Maintain instrument accuracy and increase longevity

The intended purpose is a primary factor since this defines the required accuracy. We distinguish three types of application: fee, trade, or custody transfer, which typically require certified accuracy between 0.125 to 0.25%; process management or control, where +/- 0.25 to 0.5% is usually acceptable; and process monitoring, where +/- 3% may be all that’s required.

Other important considerations include the mass of material being handled and the speed of the belt. A heavy-duty belt scale is needed for higher throughput while a lighter duty model may be sufficient, and cheaper, if flow rates allow. Regarding belt speed, faster speeds are more demanding, with more idlers required to ensure an accurate reading, all other factors being equal.

• Belt conveyor scales

The key components of a belt scale are the weigh or scale carriage, the speed sensor, and the integrator.  The weigh carriage holds load cells that deflect in response to the mass of material travelling over the idlers. The speed sensor measures belt speed. The signals from both devices are fed to the integrator, typically via a digitizer, a signal conversion device. The integrator or mass totalizer then performs the required maths, producing an accurate reading of total mass and  mass flow rate.

Many of our customers buy complete belt scale systems, and we endorse that approach, but we happily supply individual components because there are instances when this is helpful. For example, speed sensors, a relatively inexpensive part of the system, are often the first element to need replacement and keeping a spare on hand is commonplace. Digitizers and integrators on the other hand are routinely the focus of more substantial upgrades as new functionality becomes available.

• Belt conveyor scales

Yes, it is, for belt scales, and in the near future we expect it to be covering all applications including those requiring traceable, trade certification. The launch of Ramsey Flex is a good illustration of how evolving digitizer and integrator technology can prompt an upgrade, with no need to change other elements of the belt scale. It offers superior robustness, ease-of-use, and state-of-the-art connectivity, for customers looking to enhance performance. Crucially, all communication protocols are available out-of-the-box, including MODBUS RTU, MODBUS TCP, Ethernet I/P, and PROFINET; PROFIBUS is also an option. This makes upgrading relatively straight forward.

This is a difficult question because the answer depends on, for instance, the quality of what you buy, the materials being handled and maintenance practice.  However, ‘decades’ is a reasonable expectation which highlights the crucial point that these systems are a long-term investment. Obviously, upfront costs are critical but ease-of-operation, long-term reliability and supplier longevity and reputation deserve serious consideration. You will have to use and maintain this system, day in day out for a long time. It makes sense to think hard about possible weaknesses and the support you’ll be able to access should you need it.

It’s realistic to complete installation in a routine planned shutdown, over no more than a few days. You’ll need to empty the conveyor and lift it, to install the belt scale underneath. With some systems it may then be as simple as drilling a couple of mounting bolt holes but with a bigger, larger footprint scale more may be required. Access can be an issue and should be considered when deciding on a location. Aim for a flat section of the belt with no curves, away from addition or take-off points, whenever possible.

Belt scales should be relatively low maintenance and good housekeeping will go a long way to keeping them running well. Keep the belt scale and surrounding area clean and ensure that moving parts have some protection from dirt and/or falling debris. The other routine aspect of essential maintenance is to carry out zero and span calibrations. Good record keeping is worthwhile when carrying out such activities since it can make it easier to spot problems such as belt misalignment and long-term measurement errors.  

Every conveyor needs a safety pull switch for activation in the event of an emergency. It can play a critical role in protecting personnel and plant and must be 100% reliable even though it may go years without use. Here, you need something heavy duty - a truly rugged solution, engineered to sit in the process environment for years with no deterioration, even in harsh conditions.

Belt misalignment switches can be helpful in detecting a problem before belt damage occurs, typically giving the operator ample warning for remedial attention. Belt speed switches are similarly helpful in maintaining optimal performance. Choose between mechanically coupled or proximity, non-contact sensors, depending on your requirements but be mindful of selecting the correct sensor for best performance at low speeds since these present a greater monitoring challenge. Reliability and robustness may not be quite as critical for these types of switches but are still the primary factors when it comes to a choice. Look for well-engineered solutions with a track record of longevity to protect valuable assets and minimize downtime.

Nucleonic density gauges are the gold standard for measuring liquid density and the solids loading of slurries, though the need for a radiation source is undoubtedly a drawback. Set against this is the ability to generate high quality readings for the widest possible range of applications with no process flow contact. Nucleonic devices are easily installed, with no process shutdown, on the outside of pipes making them particularly valuable for abrasive and corrosive applications.