FLK Gas Sampling System - MPIP - Free

SQ253 Valve Combination
4.6 Low-pressure pressure switch
When the filter or probe is contaminated or blocked, a negative pressure is built up by the measuring gas pump.
The electrical contact device integrated into the pressure switch function for monitoring and starting the flushing process.
The magnetic snap-action contact is suitable for harsh applications which place high demands on switching capacity.
The low-pressure pressure switch is largely maintenance-free. With an erroneous indication or for no indication, the
connecting hose should be cleaned or, if necessary, the complete pressure switch replaced.
4.7 Electrically operated compressed air valve ( option )
This compressed air valve is included when a compressed air motor is used for the emergency withdrawal on the withdrawal
device.
When the voltage is switched on, the solenoid is energized and the valve switches. The compressed air supply to the
compressed air motor is shut off. The control is implemented directly from the control unit.
This Type MCH-3-1/2 can be converted by rotating the seal under the cover to the other valve version Type MOCH-3-1/2.
4.7.1 Replacing the valve
• Pull off the cable head after loosening the screw.
• Loosen the screwed joints on the housing.
• Pull off the hose from both sides after opening the hose clamps.
• Remove the valve.
• Unscrew the screw-in hose nozzles and the reducing unions.
• Before fitting the new valve
Note:
Pay attention to voltage and type of current according to the nameplate.
• Clean the hose nozzles and use PTFE tape to seal the thread.
• Screw in the hose nozzles into the new valve.
• Assembly takes place in the reverse sequence.
4.7.2 Cleaning a valve:
• Pull off the cable head after loosening the screw.
• Loosen the upper nut on the solenoid coil.
• Remove solenoid coil.
• Remove the cover after loosening the two screws.
• Remove the plunger and diaphragm. Clean and replace damaged parts if necessary.
• After removing the snap-ring on the bottom, the pilot valve can be removed.
• Clean the valve body and replace any damaged parts.
• Assembly takes place in the reverse sequence.
Note: Pay attention to the tightening torque of 1Nm for the cable head.
4.7.3 Faults:
• Check connections, operating pressure and voltage.
Solenoid does not pull in:
• Short circuit or coil interruption.
• Core or core aperture contaminated.
• Jammed core causes coil overheating on alternating current.
Copyright ® SIEMENS Page 72 04/04