This weighing approach is cost effective and quick to install, causes a minimum of production down time and is ideal as a retrofitted system. The BOSS bolt-on sensor is a well-proven robust product consisting of a strain-gauged element encased in a protective housing.  It is simply bolted to a structural member of the silo and deflects under the changing weight conditions, to give a varying electrical output relative to the load.

Bob Davies, general manager at Applied Measurements comments “with more than 25 years experience of bolt-on sensors, we assess the suitability of this method of measurement for each individual enquiry, including an on-site survey if required. This ensures the feasibility of a successful installation at the outset and we will commit to the accuracy likely to be achievable”.  The very first consideration is the available stress for the sensor to measure and this is broadly dependent on the load applied and the design of the supporting structure it is mounted on.

Bolt-on systems are more than adequate for the majority of vessel weighing or level monitoring systems, where accuracy in the order of 1% – 2% is acceptable.  We bolt the standard transducers to a suitable supporting member such as a leg, girder, channel or pipe.  However in some applications custom profiled mounting blocks may be required to suit the profile of the supporting steelwork.

For a system to be viable the load to be measured should be between 3000psi and 10,000psi.  The accuracy achieved depends on a number of factors, but most significantly the amount of available strain to be measured.

Each BOSS sensor has an average sensitivity of 1.7mV/V for 10,000PSI.

As a general rule, sensors mounted internally will give the best results. With external systems there will often be a margin of error due to zero shift, which is a result of differential expansion due to solar radiation but even this can be nullified to an extent.  The accuracy achieved will be very dependent on the positioning of the sensor on the steelwork.

Accuracy Bands

• 3,000 – 5,000     PSI     gives +/- 2 to 3% or better
• 5,000 – 7,500     PSI     gives +/- 1 to 2% or better
• 7,500 – 10,000   PSI     gives +/- 1%

Typical Application

A 220T cement silo on a 6-leg pipe section frame, giving 6000PSI total available signal.  Our customer required best accuracy for batching to supply ships and road tankers. As the available signal was good but not exceptional, we suggested 2x BOSS bolt-on sensors per leg to minimise errors and maximise accuracy.  The result is that the customer can batch to ships +/- 1Tonne in 100T and +/-0.5Tonne in 30T.  To minimise the effect of temperature, each Bolt-on sensor is fully insulated after installation

Suitable instrumentation to accompany the bolt-on sensors includes: mains or battery-operated digital displays, local amplifiers allowing the signals to be monitored in a control room or a telemetry system for wireless monitoring via a remote hand-held receiver or a control room PC system.

For more information on the range of BOSS sensors please visit our bolt-on load cells page, or call us on 0118 981 7339 or email: info@appmeas.co.uk

The sensors are designed to be attached directly to steel structures and are capable of detecting tensile, compressive and bending stresses.

Utilizing the latest strain gauge technology, each sensor is manufactured from specifically selected high grade alloy steel with thermal coefficients of expansion matched to structural steel.  Unlike some competitive units each sensor is temperature cycled and compensated to minimize the effects of temperature variation.

For installation, each unit is supplied with a template to which the two threaded mounting blocks are attached using high tensile bolts.  The mounting blocks are welded in position and the bolt-on sensor then attached in place of the template.

The sensors are fully encapsulated to ensure complete protection from all but the very harshest of environments.

Click here to visit our main Bolt-On Sensing page

The output signal from the weighing platform is fed into a digital display, which has two set point relays.  Connected to the digital there is also a touch screen display, this enables the operator to see the live reading, the batch reading, the total batches and a numeric keypad to input the individual batch size.  The touch screen controls the set point relays in the digital display.

Also built into the control panel were two further digital indicators connected to PT100 temperature probes monitoring two mixing vessels.  The complete batch weighing system was set up to let the batching control proceed, however if one of the mixing vessels temperatures went out of range the relays of the digital indicators would cut the pumps to the main mixing vessel.  The operator at a glance can see his two temperature readings, his live weight on the platform and has full control of his batching.

The total flexibility of the touch screen technology means that AML could program the batch weighing system to suit the customer’s requirements, including showing the customer’s name and logo on screen.  The use of the touch screen technology enables AML to offer a very cost effective flexible process control system for a diverse range of applications.

Specifically designed for the measurement of cable tension and under hook crane and lifting gear weighing, the complete ET Telemetry Lift Link system consists of a robust telemetry load cell with an internal data transmitter with a range of 200 metres, together with a portable handheld receiver instrument, displaying the weight digitally.

The ET telemetry load cell is available in ten different ranges from 0-1 to 0-500 tonnes and offers excellent performance with a repeatability of <0.05% of rated output.  It has been designed for use with standard lifting shackles and is sealed to IP66 for waterproofing to withstand arduous outside conditions.

The ET lift link telemetry load cell’s weight and height have been kept to a minimum, thereby reducing the overall headroom required for the installed system.  The portable instrument receives the load cell transmitted signal at typically 420MHz and displays the weigh value on the 8 character 14 segment LCD display, over the range of -4999 to 65000.  Features on the unit include a ‘hold’ control for display storage, and a ‘tare’ control for automatic zeroing of the load signal.  It operates on a 9V PP3 supply, with auto power down to conserve battery life.