Gemue 851 Variable area flowmeter for liquids, PVC float, DN 15–25
The Gemue 851 is a variable area flowmeter of the 850 series with a PVC float, designed for liquids in nominal sizes DN 15, DN 20 and DN 25. It measures purely mechanically, without auxiliary power, and displays the flow directly on the metering tube. The float has no magnet; the reading is taken directly off the metering tube and the moulded-on dovetail rails hold setpoint pointers. As an authorised dealer we stock 327 versions of this series.
Measuring range and scale
The Gemue 851 covers the narrowest span in the series: 183 versions measure from 0.5 to 1,000 l/h and 5 carry a percentage scale from 10 to 100 %. There are no versions in US units in this group, and unlike the other variants it starts only at DN 15 — a Gemue 851 in DN 10 does not exist. The reading is taken at the upper edge of the float on the scale printed directly onto the metering tube. Every scale applies to one particular medium at 20 °C — a device calibrated for water will not read the same on sodium hydroxide. The metering tube size appears as a cone in the type code: 13 sizes from cone 21 to cone 44; together with the nominal size it determines which measuring range is attainable. For the remaining versions GEMÜ does not list a measuring range; we clarify which scale is fitted on request, using the type code.
Medium, concentration and seal
The scales in this group are calibrated for three media: water (148 versions), hydrochloric acid (24) at 30 % and sodium hydroxide (23) at 30 % and 50 %. Which medium applies is held as a separate attribute on the article — together with the concentration, which GEMÜ does not supply in its search index and which we therefore took from the product data sheets. Sealing is by O-rings in EPDM, FPM and FEP encapsulated. With alkalis and acids the choice of material is not a detail but the actual selection criterion: together with the metering tube material, the seal material determines which medium is permissible. In every version the body is a straight through tube, and all 327 versions conform to RoHS.
Metering tube and connections
The metering tube is available in three materials: PVC-U (transparent), PA (transparent) and PSU. Transparent PA and PVC-U make the float easy to see, PSU is the more robust material. Connection is made via 13 connection types: union ends with inserts to DIN as a socket, for butt welding or IR butt welding, as a female thread Rp and in inches to BS, plus spigots to EN 10357, ISO 1127, DIN 11866 and ASME BPE, clamp connections and flanges. For the connection parts there are 9 material combinations: inserts in PVC-U, PP, PE, PVDF, ABS and stainless steel, union nuts in PP, PVDF or stainless steel, plus versions in malleable cast iron, stainless steel and brass. A variant entirely without insert and union nut is also available.
Selection and related series
This is the plainest group in the series and often the right one: read the value and you are done. Two things argue against it. If the flow is not just displayed but monitored, a magnet in the float is needed — the Gemue 861 is then the otherwise identical counterpart. And if DN 10 or a flow above 1,000 l/h is required, the way leads to the PP or stainless steel variants, because neither is available here. For air instead of liquid at the same nominal size, use the Gemue 875 for air. Further variable area flowmeters are available as Gemue 801, Gemue 805, Gemue 806, Gemue 807 and Gemue 811, with matching accessories under Gemue accessories for flowmeters. The other variants of this series: Gemue 855, Gemue 857, Gemue 861, Gemue 865 and Gemue 867. All series at a glance: Gemue brand page.
Your Benefits With Us
- Worldwide shipping of all valves and measuring devices
- Large stock levels for many products – current lead time available on request
- Spare parts and service kits available
- Fast shipping via UPS (parcel) or freight forwarder (pallets), express delivery available on request
- Extensive hands-on application know-how
- Personal advice on selecting the right component
