Weighing Screw Conveyor

The dust-tight weighing solution

We work with you to optimise the operation of your plant and the measurement of your bulk products

Place your request for a quotation now and we will be pleased to give you individual advice on your weighing screw conveyor application.
Wiegeschnecke Förderschnecke Rohrschnecke Trogschnecke Durchflussmessung Umrüstung

Immediate advice: +49 (0) 29 61 – 96 56 86

Ruhrkohle AG
Solvay GmbH

The added value to you

L

Expandable

Retrofitting of existing screw conveyor
U

Precise

Modern, high-precision load cells and electronic
N

Safe

Advantage of dust-tightness
9

Fast

High speed electronic with excellent resolution for high tare weight

Why is the weighing screw conveyor the right choice for my plant?

Wiegeschnecke Dosierschnecke Praxisbeispiel

With the benefit of our many years of experience we help you to select the right equipment for your system.

Place your request for an offer now and we will be pleased to help you:

+49 (0) 29 61 – 96 56 86

You are probably familiar with the following situation:

You need continuous flow measurement and would like to use existing equipment

Your product can (only) be conveyed by screw conveyors and requires a closed system.

You do not have sufficient structural height to install other solid flow measure systems like impact meter or intakes scales.

The ideal solution:

Screw conveyors are closed, dust-tight systems, which transport even difficult products reliably.

A weighing screw conveyor measures the actual material flow and the absolute during the material is conveyed.

A weighing screw conveyor can be retrofitted for many existing types of screws. Alternative we can supply the complete system consisting of screw conveyor and weighing equipment.

Upon request, we will gladly send you a series of information about our products, starting with the access to our data sheets.

How does the weighing screw conveyor work?

The screw is supported on the drive side in a maintenance-free flexure. The material is fed in symmetrically to this swivel joint; therefore, the impulse forces generated by the material feeding have only a very slight effect on the weigher. On the output side a precision tension load cell ensures that the load is weighed exactly.

The electronic unit standardises the load cell weight signal and links it to the rotation speed, which is measured by a maintenance-free, incremental rotary encoder. The product of rotation speed and net weight thus corresponds to the flow rate in kg or t per hour.

It is important that the screw conveyor is completely uncoupled from the input and the output side.  For this reason the weighing screw conveyor must be feed via a rotary valve or a second screw.

To prevent that the product is „thrown over“, the screw should be filled to a defined degree only. Furthermore, the screw volume (length and cross-section of the screw) must remain in sensible relationship with the tare-weight. A longer screw is frequently required for low product densities and low flow rates.

On request, we supply the complete weighing screw or alternatively only the weighing technology components to retrofit existing screws.

Technical data
Grain size range:
0 – 40 mm

Product density range:
200 – 4000 kg/m³

Sensor:
C3 / Stainless Steel

Supply:
5 – 15 VDC

Sensor protection class:
IP68

System accuracy:
typically 2 – 4%

Repeatability:
+/- 2%

Electronics
Display:
Colour graphic display, kg/h or t/h,
kg absolute or t absolute

Supply:
110 – 240 VAC / 12 – 30 VDC

Input:
Full Bridge Strain Gauge Sensors / inputs for tare and start batch, etc.

Output:
Counting pulses (kg/t)

Optional:
4-20 mA / RS232/485 / Profibus DP /
Profinet / Modbus / Batching contact / etc.

Enclosure:
Stainless steel

Type of protection:
IP67

Type of mounting:
Wall- or Panel mounting

Working temperature Range:
-10°C to +40°C

Frequently asked questions

What levels of accuracy can be obtained with weighing screw conveyors?
The typical measurement error for a weighing screw conveyor lies between 3% and 5%.
How can the accuracy of a weighing screw conveyor be improved?
The accuracy of a weighing screw conveyor depends on many factors. Firstly, the weight of the product in the screw must be in a sensible ratio to the weight of the screw conveyor itself. Moreover, inlet and outlet must be mechanically de-coupled by flexible compensators. Suction connections, as well as the positive or negative pressure require ventilation, since otherwise tensile or compressive force shunts can build up.

The filling degree of the screw must not exceed 40%, depending on the product and the screw rotation speed. For automatic calibration, in many applications we place a weighing container in front of the screw intake to regularly check and correct the tare load of the screw conveyor.

What measuring ranges can be covered?

Depending on the product and the screw length, mass throughputs of 10 t/h up to 500 t/h can be recorded.

For what applications are screw weighers used?
Regulation of material flows, process control, continuous dosing
What interfaces are possible and what data is transmitted?
All state of the art interfaces, such as Profibus, Profinet, analogue outputs, impulse signals, Ethernet, serial RS232/485, etc. are available. Depending on the interface, the flow (kg/h or t/h), transported quantity (kg or t), meter readings, time and date, reference values, state and status of the measurement system are transmitted.
What are the limitations of the system?
A screw weigher becomes too inaccurate for very small mass flows significantly below 300 kg/h. In addition, the measurement principle is not suitable for precision batch dosing.
Is calibration of the system necessary?
It is difficult to calibrate a screw weigher mathematically. Therefore, comparison with a known quantity must always be carried out.

We are delighted to offer personal assistance with your planning
Uncomplicated, individual and practice-oriented