9
11. Start-up and operation
11.1 BMPX
This section and the subsequent subsections make references to
the piping and instrumentation diagram, fig. 12.
1.
All valves should be in their normal operating positions.
2.
Start the sea-water feed pump (P1) with flow through the
X-Changer (X1) and through the bypass of the BMP hp feed
pump (P3).
3.
Start the BM hp circulation pump (P4) as soon as pressure
has built up in the system. See section
.
4.
Vent air from the system. Open the solenoid valve (V4) on the
BM hp circulation pump (P4) and slacken the vent plugs on
the BMP hp feed pump (P3). Let the pump run with sea water
for 5 minutes to ensure that all air is released. Close the
solenoid valve on the BM hp circulation pump and retighten
the vent plugs on the BMP hp feed pump.
5.
Adjust the low-pressure reject-water valve (V3) on the
discharge side of the X-Changer (X1) until the low-pressure
sea-water inlet flow (FM2) equals the calculated sea-water
discharge flow (FM3).
6.
Adjust the variable-frequency drive on the BM hp circulation
pump (P4) or control valve (V2) until the desired flow rate is
achieved as indicated by the high-pressure flowmeter (FM3).
FM3 = FM2 (= balanced flow). See section
for important and detailed information.
7.
All flows in and out of the X-Changer (X1) should be balanced
to within 5 % for optimum operation.
Note:
If any doubt exists in reading the flowmeter, the low-
pressure sea-water inlet should be the greater of the two
flows (FM2 > FM3). Zero mixing can be achieved by flowing
the sea-water inlet approximately 10 % higher than the sea-
water discharge.
8.
Start the BMP hp feed pump (P3).
9.
Finally, the BMPX system will produce the permeate flow
equal to the flow from the BMP hp feed pump.
The sound pressure level from the X-Changer (X1) will
increase. Small variations in sound pressure level and rotor
speed are normal.
Caution:
The low-pressure and high-pressure flows through
the X-Changer must never exceed the rated maximum flow
for the chosen X-Changer.
10. The variable-frequency drive feedback for the BM hp
circulation pump (P4) can be switched to automatic control
using FM2 compared to FM3. The solenoid valve (V4) must
be opened three times a day (every 8 hours) for 30 seconds
to allow flushing of stagnant sea water in the BM hp
circulation pump (P4).
11.2 Flow control and balancing
Flow rates and pressures in a typical BMPX system vary slightly
over the life of the system due to temperature variations,
membrane fouling or feed salinity variations. The X-Changer rotor
is powered by the flow of liquid through the unit. The speed of the
rotor is self-adjusting over the operating range of the X-Changer.
11.3 High-pressure flow control
The flow through the BM hp circulation pump (P4) is adjusted with
the control valve (V2) or a variable-frequency drive to control the
flow rate of the high-pressure sea-water discharge from the
X-Changer and high-pressure brine inlet to the X-Changer. The
high-pressure sea-water discharge flow equals the high-pressure
brine inlet flow.
11.4 Low-pressure flow control
The low-pressure reject-water valve (V3) on the discharge side of
the system must be adjusted to control the flow rate of the low-
pressure sea-water inlet and low-pressure brine discharge. This
valve also adds back-pressure on the X-Changer required to
prevent destructive cavitation. The low-pressure sea-water inlet
flow equals the high-pressure brine-reject water inlet flow.
11.5 Operation settings
The flow and discharge pressure of the BMPX system should
always be kept within the ranges for which it was originally
designed. See the "Technical specification" supplied with the
system.
If the system requires flows and pressures outside the design
range, changes are possible. Please contact Grundfos.
11.6 Balancing the X-Changer
This section and the subsequent subsections make references to
the piping and instrumentation diagram, fig. 12.
1. Start the sea-water feed pump (P1).
2. Adjust the low-pressure reject-water valve (V3) on the
discharge side of the X-Changer (X1) until the low-pressure
sea-water inlet flow (FM2) equals the calculated sea-water
discharge flow (FM3).
3. Start the BM hp circulation pump (P4). See section
.
4. Adjust the variable-frequency drive on the BM hp circulation
pump (P4) or control valve (V2) until the desired flow rate is
achieved as indicated by the high-pressure flowmeter (FM3).
FM3 = FM2 (= balanced flow).
To achieve balanced flow through the X-Changer (X1), use
flowmeters installed on the low-pressure sea-water inlet piping
and high-pressure sea-water discharge piping. All flows in and
out of the X-Changer should be balanced to within 5 % for
optimum operation.
The X-Changer is designed to operate at liquid mixing levels
below 5 %. Balanced flows control the mixing of concentrate with
the feed. Zero mixing can be achieved by flowing the sea-water
inlet approximately 10 % higher than the sea-water discharge.
Flowing the sea-water inlet much less than the sea-water
discharge will result in lower-quality permeate, increased feed
pressure and higher energy consumption.
Recommended practice for the BM hp circulation pump is to use
a slightly oversized pump to handle projected membrane
concentrate flows, taking into account seasonal variations,
membrane fouling and manifold losses. The flow and pressure of
the BM hp circulation pump can be controlled with a variable-
frequency drive (P4) or control valve (V2).
Caution
It may be necessary to let the BMP hp feed pump
(P3) run at minimum speed (to vent the system).
If so, the solenoid valve (V4) on the BM hp
circulation pump must be open.
Note
The following procedure should be applied to
achieve balanced flows.
Note
If any doubt exists in reading the flowmeter, the
low-pressure sea-water inlet should be the
greater of the two flows (FM2 > FM3).
Caution
Operating the X-Changer with unbalanced flows
may result in contamination of the sea-water feed
by the brine reject.
Caution
The low-pressure and high-pressure flows
through the X-Changer must never exceed the
rated maximum flow. The only reliable way to
determine this flow is to use a low-pressure
flowmeter (FM2) or a high-pressure flowmeter
(FM3), respectively.
