Danfoss has developed an aid/joint assembly, the 'Tapping Band', as an ultrasonic flowmeter solution that provides a highly accurate means of fixed installation of flowmeters on water or wastewater piping, especially where the pipe material does not allow the conventional welding of the flowmeter fittings.
Simple to install, the Danfoss Tapping Band is a flexible stainless steel band, modelled on a pipe repair clamp, which is installed around the pipe in two or more sections. Each section has a specially developed rubber mat bonded to the steel sheet. At the point of mounting of the transducer, the mat has extra concentric sealing rings, which provide total security and long-term stability to the band. The sections are coupled at rigid, high-strength joints, with a suitable number of evenly spaced torqued studs, which ensure optimal sealing over the full band surface and thus prevent failure due to stress concentration. An optional pressure tapping point can be fitted, and with the Danfoss pressure transmitter MBS33 provides multifunction flow metering for water distribution networks.
Clamping a small pressure plate secured with two cables/straps over each hole - as is commonly done - does not allow for optimum efficiency in pressure monitoring, as the cables concentrate stress at their contact lines and can create a 'cheese cutter' effect causing the pipe to fail around its circumference. In contrast, the Tapping Band forms an effective protection against future pipe failure.
The Tapping Band SONOFLO ultrasonic flowmeter is an accessory for 'non-welded' applications and was designed for use on cast iron or ductile iron pipes, concrete or fibreglass pipes and aging steel pipes where welding/drilling could cause premature failure. The SONOKIT Tapping Band can be mounted on empty pipes or hot tapped without process shutdown, and is available in sizes ranging from DN 80 to DN 4000.
"The SONOKIT system is not a modified repair clamp, but a complete flowmeter accessory," says John Alexander, Danfoss South Africa product manager - motion controls and flow. "The Tapping Band is fabricated in our manufacturing works to project specifications, after which the exact flowmeter geometry is measured and recorded. The geometry parameters are related to the final installation via the gaps between sections."
Tapping Bands have been used in many applications, previously considered otherwise difficult or impossible installations. This includes installation on old, brittle cast iron pipes where welding would cause cracking, including applications where the removal of existing clamps leaves holes in the pipe, which the Tapping Band effectively seals during installation of the ultrasonic flowmeter. In addition, Danfoss has successfully installed its SONOKIT system using hot tap tools at one of the largest copper mines in the world and in numerous water installations in Australasia.
The Danfoss Tapping Band is a professional solution that not only brings accuracy to flow and pressure monitoring in water and wastewater applications, but also opens up new opportunities, as it expands the possibilities for applying ultrasonic flowmeters to practically any location and pipeline style.
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