PB3 User Instruction
Page 23 of 39
The strainer may be fitted with a finer screen to filter the inlet flow. When this is done, 40 mesh screens is
typically used for start-up operation, at reduced flow rates. For final operation in a closed system, the suction
strainers are normally removed after the system is cleaned. For critical pump applications, where continuous
screening of suction flow is desirable, and in open systems, 20-mesh screening is typically used for permanent
strainers. At all times, when using screens and suction strainers, it is critical that pressure drop across the screen
and/or strainer be constantly monitored to ensure that the pump suction pressure does not fall below that
required to prevent cavitation.
When dirt and scale have been removed from the system, as indicated by no further change in pressure drop
across the strainer with time, the start-up strainer may be removed or the screen may be replaced with one
having larger openings. If a permanent strainer will be used during normal operation, the pressure differential
needs to be monitored on a continuous basis. If a permanent strainer is not used, the start-up strainer needs to be
temporarily reinstalled whenever the system is opened up for repair or routine maintenance. As long as a suction
strainer or screen remains in place, the differential pressure should be monitored on a regular basis
.
Caution
The pressure drop across the strainer is a direct reduction in the NPSH available to
the pump. NPSH available must always exceed the NPSH required by the pump.
This requirement may limit the pump flow rate, particularly during start-up operation.
Alarms or automatic pump shutdown devices should be installed to minimize the
possibility of pump damage. It is the responsibility of the pump operator to obtain
the allowable pressure drop across the strainer for safe pump operation from the
plant engineer or system designer prior to operation of the pump.
3.5.3 Coupling alignment check
Refer to section entitled shaft/coupling alignment and perform a coupling alignment check as outlined. This
check is recommended to insure the alignment has not been disturbed during installing suction and discharge
piping.
3.6 Electrical connections
DANGER
Electrical connections must be made by a qualified Electrician in accordance
with relevant local national and international regulations.
DANGER
It is important to be aware of the EUROPEAN DIRECTIVE on potentially
explosive areas where compliance with IEC60079-14 is an additional requirement
for making electrical connections.
WARNING
It is important to be aware of the EUROPEAN DIRECTIVE on electromagnetic
compatibility when wiring up and installing equipment on site. Attention must
be paid to ensure that the techniques used during wiring/installation do not
increase electromagnetic emissions or decrease the electromagnetic
immunity of the equipment, wiring or any connected devices. If in any doubt
contact PUMPIRAN for advice.
