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However, by taking advantage of the modern electronic control systems now available, a wet bag press can be highly automated and its performance increased so that its production rate rivals that of the dry bag process, without losing any of the advantages of production flexibility. It is even feasible to mark the products with bar codes; as each item enters the press, the system automatically reads these barcodes and then selects the appropriate parameters from an internal menu. One such press* that was recently installed in a manufacturing plant is capable of processing multiple components cycling every three minutes, 24 hours a day and seven days a week.
With such a high operating frequency, some unanticipated maintenance problems are bound to occur. The control system of the press recognizes when a fault has occurred, brings the press to a safe condition, alerts the operator of the problem and suggests an appropriate corrective measure. As a result, fewer qualified personnel are needed as operators. Additionally, the press is designed to have a long operating life; in fact, some vessels that are in service today have performed over 1.5 million cycles and are still running smoothly.
With this "intelligent" press design, manufacturers of high-tech components can increase their production efficiency and flexibility while minimizing unscheduled downtime.
Press OperationFigure 1 shows the components of a typical high-production wet CIP system. Not all of these components are required for all processes-for instance, the drying booth is only necessary if fluid has to be kept away from the pressed component. It should also be noted that the control system governs the entire production cycle, including the transportation, loading and unloading of the components being pressed.
To operate the press, the operator simply verifies the program on a computer monitor and presses a button. The tooling mold automatically fills with powder, closes and is cycled through the wash booth. It is then loaded on the vessel hoist and lowered into the vessel. (The vessel top closure locks to ensure safety.) The high-volume low-pressure fill pump fills the vessel, while any air escapes through an automatic air vent. When low pressure is achieved, the low-pressure pump automatically switches off and the high-pressure pump takes over, pumping the vessel chamber to the set point pressure. The vessel chamber dwells at that pressure for a predetermined amount of time (as programmed into the system), and then decompresses according to the product profile.
At this point, the drain pump drains the remaining pressurization fluid out of the vessel, and the vessel is unlocked. The top closure is lifted by the vessel hoist, and the tooling mold is removed from the vessel and transported to the drying station. From there, the tooling is sent to the strip stations to be cleaned before reentering the production cycle or being removed from the production line, depending on the process.
Each tooling base is engineered to a specific tooling. At the operator fill and strip stations, an accumulation dwell allows operators to choose the tooling they require, even though it may not be the next tooling available on the conveyor. The tooling base can be interlocked with the conveyor guide rails to eliminate the possibility of the tooling falling off the conveyor. Both the conveyor system and CIP have the ability to identify two or more different tooling configurations and automatically send the tooling to the correct strip station. This allows for better utilization of the press.
The entire process takes less than three minutes, from the time the tooling enters the vessel to the moment the press is ready to accept the next tooling.
Simplified Production and MaintenanceIn addition to its fast, user-friendly operation, the high-production wet CIP system is designed to minimize maintenance and production issues in a number of key areas, including the vessel, hoist, wash booth, filtration system and valves.
A breech top closure locking system enables quick installation, locking/unlocking and removal of the top closure. An independent top seal plate, which does not rotate with the top closure as the closure is locked, is also incorporated into the press. This prevents the top closure seal from rotating into the vessel every cycle, which can cause wear on the vessel. To accommodate the high-volume fill and drain rates necessary for efficient production, a fast fill and drain valve is used.
A blind bottom vessel is used to eliminate any bottom closure seal in the area where dirt might collect in the system. Additionally, a vessel strainer sits at the bottom of the vessel and helps prevent contaminants from getting into the decompression system. Large particles are held safely in the strainer and can be removed with periodic cleaning.
The automatic air vent valve located in the bottom of the top closure is typically a high wear item, and failure of the valve O-ring can be difficult to anticipate. For this reason, the O-ring should be changed monthly. Periodically, however, the O-ring prematurely fails even when the recommended preventative maintenance schedule has been followed. With conventional presses, it might take an experienced operator 15 to 45 minutes to troubleshoot this problem. The high-production wet CIP system features a fail-safe logic that notifies the operator immediately if an O-ring has failed, and the O-ring can typically be changed in less than five minutes.
