Canadian Plastics

Make Mine Modular

While cooling systems are essential to the injection molding process, they are often taken for granted. This attitude can not only lead to problems, it can add costs. As noted in a Regloplas technical guide on the theory and practice of cooling "T...

November 1, 2004   By Michael Legault



While cooling systems are essential to the injection molding process, they are often taken for granted. This attitude can not only lead to problems, it can add costs. As noted in a Regloplas technical guide on the theory and practice of cooling “Temperature Control by Means of Fluid Media”, today’s powerful and fast injection molding machines require increasingly tight temperature tolerances. The goal when selecting a cooling system must be “to increase quality while simultaneously decreasing operational costs and ensuring optimal operational reliability.” Modularity in equipment design and enhanced control features offer processors a better means of achieving this goal.

CENTRAL BUT MODULAR

Temperature Corporation’s water-cooled modular central chillers are compact and reliable, incorporating dual Copeland scroll compressors with dual refrigeration circuits, or a contour screw compressor with single refrigeration circuit. For use with cooling towers, the chillers come with oversized evaporators and condensers, and attain high efficiency. A unit with a scroll compressor can operate with an Energy Efficiency Rating (EER) of 15.4 or higher, while a unit equipped with a screw compressor can reach an EER of 14.3 or better, both at water temperature of 44F exiting the tower and 85F entering the tower. The modular chillers are shipped “complete”, and the only assembly required is the installation of the end panels, water heaters and the connection of the electrical bus duct.

“One advantage of modularity is that you can replace or repair one unit without shutting down the entire system,” says Roger Lambert, president of Temperature Corporation.

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Sterling’s new S Series of central chillers feature rotational compression technology, which results in 50% fewer moving parts and reduced noise and vibration. The chillers sized from 30 to 100 tons employ hermetically sealed scroll compressors. In sizes from 54 to 195 tons, the line comes with hermetically sealed screw compressors. Up to 100 tons, both types of compressors are matched to brazed plate evaporators; from 115 to 195 tons shell-and-tube evaporators are used.

The S Series offers two levels of network capable, off-the-shelf PLC control. The standard PLC screen is a graphical user interface that controls up to four compressors in one or two circuits. The advanced PLC screen is a full-color screen that allows an operator to control multiple chillers, cooling tower fans and other devices. The S Series is designed for fast installation and all major components are arranged for ease of access during maintenance.

Freeze Co. Systems has introduced a new line of modular chillers for molding operations in which space is limited. Designed specially with the smaller molder in mind, the modules of these chillers can be expanded as new machines and lines are added. The chillers are designed with a positive, full-flow, in-line strainer ahead of each heat exchanger; each unit is equipped with single point electrical and PLC controls. Air and water-cooled modules are available with compressors ranging from 20 to 120 hp per module.

Thermal Care, Inc.’s TC Series of central chillers uses an advanced compressor technology that provides a number of advantages compared with standard compressor technology. One of these is an oil-free design that eliminates the need for an oil management system and any related costs. With only one moving part, the compressor has increased reliability and is extremely quiet (71 dBA) while in operation. A built-in variable speed drive motor and frictionless, magnetic bearings help save energy by eliminating inefficient compressor cycling. Additionally the TC Series uses R-134a refrigerant and provides 79 points of diagnostic control per compressor.

PACKAGED FLEXIBILITY

Chillers and mold temperature control units sold under Conair’s Thermolator name are modular, allowing a processor to configure the most appropriate system for his/her operation. Air-cooled and water-cooled Thermolator chillers are portable, packaged units designed for tailoring to a variety of machine-side applications. Air-cooled models are available in sizes from 1/4 to 30 tons, and water-cooled models are sized from 1.5 to 30 tons. Processors can choose between a basic microprocessor control, or a fully featured flexible PLC control unit. This advanced PLC control has automatic fine-tuning of PID control parameters for uniform temperature control regardless of external loading. A two-line LCD display indicates actual and setpoint temperatures, percent loading, refrigerant pressures, run status, alarms and diagnostic information.

