5.2.1 Removing the Pump Head

5.2.1 Removing the Pump Head
PISTON SEAL REPLACEMENT INSTRUCTIONS FOR SSI
SERIES-II, SERIES-III and STANDARD DUAL-HEAD PUMPS
Removing the Pump Head
As a guide to pump head assembly, the standard pump heads are shown in Figures 1 and 2. All pump heads have a similar
arrangement.
1. Turn OFF the power to the pump and unplug the power cord.
2. Remove the inlet line and filter from the mobile phase reservoir. Be careful not to damage the inlet filter or crimp the Teflon
tubing.
3. Remove the inlet line from the inlet check valve.
4. Remove the outlet line from the outlet check valve.
5. Remove inlet and outlet flushing check valves.
6. Carefully remove the two knurled thumb screws or Allen nuts at the front of the pump head using a suitable tool.
CAUTION: Be careful not to break the piston when removing the pump head. Twisting the pump head can
cause the piston to break.
7. Carefully separate the pump head from the pump. Move the pump head straight out from the pump and remove it from the
piston. Be careful not to break or damage the piston. Also remove the seal and seal backup washer from the piston if they did
not stay in the pump head.
8. Carefully separate the flush housing from the pump. Move the flush housing straight out from the pump and remove it from
the piston. Be careful not to break or damage the piston. Also remove the self-flush seal/guide bushing from the piston if it
did not stay in the flush housing.
OUTLET FLUSHING
CHECK VALVE
PISTON
O-RING
OUTLET CHECK VALVE
SEAL BACK-UP
SELF-FLUSH SEAL or
GUIDE BUSHING
SELF-FLUSH HOUSING
INLET FLUSHING
CHECK VALVE
SEAL BACKUP WASHER
SEAL
PUMP HEAD
INLET CHECK VALVE
Figure 1: Stainless Steel Self-Flushing Pump Head Assembly
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90-2145 rev B
OUTLET FLUSHING
CHECK VALVE
O-RING
PISTON
SEAL BACK-UP
OUTLET CHECK VALVE
SELF-FLUSH SEAL or
GUIDE BUSHING
SELF-FLUSH HOUSING
INLET FLUSHING CHECK VALVE
SEAL BACKUP WASHER
SEAL
PUMP HEAD
INLET CHECK VALVE
Figure 2: PEEK Self-Flushing Pump Head Assembly
Removing the Seals
1. Insert the flanged end of the seal insertion/removal tool into the seal cavity on the pump head. Tilt it slightly so that flange is
under the seal and pull out the seal.
CAUTION: Using any other “tool” will scratch the finish of the sealing surface and create a leak.
2. Repeat the procedure for the low pressure seal/guide bushing in the flush housing.
3. Inspect, and if necessary, clean the pump head as described in the operator’s manual.
Cleaning the Piston
1. Gently remove the backup seal plate from the pump housing, using either a small screwdriver or other small tool in the slot
on top of the pump housing.
2. Grasp the metal base of the piston assembly so that you avoid exerting any side load on the sapphire rod, and remove the
piston from the slot in the carrier by sliding it up.
3. Use the scouring pad included in the seal replacement kit to clean the piston. Gently squeeze the piston within a folded
section of the pad and rub the pad along the length of the piston. Rotate the piston frequently to assure the entire surface is
scrubbed. Do not exert pressure perpendicular to the length of the piston, as this may cause the piston to break. After
scouring, use a lint-free cloth, dampened with alcohol, to wipe the piston clean.
4. Grasp the metal base of the piston assembly, and insert it into the slot in the piston carrier until it bottoms in the slot.
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90-2145 rev B
Replacing the Seals
WARNING: If you do not use the self-flush feature of this pump, you must use the guide bushing in place
of the flush seal. If this is not done; low flow rates, excessive noise and shortened pump life
will result.
1. Place a high pressure replacement seal on the rod-shaped end of the seal insertion/removal tool so that the spring is visible
when the seal is fully seated on the tool. Insert the tool into the pump head so that the open side of the seal enters first,
facing the high pressure cavity of the pump head. Be careful to line up the seal with the cavity while inserting. Then
withdraw the tool, leaving the seal in the pump head. When you look into the pump head cavity, only the polymer portion of
the seal should be visible.
2. Place a low pressure replacement seal on the seal insertion/removal tool so that the spring in the seal is visible when the seal
is on the tool. As in the previous step, insert the tool and seal into the seal cavity on the flushing housing, taking care to line
up the seal with the cavity, and then withdraw the tool. When the seal is fully inserted only the polymer part of the seal will
be visible in the seal cavity. If not using the self-flush feature replace the used guide bushing with the new guide bushing
provided in the seal replacement kit.
Replacing the Pump Head
1. Carefully align the flush housing and gently slide it into place on the pump. Make sure that the Inlet flush valve is on the
bottom and the Outlet flush valve is on the top. If misalignment with the piston occurs, gently push up on the piston holder.
2. Line up the pump head and carefully slide it into place. Be sure that the Inlet valve (1/4-28 for 1/8 tubing) is on the bottom
and the Outlet valve (#10-32 CPI for 1/16 tubing) is on the top. Do not force the pump head into place.
3. Finger tighten both knurled thumb screws or Allen nuts into place. Then tighten firmly by turning fasteners about 1/4 turn
(alternating side-to-side) while gently wiggling the pump head to center it, using a suitable tool.
4. Reattach the inlet and outlet lines. Reattach the self-flush lines. Change the flushing solution.
Conditioning New Seals
New seals should be conditioned prior to use. Conditioning is the process of running the seals wet under controlled conditions to
allow surfaces to seat and to break-in the function of the seal.
Note: Use only organic solvents to condition new seals. Buffer solutions and salt solutions should never be used to condition new
seals. Recommended solvents are HPLC-grade methanol and isopropanol, and water mixtures of either.
Suggested Conditioning Parameters: Using a restrictor coil or a suitable column, run the pump with a 50:50 solution of
isopropanol (or methanol) and water for 30 minutes at the back pressure and flow rate listed under PHASE 1 below according to
the pump head type. Then run the pump for 15 minutes at a back pressure and flow rate listed under PHASE 2 below.
PHASE 1
Pump Type
Pressure
Flow Rate
5, 10, 12 or 24 ml/min pump
2,000 psi
<3 mL/min
40 ml/min or higher pump
1,000 psi
<3 ml/min
PHASE 2
Pump Type
Pressure
Flow Rate
5, 10, 12 or 24 ml/min pump
3,000 – 4,000 psi
3 - 4 mL/min
40 ml/min or higher pump
1,500 psi
<6 ml/min
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