The oscillating piston flowmeter is the underlying principle of our PD flowmeters. The PD meter consists of a measurement chamber or flow tube in which a piston made of high durable and inert plastic is housed. The chamber is of a known volume and one revolution of the piston from mean position means a sweep of known cyclic volume. Therefore, when there is no flow in the line, the piston is stationary. When liquid begins flowing, the piston displaces liquid from inlet to outlet with a constant cyclic volume per position. This revolution is read by an electronic transducer which converts mechanical motion to electric signal. Consequently the k factor or calibration factor is also unique for different sizes of meters. The k factor is essentially a correlation between cyclic volume and electric signal.
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Suppose you are working on an application where you need to measure the flow of a liquid that has a high viscosity. In that case, an oscillating piston flowmeter is what you should consider installing.
The oscillating piston flowmeters are a sort of positive displacement flowmeter and often referred to as volumetric counters. They are flowmeters especially suited for measuring high viscosity liquids. However, they are also most suited for liquids with a low viscosity.
The flow meter is one of the oldest types of positive displacement flow meters. This oscillating piston meter is mainly similar to a nutating disc meter. Except that its measurement device is one split ring/ piston that only oscillates within a single plane and this makes it more easy to maintain and durable than any other PD meter.
Oscillating piston flow meters utilize a precision-machined chamber that contains a cylindrical piston. Liquid enters the precision-machined chamber containing an oscillating (rotating) piston. The piston is positioned to divide the chamber into compartments that hold a pre-measured exact volume. Liquid pressure propels the piston to start oscillating and rotate on its axis. The meter's operation itself is based on the movement of this rotating piston. It fills and empties a chamber of a known volume with each turn, i.e. this piston oscillates as the liquid flows.
It also has a central shaft that is constrained to run in a circular groove inside the chamber. The movement has a concentric motion about the centre chamber axis. This results in an off-centre rotating motion because the liquid sequentially enters and exits compartments shaped into the underside of this piston. Since the capacity of the compartments is already known, the volume of liquid metered per revolution is easy to calculate accurately.
The precision-machined chamber has a slotted cylinder that separates the inlet and outlet part. Center piston rotate as the liquid subsequently enters and exit from the chamber. Usually, a hydraulically floating piston does not come into contact with the chamber.
The rotation of this piston activates a reed sensor. It then emits a pulse that corresponds with the volume of this chamber. The output signal from this sensor can be used through an electronic converter.
Fluidyne's oscillating piston flowmeter series is manufactured using different materials and has varying process connections. These connections include materials and fittings for hygienic applications. We also offer unique designs for high-pressure applications.
When there is no flow inside the pipe, the piston stays stationary. When the liquid begins flowing, the piston displaces liquid from the inlet to the outlet with a constant cyclic volume per position.
The movements inside the piston's central hub are sensed through the flow meter's wall by a follower magnet. Every revolution of the piston hub is equal to a fixed volume of the fluid. This is indicated as flow by an indicator or totalizer.
Close margins between the piston and the chamber guarantee minimum liquid slippage for highly reliable and repeatable flow measurement for every volume cycle.
The Rotary piston flow meter by Fluidyne is perfect for any type of liquid application. They display excellent performance in changing process conditions. With an accuracy of ±0.2% of the measured value, the meters offer high feasibility of total cleaning and allow for easy sterilization. The best advantage of rotary piston flow meter is that the volume is directly measured and not inferred as in the case of inferential flow principles. Thus, it is the most accurate flow measurement principle in the world.
Fluidyne offers a balanced, lightweight, and rugged construction. The flanged connectors make it the best option for overhead hose reels and other liquid applications.
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Are you considering getting an oscillating piston flowmeter for any application and have doubts? Fluidyne can help you to decide which is the best option for you!
Positive Displacement (PD) Flow meters are volumetric flow instruments that measure flow by passing a precise volume of fluid with each revolution. PD flow meters are precision instruments whose internal moving components are hydraulically locked in tandem with the volume of fluid moving through the flow meter. The meters can measure intermittent flows, very low flow rates, and liquids of almost any viscosity. When fluid flows, PD meters instantly move. And when the fluid stops, the meter stops.
