Rheodyne 7125 User manual

®
Operating Instructions
Model 7125
Manual Sample Injector
1.0 DESCRIPTION
Model 7125 is a six-port sample injection
valve in which the sample is loaded through
a built-in needle port in the front of the valve.
Figure 1 shows the flow diagram of the
valve. The circles represent the ports in the
valve stator. The dark and white grooves
represent the connecting passages in the
rotor seal. The large circle represents the
needle port.
The sample loop is loaded through the
needle port in the LOAD position. Rotation
of the knob 60° switches the valve from
LOAD to INJECT. In INJECT the mobile
phase flows through the loop.
2.0 SUPPLIED WITH THE VALVE
Supplied with the valve in a separate bag
are RheFlex®fitting sets for all ports and the
items shown below. A 20 µL sample loop is
standard with the valve.
• Hex Keys
• Needle Port Cleaner
• Mounting Screws
• Vent Tubes
The #22 gauge needle supplied in the valve
should be removed from the needle port
before using the valve.
3.0 SPECIFICATIONS
• Maximum Temperature: 80°C
• Maximum Operating Pressure: 48 MPa
(482 bar, 7000 psi)
• Flow Passage Diameters: 0.6 mm (0.024")
and 0.5 mm (0.018")
• Wetted Surfaces: stainless steel, ceramic,
and an inert polymer
4.0 IMPORTANT SAFETY NOTICES
4.1 Warning: When using sample loops
larger than 100 µL, shield yourself from
mobile phase coming out of the needle port
when the valve is turned from INJECT to
LOAD. Example: 1 mL loop ejects 20 µL
upon decompression from 19 MPa (200 bar,
2898 psi).
4.2 Warning: When using the Needle Port
Cleaner, empty the syringe slowly to prevent
solvent from squirting back at you.
4.3 Caution: Rinse the valve with water
after using buffer solutions to prevent
crystals from forming, which can cause
scratches on the rotor seal.
5.0 USING PROPER SYRINGES
Use syringes with #22 gauge syringe needle,
without electro taper and with 90° point style
(square cut). Using the incorrect needle size
will damage the injector.
6.0 INSTALLATION
a) To mount the valve on a panel, remove
the handle by loosening the two handle set
screws. Use the two screws supplied to
fasten the valve to a panel.
b) Replace the handle by tightening the two
set screws on the two flats of the shaft.
c) Connect the two vent tubes (supplied) to
Ports 5 and 6. Place the outlet ends of both at
the same horizontal level as that of the
needle port to avoid siphoning. See Figure 2.
d) Connect the pump to Port 2 and the
column line to Port 3. Leave the column
disconnected from the valve during initial
flushing.
7.0 FLUSHING THE INJECTOR
In INJECT, flush the needle port with 1 mL
of mobile phase, using the Needle Port
Cleaner as shown in Figure 3. At this time,
the pump flushes the loop. See Warning 4.2.
8.0 MAKING AN INJECTION
There are two common methods of loading
the sample loop – complete or partial filling.
8.1 COMPLETE LOOP FILLING
In complete-filling, the volume of sample
injected is set by the volume of the loop (this
includes the valve passages). This method
produces the highest precision.
Overfill the loop with at least two to five
loop volumes of sample. Six to ten loop
volumes will provide even better precision.
An excess of sample is needed because
mobile phase near the wall of the loop is
displaced slowly due to the laminar flow
effect shown in Figure 4.
To completely fill the loop:
a) See Warning 4.1 and turn to LOAD.
b) Insert the syringe into the needle port.
You will feel tightness during the last 2-3
mm of travel as the needle passes through the
needle seal and then stops against the stator
face.
c) Load the sample.
d) Leave the syringe in and turn to INJECT.
8.2 PARTIAL LOOP FILLING
If you only have small quantities of sample,
this is the method of choice. In the partial-
filling method the volume of sample injected
is set by the syringe. In this method, no more
than half a loop volume of sample should be
loaded into the loop. For example, load no
more than 10 µL into a 20 µL loop. With
larger volumes some of the sample is lost out
Vent Line 6. This is because sample flows
down the center of the loop at twice the
average velocity due to the laminar flow
effect shown in Figure 4.
Waste
Waste
Position A (LOAD)
1
3
4
5
6
2
Column
Needle Port
Sample Loop
Pump
Waste
Position B (INJECT)
1
3
4
5
6
2Needle Port
Waste
Pump
Column
Sample Loop
Fig. 1. Model 7125 flow diagram.
Fig. 2. Correct position of vent lines.
Syringe Barrel
Needle Port Cleaner
Handle Assembly
Needle Guide
Fig. 3. Use of Needle Port Cleaner.
Page 1 of 2
2320157D
6/01
Fig. 4. Laminar flow effect.
Flow
Sample
Tube Wall
Mobile Phase
Rheodyne LLC • A Unit of IDEX Corporation • 600 Park Court, Rohnert Park, CA 94928 • [phone] • Fax [phone]
www.rheodyne.com

To partially load the loop:
a) In INJECT, use the Needle Port Cleaner
to flush out the needle port with about 1 mL
of mobile phase. This will flush out
contamination from the earlier injection.
This liquid will exit out Vent Line 5.
b) Follow steps a-d in Section 8.1.
9.0 ADJUSTING FOR LEAKAGE OR
HIGHER PRESSURE OPERATION
The three small set screws in the stator (see
Figure 5) have been factory set so that when
the three stator screws are fully tightened, the
spring force between the valve rotor and
stator is sufficient to hold the indicated
pressure. If leakage is to be corrected, or if
operation at a higher pressure is to be done,
proceed as follows: The three set screws
should be loosened about 1/20 turn each (18°
of rotation) and the three stator screws
tightened an equal amount. If this new
setting fails to accomplish leak-free
operation at the desired pressure, repeat the
procedure by an additional 1/20 turn. Avoid
excessive tightening which will only
increase wear of the rotor seal. If it is
necessary to loosen spring tension, either to
lower the operating pressure, or to adjust for
a new rotor seal, which may be thicker than
the one being replaced, reverse the above
procedures. For example, first loosen the
stator screws, then tighten the set screws.
