Straight down the tubes

05 July 2008

At first glance, it’s not very impressive. It looks like a section of pipe with a transmitter attached to it. But this is no ordinary section of pipe, as you would soon find out when you discover you can’t lift even one end of it. It weighs 440 kg!

Dr. Yousif Hussain
Dr. Yousif Hussain

It is in fact a very precise mass flowmeter, capable of measuring high pressure oil and gas passing through it at a rate of 10 m/sec—that’s up to 2,300,000 kg per hour—at accuracies of one-tenth of one per cent. But it also handles low flow rates well, which prevents the buildup of static in hydrocarbons. It’s good enough to be used in custody transfer operations, which is considered the pinnacle of success for a flowmeter.

Krohne’s new Optimass 2000 is a straight-tube Coriolis meter built for large diameter applications in the oil and gas industry: 100, 150, and 250mm. One larger size, a 300mm, may be added to the series. But it probably won’t get any bigger than this, says Dr. Yousif Hussain, technical director at Krohne’s Wellingborough, UK facility, where the Coriolis meters are designed and manufactured. The amount of energy needed to excite the drivers for these large meters is a limiting factor he says, especially for the hazardous areas where most of the instruments are used.

There are several reasons why industry will pay large sums of money to buy these meters. First, they are highly accurate and repeatable (to within ±0.05%). They can withstand tremendous process pressures, up to 150 bar, and the outer cylinder has a burst pressure rating in excess of 100 bar. The oil and gas industry is always nervous about spilling their products, so this is reassuring. They can be installed in tight areas, such as metering skids, because unlike other flowmeters they take up less space and don’t require straight runs of pipe before and after the flowmeter.

All wetted parts are manufactured from NACE compliant duplex Stainless Steel and the meter is supplied with standard flanges up to 1500 pounds (12 inch).

And finally, the straight tube design keeps the pressure drop low and makes draining and cleaning a lot easier.

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