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Doing more than flow

30 November 2008

To compensate for fluctuations in pressure, temperature, viscosity, and density, flowmeters are taking extra sensors on board.

Siemens’ FX 300 vortex flowmeter
Siemens’ FX 300 vortex flowmeter

When a paper mill in Canada needed a robust flowmeter with pressure and temperature capability to measure dirty methane gas being pumped from a biomass reactor, the instrumentation department selected a vortex flowmeter.

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PHOTO AT RIGHT: Siemens’ FX 300 vortex flowmeter maintains correct flow measurement even when the temperature, pressure, viscosity, and density fluctuates.

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Jeff Holt, the instrumentation superintendent at New Forest Paper Mills in Scarborough, Ontario, explained, ‘The gas is processed, the sulphur and other toxic elements are removed and it is pumped into a buffer tank.’

It’s a dirty job, but they get it done with Krohne’s Optiswirl 4070C, chosen especially because of its high turndown. ‘We needed a versatile flow meter to operate at rates of flow that can be as low as 50-60 cubic metres per minute (cmm) and as high as 600 cmm,’ says Mr. Holt. The 4070C is designed to measure accurately the operating flow, volumetric flow, and mass flow of both conductive and non-conductive materials, which can be liquids, gases or vapours. With its temperature and measurement capability, it can compensate for material fluctuations in these values.

Some of the gas is used to power boilers that make steam for pulp driers, and some is burned off as excess gas. The paper mill uses the vortex flowmeter to help it regulate the process and to measure the ‘carbon footprint.’

Krohne says its vortex flowmeter was the first on the market with integrated pressure and temperature measurement. It incorporates the company’s ISP (intelligent signal processing) technology which eliminates unwanted signal noise to deliver precise, stable measurement.

CATCHING THE COMBO IDEA

Siemens has recently launched its own ‘combination’ vortex flowmeter, the Sitrans FX300. It is equipped sensors to allow it to measure temperature, pressure, and flow of steam.

The new two-wire flowmeter is specially designed for applications requiring reliable flow measurement even when the pressure, temperature, viscosity and density of the process fluid changes—process irregularities that would have been made it impossible to get good measurements in the recent past.

The operating flow and temperature ranges are enormous: from -40° to 240°C In the case of steam and gas with flow rates of 2 to 80 meters/sec., the accuracy is 1.0 per cent, which is pretty good. In the case of liquids it gets slightly better: at rates between 0.4 and 10 meters/second, it is 0.75 per cent. The nominal diameter range is DN15 to DN300.

VARIABLE AREA FLOWMETERS

Swagelok is a familiar name in the controls industry, but not one that you would associate with flowmeters. Until now at least: the company, in fulfilling its role of being a complete supplier of fluid system components, has launched a series of variable area flowmeters (VAFs) with individually calibrated scales and 10:1 turndown ratios.

‘Our customers have asked us to provide more of the products they need, and VAFs seem to be a natural fit,’ says Swagelok’s Doug Nordstrom, analytical instrumentation market manager.

In fact, he’s going to give his customers 10 variations to choose from. Most are fitted with glass measuring tubes, which allow the operator to directly view the flow rate. For more difficult operating conditions where pressure or temperature is a factor, he’ll offer metal measuring tubes and mechanical or electronic displays. The beauty of variable area—this oldest of flowmeter designs—is that it has no moving parts to wear out.

‘Old shell, new core’ is how ABB describes it upgraded FAM540 all-metal VAF. The new core is, basically, a new display with improved readability and 4-key control which has been added because, as the ABB philosophy goes, instruments should be as easy to configure as state-of-the-art mobile telephones. ‘This allows the user to easily configure the instrument directly on site, often even without referring to the manual.’ We won’t say any more about this, we will just leave it there.

THE SMALLEST MAGMETER

ifm’s SM series may be the smallest magmeter on the market
ifm’s SM series may be the smallest magmeter on the market

Few flowmeter technologies range as much in size as electromagnetic flowmeters. These ‘magmeters’ were the first ‘electronic’ type of flowmeters and their sizes range from huge water pipes big enough to walk through, down to the almost miniature size. In fact, we think this SM Series Magmeter from ifm may be the smallest anybody ever made.

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PHOTO AT LEFT: ifm’s SM series may be the smallest magmeter on the market. It’s designed to measure flow in cooling water loops on machine tools.

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Why would somebody need such a small flowmeter? Ifm’s Lothar Zimmer explains that he’s aiming them at the machine tool market where they can be used, for instance, in measuring water in machine or welding cooling systems. It’s also good for pump protection, to guard welding equipment against the loss of cooling water.

