Chapter 6 81
Maintenance
Replacing the Light Pipe
Under normal usage conditions, the light pipe should not need to be replaced. If it
is cracked or broken, use the following procedure to replace it.
1. Using WinPulse, set the PMT voltage to zero. Disconnect the PMT HV and
the PMT signal cables from the back of the Detector Controller.
2. Turn off the Detector Controller and allow the PFPD to cool to room
temperature.
3. Detach the PMT housing assembly (Part #286096) from the PMT mounting
by loosening the PMT thumbscrew (Part #177065) (see Figure 6.3). Place it
where it cannot accidentally drop or roll.
4. Unscrew the light pipe clamp (Part #245563C) in the end of the PMT mount-
ing using a screwdriver (or other appropriate tool), and remove the light pipe
from the detector body using Teflon-coated forceps.
5. If light pipe fragments are found (due to chipped, cracked, or broken light
pipe), remove the detector cap, combustor, and detector body, and discard the
glass fragments in a safe manner to prevent injury. Using a cotton swab
dipped in methanol (or isopropanol), wipe out the light pipe tube protruding
from inside the detector body to remove all glass fragments. Discard the
cotton swab in an appropriate waste container.
6. After checking that there are no glass fragments in the combustor chamber,
inside the detector body, or in the detector base, reassemble the detector body,
combustor, and detector cap.
7. Remove the new light pipe from its protective cover using a clean lab tissue.
Examine the light pipe for smudges, cracks, chips, or other deformations. If
the light pipe has mechanical imperfections, get another light pipe for installa-
tion. If there are smudges (fingerprints, dirt, or oil) on its surface, dampen
another clean lab tissue and lightly wipe the light pipe.
8. Using another clean lab tissue, install a Viton O-ring (Part #288068) at least
1.5 cm from one end of the light pipe.
9. Install the other end of the light pipe into the light pipe housing, and thread
the light pipe clamp into the PMT mounting attached to the end of the light
pipe housing.
10. Lightly tighten the light pipe clamp slightly to compress the Viton O-ring
using a narrow screwdriver (or other appropriate tool).
!
WARNING:
Handling the
PFPD while it is
hot can cause
serious burns
!
CAUTION:
Do not scratch
the protruding
end of the light
pipe with the
screwdriver when
tightening the
light pipe clamp.
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