Oval gear flow meter

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Oval wheel principle

Oval gear flowmeters work on the principle of displacement and are used to measure, count and monitor viscous liquid flows. They work independently of the viscosity . This principle, which has been tried and tested for years, enables very precise and repeatable measurements over a large flow rate and viscosity range.

history

The first patent for an oval wheel meter was filed and protected in 1932 by the German company Bopp & Reuther GmbH, Mannheim-Waldhof. The patent referred to the oval wheel measuring principle and the measured values ​​were then transmitted to a mechanical counter via a shaft. It was a compact device with an on-site display and did not require any external energy. The transmission of measured values ​​was later replaced by a leak-free coupling. A permanent magnetic coupling causes the transfer of the rotary movement from the measuring room to the drying room.

The first custody transfer approval was granted in 1933 by the then PTR ( Physikalisch-Technische Reichsanstalt ) in Berlin.

function

Functional sequence
Signal transmission from the gear

An oval gear flow meter consists of a housing in which two toothed oval gear wheels are inserted. The medium fills the defined space between the oval gears and turns the gears depending on the volume throughput. Permanent magnet or stainless steel pins are embedded in the gears themselves; the on-site electronics detect an impulse for each intermediate gear volume transported. The volume is proportional to the detected frequency. The number of pulses is therefore also a measure of the respective flow.

A downstream electronics evaluate these signals accordingly. The values ​​can e.g. B. can be programmed in liters or gallons and also added up. The calibration factor of a measuring unit is programmed at the factory. If necessary, it can be recalibrated on site.

Applications

The oval wheel measuring principle is, next to the rotary piston meter, the most important representative of the group of direct volume meters . Oval gear flow meters are used for measuring, counting and also for monitoring liquids and liquefied gases of medium to high viscosity.

Typical fluids are mineral oils, hydraulic oils, solvents, brake oils, coolants, gear oils, heating oils, acids, alkalis, detergents, liquid soap, detergents, disinfectants, rinse aids, cleaners, soldering flux, flux, glue, solvents, resin, etc.

Oval wheel flow meters can be designed for pressure ranges up to 110 bar and temperature ranges up to 160 ° C. There are numerous materials to choose from for the sensors, such as: PVC , PTFE , aluminum, stainless steel, etc.

advantages

  • simple, reliable construction
  • On-site maintenance (low maintenance effort)
  • Impulse
  • Accuracy up to 0.5% of the measured value
  • ATEX approval
  • Plain bearings ensure perfect running of the oval wheels, high operational safety and a long service life.

disadvantage

  • high pressure loss
  • The pipeline must be completely filled with medium and therefore free of air (the absence of bubbles can often be observed on an additional sight glass)
  • A filter must be installed if the medium is contaminated
  • no cleaning with compressed air possible
  • Counter blocked in the event of a defect.
  • Underload and overload lead to incorrect measurements and wear.

Individual evidence

  1. ↑ Gear volume sensors. (No longer available online.) Archived from the original on June 3, 2012 ; accessed on March 8, 2015 .
  2. ↑ Measured variables ( Memento of the original from November 18, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.sika.net
  3. ↑ Directive 94/9 / EG (ATEX 100a)

source

literature