9
English (US)
The supply of refrigerant to the pump must come directly from a
reservoir (separator/receiver/vessel) with a bottom outlet. Do not
supply refrigerant through the top or side of the reservoir
connected to an internal stem tube.
Supply of refrigerant to pump must not come directly from a
pipeline with flow originating from other processes or supplying
other types of components.
The location of the drop leg must be placed in an undisturbed
section of the reservoir to avoid disturbances to the pump.
The available NPSH in an installation is defined below. It is
quantified as the difference in height between the minimum liquid
level in the reservoir to the inlet connection of the pump. The
reservoir minimum liquid level is 12 inches above the drop leg
connection.
The pump requirement for NPSH must be evaluated at the
nominal flow rate as a minimum. See example in section
Fig. 5
Preferred design for inlet pipe system, drop leg with
one or more pump legs
The lightweight pump design is not suitable for carrying heavy
loads from the pipe system. Large temperature and pressure
variations are to be expected during startup, operation and
service, and the pipe system must be designed for this. Loads
from the pipe system must not generate any resulting axial load
along the pump axis or any resulting torque around the pump
axis.
Allowable flange loading imposed by the piping must be in
accordance with HI 9.6.2. Ensure that the maximum allowable
forces and torques for the pipe connections are not exceeded.
The pipe system must be designed according to the special
requirements for pipe transport of refrigerants that may exist
either as a liquid or as a liquid/vapor mixture. Vapor bubbles may
form in the pump and in the inlet pipe system during standstill and
operation, and they must travel freely away from the pump and
back to the reservoir. Avoid designs that prevent back-flow of
vapor or can trap vapor.
The following issues must always be considered when designing
the pipe system:
• Possibility for sealing off the pump section for service and
replacement.
• Possibility for pump evacuation, safe discharging and charging
of refrigerant. We recommend that you use the pump drain
connection for discharging the refrigerant. The drain has
internal thread (1/4" NPT).
All piping is to be flushed before operating the pump.
5.4.1 Inlet pipe
In a single-pump setup, the length of the pipeline from the
reservoir to the pump must be as short as possible.
For multiple pumps, the drop-leg and the pump-leg are the two
sections of the pipeline, where the drop-leg is shared between all
pumps. Make sure that the pump-leg length is as short as
possible so that most of the length of the pipeline from the vessel
to the pump is made up by the drop-leg. For standby or
simultaneous operation, a design with a single large main drop-
leg and individual pump-legs is optimal. See fig.
Alternatively, consider individual drop-legs for each pump
operating simultaneously. See fig.
Fig. 6
Piping of pumps in parallel for alternating (standby) or
simultaneously operation
Fig. 7
Piping of pumps in parallel for simultaneous operation
Drop-leg(s) must always include a vortex breaker and horizontal
baffle plate in the reservoir outlet.
The continuation of the piping from the drop-leg to multiple
individual pump legs must be symmetrical to avoid differences in
flow rates/pressure drops and ability for allowing back-flow of
vapor.
The dimensioning flow rate must always be the nominal flow rate
of the pump or larger. For multiple pumps in parallel,
simultaneous operation, the dimensioning flow rate for the
common drop-leg is the sum of the individual nominal pump flow
rates or larger.
TM0
6
849
1
0
2
1
7
NPSH
Pump Leg
Oil Drain
Pumps
Drop Leg
15 degrees
Pump Leg
Vessel
(separator/receiver/intercooler)
TM
04
6
810
12
11
TM
04
68
30
12
11
Содержание CRN-H MAGdrive
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