Although the hydraulic, vertically guided hoist design used in conventional CIPs has a good performance record, extensive bearing changes and maintenance requirements can cause excessive downtime. The hoist in the high-production wet CIP avoids these issues by incorporating bearings with increased longevity and more wear-resistant surfaces. The hoist is also designed to be flexible-if the manufacturer's tooling length decreases, the hoist tooling shelf and travel can be quickly and easily adjusted. This eliminates unnecessary wear on the system and decreases CIPping cycle time.
Clean pressurization fluid is key to ensuring efficient operation of a CIP system. Additionally, clean tooling is the easiest way to improve efficiency and reduce maintenance, as well as increase the longevity of the high-pressure components. For these reasons, the wash booth in the high-production wet CIP features a self-contained pump and filtering system, as well as a nozzle design that maximizes the cleanliness of the tooling.
To further ensure the purity of the pressurization fluid, the press sends the fluid into a "dirty" reservoir. From this point, the fluid is cycled through a series of kidney filters back into the "clean" reservoir.
The dual kidney filter system automatically senses when the filters need to be changed and sends an alarm to the operator control panel. These filters can be changed without shutting down the system so that production continues uninterrupted. Additional filters on the inlet of the high-pressure pumps protect the main filters from contaminants.
Use of a corrosion-resistant additive is also crucial to the performance of the overall CIP system because it reduces corrosion and lubricates wear parts in the pumping circuit. However, this is another function the operator never has to think about. The press features a system that automatically adds the correct percentage of corrosion-resistant additive and make-up water to the reservoir, thereby minimizing maintenance costs and eliminating the chance for human error.
When forming parts through CIPping, controlling the decompression of a vessel chamber is crucial to ensuring part quality-especially in the forming of large parts, where perfectly controlled decompression is required to prevent premature cracking. However, many conventional CIPs feature manually operated valves and fixed orifice decompression systems, and the decompression cycles often vary from the first cycle with new components and the last cycle with the worn components.
In the high-production wet CIP system, a series of normally open valves have been combined with modulating valves to accurately control decompression, and the performance of these valves is constantly monitored by a programmable logic controller's (PLC) diagnostic logic. Because of this level of control over the modulating wear parts, the stems and seats can be used to their maximum potential before being replaced. (Generally these parts are made from exotic wear-resistant materials to ensure long life.) When new stems and seats are installed, the decompression profile remains exactly the same as the cycle before the valves were changed (see Figure 2). This eliminates product quality problems due to decompression variability.
Sophisticated ControlsAs noted previously, the sophisticated PLC used in the press is the key to its optimized performance. The PLC features a complex alarm and maintenance solution notification system that feeds information to operator alarm notification screens (see Figure 3). When a fault occurs, the operator is immediately notified of the problem and solution.
For example, an operator might see any of the following messages:
- Maintenance safety gate has been opened, allowing unauthorized access to the conveyor. System has shut down.
- Low-pressure pump has exceeded its allowable time to fill the vessel. Change O-ring on automatic in-vent valve.
- Decompression rate not achieved, venting vessel chamber too fast. Change modulating valve "A" stem and seat.
- Wash booth not operating; wash booth exit door stuck open. Close door.
With the advances in control system technology over the past few years, managers, supervisors and maintenance personnel can now access CIP screens from remote computers and even from home. In fact, with the increasing popularity of high-speed connections, remote access monitoring and data acquisition of cycle parameters has become the norm for many plants.
High-Performance PressingToday's high-tech component manufacturers need forming systems that are both flexible and highly efficient-they shouldn't have to choose. With the high-production wet CIP system, companies can meet their production goals while minimizing maintenance requirements and maximizing their design potential.
For more information about CIP technology, contact Engineered Pressure Systems, Inc. at 165 Ferry Rd., Haverhill, MA 01835; (978) 469-8280; e-mail firstname.lastname@example.org ; or visit http://www.epsi-highpressure.com (Outside the U.S., contact Engineered Pressure Systems International, Walgoedstraat 19, B-9140 Temse, Belgium; (32) 3-711-24-64; or e-mail email@example.com ).
*This system was designed and manufactured by Engineered Pressure Systems, Inc., Haverhill, Mass.