Thermo Scientific Dionex AXP User manual

Dionex
AXP/AXP-MS Metering Pump
Operator's Manual
Document No. 031897
Revision 05
December 2011

Dionex AXP/AXP-MS Manual
© 2011 by Thermo Fisher Scientific Inc. All rights reserved.
Chromeleon is a registered trademark of Thermo Fisher Scientific Inc. in the United States.
Autoflush and Autoprime are trademarks of Scientific Systems, Inc. PEEK is a trademark of Victrex PLC.
All other trademarks are the property of Thermo Fisher Scientific and its subsidiaries.
Thermo Fisher Scientific Inc. provides this document to its customers with a product purchase to use in the
product operation. This document is copyright protected and any reproduction of the whole or any part of this
document is strictly prohibited, except with the written authorization of Thermo Fisher Scientific Inc.
The contents of this document are subject to change without notice. All technical information in this
document is for reference purposes only. System configurations and specifications in this document supersede
all previous information received by the purchaser.
Thermo Fisher Scientific Inc. makes no representations that this document is complete, accurate or
error-free and assumes no responsibility and will not be liable for any errors, omissions, damage or loss
that might result from any use of this document, even if the information in the document is followed
properly.
This document is not part of any sales contract between Thermo Fisher Scientific Inc. and a purchaser. This
document shall in no way govern or modify any Terms and Conditions of Sale, which Terms and Conditions
of Sale shall govern all conflicting information between the two documents.
Revision history: Revision 01 released February 2003
Revision 02 released March 2004
Revision 03 released December 2005
Revision 04 released June 2006
Revision 05 released December 2011
For Research Use Only. Not for use in diagnostic procedures.
SAFETY REGULATIONS
The CE Mark label on the Dionex AXP/AXP-MS indicates that the pump is in compliance with the following
standards: EN 61010-1:1993 (safety), CAN/CSA-C22.2 No. 1010.1-92 + A2:97 (safety), UL 6101A-1
(safety), 93/68/EEC and 89/336/EEC (low-voltage directives), and the following EMC Standards: EN61000-
6-3: 2001, EN61000-6-1: 2001, EN 55022 Class A, EN 61000-3-2, EN 61000-3-3, EN 61000-4-2, EN 61000-
4-3, EN 61000-4-4, EN 61000-4-5, EN 61000-4-6, and EN 61000-4-11.

Dionex AXP/AXP-MS Manual
TABLE OF CONTENTS
1 Introduction ____________________________________________________________ 1
1.1 Description of the Dionex AXP/AXP-MS Pump ___________________________________1
1.2 Specifications for the Dionex AXP/AXP-MS Pump_________________________________3
2 Installation _____________________________________________________________ 4
2.1 Unpacking and Inspection _____________________________________________________4
2.2 Location/Environment ________________________________________________________4
2.3 Electrical Connections ________________________________________________________4
2.4 Solvent Preparation __________________________________________________________4
2.5 Instrument Installation________________________________________________________7
2.6 Preparation for Storage or Shipping_____________________________________________8
3 OPERATION __________________________________________________________ 10
3.1 Front Panel Controls and Indicators____________________________________________10
3.2 Rear Panel Remote Input_____________________________________________________13
4 THEORY OF OPERATION ______________________________________________ 14
4.1 Mechanical Operation________________________________________________________14
4.2 Electronic Control___________________________________________________________15
5 MAINTENANCE_______________________________________________________ 17
5.1 Filter Replacement __________________________________________________________17
5.2 Pump Heads________________________________________________________________17
5.3 Check Valve Cleaning and Replacement ________________________________________24
5.4 Lubrication ________________________________________________________________24
5.5 Fuse Replacement ___________________________________________________________24
5.6 Battery Replacement_________________________________________________________25
6 List of Replacement Parts ________________________________________________ 27
6.1 PEEK Head ________________________________________________________________27
6.2 Seals ______________________________________________________________________27
6.3 General____________________________________________________________________27
7 Interfacing Information__________________________________________________ 28
7.1 Rear Panel Serial Communications Port ________________________________________28
7.2 Rear Panel 6-Pin and 10-Pin Terminal Board Connectors__________________________31
7.3 Dionex AXP-MS Valve Plumbing and Port Assignments __________________________36
7.4 EZ Grip Fitting Guide _______________________________________________________37
Warranty___________________________________________________________________ 38
Customer Support ___________________________________________________________ 39

Dionex AXP/AXP-MS Manual
1
1 INTRODUCTION
This operator's manual contains information needed to install, operate,
and perform minor maintenance on the Thermo Scientific Dionex
AXP Metering Pump (P/N 063973) and the Thermo Scientific Dionex
AXP-MS Metering Pump (P/N 060925).
