The city of Rowlett, Texas, experienced an unauthorized wastewater ...
During a recent, month-long project for Puncheon Run Pumping Station Bypass in Dover, Del., the reputation and technological advancements exhibited by Godwin Pumps may have been the critical elements that led to winning the bid and exceeding customer expectations.
Most bid proposals are cut and dry. Godwin typically has the ideal pump to meet the requirements, the inventory to immediately outfit the entire pumping solution and the experience to work through any unique challenges, but this was appeared to be a tough case.
The city of Dover expected to dismantle and replace the entire pumping station including the pumps, controls and wiring. Therefore a solution was necessary that could handle 1,875 gpm at 168 ft of head to 3,000 gpm at 120 ft of head. In addition to these drastically varying flow requirements, the Puncheon Run job offered the up-front challenge of limited space availability.
With a 30-by-30-ft area for pump placement and only slightly more room for system assembly, the lack of space made it difficult to set up the job and still leave enough room for the contractor to move equipment and materials in and out of the building. This also added to the complexity of identifying pumps that could match both the flow requirements and the space restrictions.
“This was not your basic bypass,” said sales engineer Dale Brackin. “When I looked at the requirements for the job, I brainstormed with fellow employees and the contractor, C&D Contractors, Inc.”
The team of Mike Ramos, a chief engineer for Godwin, Mike Delzingaro, a sales manager for Godwin, and Brackin has over 50 years of combined experience in the pumping business. They pooled that experience with the technological input of Engineer David Heritage to create the winning proposal for C&D Contractors, Inc.
The plan of attack
“There were so many things to consider,” said Ramos. “But the starting point remains finding a pump and controls to meet the flow requirements of the system.”
Godwin’s CD160M Dri-Prime pump proved to be the pump to handle the flow and lift required for the city of Dover.
Available with diesel engines or electric motors, this particular pump is rated for 1,900 gpm at 260 ft of head. For the Puncheon Run Station, Godwin delivered two 150 hp electric drive CD160M pumps with 200 hp variable frequency drives (VFDs) incorporating level transducers and programmable logic controllers (PLCs) to serve as the primary and lag pumps to meet the flow demands.
One critically silenced 147 hp CD160M diesel pump with a Godwin PrimeGuard Controller and level transducer served as a backup. One standard 147 hp CD160M diesel pump with a PrimeGuard Controller, level transducer and hard-wired Chatter Box Auto Dialer supported the entire system in the event of major storm surges or power outages.
At roughly 11.5 ft long and 4.5 ft wide, the four CD160M pumps were compact enough to meet the space restrictions. However, when combined with all of the other equipment the job would need and the space available to piece it together, the team quickly met its next challenge.
Some assembly required
Along with the four pumps, it was determined that the Puncheon Run bypass would require the following:
Also necessary would be HDPE pipe, adapters and elbows that similarly to check valves, a discharge manifold, combo vents, a flanged reducer and ball valve, all needed to be fabricated and/or assembled on-site in a 30-by-30-ft area
Working with C&D Contractors, Inc., Godwin’s team of skilled fusion technicians assembled the HDPE sections and connections in stages, starting from the discharge point (an emergency force main connection), and crane-lifted them over the roughly 20-ft high pumping station building.
The team fused the approximately 100-ft length of HDPE discharge pipe, tying it into the single, 18-in. outlet of the discharge manifold. On the inlet side of the manifold, Godwin connected a check valve to each of the four, 8-in., 20-ft long discharge hoses that tied directly into each pump.
In the final stages of assembly, the four pumps and their controllers were brought in and connected. When it came to space limitations, the suction point was no exception. The only pickup spot for flow was a large diameter manhole located just before the pump station wet well. The manhole became home to the four, 10-in. HDPE dip tubes, four level transducers and left just enough room to install a sewer plug. The entire, assembled system provided adequate space for the contractors to move equipment in and out through the pumping station door.
Working out the logic
The plan for approaching the flow conditions was simple: the first (lead) electric drive and the second (lag) electric pump were equipped with VFDs that incorporated a level transducer and PLC that allowed the VFDs to work together. Using these controls, Godwin engineers could identify and program system variables that could vary the pump speed to keep up with the influent, start and stop pumps as demand required, and alternate lead and lag control between the two pumps to ensure that the entire system was in proper working order and that the pumps experienced an equal amount of run time/wear exposure to prolong performance.
The VFDs worked only to deliver the flow necessary for system conditions, instead of starting and stopping continuously as with a float-type system. This approach lessens the wear and tear on the pump and decreases the power surges and costs associated with the peak demand on the pump.
Likewise, the level transducers sensed the pressure as the water rose and sent a signal to the VFD to speed or slow down the motor. The challenge with using a level transducer in a manhole is the turbulence in the water. Godwin inserted a perforated tube into the manhole, creating a stilling well for the transducers. In addition to protecting the transducers from the debris in the manhole, the tube displaced the turbulence, rendering it undetectable. This created a cleaner signal, thereby avoiding rapid cycling. The level transducers were also equipped with a level signal selector switch that took the average of both transducers or would switch from one transducer to another, if a signal went bad.
Pumping on a force main requires a variable head condition that is proportional to flow. When only one pump is running, the discharge head will be much lower than with all three pumps in operation.
Excessive use of a single pump running at full speed with no head could potentially lead to cavitation and needless damage. The VFDs each had a PLC that was programmed to only allow the single pump operation to run up to a lower maximum speed unless more than one pump was required to handle the flow.
The two diesel pumps were each equipped with PrimeGuard Controllers, level transducers. These diesel-driven pumps were required as backups in the Puncheon Run bypass, and were controlled independent of the electric pumps, making them self-sufficient. In an effort to exercise the diesel pumps on a routine basis to ensure system functionality for emergency conditions, the first diesel backup would start up once a week. The system backup pump would also start once weekly, sending an alarm signal through its Auto Dialer to verify that the backup system functioned properly.
Taking advantage of the options
C&D Contractors, Inc. chose Godwin for its reputation and for its ingenuity. Those two qualities resulted in enormous benefits to the City, to C&D Contractors, Inc. and to the project.
VFDs for electric pumps and PrimeGuard Controllers for diesel pumps opened up a wider variety of capabilities and applications for temporary, portable pumps that had only previously been found in permanent applications. The ability to meet a wider range of flow requirements, including initiating backup pumping, to routinely exercise pumps and/or allow time for scheduled maintenance and to send alarm signals enabled reliability and responsiveness: two of Godwin Pumps’ hallmark characteristics.
Using electric-driven pumps as the primary pumps, C&D Contractors, Inc. only needed to fuel the two diesel backup pumps. In addition, electric pumps combined with VFDs, PLCs and transducers manage the power requirements associated with drastically varying flow levels, decreasing the electricity costs associated with power surges and minimizing the long-term wear on the pumps.
Since the Puncheon Run facility was in a residential area, the electric pumps and critically silenced pump needed to operate with minimal noise levels. The combination of electric pumps and the critically silenced pump unit emitted noise levels no greater than 68 dBA at 30 ft.
The beauty of challenging jobs that are executed with this much success is that they help to round out Godwin’s arsenal of solutions and continue to solidify Godwin Pumps’ position as a pumping solution specialist.