AC International 8200 Series Suction Piping, Suction Installations, Piping Supports Not Shown

and properly aligned, so that no strain is transmitted to the pump when the flange bolts are tightened. Use pipe hangers or other supports at necessary intervals to provide support. When expansion joints are used in the piping system, they must be installed beyond the piping supports closest to the pump. Tie bolts should be used with expansion joints to prevent pipe strain. Do not install expansion joints next to the pump or in any way that would cause a strain on the pump resulting from system pressure changes. It is usually advisable to increase the size of both suction and discharge pipes at the pump connections to decrease the loss of head from friction.

Install piping as straight as possible, avoiding unnecessary bends. Where necessary, use 45-degree or long sweep 90-degree fitting to decrease friction losses.

Make sure that all piping joints are air-tight.

Where flanged joints are used, assure that inside diameters match properly.

Remove burrs and sharp edges when making up joints.

Do not “spring” piping when making any connections.

SUCTION PIPE INSTALLED WITH A GRADUAL RISE TO PUMP

LEVEL

CENTER LINE	CORRECT
OF PIPE
	AIR POCKET
	INCORRECT

AIR POCKET

INCORRECT

AIR POCKET

INCORRECT

GRADUAL RISE

TO PUMP

CHECK VALVE GATE VALVE

INCREASER

Provide for pipe expansion when hot fluids are to be pumped.

Suction Piping

When installing the suction piping, observe the following precautions. Figure 8 shows some correct and incorrect suction piping arrangements.

The sizing and installation of the suction piping is extremely important. It must be selected and installed so that pressure losses are minimized and sufficient liquid will flow into the pump when started and operated. Many NPSH (Net Positive Suction Head) problems can be attributed directly to improper suction piping systems.

Friction losses caused by undersized suction piping can increase the fluid’s velocity into the pump. As recommended by the Hydraulic Institute Standard ANSI/HI 1.1-1.5-1994, suction pipe velocity should not exceed the velocity in the pump suction nozzle. In some situations pipe velocity may need to be further reduced to satisfy pump NPSH requirements and to control suction line losses. Pipe friction can be reduced by using pipes that are one to two sizes larger than the pump suction nozzle in order to maintain pipe velocities less than 5 feet/second.

NO AIR

POCKETS

CORRECT

NO AIR	GRADUAL RISE
POCKETS	TO PUMP

ECCENTRIC

REDUCER

CORRECT

DISTANCE PLUS

ECCENTRIC REDUCER

STRAIGNTENS FLOW

CORRECT

PATH OF WATER

INCORRECT

FIGURE 8 – SUCTION INSTALLATIONS

(PIPING SUPPORTS NOT SHOWN)

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