Linear dc drive dives deep

Oct. 1, 2008
Checking on the condition of a pipe weld is not an easy task, especially hundreds of meters deep in the ocean.

Checking on the condition of a pipe weld is not an easy task, especially hundreds of meters deep in the ocean. Specialized monitoring equipment is necessary to carry out such inspections and report results back to equipment owners and operators. One supplier in this field is Sonomatic Ltd., Warrington, England, a company that manufactures specialized, nondestructive scanners. The design includes a 200XLV low-voltage linear dc drive from Sprint Electric, West Sussex, UK, to improve the accuracy of their Nautilus scanner.

The Nautilus scanner is a diver-deployed, automated ultrasonic system that can operate in depths to 250 m. It's designed to adapt to an in-situ mineral or gas pipe junction to monitor the quality of a new weld, or the condition of an existing pipe. These pipe junctions can be on land, shipboard, or beneath the sea, but not surprisingly, the sub-sea applications present the most demanding technical conditions.

Sonomatic has developed technology to overcome the difficult task of adding a new pipe junction (or hot tap) to seabed pipelines. A habitat is constructed around the hot tap site, approximately the size of a transportation container. The habitat is filled with a mixture of helium and oxygen to allow divers to enter and work in a dry environment. With the Nautilus scanner fitted to the hot tap, Sonomatic technicians carry out inspection and analysis using the company's Microplus Digital Imaging System. Data is sent from the scanner to the technicians through a 250-m-long umbilical cable. The data allows accurate mapping and analysis of the condition of the new pipe junction’s weld.

Sonomatic chose Sprint Electric 200XLV linear drives to provide low-voltage dc control for the Nautilus’ axis motors. Typically, one motor would drive the circumferential axis to track around the pipe; the other would drive axially to move the scanner head in and out while rotating around the pipe.

The 200XLV was chosen because of its low noise signature. The low level electrical signals produced by the scanner make them very susceptible to electrical interference, especially when the signal cables are alongside power cables in the umbilical cable bundle. The 200XLV reduces the need for heavy filtering of the drive and motor cables over conventional PWM devices.

Sprint Electric’s drive is a miniature, fast response dc motor speed controller typically used for driving brushed dc motors, gearmotors, low inductance printed motors, and linear actuators rated up to 100 W. According to company sources, it's ideal for low power applications such as robotic control and antenna or security camera drives that rely on an unregulated dc or battery supply up to 48 V. Offering high bandwidth and a linear, noise-free output, the drive is suitable for control of linear actuators. Despite measuring just 40 mm wide, 82 mm high, and 50 mm deep, the 200XLV is a genuine four-quadrant drive that can motor and brake in both directions of rotation to offer excellent control of motor speed and torque.

Visit Sprint Electric for more information.

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