1.1 Description of the Dionex AXP/AXP-MS Pump
The Dionex AXP/AXP-MS high performance metering pump is
designed as a dependable metering pump for general laboratory or
industrial use.
The Dionex AXP pump flow rate can be set from 0.01 to 10.00
mL/min (in increments of 0.01 mL) with a precision of 0.5%.
The Dionex AXP-MS pump flow rate can be set from 0.01 to 1.00
mL/min (in increments of 0.01 mL) with a precision of 0.5%.
The low pulsation flow produced by the reciprocating, single-piston
pump is achieved by using an advanced rapid-refill design,
programmed stepper motor acceleration, and an internal pulse damper.
1.1.1 Pump Features
The Dionex AXP/AXP-MS Pump includes:
 Rapid refill mechanism to reduce pulsation
 PEEK™ pump head
 LED front panel readout of flow rate
 PRIME mode to flush out entrapped air bubbles upon start-up
 Flow adjustment in increments of 10 µL
 Microprocessor advanced control
 Digital stepper motor design to prevent flow rate drift
over time and temperature
 Rear panel RS-232 serial communications port for
complete control and status
Remote analog inputs to control flow rate (optional)
1.1.2 Wetted Materials
Pump heads, check valve bodies, and tubing are made of PEEK. Other
materials are synthetic ruby and sapphire (check valve internals and
piston).

Dionex AXP/AXP-MS Manual
1.1.3 Self-Flushing Pump Head
Self-flushing pump heads provide continuous washing of the piston
surface without the inconvenience of a manual flush or gravity feed
arrangement. The self-flushing pump head uses a diaphragm and
secondary set of check valves to create a continuous and positive flow
in the area behind the high pressure pump seal. The flushing solution
washes away any buffer salts that have precipitated onto the piston. If
not removed, these precipitates can abrade the high pressure seal and
cause premature seal failure, leakage, and damage to the pump.
Note: When the Dionex AXP is used as a sample loading pump for
trace ion applications, the convoluted diaphragm will cause sample
contamination. Remove the diaphragm as described in Section 5.2.1.
Once the diaphragm is removed, the seal wash feature must not be
used; if it is, wash solution will drain past the piston retainer. Rotate
the flush housing 180 degrees so that the self-flush outlet tubing is
facing down. This will allow any leaks from the high pressure seal to
drain from the head assembly.
Figure 1-1. Self-Flushing Pump Head
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Dionex AXP/AXP-MS Manual
3
1.2 Specifications for the Dionex AXP/AXP-MS Pump
Flow Rates 0.01 to 10.00 mL/min (Dionex AXP)
0.01 to 1.00 mL/min (Dionex AXP-MS)
Pressure 0 to 2500 psi
Flow Accuracy 3%
Flow Precision 0.5% RSD
Dimensions 6.25 in. high x 7.75 in. wide x 14 in. deep
Weight 15 lb
Power 100-240 VAC, 50/60 Hz (1 amp)
Features Autoprime™ purging
Autoflush™ piston wash
Remote Inputs RS-232

Dionex AXP/AXP-MS Manual
2 INSTALLATION
2.1 Unpacking and Inspection
Prior to opening the Dionex AXP/AXP-MS pump shipping container,
inspect it for damage or evidence of mishandling. If it has been
damaged or mishandled, notify the carrier before opening the
container. Once the container is opened, inspect the contents for
damage. Any damage should be reported to the carrier immediately.
Save the shipping container. Check the contents against the packing
list.
2.2 Location/Environment
The preferred environment for the Dionex AXP/AXP-MS pump is
normal laboratory conditions. The area should be clean and have a
stable temperature and humidity. The specific temperature and
humidity conditions are 10 to 30 °C and 20% to 90% relative
humidity. The instrument should be located on a flat, stable surface
with surrounding space for ventilation and the necessary electrical and
fluid connections.
