Modular skid systems are becoming increasingly popular in the process industries, as owner/operators, OEMs and plant engineers fabricate their unit operations as skids for greater efficiency and decreased site disruption. This post discusses level and flow instrumentation for batching and blending skids and is part of an occasional Magnetrol® blog series on level and flow control for skid system applications.
Batching & blending skids are used in all forms of liquids processing. The largest users are food & beverage, chemical, petrochemical, pharmaceutical, and paints & coatings industries. “Blending” refers to the in-line combining of ingredients into a single output stream. “Batching” is the dispensing of controlled quantities of process fluids into one or more vessels.
Featured Skid Application: Soft Drink Batching & Blending Skid
Nearly 35 billion gallons of soft drinks and allied products are consumed annually. Blending and batching units that combine ingredients to produce soft drinks of consistent quality are at the heart of every beverage maker.
Blending skids consist of vessels for ingredients, mixing, surge protection, and finished product storage. Syrups and concentrates are blended in a batch-mixing tank, then pumped to a proportioner to mix regulated fluid ratios, and are stored in a holding tank that feeds the carbonizer. The finished stream is then routed to filling, capping and packaging. Pumps, valves, and blend manifolds are also included on a skid.
Level and Flow Applications
- Concentrate Tanks
Syrup concentrates and additives to be blended with high fructose corn syrup (HFCS) are typically stored in stainless steel tanks with level controls that maintain safe tank levels.
Continuous Level: Eclipse® Model 706 Guided Wave Radar Transmitter; E3 Modulevel® Displacer Transmitter; Echotel® Model 355 Non-Contact Transmitter or Model R82 Radar Transmitter
Point Level: Models A15 or B15 Top-Mounted Displacer Switch
- Pump Protection
Pumps move the liquid product throughout the skid and to the packaging line. A flow switch along a pump’s discharge piping will actuate an alarm and shut down the pump when liquid flow drops below a minimum flow rate.
Flow Alarm: Thermatel® Model TD1/TD2 Thermal Dispersion Switch for low-flow cutoff
- Batch Mixing Tank
HFCS, syrup concentrates, and additives are blended in an agitator-equipped stainless steel batch mixing tank. Level controls in the tank maintain the proper level of incoming ingredients and the outgoing process stream.
ECLIPSE Model 706 Guided Wave Radar Transmitter or E3 MODULEVEL Displacer Transmitter
Models A15 or B15 Top-Mounted Displacer Switch (in stilling well) or ECHOTEL Model 961/962 Ultrasonic Switch
- Product Holding Tank
The process stream from the proportioner is pumped into a holding tank that feeds the carbonization unit. Level in the holding tank is maintained by level switches or a level transmitter.
ECLIPSE Model 706 Guided Wave Radar Transmitter; E3 MODULEVEL Displacer Transmitter or ECHOTEL Model 355 Non-Contact Ultrasonic Transmitter
Model B35 External Cage Float Switch or ECHOTEL Model 961/962 Ultrasonic Switch
- CO2 Injection
Gaseous CO2 is used for carbonation of soft drinks. Carbonator flow switches guard against no-flow conditions of the gas, whereas a flow transmitter will provide direct mass flow measurement.
THERMATEL Model TD1/TD2 Thermal Dispersion Switch for low-flow cutoff
Continuous Gas Flow Only:
THERMATEL Model TA2 Thermal Dispersion Mass Flow Meter