Welcome to the April 2016 issue of fLowdown - a quarterly Newsletter from Titan Enterprises Ltd. written to keep you informed about the latest technological developments, applications advances and breaking news in the field of flow measurement.

If a particular feature interests you, do not hesitate to contact us or follow the link for further information. We welcome your feedback.

Trevor Forster (Managing Director)

 

Trevor's
Technical Tip

Trevor Forster is Managing Director of Titan Enterpises. His experience in fluid handling dates back to the mid 1960's when he started working on rotating seals and flowmeter design for third party clients. Drawing upon over 40 years of using innovative design and production techniques, Trevor and his team have been able to produce elegant flow metering solutions for organisations around the globe.  In this issue - Trevor offers you useful technical tips on:

Metering Batches of Liquid

Metering batches of liquids is a very simple thing to do, or is it? Typically metering fixed volumes of liquid into a process e.g. adding water to a mixer for food production is easy. It requires that you put a flowmeter in the product line, connect it to an instrument, control the measurement with on-board software, wire in a valve, enter your required volume and press a button and wait for your vessel to have the right amount of liquid added. With all these steps in the process a lot of problems can occur along the way and needless to say not that easy. The following points must be considered when designing and commissioning the set-up.

    1. System repeatability is the key. The batching arrangement must have be hydraulically locked with no place for gaseous fluids to accumulate. If there is an air pocket this can be full or empty. Consequently it may cause a burst of high flow and a dynamic flow situation for part of the dispense or have no effect at all if the line is full. With a volumetric flowmeter any air passing through would be seen as part of the batch and cause a low delivery. These uncertainties will change the amount of liquid delivered and will negatively affect system repeatability.
    2. Ideally the process conditions should be constant. Changes in pressure, temperature or flow rate may cause the flowmeter to operate on a different part of its calibration curve or behave in an unpredictable dynamic way.
    3. Pulsating flow should be avoided if possible so the selection of the pump type is important. Aggressive chemicals frequently use pumps which introduce large variations in flow over an operating cycle. These problems can be limited with a pressure regulator and pulsation damper. The overall flow should be constant as the tuning of the pulsation damper is flow rate dependant.
    4. The flowmeter will perform better if the measurement point is immediately before the dispense valve. This eliminates inertia and contained fluid volume making the resulting delivery more accurate.
    5. Be aware of your flowmeter resolution. For example a water meter which gives 1 pulse per litre is never going to deliver 10 litres with an accuracy/repeatability of better than 10% unless some very clever electronics and/or calibration is involved.
    6. Consider the type of shut-off valve that is used. A solenoid is excellent with a fast open/close time but is not practical for larger pipe diameters and higher flow rates. Alternative valves will have relatively long open and close times and these must be accommodated in the batch cycle time. The valve stop signal has to be made before the batch size is reached this can be done in a number of ways. The usual method is to calibrate the system by measuring the volume dispensed for a given setting and adjusting the volume to accommodate errors in the start/stop times. The more sophisticated solution is to use a “batch overrun” program. This measures the actual volume dispensed by the flow meter and then adjusts the stop signal accordingly. It may take 3 or four runs to reach the required volume. A typical set of records may go something like this:
    Run 1 ‐ 10.13 Litres
    Run 2 ‐ 9.95 Litres
    Run 3 ‐ 10.02 Litres
    Run 4 ‐ 10.00 Litres
    This relies on the meters linearity and is not as efficient with a non-linear meter. Some instruments have 2 stage shut-off so a large valve for the first stage and a small fast one for the final shut-off.
    7. Be aware of electronic based flow meters with rapid batch cycles. A standard electromagnetic flowmeter may have an internal cycle time of perhaps 50 Hz. This means that the flow throughput is only updated every 20ms which means a 2 second dispense could be 1% out regardless of meter linearity. Special batching flowmeters accommodate this potential time delay by predicting when the stop signal should be sent before the amount of liquid has been delivered.

By taking these simple precautions when designing or specifying a system extremely good accuracy can be achieved.
Below are some results obtained from a custom Atrato ultrasonic flowmeter designed purely for batching a 3 second delivery for a 150ml bottle filling trial.

For further information on flowmeter systems for batching please contact trevor@flowmeters.co.uk.


Problem Solved

In this new feature we look to bring you an example of a customer application that was solved by a flow meter development by Titan Enterprises.

In this issue of fLowdown we report on developments made for Selmech Supplies Ltd - a leading manufacturer of...

Semi-automated additive applicators for silage

Addition of a preservative to forage crops is a common practice to prevent degradation but also to improve palatability for the animals that feed on them. Historically aggressive chemicals were added in fairly high volumes requiring very large fluid tanks or frequent refilling during harvesting. Modern silage additives tend to be applied at ever lower levels but must be applied at a rate which very accurately matches the harvesting yield and conditions. To achieve successful results it is important the additive is applied at the correct dosing level. Too little and the desired result is not achieved, too much and expensive product is wasted.

