Flowserve NMD - Manual (Page 21)

NMD, NMAD USER INSTRUCTIONS ENGLISH 71576436 - 11/09
Page 21 of 40
Alarm and trip values for installed
pumps should be based on the actual
measurements (N) taken on site on the bearing
housings of the pump in the fully commissioned as
new condition.
The example (N) value is given for the preferred
operating flow region (typically this may extend to 70
to 120 % of the pump best efficiency point); outside
the preferred flow region the actual vibration
experienced may be multiplied by up to 2.
These standard values can vary with the rotational
speed and the power absorbed by the pump. For
any special case, do not hesitate to consult us.
Measuring vibration at regular intervals will then
show any deterioration in pump or system operating
conditions.
Vibration Velocity -
unfiltered
Horizontal
Configuration
mm/s (in./s)
r.m.s.
Vertical
Configuration
mm/s (in./s)
r.m.s.
Normal N ≤ 5.6 (0.22) ≤ 7.1 (0.28)
Alarm N x 1.25 ≤ 7.1 (0.28) ≤ 9.0 (0.35)
Shutdown Trip N x 2.0 ≤
11.2 (0.44)
≤
14.2 (0.56)
5.5.6 Stop/start frequency
Pump sets are normally suitable for the number of
equally spaced stop/starts per hour shown in the
table below. Check actual capability of the driver and
control/starting system before commissioning.
Motor rating kW (hp)
Maximum stop/starts
per hour
Up to 15 (20) 15
Between 15 (20) and 90 (120) 10
90 (120) to 150 (200) 6
Above 150 (200) Refer
Where duty and standby pumps are installed it is
recommended that they are run alternately every
week.
5.6 Stopping and shutdown
5.6.1 Stopping and restarting in continuous
running
According to hydraulic conditions of the installation
and its automation degree, stop and restart
procedures can have different forms. Nevertheless
all of them must respect imperatively the following
rules:
Stopping:
a) Avoid that the unit turns in the opposite direction
to the normal running.
b) Make sure that the discharge line pressure does
not reach the foot valve.
c) Avoid a continuous running below the authorized
flow rate (see § 5.4.2).
Restart:
a) Ensure that the pump is completely full of liquid.
b) Ensure a continuous supply with a sufficient
available NPSH.
c) Ensure a backpressure so that the motor power
is not in excess.
d) Respect the starting frequency
imposed by the motor manufacturer.
e) Protect the pump against water hammer
when stopping or starting.
Shutdown:
Close the outlet valve and stop the
motor. Eventually close the inlet valve.
For prolonged shutdowns and
especially when ambient temperatures are likely to
drop below freezing point, the pump and any cooling
and flushing arrangements must be drained or
otherwise protected.
5.7 Hydraulic, mechanical and electrical
duty
This product has been supplied to meet the
performance specifications of your purchase order,
however it is understood that during the life of the
product these may change. The following notes may
help the user decide how to evaluate the
implications of any change. If in doubt contact your
nearest Flowserve office.
5.7.1 Specific gravity (SG)
Pump capacity and total head in meters (feet) do not
change with SG, however pressure displayed on a
pressure gauge is directly proportional to SG. Power
absorbed is also directly proportional to SG. It is
therefore important to check that any change in SG
will not overload the pump driver or over-pressurize
the pump.
5.7.2 Viscosity
For a given flow rate the total head reduces with
increased viscosity and increases with reduced
viscosity. Also for a given flow rate the power
absorbed increases with increased viscosity, and
reduces with reduced viscosity. It is important that
checks are made with your nearest Flowserve office
if changes in viscosity are planned.