Vacuum Priming FAQ
A vacuum priming system is an industrial quality system designed specifically for the challenges associated with priming centrifugal and turbine pumps when the water source is below the pumps (e.g. a non-flooded suction). Major components include vacuum pumps, air receivers, priming valves, and control panels. Priming systems are typically manufactured in simplex or duplex designs with rotary vane or liquid ring vacuum pumps used to produce the necessary vacuum. Fully automatic controls are most common; however, systems with manual controls are available. A well-designed priming system allows the use of more reliable, cost-effective pump technologies while ensuring that pumps are always ready to start immediately without troublesome start-up procedures.
Priming systems can be used in any application where a water source needs to be lifted to a higher elevation. Since the introduction of the Q-VAC brand in the early 1990’s, Q-VAC priming systems have been installed in municipal water plants, wastewater treatment plants, commercial ships, naval ships, marine applications, siphon control systems, irrigation systems, aquariums, steel mills, power plants, fountains, landfills, industrial applications, and other pump priming applications.
Before most pumps can begin operating they must first be filled with liquid. This process is known as priming. Priming is not difficult when the water source is above a pump, but it can be a major problem when the water source is lower. Although site excavation and several pump technologies can deal with this problem, most operators and engineers agree that common issues such as higher costs, lower reliability, and more frequent pump replacements are less than ideal. Q-VAC priming systems solve these problems and allow the use of more reliable, cost-effective pump technologies. A single Q-VAC system automatically maintains prime on every pump connected to it so pumps are ready to start immediately without troublesome start-up procedures.
The use of a well-designed priming system allows the use of more reliable, longer lasting, cost-effective pump technologies (i.e. standard, non-self-priming vs. self-priming pumps) while ensuring that pumps are always ready to start immediately without troublesome start-up procedures. They eliminate the possibility of a pump becoming air-bound or losing its prime, and they can even increase pumping efficiency by continuously evacuating air trapped in the pump volute. Finally, since only one priming system is needed to prime multiple pumps, installation costs are lower, and run-time is limited, making the overall cost of ownership is lower than other options.
If you’ve ever used a drinking straw, you’ve seen the operating principle in action. First, a vacuum line is piped from the Q-VAC system to each pump through a specially designed priming valve. When the Q-VAC system is started, a vacuum is created which removes the air from the suction piping and pumps. As the vacuum level increases, the water level rises at a predictable rate until each pump is fully flooded and the float-actuated priming valve closes. Concurrently, the pump’s prime status is verified by a proof of prime level switch wired to the customer’s controls. At this point, any pump can be started at any time.
It is important to note that a Q-VAC priming system operates independently from the pumps being primed. It ONLY cycles “on” to restore the vacuum level when it drops to a preset control setpoint. In most cases, a Q-VAC priming system only runs a few hours per day, even if the pumps are running continuously. Now that’s efficient!
Absolutely not! Although the general components of a priming system may be similar between manufacturers, there can be great differences in the quality of components, attention to detail, control panel features, and overall construction. These variances can make the difference between a system that performs well for many years, and one that fails prematurely. Q-VAC priming systems are designed with the operator in mind to provide industry leading performance and quality. Manufactured by Combined Fluid Products Company (CFP), Q-VAC is backed by a financially strong company with a responsive team and over 40 years of experience satisfying customers.
Yes, priming systems are often used to start a siphon’s flow and maintain the siphon by continuously removing any air that collects in the piping from outgassing or leaks.
A priming valve is a specially designed air release valve with a level sensitive float that opens and closes based on water level. It should be installed as the high point in the suction piping. During initial priming, or when air collects inside the valve, an internal orifice opens so the priming system can remove the air from the suction piping and pump volute. When the valve is fully flooded, the orifice will close to isolate the system and prevent water from entering the vacuum header. By automatically opening and closing based on water level, a priming valve allows continuous air removal from the process to eliminate efficiency-robbing air pockets.
Yes, it is best practice to install one priming valve for each pump.