Goulds Pumps 3311 - IOM - Manual (Page 7)

7
3 System Layout
3.1
Pipework
3.1.1 General
In short discharge lines, the nominal diameter should be
such that the piping resistance is only a small proportion
of the discharge head. For long pipelines, the most cost-
effective solution should be determined on a case-by-case
basis.
Flow velocity guidelines:
Suction line: v
s
≈ 1.5 to 2.5 m/s
max. 3 m/s
Discharge line: v
D
≈ 4 to 6 m/s
Abrupt cross-section transitions or sharp bends should be
avoided. Flow disturbances must be kept to a minimum
when making necessary branches.
Unfavorable pipework layouts may impair the
performance of the pump, especially on the suction side
(e.g. bends in several planes in front of the suction
nozzle).
• The pipework must be independently supported and
positioned such that no excessive forces and moments
are exerted on the pump flanges.
• Excessive loads could result in leakage and be
hazardous to personnel.
CAUTION
• If hot water is handled, excessive pipework loads and
moments can cause a misalignment of the coupling
between pump and driver, thus reducing the operating
safety of the unit.
Once the flange bolts have been released, the flanges must
not yield more than the amount corresponding to the
gasket thickness, nor must they be out of parallel nor bear
against each other under stress. Check that the flange
gaskets do not extend into the interior of the pipe. All pipe
components, valves and fittings and the pump nozzles
should be thoroughly cleaned before assembly.
Air-relief valves and drain valves must be installed in the
suction and discharge lines.
In order to prevent the formation of air pockets,
- a feed line (supply source above the pump) should
slope gradually downward towards the pump;
- a suction line (supply source below the pump) should
gradually rise to the pump.
Shut-off valves must be installed in the suction and
discharge lines and in all pipelines connecting the pump
with the liquid system.
The valves enable the pump to be depressurized and
dismantled without having to drain the system. Flow
regulation at constant speed is permissible from the
discharge side only.
CAUTION
• The pipes should have at least the nominal diameter of
the pump nozzles. Where this is not possible, it should
be ensured that the flow velocity in the suction or feed
line does not exceed 2 - 3 m/s.
• Flange seals must not extend into the interior of the
pipework.
• Clean the pipework prior to pump installation.
• Support the pipelines so as to prevent distortion of
pump components.
• Avoid rough cross-section transitions and sharp bends.
• Eccentric reducers must be used in the event of
different nominal diameters.
• In the event of unfavorable suction conditions, steady
flow should be ensured over a length of 15 x suction
nozzle diameter upstream from the suction nozzle.
• Shut-off valves in the suction or discharge line must
be fully open during operation and must never be
used to control the flow.