McMillan’s microturbine wheel technology utilizes the Pelton turbine wheel concept. This design allows for the use of a miniature turbine wheel to measure flow. The wheel is supported by a very small sapphire shaft held in position by two maintenance-free bearings. Due to the light weight of both the wheel and the shaft, the microturbine wheel is virtually suspended in the flow path. This suspension effect relieves friction on the shaft and bearings, eliminating wear.
As flow passes through the device, it is directed onto the very small teeth of the wheel using a high precision nozzle (see the blue arrows below). This nozzle is sized according to the flow range of the unit. The rotational speed of the turbine wheel increases proportionally to the volumetric flow rate.
McMillan incorporates multiple versions of thermal sensing technology, including:
Details for each variant of microturbine technology are outlined below.
On some microturbine models, the Pelton wheel has alternating white and black sections evenly spaced on it’s surface. As the wheel rotates (as shown with green arrows), an infrared beam (as shown with red arrows) is reflected off each white section and directed to a phototransistor which detects each reflected beam and converts them into measured pulses.
Increased flow causes the wheel to spin faster, increasing the pulse rate. When the wheel stops (under zero flow conditions), no pulses are generated. This eliminates the possibility of “zero drift” and the need for adjustments to the instrument’s zero reading. Processing circuitry provides analog and/or pulse outputs that are linearly proportional to the flow rate.
On other models, the microturbine wheel has integrated translucent sections. An infrared emitter is located on one side of the wheel and a sensor on the other. As the wheel rotates (as shown with green arrows), the infrared beam (as shown in red) is alternately interrupted and passed through the translucent sections, detecting wheel speed, and generating a pulse based on flow.
Increased flow causes the wheel to spin faster, increasing the pulse rate. When the wheel stops (under zero flow conditions), no pulses are generated. This eliminates the possibility of “zero drift” and the need for adjustments to the instrument’s zero reading. Processing circuitry provides analog and/or pulse outputs that are linearly proportional to the flow rate.
Flow controllers use an integrated flow rate sensor and control valve to regulate flow rate, regardless of inlet pressure fluctuations. A flow control set-point is provided by the user via the touchscreen, or remotely via an electronic signal. The controller then adjusts the integrated valve as needed to maintain the desired flow.
To provide responsive control of flow rate, the unit applies pressure to a large diaphragm that proportionally opens and closes the fluid pathway. This diaphragm is actuated by a precision engineered cam driven perpendicular to the diaphragm with the use of a stepper motor. As the stepper cam extends, it applies more pressure to the diaphragm.
In addition to inputs provided by the flow sensor, flow controllers are also able to predictively estimate cam location based on set-point changes. This reduces response time to achieve large changes in flow rate based on large changes in the set-point.
McMillan diaphragm valves are designed exclusively for proportional control. They are not designed for a positive shutoff.
McMillan Model U709 will precisely measure very low flow rates of virtually any photoresist chemical, whether a short burst of flow or a continuous flow. Dispenses as short as 500 milliseconds and volumes as low as 0.1 grams can be detected repeatably.
We are experts in all things flow. As a company founded and run by engineers, we seek to understand your application and then build a product solution that will solve your most difficult challenges.
McMillan Flow sales agents are strategically located across the
globe. Find your nearest distributor or office.
McMillan Company
7075 Ranch Rd 2338
Georgetown, TX 78633
sales@mcmflow.com
Phone: (844) MCM-FLOW
Copyright © 2024 McMillan Flow Products. All Rights Reserved.
McMillan Flow Products is located in the U.S.A. and all products are manufactured in our Texas plant.
"*" indicates required fields