|Affected Products:||Replacement Part:|
|21G Simpson Multi-Mull||Engineering RFQ - Discharge Door & Controls Upgrade|
|215G Simpson Multi-Mull||Engineering RFQ - Discharge Door & Controls Upgrade|
|22G Simpson Multi-Mull||Engineering RFQ - Discharge Door & Controls Upgrade|
|225G Simpson Multi-Mull||Engineering RFQ - Discharge Door & Controls Upgrade|
|23G Simpson Multi-Mull||Engineering RFQ - Discharge Door & Controls Upgrade|
The primary design objective of the Simpson Multi-Mull was to enable the preparation of large quantities of tightly controlled molding sand using less energy (horsepower), space and capital than any other muller or mixing system. To achieve this objective the Multi-Mull operates on a continuous basis and has automated process controls. When properly applied and adjusted, the Simpson Multi-Mull is a competitive advantage for the user foundry because it is capable of consistently producing higher qualities of quality molding sand at lower costs of operation than any competitive muller.
In practice, users reported the opportunity to improve the performance of the Multi-Mull due to the following issues –
With over 1,000 installations worldwide, the Simpson Multi-Mull continuous green sand muller is an industry proven standard and the only widely proven continuous mixer for foundry molding sand. Properly applied, its ability to produce consistently high quality green sand in a wide variety of applications is confirmed by years of rigorous use. These variations are often due to changes in the number of or speed of the molding lines and/or changing sand to metal ratios. In order to allow medium to high volume foundries to continue to enjoy the advantages of continuous mulling but also to optimize control over sand preparation during frequently changing conditions, Simpson Technologies has updated the discharge door and its control logic to meet these challenges. The object of the new discharge door system is to reduce or eliminate the requirement for manual adjustment to compensate for a majority of changing conditions. The new door allows any foundry to easily enhance
performance of their Simpson Multi-Mull.
For better control and more efficient operation the original double door and amperage meter system have been redesigned. They have been replaced by significant improvements in both control methodology and mechanical elements. The control of retention and discharge is no longer accomplished by monitoring single leg amperage alone. The new discharge door control system accurately and continuously measures the true energy usage at the drive motor, processes this information by comparing it to a set-point value, and adjusts the new discharge door to retain a precise mass of sand in the Simpson Multi-Mull at all times. In order to accomplish this, the new system must first accurately determine the energy required to retain a constant mass. Utilizing a power transducer, the control system first monitors three phase power at the drive motor. Unlike the old system that measured amperage from one phase, the new system monitors amperage, voltage, and phase angle from all three phases of the drive motor. By monitoring all three phases it is possible to eliminate the fluctuations found by monitoring amperage alone. Additionally, the power transducer can be adjusted to overcome the fluctuations in plant electrical power, which hampered the old door design. This provides precise monitoring of the power utilized to retain a consistent retained load of sand inside the Simpson Multi-Mull. This utilization is expressed as a percent kilowatt (or percent horsepower) demand. As the Simpson Multi-Mull operates, the transducer continuously supplies the percent kilowatt demand to the control system. This information is sent through a three mode control loop (also known as a PID Loop) and is continuously analyzed. The percent kilowatt demand is compared to a set point value. This value is preset by the user depending on the sand quantity and properties required. The three mode controller is programmed to continuously move the new discharge door into proper position so that the percent kilowatt demanded from the drive motor equals the set point value. These values are continuously compared and, over time, the three mode controller tightens the span of control. This improves retention accuracy, reduces excessive movement of the discharge door, reduces muller stopping and starting, and minimizes sand property variations. Door control set-points are input into a PLC rather than with manually set with conventional needle type meters.
In order to accomplish precise positioning of the discharge door, a new design has been created. The new door consists of a single, vertical discharge gate. This door is positioned by an electro-mechanical actuator in response to the three mode control loop. This actuator, complete with a variable frequency drive for positioning, is designed to quickly respond and locate the door to retain a constant retention time at all times manual intervention. This significantly improves the performance of the Simpson Multi-Mull during varying foundry conditions. More consistent sand properties result, even when slight fluctuations in sand composition and demand occur. If more dramatic changes in retention time are required (for example, when one of the two or more molding machines on the sand plant are taken off-line), the new discharge door system can be more quickly and easily balanced.
For existing Simpson Multi-Mull installations the system has been engineered to easily replace the old door. Field removal of old discharge section and the installation of the upgrade kit, complete with controls, can typically be accomplished in less than two shifts. For new installations, the redesigned discharge door system comes standard on all new Simpson Multi-Mulls.
The Simpson Multi-Mull Discharge Door Upgrade Kit consists of:
For better control and more efficient operation the original door and amperage meter system on the Simpson Multi-Mull® has been redesigned to improve control methodology.
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