2.3 Electrical Connections
Unpack the Dionex AXP/AXP-MS pump; position the pump so
that there is at least 4 in. of clearance on all sides to permit proper
ventilation. Using the power cord supplied with the pump, or
equivalent, plug the pump into a properly grounded electrical outlet.
WARNING: Do not bypass the safety ground connection, as
this may cause a serious shock hazard.
2.4 Solvent Preparation
Proper solvent preparation will prevent a great number of pumping
problems. The most common problem is bubble formation, which may
affect the flow rate consistency. Aside from leaky fittings, the problem
of bubble formation arises from two sources: solvent outgassing and
cavitation. Filtration of HPLC solvents is also required.
2.4.1 Solvent Outgassing and Sparging
Solvent outgassing occurs because the mobile phase contains
dissolved atmospheric gases, primarily N2 and O2. These dissolved
gases may lead to bubble formation and should be removed by
degassing the mobile phase before or during use. The best practical
4

Dionex AXP/AXP-MS Manual
technique for degassing is to sparge the solvent with standard
laboratory-grade (99.9+%) helium. Helium is only sparingly soluble in
HPLC solvents, so other gases dissolved in the solvent diffuse into the
helium bubbles and are swept from the system. Solvent filtration is not
an effective alternative to helium degassing.
It is recommended that you sparge the solvent vigorously for 10 to 15
minutes before using it. Then, maintain a trickle sparge during use to
keep atmospheric gases from dissolving back into the mobile phase.
The sparged solvent must be continually blanketed with helium at 2 to
3 psi. Non-blanketed, sparged solvents will allow atmospheric gases to
dissolve back into the mobile phase within four hours.
Solvent mixtures using water and organic solvents (like methanol or
acetonitrile) hold less dissolved gas than pure solvents. Sparging to
reduce the amount of dissolved gas is therefore particularly important
when utilizing solvent mixture.
Even with sparging, some outgassing may occur. Installation of a
backpressure regulator after the detector flow cell will help prevent
bubbles from forming and thus limit baseline noise.
WARNING: Always release pressure from the pump slowly.
A rapid pressure release could cause the pulse damper
diaphragm to rupture.
2.4.2 Cavitation
Cavitation occurs when inlet conditions restrict the flow of solvent and
vapor bubbles are formed during the inlet stroke. The key to
preventing cavitation is to reduce inlet restrictions. The most common
causes of inlet restrictions are crimped inlet lines and plugged inlet
filters. Inlet lines with tubing longer than 48 in. or with tubing of less
than 0.085-in. ID may also cause cavitation.
Placing the solvent reservoirs below the pump level also promotes
cavitation. The optimal location of the reservoirs is slightly above the
pump level, but it is adequate to have them on the same level as the
pump.
5

Dionex AXP/AXP-MS Manual
2.4.3 Filtration
Solvent filtration is good practice for the reliability of the Dionex
AXP/AXP-MS pump and other components in an HPLC system.
Solvents should always be filtered with a 0.5-micron filter prior to use.
This ensures that no particles interfere with the reliable operation of
the piston seals and check valves. Solvents in which buffers or other
salts readily precipitate out will need to be filtered more often. After
filtration, the solvents should be stored in a closed, particulate-free
bottle.
2.4.4 Solvents with Harmful Effects
Except for PEEK pump heads, all portions of the Dionex AXP/AXP-
MS pump that contact mobile phase are manufactured of type 316
stainless steel, ceramic, sapphire, or ruby. Some of these materials are
extremely sensitive to acids (including some Lewis acids) and acid
halides. Avoid using solvents that contain any hydrochloric acid.
Some solvents you should specifically avoid are:
Aqua Regia Hydrochloric Acid
Bromine Hydrofluoric Acid
Chlorine Anhydrous Hydrofluorsilicic Acid
Copper Chloride Hydrogen Peroxide
Ferric Chloride Iodine
Ferrous Chloride Mercuric Chloride
Freon 12 (wet)
Guanidine
Hydrobromic Acid
In addition, some users of HPLC systems have observed that
chloroform and carbon tetrachloride slowly decompose to liberate
hydrochloric acid, which, as noted above, attacks stainless steel. Do
not leave these solvents in the systems for a prolonged period.
