Flow Meters
The Story of Steel
October 8, 2022Thermocouples and Sensors
October 9, 2022
Portaflow Ultrasonic Clamp on Flow Meter
There are many options for flow metering, but nearly all involve the requirement to break into the pipe.
The Portaflow ultrasonic Clamp-on is different as it is installed on the outside of the pipe. Flow inside the pipe can be measured accurately by this handheld unit.
Some ultrasonic flow-meters sold in NZ in the past have worked poorly on galvanized pipe but this is not the case with the Portaflow.
Presently Homershams recommend 3 good quality instruments that work well in the NZ environment
The Fuji Portaflow C
The Honeywell 2000
The Panametrics
The Portaflow-C system consists of a handheld instrument c/w strap-on sensor bars. The sensor bars are a 1-piece setup, making alignment and setup quick and easy.
A ruled scale on the side of the bar makes for rapid setup of sensor spacing.
Accuracy for the Fuji Portaflow C is ±1% and it is unaffected by flow velocity.
How do ultrasonic flow meters work?
There are two technologies used in ultrasonic flow metering
- Doppler
- Time of flight or Transit Time
Doppler is the older of the two technologies. Most people know the Doppler effect of the approaching train that appears to change tone.
It is important to note at the time of purchase that Doppler flow meters do NOT work with ˜ultra-pures™ such as water, milk, alcohols, beers etc.
As a lack of bubbles or impurities results in no signal.
Time of Flight Flowmeters work because the ultrasonic signal passing through a pipe is slowed down when it opposes the flow.
Examples of applications include glycol refrigeration, milk, for comparison with installed flowmeters, shipboard (seawater), river water.
Variable Area Flowmeters
Familiar to anyone who’s been in hospital and seen the oxygen or suction meters above every bed, the Variable Area Flowmeter or ˜Rotameter™, remains a simple and reliable method of measuring the flow of both liquids and gases.
Technically the term Rotameter is a trade name, but as ˜Hoover™ now often means ˜vacuum cleaner™, ˜Rotameter™ now often means variable area flowmeter.
Patented in 1908, the rotameter is a tube in which a float resides. The diameter increases as the tube gets higher. Hence increasing flow produces a nearly linear display of flow.
Although data sheets rarely mention it, a rotameter must be installed for vertical upwards flow to allow the float to lift off the bottom stop and give a reading.
Homershams supply rotameters from Dwyer (USA) and Influx (U.K.) in both simple acrylic blocks and metal frames with separate tubes.
Flow Switches
Flow switches are used for pump protection and to confirm flow is happening. The simplest flow switch will usually have a reed switch mounted in the main body and a magnet on the end of the paddle. As the paddle moves back & forth with the flow, the switch is operated either on or off.
Homershams have many flow switches especially from Dwyer including paddle type and Thermal Dispersion (no moving parts). There are too many to list, but here are a few examples of our most common ones.
Homershams have many flow switches especially from Dwyer including paddle type and Thermal Dispersion (no moving parts). There are too many to list, but here are a few examples of our most common ones.
Did you know..
The term ˜Potable™ refers to water that is designated for human consumption, but many people are unsure of the correct pronunciation - Poe-ta-bull from the Latin word Potibillis meaning to drink.