Commissioning A Unigy Centralized High Pressure Pump System

Unigy Centralized Pressure Systems

The video clips at the bottom of this page are from the commissioning of a dual pump Unigy System to be used for continuous supply of heated water for a network of spray nozzles. We refer to this type of application as a Centralized Pressure System (CPS).

Application
The customer is a manufacturer in the food industry. They operate two 8 hour production shifts and spend the 3rd shift cleaning in preparation for the new day. Throughout the plant are spray nozzles, consisting of coiled hose, ball valve and nozzle. These nozzles are used as required for washing applications. Throughout the day at any given time there might be a demand for 6-10 GPM. During the cleaning shift the demand for water spikes to almost 40 GPM. The desired discharge pressure is 850 PSI and this pressure needs to be instant and available no matter how many spray nozzles are in use.

The Old System
The system that was replaced by Unigy consisted of a pair of 50HP Roto-Jet^® Pumps. They were sized for 80 GPM at 850 PSI, one pump would operate and the other was a standby pump in the event the running pump failed. The pump in operation would take the heated water (~120F) and output all 50 GPM at 850 PSI. The pressure was maintained via a pressure regulating valve. Essentially with no nozzles in operation 100% of the fluid would be bypassed back to the feed tank. As nozzles were activated the bypass valve would bypass less flow. So this system was run continuously at full flow and pressure and therefore consuming the maximum amount of energy possible regardless of the flow rate demand. This type of pump operation (constantly operating at the maximum flow and pressure with hot water) was hard on the pump. Maintenance was frequent and very costly.

The Unigy System
This system consisted of two H25 Hydra-Cell Pumps and when operated with a Unigy Drive it is capable of 50 GPM at 1000 PSI. Hydra-Cell Pumps are used because they enable 100% turndown, meaning they can maintain line pressure at zero flow. This is a unique characteristic of Hydra-Cell Pumps and the Unigy Drive. Hydra-Cell's are also sealless pumps, meaning that they have no cups, packing or mechanical seals in contact with the fluid. This enables Hydra-Cells to run dry without damage and pump hot water without concern for pump cooling. Since the customers' feed tank occasionally runs dry (resulting in thousands of dollars in Roto-Jet^® Pump repair), the ability for the Unigy System to run dry was an added bonus. Hydra-Cell's are even unaffected by a restricted or fully closed inlet!

The operating principle of a Unigy System is that the pumps are only operated at the torque required to maintain the "set condition" (in this case, 850 PSI). When no spray nozzles are being used, the only energy being consumed is whatever is required to energize the motor, about the same power consumed by a 100 watt light bulb. As spray nozzles are phased on and off, the drive reacts to maintain that torque, speeding the pump up or slowing it down as required. The changes in pump speed are instantaneous and there is no water hammer effect or delay at the spray nozzle.

The control, whether by pressure or flow, is provided strictly via torque, meaning that there is no need for instrumentation downstream to provide feedback to the pump. One way to approximate an automated variable speed pump system would be to use expensive instrumentation downstream, send signals to a variable frequency drive and interpret the results via custom programming of the variable frequency drive. None of this is required with Unigy, not even bypass relief line. The electrical connections are the standard 3 phase motor wiring plus the shaft encoder. As you can see below, you are up-and-running in only minutes.

Results
Since the demand is usually relatively low, this customer will realize a reduction in energy consumption of approximately 84%, equating to about $24,000 annually in kWHr costs alone. Since Unigy CPS only operate when needed instead of continuously, the pump components are subject to much less wear. The entire pump can be rebuilt for $250 and does not require removal from the pump pad for maintenance. The recommended preventative maintenance schedule is installing a pump end kit annually and to change-out the 2.5 quarts of oil in each pump every 4,000 hours (about 3 times per year). This customer uses a special food grade oil, customers that are not in the food, beverage or pharmaceutical industries typically use standard synthetic motor oil such as Mobil-1.

Since this is a dual pump system, either one can be isolated and serviced while the other is in service, therefore having a duplicate pump system in "standby" was considered unnecessary. This significantly reduced the system cost and the customer is very pleased to have eliminated the maintenance costs and time related to Roto-Jet^® Pumps.

The operating noise has been significantly reduced as evidenced in clip #4. The operating pressure, flow rate, energy consumption and several other operating parameters are continuously being data logged and can easily be retrieved for analysis if desired.

Please refer to the following web pages for additional information about the built-in functions provided by Unigy Drives, such as spray nozzle wear indication.

Case Study Related Links (PDF Files):

	T.P.S., Inc. Blairstown NJ 07825
	Phone: 908.362.9981	Fax: 908.362.5631	inquiry@fluidproducts.com