You may also want to avoid ammonium hydroxide. Although
ammonium hydroxide will not harm the pump itself, it is likely to
damage the stator and rotor in injection valves.
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Dionex AXP/AXP-MS Manual
2.5 Instrument Installation
2.5.1 Mobile Phase Reservoirs
The mobile phase reservoir should be placed at the same level or
slightly higher than the pump, never below the pump, and the inlet
tubing should be as short as practical. These steps minimize pressure
losses on the inlet side of the pump during refill and help to avoid
bubble formation. These steps are particularly important when using
high vapor pressure solvents (hexane, methylene chloride, etc.).
Mobile phases should be degassed, filtered, and covered (see Section
2.4).
2.5.2 Self-Flush Solution
Self-flush heads require 250 to 500 mL of 20% methanol in water as
a flushing solution. A pH indicator that will indicate the concentration
of salts in the solution is recommended as a reminder to change the
solution. This flush solution should be replaced with a fresh solution
weekly to avoid frequent pump maintenance.
2.5.3 Inlet Tubing and Filters
The replacement parts list shows the inlet tubing and filter used in the
Dionex AXP/AXP-MS pump. All inlet lines are 30 in. long and are
made of a fluoropolymer material.
2.5.4 Outlet Tubing
Outlet tubing (not supplied with the pump) should have a 1/16-in.
outer diameter. It is available in PEEK with a 0.020-in. inner diameter
and is normally used before the injection valve. Tubing with a 0.010-
in. inner diameter is normally used after the injection valve. The
tubing must be cut squarely and with no burrs. The tube itself should
not be crimped and the center hole must be open. PEEK tubing may be
cut with a plastic tubing cutter or razor knife.
If the Dionex AXP is being used as a sample loading pump for trace
ion applications, the convoluted diaphragm will cause sample
contamination. Remove the convoluted diaphragm as described in
Section 5.2.1. Once the diaphragm is removed, the seal wash feature
cannot be used; if it is, wash solution will drain past the piston
retainer. Rotate the flush housing 180 degrees so that the self-flush
outlet tubing is facing down. This will allow any leaks from the high
pressure seal to drain from the head assembly.
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Dionex AXP/AXP-MS Manual
2.5.5 Priming the Pump and the Flushing Lines
Connect a syringe to the priming adapter. Run the pump at a flow rate
of 3.00 to 5.00 mL/min. Prime the pump by pulling mobile phase and
any air bubbles through the system and into the syringe (a minimum of
20 mL).
To prime the flush lines for a self-flush head, simply place the inlet
line in the flush solution and connect a syringe to the outlet line and
apply suction until the line is filled with flush solution. Place the outlet
line in the flush solution. Secure both flush lines in the flush solution
container so they stay immersed during pump operation.
2.5.6 Long-Term Pressure Calibration Accuracy
This note applies if your pump is equipped with an electronic pressure
transducer. The transducer has been zeroed and calibrated at the
factory. Over the life of the pump, some drift may occur. For example,
it is typical for the zero to drift <10 psi after about one year of
operation (i.e., with no backpressure on the pump, a reading of 1 to 9
psi may be displayed). A similar drift may also occur at higher
pressures, and is typically less than 1% (e.g., <50 psi at 6000 psi
backpressure).
If pressure calibration and/or drift is a concern, contact Technical
Support for Dionex products. The pump can be shipped back for
recalibration. Alternatively, written calibration and zero-reset
procedures are available. To obtain a copy of these instructions,
contact Technical Support for Dionex products.
2.6 Preparation for Storage or Shipping
2.6.1 Isopropanol Flush
Disconnect the outlet tubing from the pump. Place the inlet filter in
isopropanol. Use a syringe to draw a minimum of 50 mL through the
pump. Pump a minimum of 5 mL of isopropanol to exit. Leave the
inlet tubing connected to the pump. Place the inlet filter in a small
plastic bag and attach it to the tubing with a rubber band. Plug the
outlet port with the shipping plug, leave a length of outlet tubing on
the pump, or cover the outlet port with plastic film.
