Custom Pelton Wheel flowmeter designs

Litre Meter have manufactured pelton wheel flowmeters since 1975.  They are based on a light-weight, low inertia, plastic rotor spinning on jewelled bearings and monitored by a no-drag pick off.

The standard range covers many flow rates, materials, end connections and pressure ratings.  The wide rangeability and compactness lends their design to a multitude of applications.  Every now and then, customers request some interesting variations, for a variety of reasons.

Company A. Our oldest current client first bought meters from us in 1980. Their remit was an all stainless design with welded connections. Something compact was a benefit so Litre Meter varied the design of the then LM220-20bar. 1/4″NPT end connections were added and hundreds have been sold over the years.  Issues were found on some older units in high humidity locations so the meters were redesigned to meet EP455. Additionally, the redesign was an ideal opportunity to integrate some of the customers own modifications. The current version has an internal ‘divide by 10’ circuit to reduce the output frequency.  Meters are provided within a specific range of meter factors and have full immersion tests on a batch basis.

LM220 with 1/4″NPT connections, welded construction, wide flow range

Company B. This customer purchased hundreds of flowmeters for the measurement of  32% Caustic, 40% Nitric or 3% Peracetic Acid. The major material was 316SS whilst plastic wetted parts were either Polypropylene or PVDF; seals were FPM or EPDM both depending on the fluid. Unique modifications included in-line 1/2″ Table D flanged connections and a scaling feature enabling the output to be 10 pulses per litre.

Company C. In the automotive sector, one customer started customising the Pelton Wheel meter themselves.  They substituted the standard nylon flow body with stainless steel. Litre Meter stepped in and offered a slimline stainless steel body with metric OD pipe connections. Hundreds were subsequently ordered over two continents for fuel flow measurement.

Flowmeter M8
Development phase, with brass unions, later replaced with 316 stainless steel to match the rest of the construction.

Company D. Amine is used in the casting industry to set the sand in place prior to casting. Sand moulds are cheap and suit the casting process. The sand is bonded together with a chemical binder – in this case an amine. It is liquid through the flowmeter and turns to gas within the core. The customisation relates to 3 different aspects. Firstly, and perhaps most importantly, the ‘on’ time for the meter is very short, in the region of a few seconds. The meter has to ramp up very quickly, provide enough pulses to be useful and accurate. Secondly, the meter had to fit within an existing pipework configuration, This resulted in a unique configuration:

Unique Orientation
Pelton Wheel meter with welded pipes

Thirdly, because the amine is very low viscosity, calibration was changed to acetone rather than water.

Company E. The customer had purchased various custom pelton wheel meters over the years for progressively higher and higher specifications. Most were the LM220 which has an enormous flow range.  All were for aerospace applications measuring jet fuel or similar on-board an aircraft. The image below shows the latest one, carefully engineered to provide the best linearity within a very tight, odd-shaped, envelope.

Pelton Wheel
Custom Pelton Wheel for limited space, manifold connection

The testing regime involved simulating not just flight but also transport to the aircraft, by various means, and take-off under extremes of temperature.  This was as much a test of the flowmeter as it was for the laboratory.  The design incorporated a pressure sensor and a manifold connection for the customers valve plus a new sensing method.

 

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