04-22-19-R - Laserfiche WebLink

Home Browse Search

City of Arden Hills Technical Memorandum – SCADA System Recommendations Page 3 of 8 clearly indicates a procedure for removing the old and installing the new modem card. The cost is $300 per unit, parts only. Recommendation: Upgrade the existing OmniSite Crystal Ball cellular modems. The Existing HighTide cellular equipment installations were investigated and the Engineer is not at all surprised that it is not working well. 1. For one, these types of cellular modems (including OmniSite) were never intended for closed loop control situations. These types of cellular modems report changes by exception, time (typically only every 24 hrs.) or instantaneously for alarms only. In other words, there could be large time lapses between the level of the tower being reported back to the booster pump station. 2. The location of the cellular antenna on the north tower is underneath a large steel tank and very low to the ground; therefore, the signal is likely to be unreliable. Recommendation: Replace the HighTide cellular modem with an OmniSite Crystal Ball, Booster Station only. 2.2 Communications Upgrades 1. To establish reliable communication between the Booster Station and the North Tower, the Engineer recommends standard radio telemetry equipment. This will provide updates to the Booster Station in less than one second. However, their antennas will need to be elevated, preferable to the top of each tower. The Satellite photos indicate there are no antennas at the top of the South Tower but there appears to be something on the top of the North Tower. Assuming that there are no conflicts on either tower, the existing hand-railing could be used to simply mount the radio antennas. The North Tower’s HighTide RTU could be eliminated. To keep costs lower, there are radios that have embedded I/O on them which eliminates the need for a PLC. Also, to reduce costs, radios can be purchased utilizing unlicensed spread spectrum frequencies. It should be noted that even if the City decides to purchase a licensed frequency in the future, the same coaxial cable can be used for different frequencies. Thus a change in frequency only requires changing the radio and the antenna. The rest can remain. NOTE: embedded I/O radios are only available in unlicensed spread spectrum radios. Recommendation (referred to as Alternative 1 in DRAFT memo): Install radio telemetry at both tower locations. 2.3 Booster Pump Building The existing Booster Pump Station at the South Tower has an outdated PLC that is no longer supported by Allen Bradley. This PLC and its associated I/O and PanelView should be replaced as part of the SCADA system upgrades. The main reason is that a newer PLC would be complete with Ethernet communications that is the current standard with no need to upgrade to a different protocol in the near future (10-20yrs.). Now this entire system would be modernized and ready for future add- ons/improvements, not necessarily part of this project. By upgrading to Allen Bradley’s new PLC and PanelView, the labor investment is minimized by transferring the same program into the new PLC as well as the PanelView. The only labor intensive part is installing the new PLC and I/O onsite, which may require new wiring to reach the new footprint of the PLC and I/O. Recommendation: Install new PLC (at the Booster Station) as part of the SCADA system upgrade project to gain efficiencies in Systems Integrator costs. 3. NOT RECOMMENDED 3.1 Entire New Private Radio System As stated in section 2.1, the existing RTUs are of good quality, operate reliably and are well understood by the operations staff. The Engineer anticipates that the current OmniSite RTUs should be supported and sufficient for the next 10 years. If OmniSite is readily making upgrade kits available, this is evidence that the company will continue to support their Crystal Ball product into the near future. The Engineer has estimated that an entire SCADA system replacement with private radios could be beyond $200,000. Since