8

Dionex AXP/AXP-MS Manual
2.6.2 Packaging for Shipping
CAUTION: Reship the AXP/Dionex AXP-MS in the original carton, if possible. If the
original carton is not available, wrap the pump in several layers of bubble wrap and
cushion the bottom, top, and all four sides with 2 in. of packaging foam. Although heavy,
an HPLC pump is a delicate instrument and must be carefully packaged to withstand the
shocks and vibration of shipment.
9

Dionex AXP/AXP-MS Manual
3 OPERATION
3.1 Front Panel Controls and Indicators
ON / OFF
Figure 3-1. AXP/Dionex AXP-MS Pump Front Panel
3.1.1 Control Panel
3.1.1.1 Digital Display
The three-digit display shows the pump flow rate (mL/min), the
system pressure (psi), or the selected upper or lower pressure limit
(psi) when operating. Choice of display is selected with the MODE
key.
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Dionex AXP/AXP-MS Manual
3.1.1.2 Keypad
RUN/
STOP When pressed, this button alternately starts and
stops the pump.
When pressed, this button increases the flow rate.
When pressed, this button decreases the flow rate.
PRIME When the PRIME button is pressed, the pump runs
at the maximum flow rate for the pump head. It will
stop when any button is pressed.
MODE
Use this button to cycle through the four display
modes: flow rate, pressure, upper pressure limit, or
lower pressure limit. A status LED to the right of
the digital display indicates which mode is active.
Fast and Slow Button Repeat on the Up and Down Arrow Buttons: If
the up arrow or down arrow button is held down for m ore than
approximately one-half of one second, the button press will repeat at a
slow rate of approxim ately 10 tim es per second. Once slow button
repeat has begun, fast button repeat can be initiated by using a second
finger to press down the second arrow button. During fast button
repeat, the button press will repeat at a rate of approxim ately 100
times per second. To switch back and forth between repeat speeds,
press and release the second arro w button while keeping the first
arrow button held down.
3.1.1.3 Status LEDs
ML/MIN When lit, the digital display shows the flow rate in mL/min.
PSI When lit, the digital display shows the system pressure in psi.
HI PRESS When lit, the display shows the user-set upper pressure limit in psi.
LO
PRESS When lit, the display shows the user-set lower pressure limit in psi.
PUMP
RUN Lights to indicate that the pump is running.
FAULT Lights when a fault occurs and stops the pump.
11

Dionex AXP/AXP-MS Manual
3.1.1.4 Power-up Configuration
Pressure Compensation: On power-up, press the PRIME button on the
front panel while pressing the Power On switch on the rear of the
pump. The pump will display a number from 0 to 60 that represents
the running pressure of the pump from 0 to 6000 psi. Each digit
represents 100 psi. To change the pressure compensation number, use
the up arrow and down arrow buttons. When you have selected the
correct pressure compensation, press the RUN button to resume
normal pump operation.
Nonvolatile Memory Reset: If the pump is operating erratically, the
memory may have been corrupted. To reset the memory and restore
the pump to its default parameters, press and hold the up arrow button
when the power is switched on. Release the button when the display
reads rES. The parameters stored in nonvolatile memory (i.e., the flow
rate, pressure compensation, voltage/frequency selection, lower
pressure limit, and upper pressure limit) will be set to the factory-
default values. The head type setting is the only parameter not changed
by the nonvolatile memory reset function. If the firmware is upgraded
to a newer version, a nonvolatile memory reset will automatically
occur the first time the power is switched on.
3.1.1.5 Power-Up Tests
Display Firmware Version Mode: The firmware version can be
displayed during power-up by pressing and holding the RUN/STOP
and the up arrow buttons when the power is switched on. Release the
buttons when the display reads UEr. The decimal point number
displayed on the display is the firmware version. To exit this mode,
press the RUN/STOP button.
Align Refill Switch Mode: The signal that initiates the refill phase can
be displayed during power-up by pressing and holding the PRIME and
the up arrow buttons when the power is switched on. Release the
buttons when the display reads rFL. When the slotted disk allows the
light beam to pass from the emitter to the detector on the slotted
optical switch, a pulse will be generated to signal the beginning of
refill. When this pulse occurs, the three horizontal segments displayed
at the top of the display will turn off and the three horizontal segments
at the bottom of the display will turn on. To exit this mode, press the
RUN/STOP button.
