Instrumentation for the Sugar Industry

Syrup Concentration Monitor 971-C

Syrup from an evaporator body tends to be stratified as it flows to the outlet pipe, so it is better to have the probe in the line just below the body so that the heavy and light streams will be mixed and averaged by the spinning rotor. Even though outflow is stopped entirely, the heavier syrup streams will settle to the rotor area and show the increasing concentration so that feed and withdrawal can be increased before the syrup rises excessively. Shut-off and bypass valves are recommended in the event that the probe must be withdrawn for examination or maintenance without interrupting evaporator operation. This is illustrated in the leftmost diagram.

Typical in-line chamber installation is shown in the center. These installations are suitable for lines carrying small or moderate syrup flow.

Syrup tanks and melters are generally open vessels so a variety of probe mounting arrangements are possible, as shown in the rightmost diagram.

Installation & Instruction Manual

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FEATURES

The Model 971-C uses the same measuring probe as our Model 970-C Sugar Consistency Monitor. A small shunt-type DC motor rotates the 971-C's larger 3" rotor at approximately 1500RPM. The 971-C measures viscous drag from changes in armature current, then amplifies and linearizes the current to actuate the indicating meter and the transmitter output signal.

Temperature has quite an effect on most syrup properties and viscosity is no exception. In the 45% to 95% range, it is about 0.25 Brix/oC. In factory processing operations, temperatures are generally quite constant and infrequent manual adjustment by means of a calibrated dial on the monitor is adequate. However, the 971-C can optionally be supplied with automatic compensation for wide variations in temperature -- by means of a thermal element mounted in the syrup near the viscosity probe that connects electrically to the 971-C monitor.

Viscosity is a syrup property rarely used industrially for determining solids content, primarily because it is such a non-linear relationship. But the 971-C takes advantage of a unique principle -- the probe gives an output that varies as the logarithm of viscosity over a range in excess of 100 to 1. The 971-C extracts a second logarithmic function to produce the linear concentration scal.

Viscosity has several advantages over other methods of measuring syrup concentration. To eliminate excessive errors, density methods require that material is thoroughly de-aerated before measurement. This can create intolerable time lag in control circuits. By contrast, the Model 971-C is hardly affected by the presence of entrained air bubbles and the high peripheral velocity of its rotor discourages scale accumulation.

The 971-C is only sensitive to a relatively thin syrup film in contact with the disc and is not affected by the direction or velocity of flow past it. In stagnant syrups, its rotation provides considerable agitation to mix stratified streams as found in syrups leaving evaporator bodies. Thus, it can be installed directly under an evaporator body and provide good average readings even under very low flow conditions with minimum measurement lag.

Specifications

  • Wide dynamic range
  • Simple installation
  • Linear-isolated output
  • Stainless steel sensor
  • Designed for durability
  • High accuracy and reliability
  • Low maintenance
  • Field-serviceable
  • One-year limited warranty

Parts

Please refer to our parts list for part numbers and pricing.

Pricing

All prices in US Dollars and do not include applicable taxes, shipping, duties and customs fees. Prices guaranteed through 2020. Please contact us for quantity discount and reseller information.

Type Insertion Probe
Rotor Size 3 inches
Wetted Parts 316 Stainless Steel, High Temperature Plastic
Process Temperature 0-125C (32-250F)
Pressure 0-30 psia
Water Supply <0.5 gallons per hour at 10 psi above process
Mounting 2 inch NPT male
Wiring #22 AWG or larger, 2-conductor
Diameter 1.75 inches
Length 24 inches
Junction Box 6 inches x 6 inches x 6 inches

 

Sensor

Transmitter

Display 3.5 digit LCD (0-199.9 scale)
Range 45%-95% Sugar by Weight (Brix)
Input Model 971-C Sensor
Output 4-20mA into 600 ohms max. isolated; other outputs available
Resolution 0.2% of Full Scale
Repeatability 1.0% of Full Scale
Accuracy 2% of Reading
Ambient Temperature 0-50C (32-120F)
Enclosure NEMA 1 (standard) or NEMA 4X (optional)
Dimensions NEMA1: 11 inches wide x 6 inches high x 4 inches deep NEMA4X: 11.875 inches wide x 7.25 inches high x 6.75 inches deep
Mounting Panel or wall mount (NEMA 1) Wall or pipe mount (NEMA 4X)
Power 115 or 230 VAC @ 50/60 Hz, 25 Watts
Shipping Weight (complete unit) 20-25 pounds, depending on options

The Model 971-C Syrup Concentration Monitor measures syrup concentration up to 95% in tanks or pipelines. The instrument operates under pressure or vacuum and is unaffected by direction or velocity of syrup flow. The probe can be installed directly in equipment at a favorable point to minimize measurement lag, improve control of concentration and eliminate troublesome sample withdrawal problems.

Typical Sensor Mounting

The probe rotor must be completely immersed in syrup at a point where concentration changes will be quickly sensed. For inline installation, a minimum pipe or chamber size of 4" is required since the rotor disk is 3" diameter. Horizontal mounting is preferred but the probe can be mounted with the drive motor above the rotor at any angle up to vertical. With the motor below the probe, the maximum angle should not exceed 75 degrees from horizontal or there is danger of purge water from the outer shaft bearing leaking into the motor ball bearings. Typical installation arrangements are shown in the image.