Moving in lock step with the fluid also means that measurements are not affected by the liquid&#;s viscosity, density or turbulence in the pipe. Each measured volume of fluid is uniquely separated from the next by a frictionless liquid seal. The sealing effectiveness is a function of manufacturing precision and the ease of rotation of the meter&#;s components. The same close clearances that make the precision parts work also mean that relatively clean fluids must be measured. Materials of construction vary widely and allow the family of PD meters to measure a wide variety of process liquids. Their high precision has allowed PD flow meters to be almost universally accepted for billing and transfer standard applications, such as dispensing gasoline, fuel oil, and natural gas or water measurement.
There are a variety of methods to provide output signals and readouts. PD meters have the ability to offer simple once per revolution counting to high resolution encoder equivalent signals which can take more than measurements per revolution. Because these measurements are not sensitive to changes in pressure, temperature, or viscosity, the meter&#;s K-Factor typically does not need to be compensated for during use.
Accuracy and operating range, or turndown ratio, varies widely by type and manufacturer, but many meters fall in the range of 0.1% to 1.0% of reading, with turndown ranging from 10:1 to 200:1 or more. Due to their high accuracy, PD meters are the most widely used meters for custody transfer applications.
With such a large variety and diverse operating range, prices of positive displacement meters can vary widely. A simple water meter for your home may cost less than $100, while prices for the most sophisticated and largest meters can run up to several thousand dollars.
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PD meters are an established technology that covers the spectrum of measurement devices from some of the most widespread, easiest to use, and most affordable, like rotary piston or nutating disc meters, to some of the highest precision, highest accuracy, highest resolution meters available today, like reciprocating piston meters. New materials, like composites, new manufacturing techniques, like additive manufacturing, and new electronic sensing technology, like high resolution hall effect sensing, continue to keep the basic idea of measuring a known volume of fluid at the forefront of the fluid measurement industry.
There are many types of positive displacement flow meters, including; reciprocating piston, oscillating or rotary piston, bi-rotor types (spur gear, oval gear, helical gear, rotary vane), and nutating disc (wobble plate). Some examples are listed below:
Piston flow meters are of single and multiple-piston types. They function by rotating, oscillating, or reciprocating. For any motion, the pistons displace fluid in the same way that a syringe operates. Each piston displacement captures the same amount of fluid.
Oscillating Piston Meters
Typically seen in residential water service and to measure relatively viscous fuels, these meters are a single piston design that oscillates between the inlet and outlet ports as fluid flows. Measurement output is usually achieved by having a magnet installed on the piston and a transmitter picks up the change in the magnetic field as the piston moves.
Reciprocating Piston Meters
Typically linked via a crankshaft and opening and closing ports in the cylinder, reciprocating piston meters act similarly to piston engines that power most automobiles and trucks. The sensor output is usually driven from the rotating crankshaft and can be mechanical, electrical, optical, or magnetic. These meters are mainly used to measure very low flow rates, down to 0.005 cc/min.
Gear flow meters use two round gears that are mounted in overlapping compartments. The measured fluid is trapped in the voids of the gear teeth and transported from the inlet port to the outlet port as the fluid flow causes the gears to rotate.
Oval-gear meters have two rotating, oval-shaped gears with synchronized, close fitting teeth. A fixed quantity of liquid passes through the meter for each revolution.
Helical [Gear] Flow Meters use two screw-shaped rotors to slice the fluid stream into fixed displacement volumes. The rotors&#; orientation is in-line with the fluid flow path. These meters rotate with very low pressure drop, and can turn at high rpm&#;s making them accurate over wide flow ranges and compatible with very high viscosity fluid applications.
Rotary vane meters consist of equally divided, rotating impellers, in two or more compartments, inside the meter&#;s housings. The impellers are in continuous contact with the casing. A fixed volume of liquid is swept to the meter&#;s outlet from each compartment as the impeller rotates.
Nutating disk meters have a moveable disk mounted on a concentric sphere located in spherical side-walled chambers. The pressure of the liquid passing through the measuring chamber causes the disk to rock (wobble) in a circulating path without rotating on its axis. The disk/sphere is the only moving part in the measuring chamber.
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