To address this challenge, Selmech Supplies partnered with Titan to develop a new generation of semi-automated additive applicator able to precisely measure additive flow rates and adjust pump drive levels to maintain correct application levels. Selmech Supplies chose to integrate the 800 Series flowmeter into its additive applicator systems because it offered a good cost / performance balance and most importantly was tolerant of the aggressive chemicals its customers sometimes use.

To cover varying application ranges Selmech use three different versions of the 800 flowmeter in its semi-automated additive applicator system. Beneficially each 800 Series flowmeter supplied has the same mechanical form factor and the same electrical output ensuring result consistency and reproducibility from applicator system to system.

Operating over 6 flow ranges from 0.05 to 15 litres per minute, the Titan Enterprises 800 Series turbine flowmeter combines high performance and competitive pricing. Using totally non-metallic wetted components makes the 800 Series an ideal choice for the metering of aggressive chemicals in particular. For further information on the 800 Series turbine flowmeter please visit www.flowmeters.co.uk/pd_800series.htm or contact Titan Enterprises on +44-1935-812790 / sales@flowmeters.co.uk.

Flow Technology Spotlight

In each issue of fLowdown we review a particular flow metering technique, its benefits, shortfalls and the applications to which it is best suited. In this issue we look at...

How does a Coriolis flow meter work?

Coriolis meters are one of the most, if not the most, accurate flow meters on the market, but how is this achieved? They are used in critical situations such as custody transfer as well as general process control. The operating principle of Coriolis meters is extremely simple, subject a moving flow to a force at ninety degrees to its path of movement and it will be deflected. This deflection will be proportional to the mass and velocity of the flow movement. If the moving flow is fluid inside a pipe you will be able to determine the mass flow rate of that fluid. Unfortunately the problem comes with how to make a practical flow meter based upon this principle.

Early flow meters based upon the Coriolis principle used a pair of looped tubes which were vibrated. As the fluid in such devices flows the vibration induces acceleration and deceleration of the fluid in the loops. This induces a differential vibration in the upstream and downstream arms of the flowmeter. Sensors measure the phase difference between these two arms and this phase difference is a measure of the mass flow. Some manufacturers still use this technique with great success.


No flow Parallel movement


With flow upstream and downstream arms show differential movement.

Sensors positioned at positions A & B will have the outputs shown below:-

Measuring the mass flow is fine if you know the density of the fluid. However if the density is unknown or varies you may have another problem. Fortunately the natural frequency of the vibrating tubes is dependent upon the tubes mass and this will vary with fluid density so determining the density can also be achieved by measuring the natural frequency of the tubes. You now have both mass and volumetric measurement from a single sensor. One of the problems with this arrangement is the increased pressure drop because of the loop.

Another version of this type of Coriolis flowmeter uses a straight tube. In this design the straight tube is vibrated in the middle so the flow on the upstream and downstream arms of the flowmeter are still subjected to differential accelerations causing the tube to “twist” with mass flow. This is a more compact system which often makes it a more popular solution.

The black line in the diagram above depicts the flexible part of the tube at one extreme of its vibration, the grey line is the other extreme. The red and blue lines show the tube distortion due to flow in the centrally vibrated tube. This twisting of the tube is seen differently at sensors A & B. The output sine waves are virtually identical to the twin tube system.

Unfortunately designing flowmeters with all this inherent technology is costly, Coriolis meters are consequently not cheap but do fulfil certain needs across a wide range of industries.

For further information on affordable, high performance alternatives to Coriolis flowmeters sales@flowmeters.co.uk.

How do I measure?

In this issue of fLowdown we discuss in ‘How do I measure’ an issue of general interest to all of us – beverages - in this case - coffee!

Coffee machine ultrasonic flow measurement.

Titan were recently approached and asked if we could make a $1 flowmeter for use in coffee dispensing machines which would be more reliable than the current $1 turbine meters. Leveraging technological innovations detailed in one of our recent ultrasonic flowmeter patent applications we produced a flow metering system that used the already on-board microprocessor and it performed very well for the top half of the water storage. The first 4 or 5 cups were at acceptable volumes but as the water in the reservoir reduced the performance became unacceptable. See Figure 1.

Unfortunately as this was a traditional filter coffee machine powered by boiling water we had difficulties with lower pressure heads and gas break-out which is a problem with all ultrasonic flowmeters. However drawing upon our knowledge of turbine flowmeters we were able to identify for the customer the actual fluid movement within their pipes which helped to explain some of the anomalies they had been experiencing with their $1 turbine. Figure 2 below clearly shows both forward and reverse flow as the flash boiler charges and discharges. The turbine flow remains positive due to the inertia in the turbine whilst the actual flow shows reversals as seen by the ultrasonic flow signal from the inherently bi-directional meter.

Figure 2 blue line is the turbine frequency, yellow line ultrasonic flow meter reading.


Figure 1


Figure 2

For a no-commitment discussion on problems that you are experiencing with your current flow meter technology, and how it might be solved, please contact Trevor Forster (trevor@flowmeters.co.uk).

