YOKOGAWA PH450G

<6. Troubleshooting>
6-2
IM 12B07W01-04EN 1st Edition : Nov 11, 2016-00
6.2 A Smaller Quantity of Chemical Solution Is
Fed to Holder
One of the reasons for this is that the thin covering in the bottom of the metering tank does not
serve as a check valve. Normally, the covering shuts off the uid inlet when the appropriate
pneumatic pressure is applied to the metering tank, resulting in the liquid inside owing only into
the holder. If the covering fails to shut off the uid inlet due to deterioration or damage, the liquid
inside ows back into the holding tank, thus allowing a smaller quantity of the liquid to be sent to
the holder.
l Corrective action
Inspect the thin covering and replace it if deteriorated or damaged.
NOTE
lf no defects are found in the thin covering, check for possible leakage around the SV1 solenoid
valve used for forced feeding of the chemical solution which is located in the control box. If air
ows through the valve while it remains closed, replace it with a new valve. Also, check the
chemical solution in the cleaning chamber for traces that shows the chemical solution owed
back into the chemical tank. If the bleed valve (see Figure 6.1) has become clogged due to a
reverse ow of the solution, the system is no longer able to measure the specied quantity of
solution. If the bleed valve is clogged, clean it.
6.3 CYLINDER FAIL Signal Appears
Possible causes are:
• There is slack in the connections of the line for driving the cylinder.
• The specied pneumatic pressure is not possible.
• The cylinder barrel of the PH8HS3 is dirty.
• The capability of the lubricating grease applied to the cylinder barrel has degraded.
• Limit switch circuits have anomaly.
First conrm that the PG2 pressure gauge in the control box indicates the preset value (with
the system set in the cleaning mode). If the gauge reads smaller than the preset value, readjust
it after conrming that the connections are not loosened. When the slide of the cylinder is in a
upper position, refer to 6.5 and proceed along with it.
Next remove dirt from the cylinder barrel and then apply a thin lm of grease to the barrel.
6.4 When Liquid keeps leaking from bottom
plate of Cleaning Chamber
THe continuous leakage even after replacement of the gasket and adjustment of the height of
the stopper (see Subsection 5.2.2) may be caused by the reduced pressure of the spring due to
deterioration (corrosion) of its material. Inspect the spring visually and replace it if it is defective.
l How to replace spring
(1) Remove the two screws which secure the guide plate to the chassis.
(2) Remove the screw set at the tip of the rod.
(3) Remove the assembled components, such as the guide plate, from the rod.