Product Manual

SP introduction
SQ, SQE, CU 331, and SP
12
60
Check valve
All pumps are equipped with a reliable check valve in
the valve casing preventing back flow in connection
with pump stoppage.
Furthermore, the short closing time of the check valve
means that the risk of destructive water hammer is
reduced to a minimum.
The valve casing is designed for optimum hydraulic
properties to minimize the pressure loss across the
valve and thus to contribute to the high efficiency of
the pump.
Note: As shown in fig. 54 the check valve is spring
assisted intended for vertical pump applications. When
installing pump at an angle, installation requires an
additional check valve installed in the discharge piping.
This prevents misalignment or failure to seat the pump
check valve at an angle. Additional check valve in
discharge piping sold separately.
Fig. 54 Check valve
Priming screw
All Grundfos 4" pumps are fitted with a priming screw.
Consequently, dry running is prevented, because the
priming screw will make sure that pump bearings are
always lubricated.
Due to the semi-axial impellers of large SP pumps this
priming is provided automatically.
However, it applies to all pump types that if the water
table is lowered to a level below the pump inlet neither
pump nor motor will be protected against dry running.
Fig. 55 Priming screw
Stop ring
The stop ring prevents damage to the pump during
transport and in case of up-thrust in connection with
start-up.
The stop ring, which is designed as a thrust bearing,
limits axial movements of the pump shaft.
Example: SP 385S
The stationary part of the stop ring (A) is secured in the
upper intermediate chamber.
The rotating part (B) is fitted above the split cone (C).
Fig. 56 Stop ring (rotating and stationary part) and the split
cone
TM01 2499 1798TM00 7304 1096
Valve flap
TM01 3327 0412
A
B
C