Welcome to the September 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...

How to write a technical article?

Communication of technological innovations and applications advances has today many routes from vendor to potentially interested end users. However the good old fashioned technical article (informative rather than a commercial message) remains a favourite information source with many end users. But how do you make your article stand out from the crowd ? Here are some tips I have distilled from many years of searching for a successful formula for writing technical articles.

Keep your statements short. People will absorb the information better. Technical people (like myself) often have a tendency to write very long sentences which are full of distractions that simply drag on and do not change the primary content in any way shape or form. By contrast many popular authors write short, precise sentences.

Do not use metaphors. Constrain your script to facts and keep it direct. I have often found that you might not get the message completely correct first time. Put your manuscript aside and then go back with a fresh mind to refine and improve your article.

To create emphasis politicians use the tactic of repeating things three times. Not once. Not twice. But three times ! There is good reason for this as it stresses your point and adds some rhythm to the text.

Be careful about including humour as what might be funny to you may not be understood or worse negatively misconstrued by others. This is the reason we keep our light-hearted “joke” section separate to the features and articles. Any jokes I do put in the main content are removed by my more discerning colleagues !

Should you pose questions? I am not a marketing man but I have noticed a tendency for some technical writers to ask questions to stimulate their target reader’s curiosity?

Articles with topical content often serve to relay a message better than statements. Bullet points may give the technical information but if the content has human interest or relates real potential benefits to the reader it will be read. Our customer story below on scalp cooling during chemotherapy is an example of a topic with wide appeal beyond people working in that area.

My own writing style is informal and not for everyone. Typically it requires editing to make it into something that can be easily read. Thank heavens for professional wordsmiths and spelling checker software.


Product Update

Flowmeter for viscous fluids

Built for metering viscous fluids, such as hydraulic oils used in heavy machinery, at pressures of up to 700 bar and temperatures up to 150°C, the OG-2 700 bar flowmeter is designed to be fully IP67 / NEMA 4 compliant. With a standard flow range from 0.03 to 4.0 litres / minute on 30Cstk oil the flowmeter is able to routinely achieve outstanding accuracy (0.5%) and repeatability (0.1%). Combining robust 316 stainless steel design, durable construction materials and proven technology ensures the OG2-700 bar flowmeter will provide reliable, accurate operation over an extended product lifetime.


Humour

Our humour in this issue of fLowdown was influenced by the 'How to write a technical article' feature above.


People often accuse me of "stealing other's jokes" and being "a plagiarist." Their words not mine...


If writers were good businessmen, they'd have too much sense to be writers.
- Irvin S. Cobb


Real seriousness in regard to writing is one of two absolute necessities. The other, unfortunately, is talent.
- Ernest Hemingway


A linguistics professor was lecturing to his class one day. "In English," he said, "a double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative." A voice from the back of the room piped up, "Yeah, right."


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...

Vortex shedding meters

If you place an obstruction (such as a bluff body) in a fluid stream vortices will be formed downstream of the impediment. If the arrangement is symmetrical the swirls will be shed from alternate sides of the obstruction. The frequency of the vortices will be directly proportional to the fluid characteristics and the velocity of the fluid stream.

This is true for both gases and liquids making this phenomenon the ideal basis for a flow meter. Interestingly this phenomenon can be seen to occur in everyday life. The flapping of a flag is probably the most common example of this effect. Other common examples of the effect include the rattling of wires on yacht masts or the "keening" heard near power lines in high winds. Many metal chimneys or vent pipes have spiral elements on the outer surface these are there to break up the vortex shedding and prevent the tube vibrating. There are numerous methods for detecting the frequency of the vortexes varying from strain gauges on the obstruction in the fluid stream to ultrasonic detection of variations in fluid movement further downstream.

This illustration shows the alternate shedding of fluid known as the Karman Vortex Street effect. The effect may be defined as follows:

F=St(v/d)

Where: f= Karman vortex frequency
St= Strouhal number
V= Velocity
D= Width of the bluff body

Putting an obstruction in a fluid conduit and measuring the frequency of the induced oscillations is a relatively simple thing to do and there are a large number of ways to detect the induced disturbances in the flow stream. Generally flow meters based upon ‘Vortex shedding’ require flow in the turbulent region so are most suitable for gases and low viscosity liquids. Currently this technology has had most success in the measurement of steam flow and corrosive or cryogenic liquids where other metering methods cannot handle the operational envelope. Being fluidic devices, the pipes can be blown dry with high velocity air with no damage to the meter.

For further information please click here


How do I measure?

In this issue of fLowdown we discuss in 'How do I measure'

High viscosity fluids

High viscosity liquids pose a problem for many flow meter types, such as the vortex meter discussed in the newsletter. Turbine meters, differential pressure devices and quite frequently velocity measuring devices rely on a minimum liquid speed and consequently are challenged by high viscosity fluids. To use these techniques with high viscosity fluids it is common to use larger diameter pipes to maintain line pressure drop and keep liquid transport costs as low as possible. Many flow meters technologies operate best in the turbulent flow region i.e. with Reynolds numbers above ~2000. This is a dimensionless number that characterises fluid motion. In Figure 1 below the tap on the left shows laminar flow where the stream is clean. The tap illustrated on the right shows turbulent flow where the surface, and indeed the internal flow is random. Most high viscosity flows will be laminar.