The first one, shown at SPS/IPC/Drives last year measures up to 25 litres per minute; larger volumes will be introduced later.

He describes the tiny flowmeter, which is small enough to fit in the palm of your hand, as a ‘wellness’ sensor for cooling systems. ‘It gives enough information to diagnose simple problems, such as leaks or the condition of the pump,’ he says. It detects very small deviations from the specified volumetric flow, and monitors at the same time the temperature of the fluid, as a guarantee of process safety. The sensor sells for 300 to 400 euros.

The sensor offers high accuracy with a response time of less than 0.15 seconds and a repeatability of ±0.2%. It is amusing to see the sales brochure illustrate the Faraday principle to explain how the flowmeter works—this is something completely new to the machinery market, but it is a well known staple item in the process automation world.

GOING FOR LOW FLOW

Another recently released small magmeter is the EL 500 (the EL stands for extended linearity) from Flow Technology Inc (FTI) in Tempe, Arizona. Ranging in size from 3mm to 20mm, the meters are designed for low-flow applications—down to as low as 0.083 litres per minute.

This is accomplished, says FTI, with a ‘unique’ electromagnetic field profile ensuring accuracy not only in turbulent flow, but also during the transitional and laminar flow regimes. The measurement range is quite wide: 1000:1, without, they hasten to add, the aid of linearisation software.

Where you can put this little instrument is also unusual. Like most small flowmeters, the electronics can be attached directly to the meter. But if you need to put the flowmeter in an hard to reach place, the electronics can be detached and located separately. Without the electronics the flowmeter meets IP68 protection standards, which means it could be permanently submerged in water up to a depth of 1.5 metres, and this can optionally be extended to 10 metres.

THE LATEST IN CORIOLIS

Emerson is calling their new two-wire Micro Motion Coriolis meter ‘revolutionary.’ While the flowmeter itself hasn’t changed, the electronics have been adapted to work on much lower currents, and this positions the meter as a replacement for other loop-powered flowmeters that may have been used in plants. Emerson insists it has the same measurement accuracy, repeatability and operational savings as the four-wire versions, quoting ±0.10% liquid flow and ±0.0005 g/cm3 liquid density accuracy.

‘The introduction of Emerson’s two-wire Coriolis transmitter represents a significant milestone in the development of Micro Motion measurement technologies. We know that customers have been waiting for a breakthrough that would enable them to replace previous generation two-wire flow meters with highly accurate and reliable Coriolis meters—without incurring the costs of additional wiring and power,’ said Tom Moser, president, Micro Motion division of Emerson Process Management. ‘This new development expands the range of plant applications to adopt Coriolis technology.’

And while ABB is not one of the names that comes to mind in Coriolis, the company was making a big splash of its ‘latest generation’ double tube S-design CoriolisMaster at Hannover Fair 2008. Enhancements to signal processing technology gives the meter ‘a considerable increase in dynamics (up to 1:2000) and an improved zero stability.’ Density measurement is said to have its precision improved to one gram per litre, ‘even under changing environmental conditions.’

Another area of improvement is in the DensiMass software, which is capable of deriving concentrations, net oil portions in water-oil-mixtures or Brix values. ABB is especially proud of its simplified navigation, requiring only three keys, allowing you to control the device from the text display ‘without the need to read the operating instructions in detail.’

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PHOTO BELOW: ABB turned up at Hannover Fair 2008 with this improved CoriolisMaster.

ABB's improved CoriolisMaster
ABB's improved CoriolisMaster

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KROHNE’S MASSIVE STRAIGHT-TUBE CORIOLIS

A notable Coriolis event this year was Krohne’s introduction of its large straight tube Optimass 2000. The double-tube meter ranges in size up to 250mm in diameter and is capable of measuring 2.3 million kilograms per hour at accuracies of one-tenth of one per cent.

The meter was our cover story for the June issue; you can read about it here

********** SHORT TUTORIAL: DIFFERENTIAL PRESSURE FLOWMETERS **********

While electronic technologies are displacing traditional approaches to flow metering, differential pressure (DP) based devices continue to be among the top five most popular flowmeters.

This short tutorial outlines what DP meters are and how they work.

********** UPGRADING FLOWMETER STABILISES SLURRY FLOW ************

Replacing a magmeter with new advanced design helped eliminate erratic flow signals, resulting in improved control of catalyst slurry flow through a 75mm pipe.

You can read this application story here.


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