Product Update 1

Introducing the Process Atrato

The Process Atrato is a new low volume, high performance ultrasonic flow meter packaged for the process and control environment. Compact in design, the Process Atrato flow meter combines all the technological advantages of Atrato ultrasonic technology (high linearity, high sensitivity, wide flow range linearity, no moving parts, fast response time, can be installed anywhere) with a new durable construction.

Built from 316 stainless steel and PEEK – the Process Atrato is supplied sealed to the IP65 standard. The combination of durable housing and top performance, in a very reliable flow meter, delivers a new tool for engineers at a reduced cost of ownership compared to existing flow measurement technologies serving the process and control market.

Rated for use up to 65°C and 20 Bar the Process Atrato is available in 4 models operating over flow ranges from 2 ml/min to 15 litres per minute, accuracy is ±1% over the whole flow range. Each Process Atrato is calibrated with a pre-set 'K' factor so all meters of the same flow range are fully interchangeable simplifying assembly and set-up procedures for OEM manufacturers looking to integrate the flow meter into their process and control set-up.




Product Update 2

Using Data Matrix bar codes to carry calibration information on flow meters

One of the challenges of supplying thousands of flow meters a year is the storage and accessibility of the calibration information. Not a week goes by without a customer requesting a lost calibration certificate or in one case 300 lost calibration certificates ! To facilitate easy response to these calibration certificate losses - Titan has traditionally stored all flowmeter calibration certificates as pdf's.

Recently a customer has requested a comma separated label on each supplied flowmeter containing the meter serial number and the 'K' factors at specific flow rates. A very simple data package. The idea being that when the meter is installed a quick scan will upload the calibration information directly into their computer. This started us thinking.

With the proliferation of mobile phones nearly everyone has access to a bar code reader so why not put a compact version of the calibration certificate on each meter.

The data matrix label Titan are considering can handle a large amount of information. We are tempted by this idea and would appreciate customer feedback on the perceived merits of such a system.


and tell us if there is enough data there if you are stuck for calibration data and have misplaced your certificate?

Bulletin Board




To enable you to make informed decisions about the flow metering challenges facing your organisation this newsletter feature keeps you up-to-date on the latest literature, hints and tips, initiatives and company news from Titan Enterprises.

New Article: Low Flow Rate Ultrasonic Flowmeter for Liquids – a Novel Approach

Abstract:
Across the industrialised world there is an increase in demand for liquid flow measurement systems operating at low flow rates. The range of applications that might benefit from such systems is very wide and includes offshore, industrial, medical, food, beverage, pharmaceutical and laboratories. The requirements on flow meters to fulfil these applications are also becoming more demanding. An ideal flow meter might have through flow design with minimum pressure drop and improved accuracy as well as offering operation at higher pressures / temperatures and across wide flow ranges with greater accuracy. A meter which can be easily cleaned either chemically or with a “pig” and be able to operate over a wide range of Reynolds numbers would be a great advantage.

Typically the three most popular current technologies for such flow meters are electromagnetic, Coriolis and ultrasonic. Electromagnetic meters are restricted to conductive fluids and Coriolis meters are expensive which leaves ultrasonic as being the most widely viable meter type for these applications.

Of the two ultrasonic technologies, Doppler shift and time-of-flight (TOF), the latter offers the best performance over the widest range of operating conditions. Time-of-flight ultrasonic flow meters are generally suited to larger pipe sizes but they offer the potential for smaller tube sizes.

This paper describes the design and performance of a novel, small bore ultrasonic flow meter which operates in pipe diameters where traditional meters of this type stop working. Initially the meter was developed as a replacement for small turbine meters in laboratory, industrial and beverage applications. The achieved performance has far exceeded expectations making the meter suitable for a far wider range of applications. The patented technological approach has enabled a wide variety of different flow measurement, dosing and control applications to be addressed. Using the same electronics with an appropriately sized flow tube it is possible for the meter to monitor a range of flows from 3m3/hr to 0.12l/hr with an accuracy of better than ±1% over a flow range of exceeding 200 to 1 when used with pipe sizes as small as 1mm in diameter. The described ultrasonic flow meter is capable of providing an update rate of 0.05s and is therefore suitable also for batching type applications.

This article has been accepted for publication in the May 2016 issue of Fluid Handling Magazine, to be sent a copy after publication, please register your interest here.


Humour


Engineers aren't boring people. We just get excited over boring things.


Einstein is on a train when a fellow traveller asks him "does London stop at this train?"


Arguing with an engineer is a lot like wrestling in the mud with a pig. After a few hours, you realise that he likes it.

Click here for a printable version of Flowdown.

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Titan Enterprises Ltd, Unit 2, 5A Cold Harbour Business Park, Sherborne, Dorset, DT9 4JW. UK
Telephone: +44 (0)1935 812790   -   Fax: +44 (0)1935 812890   -   Email: sales@flowmeters.co.uk