Figure 1.
This laminar flow affects the velocity profile of the fluid within the tube. At high viscosity (low Reynolds numbers) the velocity profile of a fluid is rather like a parabola with the centre liquid traveling at a higher speed than the fluid close to the pipe wall (see Figure 2 below). This is because of the viscous drag created against the static boundary. In lower viscosity fluids by comparison the velocity profile is “fully developed” i.e. the flow is mostly traveling at the same speed except for a small area close to the pipe wall.


Figure 2.

These are representative illustrations and reality will be somewhere in between in each case. Ideally the flow will be steady and driven by perhaps pressure but usually a pump is used. In addition to varying velocity profile according to a fluids viscosity is the fact that flow will also vary within the pipe and sometimes may even be momentarily stationary. Diaphragm, piston, gear and even peristaltic pumps are used to pump viscous fluids, all introduce pulsations into the flow. The frequency and amplitude of these pulsations can cause problems to some flow meter types and should therefore be removed. With electronic meters the danger comes with aliasing where the sample time for the meter and the ripple in the flow are close to or at the same frequencies. For all these reasons positive displacement meters are often the preferred choice for viscous fluids.

Positive displacement flow meters vary in design and working principle but the fundamental operation is the same. They all take a discrete package of fluid and pass it from the inlet to outlet with little or no liquid loss or slippage. Gear flow meters are very popular but almost by definition can have problems with high viscosity fluids as the gear teeth themselves can cause “hydraulic locks”. With a classical gear tooth profile the volume of fluid at the tooth root cavity has effectively no escape. Gear meter manufacturers counteract this by either making the tooth engagement deliberately “loose” or by removing certain parts of the gear profiles to permit the excess fluid to extrude and escape the gear root rather than lock the gears. Screw gear devices are very efficient with very high viscosity liquids and return startling performance but are also expensive.

For further information on optimised flowmeters for measuring viscous fluids please click here

Problem Solved

In this issue of fLowdown feature we share with you two examples of customer applications solved by a flow meter development by Titan Enterprises.

Solution 1

Optimising coolant flow during chemotherapy treatment

Paxman Coolers Ltd. has been pioneering scalp cooling technology worldwide for over 25 years and are committed to improving the efficacy of scalp cooling for all cancer treatment patients across the world. The Paxman scalp cooler has been used by over 100,000 patients in 32 countries and is responsible for helping patients to keep their hair and retain normality during chemotherapy. The treatment works by lowering scalp temperature before, during and after the administration of chemotherapy. Hair loss is considered one of the most negative factors in a cancer patient’s care. About 65% of patients will undergo a chemotherapy that will cause hair loss. Therefore today approximately 4 million patients worldwide will lose their hair every year and by 2030 over 6.7 million patients will lose their hair without scalp cooling.

To address this challenge, Paxman Coolers Ltd. turned to Titan Enterprises to develop a flowmeter to monitor the rate of coolant flow around their patented cooling cap. Based upon their 800-Series turbine flowmeter – Titan Enterprises were able to provide Paxman with the technology to ensure that the coolant flow rate is kept within an optimum range to provide the patient with the best possible chance of keeping their hair.

Kathryn Daniel, Marketing & Communications manager of Paxman commented "We chose to integrate the Titan Enterprises 800 Series flowmeter into our Scalp Cooling System because it offered an excellent balance of measurement accuracy, long term resistance to coolant fluids, high reliability and proved easy to maintain".

For further information on the 800 Series turbine flowmeter please click here.


Solution 2

Measuring process flow accurately over a wide dynamic range

Recently Titan Enterprises was approached by a European customer who had a specific set of problems with their process. Their requirement was for a flow meter which was capable of very low flows, had a rapid response time, excellent chemical resistance and was also self-purging.

Traditionally they had used two flow meters as their required flow range was very wide. The process to be metered involved charging the system with fluid, delivering a pre-determined volume over a period of time and then sucking the fluid back out of the system. To ensure repeatability and reliability of measurements the system should have no air pockets which would upset the readings as the air cleared. The customer’s current flow metering protocol involved purging the system repeatedly prior to starting the metering process. The thermal meter used for measurement at low flows suffered from a relatively slow response time and poor accuracy.

To address the customer’s needs - Titan built two prototype meters based on its Process Atrato ultrasonic flowmeter. Beneficially the Process Atrato could be configured with a continuous 1mm bore flow pathway with no changes in section so is self-purging. The metering tube is some 330mm long giving a measurable phase shift even at very low fluid velocities whilst have a low “dead” volume of around 1cm3.


Figure 3.

The customer required flow measurement from 1 to 100 ml/minute with the best possible accuracy. Figure 3 above shows the performance of the two meters with linearity, repeatability and average readings. This data shows that the meters are accurate to around ±1.0% of reading over the whole range. The response time is from ~2 seconds at 0.5ml/minute to a few hundred milliseconds at 120 ml/min.

To provide the computing power for this demanding application a new software platform was developed for these customer application optimised Process Atrato units. Initial trials of the units with the customer are showing great promise with significant improvements (over the traditional flow measurement system) including the required rapid response time, improved accuracy and simplicity of use already having been achieved.

For further information on the Process Atrato ultrasonic flowmeter please click here.


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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