Going with the flow

Flow meters provide measurement points for gases or liquids that can flag up inefficiencies and system leakages or simply provide custody transfer records for billing purposes.

Their application in the Middle East is growing, given the huge investment in the hydrocarbon and utility sectors, which are prime end-users of the technology.

“In this region the oil and gas industry is making great investment in areas where they can improve the production of the basic hydrocarbons, also we are seeing across the board investments in the downstream petrochemical processes in order to monetise that core hydrocarbon, be it a crude oil or a gas product,” observes Keven Dunphy, director of Emerson Process Management’s flow division for the Middle East and Africa.

“On top of that, there is infrastructure development for power and water as the region grows more hotels and as we build the economic diversity outside the hydrocarbon industry. As a result, we are seeing growth greater than 20% per year on both revenue and flow meter units sold in the region.”

Within the utility sector, the main applications for flow meters would be to measure the power source into a power plant, such as gas or fuel oil; to control the processes in water, steam and electricity production; to regulate the distribution of steam, water, wastewater and treated water around networks; and for fiscal transfer records.

A desalination facility for instance might have 100-200 devices installed. The district cooling industry also employs flow meters to track the movement of chilled water around networks.

A choice selection

The wide variety of meters on the market take flow readings using different methods, among them turbine, positive displacement, ultrasonic, electromagnetic and vortex meters. The choice of meter is generally determined not merely by price but also by the level of accuracy required and the specific application.

“Depending on the process, you might want an indication of your flow with plus or minus 10% of accuracy, so you would take a cheap meter,” says GE Sensing’s Hilko den Hollander.

“But when you look at the oil and gas industry for custody transfer meters, where somebody is going to pay for the amount of oil or gas delivered, you want a very accurate measurement so you would go for high-end solutions.

With gas, obviously you want to measure for control purposes and to check there are no leaks in your pipelines, but then in the end you are going to sell your gas to somebody so you also want to make a custody transfer measurement, with water it is much the same thing.”

Maintenance needs

A further consideration in flow meter selection is the simplicity of use and the device’s maintenance needs. “If you use the old-style positive displacement meter you have to do a lot of maintenance,” notes den Hollander.

“There is a wheel with small chambers in, and if you draw water the wheel is going to turn a number of rotations to determine how much water you have taken.

The problem there is that there are moving mechanical parts that wear out, so your accuracy is changing because of mechanical wear.

With ultrasonic devices there is nothing moving, you just have transducers that send acoustic pulses, so there is no wear in the flow meter, which means the measurement result is valid even after ten years and the meter doesn’t need to be recalibrated.”

In ultrasonic meters, each transducer functions as a transmitter, generating a certain number of acoustic pulses. They then act as a receiver for an identical number of pulses and the time interval between transmission and reception of the ultrasonic signals is measured in both directions.

The difference between downstream and upstream transit times is proportional to the velocity of the liquid and indicates the direction of the flow.

“There is also the issue of pressure drop,” den Hollander continues. “If you have a pipeline of course you have a pump somewhere in your factory, pumping something.

You want the pump to be as small as possible and to consume as little electricity as possible, so you don’t want pressure drop in your pipeline and therefore you don’t want any moving parts or obstructions. An ultrasonic flowmeter is full bore so there is very low pressure drop.”
 

Modern high-end solution meters, such as ultrasonic and electromagnetic meters, boast a much longer lifespan than the conventional ones with their multiple moving parts. This obviously brings cost savings in terms of maintenance, replacement and process outages.

“With these ultrasonic ones, technically there is no end of life,” den Hollander remarks. “If there is no chemical problem like corrosion or something, they will go on forever.

They don’t wear out, unlike the old fashioned types which have rotating parts and bearings that will wear out and you need to recalibrate them often – every one or two or maybe five years, it depends a little on the process.”

As demands for greater process efficiency and billing accuracy grow, operators are increasingly turning to the more sophisticated solutions and these types of devices are gaining in market share.

“The electromagnetic principle essentially is you put two magnets on the outside of a pipeline, thereby magnetising the water in the pipeline as it is flowing,” den Hollander explains.

“As the water is conductive it creates a small current and from there you can calculate the flow. It will only work if the medium in the pipeline is electrically conductive so it will only work with water or water-based solutions. For water applications you can use either ultrasonic or electromagnetic flow meters, but in the oil industry as oil is not conductive you can only use ultrasonic devices.”

Enhanced functionality

Equipment producers are constantly working to improve the design and usability of flow meters, in part to keep ahead of the lower priced imitations coming out of countries such as China.

At present, there is a trend within the industry towards adding enhanced functionality, so that the next generation meters provide more than one measurement.

“The vortex meter is a new design and the thing that is unique is it includes pressure and temperature in one flow meter. In this case it is a really multi-variable flow meter: it measures flow by the vortex principle but also pressure and temperature.

The other ones just measure flow and we would have to add an additional pressure and temperature sensors,” den Hollander says.

The advantages of integrated metering are clear, such as reduced capital outlay and installation costs. Furthermore, simultaneous temperature and mass flow monitoring can help to improve the energy efficiency of a facility or process.

“Customers are interested in developments that improve reliability,” states Dunphy. “The less they have interact with these devices the more interested they are in finding new advances, so improving reliability by combining multiple measurements in one device and by making it easier to extract the information through advanced communication or advanced diagnostics are areas that customers are finding very valuable.”

Measurements taken by flow meters are displayed on LCD panels on the front of the units, but the information is also fed automatically into the main control room so that operators can access the readings easily.

The way the data is relayed back to the control room is another area where huge technological improvements are currently being seen, namely through the advent of wireless communication techniques.

“Should we go wireless is now a question for everybody and a thing most firms are looking into,” comments den Hollander. “This technology is available but not many customers use it yet.

The discussion today is about if I have a plant do I want to communicate my instruments over a wired link? If you wire it up someone has to come in and run wires or I do it wirelessly and save on wiring costs. I think it is going to be the topic for the near future.”

Emerson’s Dunphy, however, harbours no doubts that wireless is where the flow meter market and the process industry in general should be headed.

“We are leading the industry in the introduction of practical wireless solutions, while lots of folks are talking about the appeal and theory of how we can use these, Emerson already has these devices available today,” he says.

“It is absolutely something new, but I wouldn’t say it is slow to catch on, I would say people were being deliberate in their considerations and they are easily finding small applications where they can try the technology and understand how it works and confirm that it is not just hype and that the equipment actually works.

Once they have reached that level of understanding, we are finding that they are expanding the applications very rapidly. But we are very much in that first phase of finding small applications and gaining experience with the technology and equipment.”

“In the case of flow meters and wireless we are still bringing power to the devices but then we are using the wireless communication capabilities to extract diagnostic information as an optional device, both integrated within the flow meter and as an add one,” he continues, adding: “Wireless is driven by how do I get more information out of these devices without having to spend a whole load more money running wires and things that aren’t practical?”

Indeed, it is practicalities that are the driving force behind research and development in the flow meter industry. End-users can expect to see continued improvements in diagnostics and accuracy as manufacturers compete to win customer loyalty.

This comes as good news in these times of soaring feedstock and operating costs when process efficiency is more vital than ever.