Thermo Scientific 49i, Instruction Manual, Page: 159 / 314

Preventive Maintenance
Leak Test and Pump Checkout
Thermo Fisher Scientific Model 49
i
Instruction Manual 5-9
4. Use to move the cursor to Cell A/B O3 and press
to display the O3 PPB screen. This display presents the concentration
for each cell.
Once the instrument stabilizes, the average of 10 successive
simultaneous readings should agree within
±
3 percent.
A balanced measurement of better than 3 percent indicates that there
are no leaks across the solenoid.
A constant low reading from one cell indicates an imbalance. The
imbalance can be caused by a dirty cell, dirty lines to that cell, or by a
leaky valve. Refer to the “Solenoid Leak Test” procedure that follows to
check for a leaky solenoid.
To check if the imbalance is caused by an absorption cell, interchange
the cells. If the imbalanced side switches, the imbalance is caused by the
cell.
Solenoid Leak Test
Use the following procedure to test the solenoid valve for leaks.
1. Remove the solenoid valve that appears to be faulty.
2. Connect the pump directly to the common solenoid port.
3. Connect the pressure transducer to the normally open solenoid port.
4. Press to display the Main Menu.
5. Press to scroll to Diagnostics and press to display
the Diagnostics menu.
6. Use to scroll to Pressure and press to display the
Pressure screen.
7. Note the pressure as P
NO
.
8. Connect the pressure transducer to the normally closed solenoid port.