Serial Port Loopback Test Mode: If an external device will not
communicate with the pump via the serial port, the serial port
loopback test can be used to verify that the serial port is functioning
properly. During power-up, press and hold the up arrow and the down
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Dionex AXP/AXP-MS Manual
arrow buttons and then release the buttons. The display must read C00
for the first half of the test to pass. Plug in the serial port loopback
plug (a modular plug with pins 2 and 5 jumpered together and pins 3
and 4 jumpered together). The display must read C11 for the second
half of the test to pass. To exit this mode, press the RUN/STOP button.
3.2 Rear Panel Remote Input
An RS-232C modular jack is provided on the rear panel. To control
the pump using Chromeleon version 6.80 (or later), connect the pump
to the serial or USB port on the Chromeleon PC, using the cables
included in the Ship Kit. When connecting to a USB port, the driver
provided with the serial-to-USB adapter must be installed on the PC
before the converter cable is attached to the USB port. See Section 7
for details on connection and operation.
Figure 3-2. Dionex AXP/AXP-MS Pump Rear Panel
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Dionex AXP/AXP-MS Manual
4 THEORY OF OPERATION
4.1 Mechanical Operation
4.1.1 Liquid System Flow Path
The flow path of the Dionex AXP/AXP-MS pump starts at the inlet
reservoir filter, passes through the inlet check valve, then through the
pump head, and finally exits through the outlet check valve.
4.1.2 Pump Cycle
The pump cycle consists of two phases: the pumping phase, when
fluid is metered out of the pump at high pressure, and the refill phase,
when fluid is rapidly drawn into the pump.
During the pumping phase, the pump piston moves forward at a
programmed speed; this results in a stable flow from the pump. The
piston is driven by an eccentric bearing which is directly driven by the
motor.
At the end of the pumping phase, the pump enters the refill phase. The
piston quickly retracts, refilling the pump head with solvent, and the
piston begins to move forward again as the pumping phase begins. The
motor speed is increased during refill to reduce refill time and to pre-
compress the solvent at the beginning of the pumping phase.
For optimal operation of the check valves, a backpressure of at least 25
psi is required. Operating at lower pressures can lead to improper
seating of the valves and cause inaccurate flow rates.
4.1.3 Pulse Damping
The diaphragm-type pulse damper consists of a compressible fluid
(isopropanol) held in an isolated cavity by an inert but flexible
diaphragm. During the pumping phase of the pump cycle, the fluid
pressure of the mobile phase displaces the diaphragm, compressing the
fluid in the cavity and storing energy. During the pump refill phase,
the pressure on the diaphragm is reduced and the compressed fluid
expands, releasing the energy it has stored. This helps to stabilize flow
rate and pressure. The amount of mobile phase in contact with the
pulse damper is small, only 0.9 mL at 2500 psi, and the geometry used
ensures that the flow path is completely swept, so solvent “memory
effects” are virtually eliminated.
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Dionex AXP/AXP-MS Manual
To be effective, the pulse damper requires a backpressure of
approximately 500 psi or greater. If the system does not generate 500
psi, a length of small bore tubing (restrictor) can be used between the
pulse damper and the application.
4.2 Electronic Control
4.2.1 Microprocessor Control
The pump is controlled by hybrid microprocessor circuitry which (1)
provides control signals to the motor drive circuitry, (2) interfaces
with the keyboard/display, (3) receives signals from the refill flag, and
(4) provides external input/output (RS-232) interfacing. Firmware
programming is stored in an EPROM.
An eccentric cam provides refill in a fraction of the full cam cycle.
The remaining revolution of the cam provides piston displacement for
outward flow of the mobile phase. In addition to the rapid refill
characteristics of the drive, the onset of refill is detected by an infrared
optical sensor. The microprocessor changes the refill speed of the
motor to an optimum for the set flow rate. At 1.00 mL/min, the refill
rate is more than five times faster than if the motor operated at
constant speed. The optimum refill rate minimizes the resulting
pulsation while avoiding cavitation in the pump head.
The flow rate of any high pressure pump can vary, depending on the
operating pressure and the compressibility of the fluid being pumped.
The Dionex AXP/AXP-MS pump is calibrated at 1000 psi, using an
80:20 mixture of water and isopropanol.
