5
Maintenance
Removing Air from the Piston Chambers
106
Accela 600 and 1250 Pump Hardware Manual
Thermo Scientific
Removing Air from the Piston Chambers
Air trapped in the piston chambers causes an excessive variation in the backpressure.
To purge air out of the piston chambers
1. Open the purge valve by turning its wing nut counterclockwise (see
2. To collect the solvent being pumped through the LDA, insert the tip of a
10 mL disposable syringe into the tubing attached to the purge valve.
Figure 106.
Purge valve with tubing attached
3. Pump 100% methanol or 100% acetonitrile through the LDA at a flow rate of
200 μL/min for 10 to 15 minutes.
4. Close the purge valve, remove the syringe, and return to the initial conditions.
5. Check the pressure variation to determine if removing the trapped air stabilized the
system pressure.
Note
All low-pressure mixing HPLC pumps require eluents that have been properly
degassed. The pump has a built-in vacuum degasser. Plumbing the pump to bypass this
degasser introduces a potentially unacceptable level of air into the piston chambers.
Tip
Purging the pump at a low flow rate with 100% organic solvent works much
better than purging the pump at a high flow rate with (partly) aqueous eluents.
Note
Due to seal friction, the system backpressure does not drop to zero when you
pump solvent through the open purge valve. Depending on the flow rate and solvent
composition, typical backpressure values range from 5 to 15 bar.
Tubing
(with fitting
for syringe)
Purge valve wing nut
CAUTION
Wear safety gloves when handling solvents.
