁇ s.
• the parts were stacked in an autoclave, the pressure was reduced to 8 mbar for 15 minutes, the parts were then covered with the resin and the pressure increased to 10 bar. To cure the resin, the parts were finally heated to 100 ° C. and held at this temperature for 15 minutes.
• Oil-lubricated pumps made of the same material behave essentially like the pumps examined in dry running.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Details And Applications Of Rotary Liquid Pumps (AREA)
• Rotary Pumps (AREA)
• Applications Or Details Of Rotary Compressors (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6278467

Family Applications (1)

Country Status (2)

Cited By (1)

Families Citing this family (3)

Family Cites Families (5)

• 1985
  • 1985-08-14 DE DE19853529106 patent/DE3529106A1/de not_active Withdrawn
• 1986
  • 1986-07-15 EP EP86109683A patent/EP0212250A3/fr not_active Withdrawn

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