4.2.2 DC Power Supply
Power for the pump is provided by an isolation transformer which has
taps to accommodate voltages of 110-120 or 220-240 VAC. Selection
is accomplished by changing the transformer jumpers. A different
transformer is supplied for use at 100 VAC. The transformer input is
provided with two fuses for line current. A linear rectifier circuit
provides 36 VDC, which also has a fuse, to drive the stepping motor.
A switching 5 VDC supply is provided to power control and display
circuits.
4.2.3 Motor Stall Detector
The motor can stall and create a loud buzzing sound if the flow path
connected to the pump's outlet becomes plugged, if the pressure
exceeds the maximum pressure rating of the pump, or if the
mechanism jams. If the motor stalls, the electrical current being
supplied to the motor is turned off and the fault light is turned on.
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Dionex AXP/AXP-MS Manual
16
The motor stall detector is enabled or disabled during power-up by
pressing and holding the RUN/STOP and the PRIME buttons while
the power is switched on. Release the buttons when the display reads
SFE. To enable the motor stall detector, press the up arrow button and
the display will read ON. To disable the motor stall detector, press the
down arrow button and the display will read OFF. To exit this mode
and store the current setting in nonvolatile memory, press the
RUN/STOP button.
The motor stall detector uses a timer to determine if the camshaft has
stopped turning or if the refill switch is defective. The timer begins
timing after the pump accelerates or decelerates to its set point flow
rate. If the motor stall detector has been enabled, and the camshaft
stops turning or the refill switch stops operating, the fault will be
detected between the time it takes to complete one to two pump cycles.
A pump cycle is defined as the time it takes for the camshaft to
complete one complete revolution. One revolution of the camshaft
produces a delivery phase and a refill phase. Each specific flow rate
has a corresponding cycle time: the cycle time is approximately
30 seconds at 0.1 mL/min, 3 seconds at 1.00 mL/min, and 0.3 second
at 10.00 mL/min.
The fault is canceled by using one of the following methods: (1) by
pressing the RUN/STOP button on the front panel, (2) by sending a
stop command (ST) via the serial communications port on the rear
panel, or (3) by connecting the PUMP-STOP input to COM on the rear
panel, or removing the connection between the PUMP-RUN input and
COM if the PUMP-STOP input is permanently jumpered to COM on
the rear panel.
4.2.4 Remote Interfacing
An RS-232C modular jack is provided on the rear panel. To control
the pump using Chromeleon version 6.80 (or later), connect the pump
to the serial or USB port on the Chromeleon PC, using the cables
included in the Ship Kit. When connecting to a USB port, the driver
provided with the serial-to-USB adapter must be installed on the PC
before the converter cable is attached to the USB port. See Section 7
for details on connection and operation.

Dionex AXP/AXP-MS Manual
5 MAINTENANCE
Cleaning and minor repairs of the Dionex AXP/AXP-MS pump can be
performed as outlined below.
5.1 Filter Replacement
5.1.1 Inlet Filters
Inlet filters should be checked periodically to ensure that they are
clean and do not restrict flow. A restriction could cause cavitation and
flow loss in the pump. Two problems that can plug an inlet filter are
microbial growth and impure solvents. To prevent microbial growth,
use at least 10% to 20% organic solvent in the mobile phase or add a
growth-inhibiting compound. If you pump 100% water or an aqueous
solution without any inhibitors, microbes will grow in the inlet filter
over time, even if you make fresh solution every day. Always use
well-filtered, HPLC-grade solvents for your mobile phase.
5.2 Pump Heads
5.2.1 Removing the Pump Head
As a guide to pump head assembly, the pump head is shown in Figures
5-1 and 5-2.
1. Turn OFF the power to the Dionex AXP/AXP-MS pump.
2. Remove the inlet line and filter from the mobile phase reservoir.
Be careful not to damage the inlet filter or crimp the PTFE
(polytetrafluoroethylene) tubing.
3. (Optional) Remove the outlet line from the outlet check valve.
4. Momentarily turn ON the pump and quickly turn OFF the power
upon hearing the refill stroke. This reduces the extension of the
piston and decreases the possibility of piston breakage.
5. Unplug the power cord.
6. Carefully remove the two knurled nuts at the front of the pump
head.
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