If leakage cannot be stopped by tightening
the valve, or if, as a result of tightening to
stop the leakage, the handle is too hard to
turn, the rotor seal needs replacing. See next
section.
10.0 MAINTENANCE
The only parts that may need eventual
replacement are the rotor seal and stator face
assembly.
The main causes of early failure are:
a) The wrong needle tip can damage the
ceramic stator face which then causes deep
scratching of the rotor seal surface.
b) Abrasive particles in the sample can
scratch the rotor seal surface.
10.1 DISASSEMBLY
To disassemble the valve, refer to Figure 5
and proceed as follows:
a) Remove the three stator screws.
b) Remove the stator, stator face assembly,
and stator ring from body.
c) Pull the rotor seal off the pins.
d) Remove the isolation seal.
10.2 REASSEMBLY
To reassemble the valve, refer to Figures 5
and 6 and proceed as follows:
a) Slip the new isolation seal (open side
facing the handle) onto the stator end of the
shaft assembly next to the bearing ring.
b) Line up the rotor seal as shown in Figure
6. The rotor seal slots face the stator.
c) Replace the stator ring so that the 60°
stop pins enter the mating holes in the stator
ring.
d) Put the stator face assembly on the stator.
The assembly is symmetrical and can be
mounted either of two ways.
e) Replace the stator face assembly and
stator on the valve so that the pin in the stator
ring enters the mating hole in the stator.
f) Replace the three stator screws and
tighten each screw a little at a time to keep
the stator surface parallel to the stator ring
surface. If the three set screws in the stator
were left unchanged, tighten the three stator
screws a 1/2 turn past fingertight. The three
set screws will ensure that the gap between
stator and stator ring is uniform and in the
original position before disassembly.
g) If the set screws need adjusting because
a new rotor seal was installed or because
leakage has to be stopped, each set screw
should be turned an equal amount to ensure
that after the stator screws are retightened the
gap between the stator and stator ring is
uniform all around. Refer also to Section 9.0.
11.0 OPERATING SUGGESTIONS AND
TROUBLESHOOTING
11.1 LEAKAGE
If you see liquid between the stator and
stator ring, or from the needle port or a vent
tube, tighten the pressure adjusting screw as
explained in Section 9.0. If this fails to stop
the leak then replace the rotor seal and/or
stator face assembly.
11.2 NEEDLE SEAL LEAKAGE
Since the outside diameter of syringe
needles can vary, the needle seal (Teflon1
sleeve in the rotor seal) may not seal firmly
around a needle that is smaller than average.
This will result in the loss of accuracy in
loading the sample. To make a good seal,
remove the needle from the needle port and
push in on the plastic needle guide with the
eraser end of a pencil. Repeat if necessary.
11.3 USE OF AQUEOUS BUFFERS OR
SALT SOLUTIONS
To prevent the formation of salt crystals in
the valve which can scratch the rotor seal,
flush out the flow passages and the needle
port with water after using salt solutions.
11.4 USE OF HIGH pH SOLUTIONS
The standard rotor seal in Model 7125 is
Vespel1, a polyimide with good wear
resistance. Vespel is sensitive to alkaline
attack when exposed to solutions having a
pH of 10 or more. Use a PEEK or Tefzel1
rotor seal, which tolerates pH 0 to 14, for
alkaline solutions.
11.5 ACCURACY OF SAMPLE LOOPS
Sample loop sizes are not actual values.The
actual volume can differ by ± 10% for a 20
µL loop. There is a greater difference for
smaller loops. Use partial-filling if you must
know the actual volume injected.
12.0 RECOMMENDED SPARE PARTS
Rheodyne offers a RheBuild™Kit for
Model 7125 that includes all parts, tools, and
instructions to maintain the quality
performance of your valve without separate
part ordering.
7125-999 RheBuild Kit for 7125
13.0 WARRANTY
All Rheodyne products are warranted
against defects in materials and
workmanship for a period of one year
following the date of shipment by Rheodyne.
Rheodyne will repair or replace any
Rheodyne product that fails during the
warranty period due to a defect in materials
or workmanship at no charge to the
customer. The product must be returned to
Rheodyne’s factory in original packaging or
equivalent, transportation prepaid. Damage
occurring in transit is not covered by the
warranty. This limited warranty is
Rheodyne’s sole warranty of its products,
and all other warranties of merchantability or
fitness for any particular purpose are hereby
disclaimed. Under no circumstances will
Rheodyne be liable for any consequential or
incidental damages attributable to a claimed
failure of a Rheodyne product, even if
Rheodyne has been placed on notice of
possibility of such damages.
Page 2 of 2
2320157D
6/01
Fig. 6. Correct position of rotor seal (slots face
the stator).
Fig. 5. Exploded view of Model 7125.
Handle Assembly
Handle Set Screws (2)
Needle Guide
Shaft Assembly
Body
Thrust Bearing
Spring Washers (4)
Needle Port Tube
Assembly
Bearing Ring
Isolation Seal
Rotor Seal
Stop Pins (2)
Stator Ring
Stator Face Assembly
Stator Set Screws (3)
Stator
Stator Screws (3)
1 Teflon, Vespel, and Tefzel are
trademarks of E.I. DuPont
Rheodyne LLC • A Unit of IDEX Corporation • 600 Park Court, Rohnert Park, CA 94928 • [phone] • Fax [phone]
www.rheodyne.com