Inadequate inlet conditions can cause serious malfunctions in the best-designed pump. Surprisingly, the simplest of things can cause the most severe problems or go unnoticed by the unfamiliar or untrained eye. REVIEW THIS CHECKLIST BEFORE THE OPERATION OF ANY SYSTEM. Remember, no two systems are alike, so there can be no ONE best way to set up a system. All factors must be carefully considered. INLET SUPPLY should exceed the pump’s maximum flow to ensure proper performance.
❏ Open the inlet shut-off valve and turn on the water supply to avoid starving the pump. DO NOT RUN THE PUMP DRY.
❏ Temperatures above 130°F are permissible. Add 1/2 PSI inlet pressure per degree F over 130°F. Elastomer or RPM changes may be required. See Tech Bulletin 002 or call CAT PUMPS for recommendations.
❏ Avoid closed-loop systems, especially with high temperatures, ultra-high pressure, or large volumes. Conditions vary with regulating/unloading valves.
❏ Low vapour pressure liquids, such as solvents, require a booster pump and CAT to maintain an adequate inlet supply.
❏ Higher viscosity liquids require a positive head and a CAT to ensure adequate inlet supply.
❏ Higher-temperature liquids tend to vaporize and require positive heads and CAT to ensure adequate inlet supply.
❏ When using an inlet supply reservoir, size it to provide adequate liquid to accommodate the maximum output of the pump, generally a minimum of 6 to 10 times the GPM (however, a combination of system factors can change this requirement); provide adequate baffling in the tank to eliminate air bubbles and turbulence; install diffusers on all return lines to the tank. INLET LINE SIZE should be adequate to avoid starving the pump.
❏ Line size must be a minimum of one size larger than the pump inlet fitting. Avoid tees, 90-degree elbows, or valves in the inlet line of the pump to reduce the risk of flow restriction and cavitation.
❏ The line MUST be a FLEXIBLE hose, NOT a rigid pipe, and reinforced on SUCTION systems to avoid collapsing.
❏ The simpler the inlet plumbing the less the potential for problems. Keep the length to a minimum, the number of elbows and joints to a minimum (ideally no elbows), and the inlet accessories to a minimum.
❏ Use pipe sealant to ensure air-tight, positive sealing pipe joints. INLET PRESSURE should fall within the specifications of the pump.
❏ Acceleration loss of liquids may be increased by high RPM, high temperatures, low vapour pressures, or high viscosity and may require a pressurized inlet and CAT to maintain adequate inlet supply. DO NOT USE A CAT WITH A SUCTION INLET.
❏ Optimum pump performance is obtained with +20 PSI (1.4 BAR) inlet pressure and a CAT for specific applications. With adequate inlet plumbing, most pumps will perform with flooded suction. The maximum inlet pressure is 70 PSI (4.9 BAR).
❏ After prolonged storage, the pump should be rotated by hand and purged of air to facilitate priming. Disconnect the discharge port allowing liquid to pass through the pump and measure flow. INLET ACCESSORIES are designed to protect against overpressurization, control inlet flow, contamination, or temperature, and provide ease of service.
❏ A shut-off valve is recommended to facilitate maintenance.
❏ Installation of a CAT is essential in applications with stressful conditions such as high temperatures, booster pump feed, or long inlet lines. Do not use CAT. with negative inlet pressure.
❏ A standpipe can be used in some applications to help maintain a positive head at the pump inlet line.
❏ Inspect and clean inlet filters on a regular schedule to avoid flow restrictions.
❏ A pressure transducer is necessary to accurately read inlet pressure. Short-term, intermittent cavitation will not register on a standard gauge.
❏ All accessories should be sized to avoid restricting the inlet flow.
❏ All accessories should be compatible with the solution being pumped to prevent premature failure or malfunction.
❏ Optional inlet protection can be achieved by installing a pressure cut-off switch between the inlet filter and the pump to shut off the pump when there is no positive inlet pressure. BY-PASS TO INLET Care should be exercised when deciding the method of the bypass from control valves.
❏ It is recommended the by-pass be directed to a baffled reservoir tank, with at least one baffle between the by-pass line and the inlet line to the pump.
❏ Although not recommended, by-pass liquid may be returned to the inlet line of the pump if the system is properly designed to protect your pump. When a pulsation dampener is used, a PRESSURE REDUCING VALVE must be installed on the inlet line (BETWEEN THE BY-PASS CONNECTION AND THE INLET TO THE PUMP) to avoid excessive pressure on the inlet of the pump. It is also recommended that a THERMO VALVE be used in the by-pass line to monitor the temperature build-up in the by-pass loop to avoid premature seal failure.
❏ A reinforced, flexible, low-pressure hose rated up to 300 PSI should be used for routing by-pass back to the pump inlet.
❏ Caution should be exercised not to undersize the by-pass hose diameter and length. Refer to Technical Bulletin 064 for additional information on the size and length of the by-pass line.
❏ Check the pressure in the by-pass line to avoid overpressurizing the inlet.
❏ The by-pass line should be connected to the pump inlet line at a gentle angle of 45° or less and no closer than 10 times the pump inlet port diameter e.g., 1-1/2″ port size = 15″ distance from the pump inlet port.