Hach-Lange ORBISPHERE 31xxx Thermal Basic User Manual - Manual (Page 12)

The primary membrane, or top membrane, determines the rate at which the H
2
gas enters the
measurement chamber of the sensor. The secondary membrane, or support membrane on the
bottom, is extremely permeable and is installed to stabilize the position of the primary membrane.
Two primary membrane types are used for H
2
measurement depending on the type of application:
• 29561A - used for waste gas, off gas and dH
2
in a boiling water reactor
• 2952A - used for dH
2
in reactor cooling systems of a pressurized water reactor.
The support or secondary membrane for all H
2
measurement applications is the 29562A.
As two membranes will be mounted together, the mounting ring used must be part number 29229
which is designed for a thickness of 50 microns or more. Mounting ring part number 29228 is
designed for a single membrane and should not be used for mounting dual membranes.
Membrane replacement
Removing the membrane
1. 2. 3. 4.
1. Place the thermal conductivity sensor vertical with the head up. Remove the plastic storage cap.
2. Unscrew the protection cap, using the tool provided in the maintenance kit.
C A U T I O N
Never remove the protection cap, unless you plan to replace the membrane.
3. Pay attention to the components inside the protection cap. Note the assembly order of each item.
4. Pull up the membrane holding ring with the tool provided in the maintenance kit. The membrane
holding ring comes in two slightly different internal diameters, depending on the membrane(s)
total thickness. Remove membrane(s).
Installing the membrane
For correct membrane selection, please refer to Sensor membrane specifications on page 4.
1.
2.
3.
1. The membrane mounting surface must be clean and even. Replace the membrane O-ring on the
sensor head with a new one.
12 English