Varian Medical Systems Clinac 21EX/23EX
Varian Medical Systems · Model Clinac 21EX/23EX
Two selectable photon beam energies Selectable dose rate up to 600MU/min Choice of electron energies to meet clinical needs, with electron applicators included Tight isocenter alignment of the gantry, couch, collimator, and imagers Reproducible, stable, and accurate machine positioning Exact couch for accurate reproducible patient positioning Modes for special clinical procedures, e.g. high dose total skin electron mode and total body X-ray mode Enhanced dynamic wedge saves time and the need to reenter the treatment room Auto field sequencing Dynamic procedure modes for photon arcs SmartConnect remote access technology provides access to Varian customer support expert assistance and online remote analysis.
Typical Failure Modes
Compiled for this model from its own documentation and established engineering knowledge for this equipment class - not from a verified service record. Confirm against the manufacturer's service manual.
RF / klystron (or magnetron) output instability
HighSymptoms: Beam-on faults, dose-rate low or unstable, RF/HV or arc interlocks.
Root cause: Klystron / magnetron or thyratron at end of life, HV supply, or waveguide arcing / SF6 pressure loss.
MLC leaf fault
HighSymptoms: Leaf stuck or out of position, delivery interlock, QA fluence errors.
Root cause: Millennium MLC leaf motor, leaf-guide wear, or a leaf position-readout fault.
Gantry / collimator / couch drive fault
MediumSymptoms: Rotation, field-size or couch position error, position interlock.
Root cause: Drive motor, encoder, or brake.
Onboard imaging fault (OBI / PortalVision / CBCT)
MediumSymptoms: kV or MV imaging degraded, poor image for setup, imaging-arm deploy errors.
Root cause: kV X-ray tube, amorphous-silicon panel, or the imaging-arm (Exact arm) drive.
Dosimetry / ion-chamber drift
HighSymptoms: Output constancy checks trend out, symmetry/flatness off, chamber interlock.
Root cause: Monitor ion-chamber aging or a dose-servo fault.
Water / thermal management fault
MediumSymptoms: Over-temperature interlocks, dose-rate instability, coolant-flow alarm.
Root cause: Chiller pump, heat-exchanger fouling, or low coolant.
Serviceable Parts & Consumables
Serviceable items for this model, compiled from its documentation and engineering knowledge for this equipment class. Service class and relative cost are estimates, not manufacturer figures; no part numbers are given. Confirm intervals and pricing against the manufacturer.
Klystron / magnetron
OEM service; dosimetry re-commissioning required.
Class Periodic replacementRel. cost $$$$R&R Expert-level
Thyratron
Class Periodic replacementRel. cost $$$$R&R Expert-level
MLC leaf motor / drive assembly
Class Major service partRel. cost $$$$R&R Expert-level
kV X-ray tube / a-Si imaging panel
Class Major service partRel. cost $$$$R&R Expert-level
Monitor ion chamber
Class Major service partRel. cost $$$$R&R Expert-level
Chiller pump / heat exchanger
Class Major service partRel. cost $$$R&R Difficult
| Part | Service class | Relative cost | R&R difficulty |
|---|---|---|---|
| Klystron / magnetron OEM service; dosimetry re-commissioning required. | Periodic replacement | $$$$ | Expert-level |
| Thyratron | Periodic replacement | $$$$ | Expert-level |
| MLC leaf motor / drive assembly | Major service part | $$$$ | Expert-level |
| kV X-ray tube / a-Si imaging panel | Major service part | $$$$ | Expert-level |
| Monitor ion chamber | Major service part | $$$$ | Expert-level |
| Chiller pump / heat exchanger | Major service part | $$$ | Difficult |
Relative cost: $ lowest · $$$$ highest service-part cost for this equipment class. Not a price.
Troubleshooting Approach
A starting sequence for this model, compiled from its documentation and engineering knowledge for this equipment class. Follow the manufacturer's service documentation for the actual procedure.
Symptom: Beam-on / RF fault
- This is an OEM-service linac - the BMET role is triage and coordination with Varian.
- Record the exact fault codes from the console and the modulator / equipment-room logs.
- Check chiller status and coolant flow first - thermal faults mimic RF faults.
- Verify SF6 / waveguide pressure.
- Escalate a confirmed klystron / thyratron / waveguide fault to Varian; keep the unit down until physics re-verifies output.
Symptom: MLC or field-size interlock
- Note the leaf / diaphragm and the exact interlock.
- Review the daily QA and delivery-log trend.
- Run the MLC calibration / diagnostic where the procedures allow.
- Escalate a confirmed leaf-drive or readout fault to Varian.
- Coordinate with physics before resuming clinical use.
Documents & Manuals
No documents available for this device yet.
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