When you install a new submersible pump, you expect consistent operation that will last for several years. But, chances are, the submersible pump will be performing in rugged conditions that can eventually take a toll on a pump. Proper preventive maintenance can help prolong the service life of your submersible pump, allowing smooth operation at optimal levels.
Upon installation of your new submersible pump, your technician will test it and provide a start-up report. The report compares the data sheet specifications to your actual operational performance at the time of pump startup. If you experience performance changes with your pump over time, you can refer back to the start-up report and compare the current measured performance data with the original performance data.
Routine preventive maintenance inspections can help address possible issues before they become major or even catastrophic problems. Preventative maintenance also helps you troubleshoot or identify root causes of issues and helps drive corrective action to resolve and prevent these events from occurring in the future. There are four key areas to be sure to include in your maintenance checklist.
1. Electrical Check
Your submersible pump is powered by electricity. Monitoring the electrical use can help identify a problem with your pump’s operation. The amperage load is the amount of current (amps) the pump motor draws from the electrical system. With submersible centrifugal pumps, the increase in current flow (measured in amperage) corresponds to an increase in flow or solids loading.
The amp draw will be less when there is no flow, while maximum flow should increase the amperage draw to the rated amperage or Full Load Amp draw (FLA) found on the product nameplate and data sheet specifications. Most submersible pump motors have a service factor that will allow safe operation to a slightly higher level as needed for higher pump loading.
Two critical electrical attributes that should always be measured on a submersible pump electric motor are the input voltage and the output current draw. The input voltage should match the nameplate specifications by +/- 10 percent.
The voltage measured during the initial starting should not drop by more than 5 percent of the measured line voltage with no loading. The voltage supplied to each leg of a three-phase motor design should show no more than a 2 percent variation.
The measured amp draw of the motor should not see a variation more than 5 percent on each leg and should be within the nameplate specifications of the pump. As part of a good preventative maintenance program, the voltage and amperage draw are periodically measured and compared to the original start-up data.
2. Alarm Monitoring
A submersible pumping system can be setup with monitoring devices that will alarm if a potential failure threshold has been reached. One of the most important criteria to monitor on a submersible pump is the mechanical seal chamber. Many submersible pumps incorporate a seal failure control circuit in the controls that works in conjunction with a seal minder probe located in the pumps mechanical seal chamber.
A seal failure circuit (or moisture detection circuit) is designed to monitor the amount of moisture within the mechanical chamber. Once a critical level of moisture has entered the mechanical seal chamber, an alarm is initiated. This early warning can allow the operator to schedule repair and inspection of the pump, preventing costly catastrophic failure and unscheduled downtime.
If a seal minder alarm is initiated, a sample of the seal chamber oil should be taken to verify the amount of water/contaminates present in the mechanical seal chamber. The seal should be replaced if the fluid removed is milky or shows a high level of water/contaminants.
Various types of preventive alarms can be installed on a submersible pump and the associated control system. These include motor temperature sensor alarms, high fluid level alarms, over and under current alarms, just to name a few. The requirements of each application will determine the proper system alarming that is beneficial for a given application.
3. Pressure and Flow Checks
Consistent hydraulic performance of a pump is critical to an operation. A submersible pump should perform at the same flow and pressure output that was measured and noted in the start-up report.
A pressure gauge should be located as close to the piping discharge as possible. The pressure gauge reading will indicate the psi (pounds per square inch) performance level of the pump in the piping system and should stay the same as long as no changes have occurred in the pumping system.
If there is a discrepancy between current operation and the start-up report, check for possible hydraulic issues. Clogging can occur within the pipes, check valves can stick, control valve settings can be changed, or critical piping system changes may have been made.
Changes in the fluid entering the sump basin can also change the performance of a submersible pump. Excessive solids, fluid specific gravity, and chemical changes are just a few parameters that can affect a submersible pump’s performance.
4. Visual Inspection
During preventative maintenance, the submersible pump should be pulled for a visual inspection.
- Are there debris jammed in the suction inlet, pump housing or stuck around the impeller?
- Is the pump showing any signs of physical damage?
- Are solids like milk fats, animal fats or sticky materials adhered to the pumping elements?
- Have critical pumping elements seen physical damage, chemical attack or erosion?
Exterior surfaces should be checked for dents, corrosion or abrasion. The electrical power and sensor cables should be free of cuts or frays and be properly supported by the strain relief mechanism. The sump basin should be checked for excessive solids build up.
Call Your Local Distributor
Most routine maintenance and repairs can be performed in-house by a qualified maintenance technician. However, when there has been a change in pump performance, and preventative maintenance checks do not define a clear path to a root cause solution, assistance may be required from your local distributor. These may include:
- Megger testing to check for insulation faults to ground.
- Winding resistance check to confirm resistance balance and confirm no motor winding degradation has occurred.
- Damage to critical pump components.
– Impeller vanes and shredding components.
– Suction cover and pump housing.
– Power/sensor cable and the associated sealing systems.
– Motor housing, pump cover, lifting devices.
- Any unexplained change in pump performance (flow, pressure, amp draw, etc.)
With proper periodic maintenance, including checking the amp draw, pump function and routine visual inspection, a quality submersible pump will last for years without degradation.
For more than 35 years, BJM Pumps and its highly qualified expert distributors have provided reliable, long-lasting pumps for industries ranging from food and beverage to power generation and utilities. Customers receive unparalleled service from specification through installation and continued support throughout the life of the pump.
BJM Pumps, www.bjmpumps.com