Maximizing Pump Life
Maximizing pump (and system) life is achieved by considering three basic pump system elements: selection, installation and maintenance. Selecting a pump designed for the application is the initial step. Once the appropriate pump has been selected, proper installation is crucial. Finally, establishing a regularly scheduled preventative maintenance program will optimize pump and system life.
Not all pumps are created equal. Therefore, to maximize pump life, it is very important to select a pump designed for the application. Take the time to gather information about various pumps to determine their suitability to the application and the desired performance. At a minimum, proper pump selection should include consideration of duty cycle, flow and pressure, power supply, liquid compatibility and temperature, installation location, and method of feeding the pump.
Most pumps carry standard specifications for normal operation; however, few pumps will operate at all maximums under continuous-duty conditions. Do not exceed the rated specifications of the pump. To achieve optimum performance, multiple pumps that engage as demand fluctuates may need to be considered. If space is a consideration, a compact, lightweight pump that permits a stacked mounting will provide a smaller footprint than the standard horizontal mounting. Consider whether the pump will encounter freezing or extremely hot temperatures, or be subjected to direct water spray. Check the local voltage to ensure adequate horsepower can be delivered to operate the pump at full load. Good technical support and a reputation for dependability are critical factors that should not be overlooked when selecting a pump.
Even the best pump will fail if the steps for proper installation are ignored. A good installation should include careful consideration of several enemies of every pump system: starvation, cavitation, pulsation, abrasion and overpressure.
Starvation. Starvation is the restriction of inlet liquid flow to the pump. The result is a pump that runs dry and overheats, which will quickly destroy the pump seals and valves.
Liquid pumps are designed to contain liquid at all times to provide lubrication to the seals. To assure a positive feed to the pump inlet, size the inlet feed line one size larger than the pump inlet port, shorten the line length, replace 90-degree elbows with swept elbows and consider adding a booster pump. Install adequately-sized filters to avoid frequent clogging, and size the supply tank to sufficiently cover the system demand. Consider heat introduced from bypass, and review the total demands on the facility water supply to reduce the risk of starvation.
Cavitation. Cavitation is the formation and collapse of vapor bubbles in the pumped liquid. The energy released from the collapse of these bubbles during the suction stroke causes erosion, and this condition will result in severe damage to the pump.
Cavitation can be minimized by keeping a consistent inlet pressure, protecting the pump from excessive heat, increasing the inlet supply line, minimizing the number of elbows and eliminating excess turbulence when using a supply tank. Sudden changes in water velocity (often found with long feed lines) can create a water hammering effect with extremely high impact loads. Most piston and plunger pumps operate with a flooded suction to 60-psi inlet pressure. Feeding the pump from a properly sized, baffled (minimum two baffles) supply tank (six to 10 times system capacity) is a proven and preferred method.
Some liquids, however, such as high vapor and high temperature liquids, may require a pressurized feed. Both booster feed and long inlet lines benefit from a captive acceleration tube (CAT) at the inlet of the pump that is designed to provide a stable inlet pressure and enhance the life of the pump.
Pulsation. Pulsation refers to repetitious surges in the system liquid that can cause fatigue to the pump components, fittings, accessories and plumbing. The triplex pump design minimizes pulsations from the pump. A pulsation dampener at the head of the pump and the CAT at the pump inlet will help control system pulsations. Installing a reinforced flexible hose between the pump and any hard plumbing will also help absorb flow surges and extend the life of the pump.
Abrasion. Standard piston and plunger pumps do not tolerate abrasive liquids, which will prematurely wear seals and valves. If pumping recycled liquids, installation of an inexpensive inlet strainer or special smaller micron filtration can control abrasion. Some systems may call for larger capacity or dual filters to prevent frequent clogging. Some local water conditions may require water softening to prevent scale buildup in the pump and plumbing.
Overpressure. Protecting the pump from overpressure is a critical life factor. It is recommended that every high-pressure system include a primary and secondary safety valve. The primary valve is for setting system pressure and protection against overpressure caused by discharge line obstructions. A secondary safety valve is typically set approximately 200 psi above the system pressure and only goes into bypass should the primary valve fail.
Equally important is a pressure gauge. This inexpensive accessory is the system monitor. Low or fluctuating pressure readings indicate the system is not functioning correctly and prompts users to initiate scheduled maintenance. Excessive inlet pressure can result in premature seal failure. This can be prevented with the installation of a pressure-reducing valve in the inlet line. To optimize the pump life, these primary system accessories should be included in the pump system.
Preventative maintenance is the easiest and least expensive step in maximizing pump life. Each system is different, so it is important to establish a regularly scheduled preventative maintenance program that is exclusive for the system.
Following initial start-up, inspect the seals and valves for wear after the first oil change, typically around 500 hours. If no wear is visible, check again at 1,000 and 1,500 hours or until wear is noticed. This time frame will become the maintenance schedule. Use genuine original manufacturers’ service parts to assure full rated performance and maximum pump life. Refer to manufacturers’ owner’s manuals for service procedures and identifying potential system problems.
Following these basic selection, installation and maintenance guidelines will help maximize pump life and produce the greatest return on pump investment.