Syrup Concentration Monitor 971-C

The Syrup Concentration Monitor Model 971-C is designed to measure syrup viscosity in tanks or pipe lines and convert to a linear reading of percent dry substance. The instrument will 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.

The Model 971-C Monitor employs the same measuring probe as the 970-C which has long been used to measure massecuite consistency in vacuum pans but with a larger rotor; a 3" diameter stainless steel disc for the 50 to 75% range. The rotor, immersed in the syrup, is rotated by a small shunt type DC motor at approximately 1500 RPM and the viscous drag is measured by the 971-C as changes in armature current. This current is amplified and linearized 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 50 to 75% range it is about 0.25 Brix/^oC. However 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, automatic compensation for wide variations in temperature can be supplied in the form of a thermal element mounted in the syrup near the viscosity probe and electrically connected to the 971-C monitor.

Viscosity is a syrup property that has been little used industrially for determining their solids content, primarily because it is such a non-linear relationship. But in the 971-C, advantage is taken of a unique principle of the 970-C Monitor; 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 scale.

Viscosity has several advantages over conventional methods of measuring syrup concentration. It is scarcely affected by the presence of entrained air bubbles as compared to any device based on syrup density which require that material must be thoroughly de-aerated before measurement to eliminate excessive errors. This can create intolerable time lag in control circuits. Scale accumulation on nuclear gauging devices causes cumulative errors and maintenance is often required to keep them within acceptable limits. The high peripheral velocity of the 971-C rotor discourages scale accumulation and even so it has minimal effect.

The 971-C is only sensitive to a relatively thin syrup film in contact with the disc and so is not affected by the direction or velocity of flow past it. In stagnant syrups, its rotation provides considerable agitation to mix stratified streams such as appear 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. A refractive index measuring device is sensitive only to an extremely thin syrup film in contact with its prism and so requires high syrup velocity or mechanical assistance to keep an updated sample in the measuring zone.

For more details, please download our 971-C Installation Manual.