Design Standards For Suction Pumps: What You Need To Know

September 8, 2022

A single-stage pump with only one impeller is what is known as an end suction pump. This type of pump comes with isolation valves, vibration isolators, a suction strainer, long-radius ell and reducer at the inlet, a spring-supported inertia block, drain pan, and other amenities typically associated with hydronic service. If isolation valves are necessary, they can often take the form of a butterfly, gate, plug, or ball valves, depending on the size of the line and the duty requirements. In most cases, the overhead suspension supports the weight of the pipe connected to the vibration isolation fittings.

The Strainer

To capture material in the system, a strainer is necessary. The strainer has a blowdown provision that allows loose particles to be flushed from the strainer when the pump input valve is closed, and backflow from the pump discharge occurs through the flush valve. The flush valve is usually a 2-inch or larger ball valve equipped with a pipe "tailpiece" directed to a floor drain for spill control. The strainer's screen should be particularly designed for usage in a water system. If a strainer is used in a condenser water system, it should have wider apertures than those used for cold water supply. The strainer in the cooling tower base is often sufficient for this function, and the one in the piping is unnecessary. Because strainers can be purchased as part of air separators and pump suction diffusers, plans and specifications should be carefully coordinated to guarantee that a chilled or hot water hydronic system only has one strainer.

Inlet to the pump

A suction diffuser or a straight length of pipe into the pump suction is required for an end suction pump. If a straight pipe section feeds the pump, it should be at least three pipe diameters long, supplied through a long radius elbow, and have a reducer fitting at the pump input. All of these factors contribute to consistent flow into the pump impeller. A stanchion pipe support may be necessary depending on the weight of the pump intake piping from the vibration isolator downward. If necessary, the stanchion should be supported from the pump base, and no spring-isolated inertia pad is employed. A spring-isolation inertia pad is not usually required with tiny pumps.

Pump Release

An increaser at the pump output is typical and required in hydronic systems. This is due to the noise of the high-velocity flow during pump discharge. When pumps operate in parallel or water must be held in a system to keep it full, such as a cooling tower positioned at rooftop level above a mechanical equipment room, a check valve is necessary for the pump discharge.

Ports of Pressure

All pumps should have provisions for detecting differential pressures so that pump flow may be calculated using the manufacturer's pump curves. The configuration enables pressure measurements to be taken with a single gauge. Pete's plugs are recommended in cases where pressures are not too high (200 psi), and operating temperatures allow it. Other ports and taps are occasionally accessible in the pump's suction and discharge flanges. If they exist, they should be used for pressure measurement throughout the pumps since the manufacturer has most likely used measurements in these places to generate pump curves.

Piping Isolation

Pipe vibration isolation fittings, which are usually made of rubber bellows and sometimes mounted in a stainless-steel braided wire jacket when service limits require it, are sold by several companies. When the vibration is small, grooved couplings can be used at the pump and at the top of the discharge pump riser, where it goes into a manifold or changes direction. This is a cheap way to keep noise from getting through the pipes and stop vibrations. But the use of grooved couplings is also limited by the type of fluid service and the expected amount of vibration.

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