MRS Monorail Scale

How the MRS is built: two load cells, one weigh rail

In the MRS, a short length of the carcass rail is separated from the rest of the line and turned into a weigh rail. This piece is not fixed directly to the supporting structure but hangs from it through two flat-beam load cells. When the trolley rolls onto the weigh rail, carcass, hook and trolley together load the two cells, each taking part of the weight; the indicator adds the two signals together and shows the result as a single figure.

Thanks to its flat body, a flat-beam load cell fits into the narrow gap between rail and support and senses the force from the hanging load directly. With two cells, the total load is measured wherever the trolley stops along the weigh rail. The carcass therefore does not need to stop exactly in the middle of the weighing section; as long as the trolley stays within it, the reading is correct.

A 24-bit converter in the indicator turns the faint signal from the load cells into a digital value. Even a carcass swinging gently on its hook is read in small, steady steps once the swing dies down.

Fitting your existing line

Rather than calling for a new line, the MRS is built to join a monorail system that is already running. The weigh rail is made to the same section as the rail on your line, and the joints are kept level with the existing rail so the trolley does not catch as it enters or leaves. Installed at the end of the line, the last point before carcasses go to chilling, cutting or dispatch, it records the finished weight of every carcass in one place.

Two frame materials are available. In slaughter halls with frequent pressure washing and constant contact with blood and cleaning chemicals, stainless steel needs less maintenance over the long run. In drier or partly dry areas, where the supporting structure gets less wet, hot-dip galvanising is an economical solution that protects the steel against corrosion with a thick zinc layer. When deciding, look at how close the weighing point is to the wash-down area and which cleaning products the plant uses.

Tare: taking hook and trolley out of the reading

In overhead rail weighing, the load reaching the indicator is not just the carcass; the hook and trolley carrying it also bear on the load cells. The MRS indicator deducts this weight as tare. Tare can be taken automatically while an empty hook sits on the weigh rail, or keyed in by hand for a hook-and-trolley set of known weight.

A simple example: say the hook and trolley together weigh 5 kg. For a load reading 285 kg on the weigh rail, the carcass itself weighs 285 − 5 = 280 kg. Once tare is entered, this subtraction happens automatically at every weighing and the display shows 280 kg directly. If different types of hook are used on the line, the weight of each type should be established once and written down, and the correct tare selected when weighing; otherwise the difference between hooks goes straight into the carcass weight.

At switch-on, the indicator sets its zero point automatically. If fat or blood builds up on the weigh rail during the day, manual zeroing corrects the starting value again.

Indicator, battery and data transfer

For the MRS you can choose a weight indicator with either an LCD or an LED display. Choose a bright LED display if the operator has to read the figure from a few metres away along the line, and an LCD where power consumption matters.

The indicator runs for about 100 hours on its built-in rechargeable battery. In a slaughterhouse working one 8-hour shift a day, for instance, that equals 100 ÷ 8 = 12.5 working days; even with 12-hour shifts in busy periods such as the run-up to the festival, it covers 100 ÷ 12 ≈ 8 working days without charging. When the line stands still, the indicator saves power and eventually switches off, so the battery is not wasted. Battery operation also reduces the need to run mains cables into a wet slaughter hall.

Weights can be sent over RS 232 to a computer, a printer or a label printer. The wireless communication option helps where cabling across the slaughter hall is difficult, or where data is to be collected on a computer in the office. The unit can be switched from kilograms to pounds when needed, which is handy for shipments to buyers who work in pounds.

The first days after installation

A few checks in the first days after the MRS is fitted lay the groundwork for reliable weighing in the months ahead:

• Suspend a test load whose weight is known from the weigh rail and compare the display reading, repeating the check with the trolley at the start, middle and end of the section.
• Watch whether the trolley jolts as it enters and leaves the weigh rail; if it does, readjust the joint levels.
• Establish the tare of each hook type in use and show operators which tare to select and when.
• Check that the indicator and cable entries stay protected from water during washing.