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Protecting Precious Pumps

Flow Switch Can Reduce Pump Maintenance and Extend Life

04.07.2007 | Editor: Dr. Jörg Kempf

With the FLT, a single switch monitors both key variables necessary to protect pumps, measuring liquid flow and temperature simultaneously with high accuracy and reliability.
With the FLT, a single switch monitors both key variables necessary to protect pumps, measuring liquid flow and temperature simultaneously with high accuracy and reliability.

Almost everybody in the chemical industry is talking about reducing maintenance costs. Liquid flow switches and air/gas flow switches for industrial process measurement and automation are helpful in pump protection.

Process and plant engineers may tire of repairing or replacing pumps because unpredictable liquid or slurry flows in their pipelines cause pumps to overheat and fail. In such cases a new pump protection flow switch improves process control by adding an extra margin of safety. The device keeps pumps running longer, more reliably and with less-frequent maintenance, so reducing total operating costs.

The Flow/Level/Temperature (FLT) Pump Protection Flow Switch from Fluid Components International reliably monitors the flow and temperature of liquids, gases, slurries, syrups, lubricants, coolants and more. According to the supplier it is ideal for wet/dry detection in pump systems, where sudden, unexpected reductions in flowrate may leave pumps vulnerable to overheating. This in turn can result in bearing or seal damage that may require major repairs, or shortens the useful life of these components.

The new flow switch, with its no-moving-parts design, offers a highly robust scheme for pump protection thanks to its dual alarm capability. On the first alarm level, the switch will detect a low-flow situation at a fluid velocity that can be pre-set in the range 0.003–0.9 m/s. This low-flow alarm can be regarded as a pre-warning signal for the control system or operator. The system or operator can then decide to keep the pump running or to shut it down.

If a second-level alarm occurs because the feed line to the pump is running dry, this condition would be an emergency signal to shut down the pump immediately because the bearings now see gas instead of a liquid as their heat transfer medium. In such situations, the temperature of the bearings may rise very fast. Using a flow switch prevents permanent damage to the pump’s bearings that will require an overhaul of the pump before more damage occurs.

A dual-function instrument

The FLT flow switch is a dual-function instrument that indicates both flow and temperature, and/or level sensing in a single device. It can be specified in either insertion or in-line styles for pipe or tube installation. With the FLT, a single switch monitors both key variables necessary to protect pumps, measuring liquid flow and temperature simultaneously with high accuracy and reliability. Dual 6 A relay outputs are standard and are assignable to flow, level or temperature.

The FLT features a wide setpoint range, which varies according to the service medium (liquid, gas or foam). It is hydrostatically proof pressure tested to 240 bar g at 21 °C. De-rated with temperature, the highest operating pressure recommended at 260 °C is 162 bar g. Higher ratings are available with special construction and test certification. Agency approvals include: FM, Atex, CSA, CRN and CE.

Versatile and highly dependable, the FLT provides precise, rapid flow or level control in liquids or slurries, as well as temperature measurement. The device is ideal for applications in many demanding process industries, including chemical processing, food/beverage, mining/milling, oil/gas, pulp/paper, pharmaceutical, water and wastewater treatment.

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