Flowserve LPNV Worthington - Manual (Page 29)

LPNV USER INSTRUCTIONS ENGLISH 87900031 – 06/14
Page 29 of 48
5.7.5 Normal vibration levels, alarm and trip
For guidance, pumps generally fall under a
classification for rigid support machines within the
International rotating machinery standards and the
recommended maximum levels below are based on
those standards.
Alarm and trip values for installed
pumps should be based on the actual
measurements (N) taken on the pump in the fully
commissioned as new condition. Measuring
vibration at regular intervals will then show any
deterioration in pump or system operating
conditions.
Vibration velocity – unfiltered
mm/s (in./s) r.m.s. LPNV
mm/s (in./s) r.m.s.
Normal N  5 (0.2)
Alarm N x 1.25  6.2 (0.25)
Shutdown trip N x 2.0  10 (0.4)
5.7.6 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
Above 90 (120) 6
Where duty and standby pumps are installed it is
recommended that they are run alternately every
week
.
5.8 Normal Start Up
The starting procedure to be followed for normal
start up is the same as that for initial starting with the
exception that Step (J) section 5.6 "CHECK
ROTATION" does not have to be repeated as long
as driver systems have not been changed since last
pump operation.
5.9 Stopping the pump
a) Shut down driver.
The pump should be shut down
rapidly to protect the internal wearing parts
which are lubricated by the liquid being pumped.
If pump stops abruptly when driver is shut
down, investigate for pump binding. Take necessary
remedial action before restarting pump.
b) Close the pump discharge valve, while the
suction valve normally remains open.
c) Close valve in bypass line and closed whenever
possible, switch off flushing and/or cooling liquid
supplies.
If pump is subjected to freezing
temperatures the pump must be drained of liquid
to prevent damage to the pump.
For pumping hot liquid or fluid
subject to crystallize, the flush supply must be
maintained on completion of pumping, to avoid
seals damage.
In some installations the use of a check
valve is not feasible due to the creation of pressure
surges or water hammer as a result of the sudden
closing of the valve under high discharge pressure.
In such cases the discharge valve should be closed
slowly prior to stopping the driver to eliminate the
possibility of water hammer
.
5.10 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 notes on section
3.4 may help the user decide how to evaluate the
implications of any change. If in doubt contact your
nearest Flowserve office.