6
Maintenance
Minimizing Pump Pulsation
Thermo Scientific
Accela Pump Hardware Manual
55
Minimizing Pump Pulsation
Trapped air bubbles, contaminated proportioning valves, or contaminated check valves can
cause excessive pump pulsation. If the pulsation of the pump is greater than 1 percent at
pressures greater than 100 bar, purge air out of the piston chambers, and clean the
proportioning valves and the check valves.
If you cannot reduce the variation in backpressure by performing these procedures,
disassemble and clean the LDA, and replace the primary piston seals as described in
“Replacing the Primary Pistons Seals”
on
page 67
.
To reduce pump pulsation, follow these procedures:
•
Removing Air from the Piston Chambers
•
Cleaning the LDA Components without Disassembling the LDA
Removing Air from the Piston Chambers
Air trapped in the piston chambers causes an excessive variation in the backpressure.
Y
To purge air out of the piston chambers
1. Open the purge valve by turning its wingnut counterclockwise (see
Figure 37
).
2. Insert the 10 mL syringe, which is supplied in the accessory kit, into the tubing attached
to the purge valve.
3. Pump 100% methanol or 100% acetonitrile through the liquid displacement assembly
(LDA) at a flow rate of 200
μ
L/min for 10 to 15 minutes.
4. Close the purge valve and return to the initial conditions.
5. Check the pressure variation to determine if performing this procedure remedied the
pressure stability problem.
Note
All low-pressure HPLC pumps require eluents that have been properly degassed.
The Accela 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.
Note
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.
