Business drivers: A powerful incentive for the adoption of Smart Water systems is to

warn and prevent water system failure, water loss at critical times, and excessive operating and capital cost outlays.

 

As discussed below, the causes of overload are many, but the common precipitators are 1- declining aquifer pumping levels where minimum positive suction head is no longer met and cavitation occurs, as well as 2- pump and driver misalignment, and 3- mechanical wear and failure.

 

Overloading effects: Overloading occurs in centrifugal pumps when the driving motor draws excess current and causes a rise in power consumption. (Vertical turbine pumps are centrifugal pumps designed to lift water from an underground well or reservoir). The problems that may occur include cavitation, shaft deflection, and stress on mechanical seals and bearings. As the pump efficiency decreases and power consumption increases, the motor will start to trip.

​

The dramatic effects of overloading can be illustrated in our case study of a large irrigation well in the Central Valley of California. The pump is rated at 600 HP and is designed to pump 4,000 gpm at the BEP. The well motor started to trip several times per day and send out multiple alerts. The performance data in UAM’s Smart Water System pointed to declining flow, high amp spikes and unbalance, and a rise in kW power consumption. Motor vibration levels and voltage balance were within acceptable ranges. The magnitude of the change in key performance indicators is illustrated below.

 

The maximum amps drawn by the system often exceeded 15% of its rating (640A) and at times exceeded 750A. The power consumption increased by nearly 18% over the previous quarter’s average.

​

​

​

​

​

​

​

​

​

​

 

In addition, the current (in the graph below) became unbalanced by as much as 6% in the three phase system, with serious performance and cost impacts. The unbalance decreases the motor efficiency by causing extra heating in the motor and the excess heat decreases the equipment life by increasing the operating temperature, decomposing the grease or oil in the bearing, and de-rating the motor windings. A 4% unbalance will cause a 20% de-rating, meaning that 20% of the current in the cable will be unproductive and copper losses in the cable will rise by 25%.

 

Common causes of overload: Enggcyclopedia states that a centrifugal pump may draw high ampere due to the following reasons:

​

1.  Speed too high

2.  Higher viscosity of pumped fluid

3.  Oversized impeller installed

4.  Total head of system either higher or lower than expected.

5.  Misalignment between pump and driver- a common reason for pump damage and trip as it can cause damage to 
   stuffing box, failure of mechanical seal and bearing, pump overheating or seizure.

6.  Rotating parts come in contact with stationary parts.

7.  Worn or damaged bearings.

8.  Mechanical seal exerts excessive pressure on seat.

9.  Bent shaft that could lead to fatigue cracking and an eventual breakage of the shaft.

10. Pump operating too far out on pump performance curve.
    
                      https://www.enggcyclopedia.com/2011/12/pump-overloading-causes

 

Remediation: The first remedial action was to choke back the flow of the pump on the discharge side until the pump operated at a better efficiency point, Cavitation was prevented but this came with a significant reduction in flow (-30% compared to BEP) and the motor continued to trip, albeit less frequently.  

     

Subsequently, the well was shut down, and after thorough review of the system diagnostics, the pump was lowered, and mechanical and electrical maintenance operations were performed to restore the pump to its BEP.

 

Call to Action: Our Smart Water monitoring system provides users with an comprehensive suite of analytics as well as alert/alarms to identify unsafe operating conditions, including monitoring and alerting for salient drops in well depth and flow, amp spikes, voltage imbalance, excess temperature and vibration, as well as vibration harmonics that help pinpoint problem areas. To learn more about how you can improve your water system’s performance, please visit us at www.uamllc.com and book a demonstration of our Smart Water Solutions.

​

​

​