How to Prevent Common Pumping Mistakes
Whether you're managing operations in a large industrial facility or dealing with a system at home, pumping problems can disrupt daily routines in ways we often don’t anticipate. Effective pumping relies on sound engineering, and when issues arise, they can cause significant downtime and costly repairs. To avoid these disruptions, it’s important to recognize and address five common pumping mistakes:
1) Regular Pump Inspection
When pump issues occur, the first step is often to check the pump itself. While the problem may seem serious, it could be something as simple as a clogged suction line or improper maintenance. Regularly monitoring the pump's flow and adjusting it as necessary helps to ensure optimal performance.
However, never vent a running pump. If you do, air can become trapped in the middle of the pump casing while heavier fluids are pushed to the outside. Even a small amount of air—just 2 to 4 percent—can cause air binding in a standard pump. To prevent this, maintain adequate submergence to avoid vortexing, and ensure the net positive suction head is sufficient.
2) Pump Seals: Packing vs. Mechanical Seals
A common misconception is that packing is a cheaper alternative to mechanical seals. While packing may initially seem more cost-effective, the long-term expenses add up when you consider the frequent adjustments needed, excessive water usage, shaft damage, and corrosion. In the long run, mechanical seals may save more money, and in some regions, rebates may even be available for reducing water consumption.
3) Suction Lift Pumps: Watch for Air Leaks
When working with suction lift pumps, it's essential to monitor for air leaks in the suction system. While fluid may not leak out, air can easily leak in, reducing pump efficiency. In ideal conditions, the maximum suction lift at sea level is under 34 feet, but real-world factors such as friction and vapor pressure lower this figure. Challenges are further compounded at higher altitudes, with warmer fluids, or when dealing with vertical lifts.
A common mistake when maintaining suction lift pumps is installing the wrong impeller or the correct impeller at the wrong diameter. These errors can significantly impact the pump's performance.
4) Centrifugal Pumps: Stay Within the System Curve
Centrifugal pumps operate strictly within the system curve, which is influenced by the system's static head, pressure head, velocity head, and friction head. If a pump isn't functioning as expected, it’s a good idea to review the system curve and confirm that all factors—such as flow rate, elevation changes, and pipe size—are properly accounted for.
It's important to note that system curves are dynamic and can change over time due to factors like elevation shifts, valve adjustments, or system aging. Regular inspections of the system can help identify and rectify issues before they cause serious problems.
5) Understanding the Pump Performance Curve
When a pump begins operation, running it at either end of its performance curve can lead to issues such as cavitation, separation, or recirculation. Manufacturers base their performance curves on water pumped at around 68°F, with a specific gravity of 1.0 and a viscosity below 30 centipoises. However, real-world conditions may differ.
Additionally, manufacturer curves are usually calculated at a specified speed, which can differ from actual speed in the field. This discrepancy often occurs because the induction motor isn’t fully loaded, or due to voltage variations. A slight difference of 30-50 rpm can significantly affect pump performance.
To address this issue, check the motor’s nameplate and consult the manufacturer for the full load speed and expected percentage of slip. As variable speed drives have become more common in the past two decades, these speed-related problems have become more prevalent.
Rotech Pumps & Systems: Solutions for Pumping Problems
Rotech Pumps & Systems offers a wide range of pumps, mechanical seals, and valves designed to address various pumping challenges. We provide quick support and solutions to help our customers overcome common pumping mistakes, ensuring the efficient operation of their systems.
Our team is committed to being a reliable resource for customers, offering tailored solutions that meet their unique needs. At Rotech, we continue to grow beyond our origins as a pumping systems company, striving to deliver high-quality, efficient products.
