Wireless sensor can detect abnormal vibrations offshore

Oil & Gas Engineer - Communications

Source: www.engineerlive.com

Abnormal vibrations can be among the first signs that a machine is about to break down. However, monitoring them can be a tricky procedure, especially in offshore situations. Help is now at hand in the form of a new sensor that is being developed as part of the Vivib research project based at Sintef’s head office in Trondheim, Norway. Sintef is the largest independent research organisation in Scandinavia and every year supports the development of over 2000 home and overseas companies via its R&D activities. It has approximately 1900 employees, 1300 of which are located in Trondheim and 450 in Oslo. The rest work at offices in Bergen, Stavanger and Alesund, in addition to offices in Houston, Skopje, Warsaw, Cracow (Poland), and a laboratory in Hirtshals, Denmark.

For its part, the Vivib project is being carried out as part of a collaboration with ABB and SKF. It’s an interesting tie-up, with ABB being a pioneer in machine condition analysis technology and now having over 40 years of condition assessment experience already. Today the company offers a wide range of products and solutions to monitor vibration and assess the condition of rotating machinery. Starting with measurement of vibration data up to diagnostic expert systems, ABB has the solution to fulfil condition assessment requirements allowing cost effective planning of maintenance needs.

The SKF Group is one of the leading global supplier of products, solutions and services in the area comprising rolling bearings, seals, mechatronics, services and lubrication systems. The group’s service offer also includes technical support, maintenance services, condition monitoring and training.

The new sensor under development is capable of registering abnormal vibration patterns in machinery on board offshore platforms.

nitially the sensor is intended to be used on offshore platform machinery, and will be installed as a package comprising battery, antenna and circuit board.“Together, these components will give us a sensor node that can communicate wirelessly with other sensor nodes and with a central unit. This makes it possible to remain onshore and follow up individual machines hundreds of kilometres offshore,” explains Maaike Taklo, who works at Sintefs MiNaLab.“At present, oil companies are forced to send personnel out to the platform to test machines one at a time, unless fixed sensors have been cabled up,” he added.

Microsystem technology

The sensor nodes need to be cost-effective, so it is an advantage to make use of microsystem technology that tends to make mass production advantageous. The scientists are working on silicon wafers on which a large number of sensor chips are added simultaneously, one layer at a time. Instead of laying a ‘cover’ on each individual chip, a glass disc is attached to the upper and lower surfaces of all the chips at the same time, before the disc is cut into individual chips.

The sensors and the wireless communication unit have been tested, and the results are very promising.

“If the balls in a ball bearing are faulty, they generate a high-frequency ringing noise, while machines produce a low-frequency thumping sound with other types of wear. The new sensor is capable of measuring both types of sound simultaneously,” says Taklo. The Vivib project is financially supported by the Research Council of Norway through its PETROMAKS Programme, which is aimed at the petroleum industry. Sintef is responsible for supplying the sensor chips, while ABB and SKF are responsible for the wireless communication system and the interpretation of the vibration signals. The project started in 2006 and continues until the end of 2008. Several oil companies, including BP, are members of the consortium that is helping to finance the project.

Further details about the new sensor were due to be released by Taklo during his Vibration sensor for wireless condition monitoring talk at the Pan Pacific Microelectronics Symposium, at the Sheraton Kauai resort in Kauai, Hawaii, in January. Sintef’s other activities have focused on sensors for high-temperature applications and sensors for mechanically harsh environments. Such sensors are needed in oil wells, engines and for industrial production monitoring. The organisation’s silicon micromachined sensors have advantages in such applications due to their long-term stability and small size. In particular, Sintef’s expertise is based on:

1. Long experience in integrated design of package and silicon sensor. This in turn minimises the environmental influence on the sensing element.

2. Strong expertise on application-specific integrated circuits (ASICs) for high-temperature applications (HT-ASICs).

3. Fusion bonding processes that create very durable and strong seals between silicon layers. The result is sensors that can withstand both mechanically harsh conditions and high temperatures.

4. Experience in packaging of sensors for high temperature applications.

5. Close collaboration with the company PreSens on development and production of silicon high-pressure sensors.

6. Successful design and manufacturing of a complete measuring system for oil well monitoring.

7. Successful development of high-temperature piezoresistive pressure sensors based on Silicon on Insulator (SOI) technology.

8. Room-temperature deposition of protection nitrides.

nother recent development is a silicon pressure sensor that operates at high temperatures (200°C) and is designed and packaged to withstand rough mechanical conditions. The sensor is a part of a large oil well monitoring system developed by a collaboration of Sintef departments and has already been successfully tested by the customer Maritime Well Services.