Thermolator air-cooled chillers can be configured for high-temperature plant conditions, with special fans and condensers to allow normal operation in an ambient air temperature up to 120F. Processors using water-cooled units can opt for shell and tube condensers, which can be opened for cleaning, alleviating worries about water contamination.

Temperature Corporation has designed a water-cooled chiller and a remote condenser air-cooled chiller with one of the smallest footprints in the industry. The company’s SSRC-DP (single compressor) and DSRC-DP (double compressor) remote air-cooled, self-contained chillers come with single or double pump tanks. The chillers are available in five models ranging from 30 to 80 tons. During winter months, fan cycling and speed for head pressure can be controlled for maximum efficiency. The company’s WCP series of water-cooled condenser portable chillers feature Copeland scroll compressors and a water regulating valve for head pressure control. The WCP series comes in seven models ranging from 4.5 tons to 30 tons. Both air-cooled and water-cooled chillers feature all steel tanks and non-ferrous, non-rusting water piping.

Regloplas supplies a full line of packaged portable chillers from 1/2 ton to 50 ton designed specifically for the plastics industry. The company’s RMPC line is one of the few chiller systems produced today that is designed to cycle itself on and off, based on the heat load carried out of the process. A lighter heat load transfer (for example, in a smaller mold) results in a lower number of operating hours for the chiller, and a longer life span for chiller components.

In plants with a modular production design, the RMCP line of chillers allows a plant engineer to change molds or production rates without having to worry about altering each chiller’s cooling rate. The chillers adapt to the changing conditions. Standard features include microprocessor controls, stainless steel circulation pump and an oversized stainless steel storage reservoir. The reservoir serves an important energy-saving function. It holds cool supply water so the chiller consumes only the energy required to meet a current demand.

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TEMPERATURE CONTROL CRITICAL

Advantage Engineering Inc.’s Sentra temperature controllers use a third-generation Advanced Valve Technology (AVT) modulating valve to precisely meter-in cooling water while eliminating water hammer caused by on/off solenoid style cooling valves used in other types of temperature controllers. The AVT uses a square drive stem, which provides a more precise transfer of motor movements through the one-piece coupling, resulting in better temperature control of the process fluid. As well, the drive stem uses a replaceable O-ring stem seal that gives the valve up to four times longer life and reduces maintenance. The valve has a rigid flange mount for a more secure attachment to the cooling cylinder, eliminating alignment issues that can result in uneven stem wear and poor valve performance.

Conair’s Thermolator temperature control units (TCUs) allow users to match pumps sized from 3/4 to 7.5 hp with heaters from 9 to 48 kW as well as cooling valves to meet process requirements. Processors can choose standard easy-to-use microprocessor controls or get a higher level of TCU performance with a package that features, among other things, simultaneous display of setpoint and actual temperatures, temperature control based on readings at supply o
r return points, or an average, and auto-start capability.

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CHANGING DIMENSIONS IN CHILLING SYSTEMS

The days when a customer gave the ballpark specifications on his molding requirements and a supplier consulted large three-ring binders trying to come up with components for a chilling system that would do the job may soon go the way of the typewriter.

“We’ve developed an in-house program that helps us coordinate and specify a customer’s equipment requirements based on what he tells us,” says Steve Goudie, vice president sales and marketing, Berg Chilling Systems, Ltd. “It’s a huge leap forward in helping us meet the exact needs of the customer.”

Goudie says the Parametric Program, Berg’s name for the internal program, eliminates much of the guess work traditionally associated with specifying chilling equipment. It also saves significant time, which is a value-added feature for customers.

“The concept came up a few years ago,” says Goudie. “It is very complicated and time consuming to match the right compressor, with the right pumps, with the right electrical requirements. We felt there had to be a better way.”

Things are also changing on the shop floor, according to another supplier of chilling equipment.

“Chillers now have the better ability to communicate and interface with existing plant monitoring systems,” says Ziggy Weibe, president of Chillers Inc.

Such interfaces often allow operators to monitor and control multiple chillers, cooling tower fans and other devices from a single remote location.

“Customers want this level of control because it allows them to be more efficient,” Weibe says.


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