14 FLEXIM GmbH
Non-Invasive Flow Measurement of Process Gas Using Clamp-On Ultrasonic Technology
In the chemical industry, where aggressive and hazardous media are often used, experts are happy to resort to clamp-on technology for flow measurement. Long established as a standard method for measuring liquid flow, the non-invasive, acoustic method is also being used more and more to measure the flow of gases.
Among the various flow measurement techniques, clamp-on ultrasonic measurement has been an outsider technology for quite some time. Due to its practical benefits, it has now become a widely used standard measurement method. Nowadays, it is an outsider technology only in the technical sense, since the transducers are simply clamped onto the outside of the pipe and therefore measure from the safe side, as it were. As a result, they are not subjected to wear and tear by the medium flowing in the pipe, they do not cause any pressure loss whatsoever nor any risk of leakage.
Due to its practical benefits, non-invasive, ultrasonic technology has long been well established amongst the common measurement methods. The development of the gaseous state of aggregation is relatively recent. An application example from Poland illustrates the characteristic features of the method as an example.
On the safe side: clamp-on ultrasonic transducers measure flow from the outside of the pipe – ammonia gas in this instance.
use so-called Lamb wave transducers as their excitation frequency means the pipe wall resonance adds to the signal insertion. As a result, the measuring signal is irradiated optimally into the medium flowing in the pipe. Practical devices that damp the ambient noise and sophisticated algorithms that filter useful and pipe wall signals into the measurement transmitter do the rest.
Conclusive test measurement
Of course, before making any final decision to go with the acoustic measurement method, the open-minded process engineers of the refinery asked for reliable proof of its suitability, reliability and accuracy. “A successful test measurement was certainly a precondition”, reports Maksym Cichón. He was convincing from the word “go” with his portable ultrasonic FLUXUS®
G601
The explosion-proof FLUXUS®
G 800 measuring
transmitter reliably detects the flow of hydrogen gas flowing through the pipes.
FLEXIM's newest product development: the ATEX-certified FLUXUS® measurement in potentially explosive areas.
F/G608 for mobile, non-invasive flow
flowmeter. “We only needed a half hour to set up the measurement point and without any affect whatsoever on plant operation. After we attached the clamp-on transducers to the pipe, the measurement transmitter showed a strong and stable measurement signal. We left the measurement running for a few hours and the measured values were stored in the internal memory. We read them out afterward and handed them over to the customer so he could compare them with his data in the process control system”.
Advantage over vortex
Maksym Cichón, FLEXIM's flow expert and product manager at Introl sp. z o. o.
“The crucial advantage is the fact that the system can be installed without interrupting operation and without any pipework“, states Maksym Cichón, FLEXIM Product Manager at Introl sp. z o. o. The Katowice-based company offers solutions for process control and automation and has been FLEXIM's sales partner on the Polish market since 2010. Maksym Cichón reports on his first experiences with non- invasive measurement technology using the clamp-on, ultrasonic method and comments on enthusiastic users: “we received a request from a refinery to measure the hydrogen flow. Initially, we offered a vortex meter since we have had them in our product portfolio for many years. However, this solution has a serious drawback: the measuring instrument is installed in the pipeline resulting in pipework and, therefore, an
interruption to operation. Our work with FLEXIM began during the first phase of the project. The Berlin flow experts not only provide clamp-on solutions for liquids but are also leaders in the area of non-invasive, ultrasonic flow measurement of gases. We then offered a clamp-on, ultrasonic flowmeter instead of the vortex meter. This suggestion was met with great interest by refinery engineers.”
Demanding acoustics
Hydrogen is generally considered a complex medium. It is highly flammable, highly volatile and forms highly explosive mixtures on contact with the air. It is no wonder that experts are keen to avoid pipework involving extensive planning and safety measures. The low density of non-invasive flow measurement technology is something of a challenge. As a general rule, the higher the density, the easier and better the measurement. Since the density of gas also increases with rising pressure, the non-invasive measurement method works very well at high and extremely high operating pressures which are associated with high costs and a great deal of effort in many other processes.
“The pressure at the measuring point is approximately 29 bar”, reports Maksym Cichón. “One cubic meter of hydrogen only weighs about 2.5 kg at 29 bar”. This results in a low radiation level of the ultrasonic signals into the medium. A large proportion of the signals created by the sound transducers spreads to the pipe wall as ambient noise. For this reason, Maksym Cichón decided to
The measured values were also convincing. Introl was given the task of setting up the measurement point with a permanently installed FLUXUS®
G800. FLUXUS® G800 measurement transmitters are
explosion proof and certified for use in the potentially explosive area of Zone 1 (ATEX), as well as the transducers used. Due to the non-invasive solution, not only operation downtimes were avoided but also extensive planning and bureaucracy. The installation of a wetted measuring system would have required the time-consuming production of dimensional drawings and possibly drawn-out approval from the national technical supervisory board.
Maksym Cichón sums up: “It's always best when the user himself comes to the conclusion that the non-invasive solution is the best for him”. Following this successful installation, more measurement points were to be set up with FLEXIM's clamp-on ultrasonic technology, including for non-invasive flow measurement of heavy crude oil.
Flexibility in Ex areas
Maksym Cichón admits that his test measurement was not plain sailing without some paperwork. The portable FLUXUS®
G601 does not have any ATEX certification, just as little as all other portable
ultrasonic measuring systems. Since the revised version of explosion protection directives, there is no longer any portable ultrasonic flow measurement system that meets current ATEX standards. Since there is practically no alternative to non-invasive ultrasonic technology when it comes to a quick set- up of temporary flow measurement points, plant operators make do with special permits and gas warning devices
All the more reason for Maksym Cichón to welcome FLEXIM's latest product development. With the new FLUXUS®
are a thing of the past. In terms of technology, the FLUXUS® well-proven and versatile FLUXUS® use in potentially explosive areas.
Jörg Sacher, FLEXIM GmbH Flexible Industriemesstechnik GmbH Wolfener Straße 36 D-12681 Berlin
Tel: +49 (0) 30 / 93 66 76 60 Fax: +49 (0) 30 / 93 66 76 80
Jörg Sacher, FLEXIM GmbH AUGUST / SEPTEMBER 2013 •
WWW.PETRO-ONLINE.COM
F/G608, unsatisfactory solutions with increased administrative and personnel costs F/G608 is based on the platform of the
F/G601. It is just as flexible and easy to use and is certified for
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