Piping; General Precaution; Suction Piping - Grundfos LS 500-300-490E Installation And Operating Instructions Manual

5. Piping

5.1 General precaution

Do not use pump as a support for piping.
• Use pipe hangers or other supports at proper
intervals to provide complete piping support near
the pump.
• Both suction and discharge piping should be
independently supported and properly aligned so
that no strain is transmitted to the pump when
flange bolts are tightened.
• Do not spring or force piping when making any
connections.
• Make sure piping is as straight as possible,
avoiding unnecessary bends and fittings.

5.2 Suction piping

The sizing and installation of suction piping is
particularly important. It must be selected and
installed in a manner that minimizes pressure loss
and permits sufficient liquid flow into the pump during
starting and operation. Many NPSH problems can be
traced directly to improper design of suction piping
systems. Observe the following precautions when
installing suction piping:
• Suction piping should be as straight as possible,
and ideally the pipe length should be at least
seven times the pipe diameter. Short suction
piping can be the same diameter as the suction
opening. Longer piping should be one or two
sizes larger (depending on length), reducing to the
diameter of the pump suction opening.
• Use an eccentric reducer, with the eccentric side
down, when reducing the pipe diameter to the
diameter of suction opening.
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5
2
4
6
Suction piping eccentric vs. concentric
Pos. Description
1 Right
2 Wrong
3 Taper is down
4 Air pocket
5 Eccentric reducer
6 Concentric reducer
• At no point should suction piping be smaller in
diameter than the pump suction opening.
• Horizontal suction lines should follow an even
gradient, if possible. A gradual upward slope to
the pump is recommended for suction lift
conditions.
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