Bio-Rad PDS-1000 / He™ and Hepta™ Systems - Manual (Page 40)

Section 6
Troubleshooting
6.1 Rupture Disk Bursts at Incorrect Pressure
Probable Cause Action
1. The helium flow rate is too fast. Note the helium burst pressure by observing the
helium pressure gauge at the top of the main unit. A
factory pre-set metering valve (black knob) on the
external 3-way helium metering (solenoid) valve
assembly controls the fill rate of the gas accelera-
tion tube. The proper fill rate is 12–15 seconds to
burst a rupture disk when the helium pressure is set
200 psi over the rated rupture pressure. A more rapid
fill rate may result in what appears to be a lower
burst pressure, due to a lag of needle movement in
the oil-filled gauge.
The metering valve (black knob) may be adjusted if
desired. Adjust knob in small increments: a clockwise
rotation of the black knob will lengthen the fill rate.
2. The improper disk was inserted or Replace with single, desired psi rupture disk.
two disks are sandwiched together.
3. The retaining cap was not securely This is frequently the case when the disk slips out
tightened. of the retaining cap. It is important to screw the
cap onto the end of the gas acceleration tube by
hand and then use the torque wrench.
4. The rupture disks are not clean. Use tweezers or disc-vac to handle the disks after
briefly rinsing in isopropanol. Do not handle with
bare or gloved hands (grease and powder source).
5. The sealing edge of the Gas Occasionally adhesive from the rupture disks
Acceleration Tube is not clean. (laminated disks) may build up on the edge of this
part. This can be cleaned by using a mild, non-
abrasive detergent, like dish soap, to remove the
accumulated adhesive.
6. The sealing edge (inside The edge of this part is susceptible to physical
bombardment chamber) of the damage if the retaining cap is tightened without a
Gas Acceleration Tube is damaged. rupture disk in place. If damage has occurred such that
the disk will not rupture, you must replace this part.
7. Rupture disk is defective. Replace.
6.2 Stopping Screen Forced Through Screen Support Ring
Probable Cause Action
1. The screen has been “unseated” Carefully insert the Microcarrier Launch Assembly into
from support bombardment chamber to prevent movement of stop-
ping screen. This screen movement can also occur if
you close the bombardment chamber door too forcefully.
2. The stopping screen support ring Examine the support ring for evidence of scratches
is damaged. or dents on the support ring that might prevent the
screen from seating properly.
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