Mindray WATO EX Series

Asset Type

Anesthesia Machine

Manufacturer

Mindray

Model

WATO EX Series

Manual Reference

WATO EX-55/65 Anesthesia Machine Service Manual, Revision 1.1, March 2009.

Manufacturer Recommendation / AEM Status

Mindray lists a 12-month maintenance interval based on typical use of approximately 2,000 operating hours per year. Equipment used more heavily should be serviced more frequently.

Manufacturer-Listed Annual Maintenance

• Replace applicable one-year service-package components.
• Perform the system inspection.
• Test pipeline and cylinder gas supplies.
• Test the flow-control system.
• Test vaporizer mounting, interlock, and back pressure.
• Test the O₂ flush.
• Inspect and test the breathing circuit.
• Test the pressure-relief valve when ACGO is configured.
• Test alarms.
• Inspect the AGSS.
• Test power-failure and battery operation.
• Perform electrical safety testing.
• Verify or calibrate flow sensors.
• Calibrate the O₂ sensor when configured.
• Zero the airway-pressure gauge.
• Verify or adjust APL-valve accuracy.
• Perform low-pressure pneumatic leak testing.

Manufacturer-Listed Three-Year Replacement Items

• M05-010001-06: Lithium-ion battery, 11.1 V, 4400 mAh, LI23S001A — quantity 1.
• M05-010R03---: Lithium cell battery, 3 V, 35 mAh — quantity 1.

After servicing the equipment or replacing components, fully reassemble the machine, complete all necessary calibrations, and perform the applicable checkout tests in the service manual before returning the machine to service.

If the facility performs this PM at a different interval or changes the listed activities, those changes should be managed under the facility’s approved AEM program, documented risk assessment, maintenance history, and applicable regulatory requirements.

What This PM Procedure Covers

• Annual inspection and manufacturer-listed functional testing.
• Pneumatic, breathing-system, ventilation, and alarm checks.
• Manufacturer-listed annual parts replacement.
• Three-year battery replacement review.
• Calibration and measurement-verification checks.
• Electrical safety testing.
• Return-to-service documentation.

Required Tools and Equipment

• Appropriate pipeline gas supplies.
• Compatible gas cylinders when cylinder testing is applicable.
• Test lung or 2 L test bag.
• Manual breathing bag.
• Patient circuit and Y-piece.
• Manufacturer leak-test plug or suitable test plug.
• Certified electrical safety analyzer.
• Calibrated pressure and flow measurement equipment.
• Mindray anesthesia-machine calibration device or equivalent equipment capable of the required measurements.
• Circuit-adapter test fixture when performing the ACGO pressure-relief valve test.
• 100 mL syringe, tubing, and Y-piece for the pressure-relief valve test.
• Hand tools required for manufacturer-listed component replacement.
• Approved waste-anesthetic-gas collection or scavenging method.
• Replacement parts applicable to the unit’s configuration and maintenance history.

Facility policy may require additional equipment such as an independent oxygen analyzer, vaporizer analyzer, gas-pressure gauges, or documentation of test-equipment calibration status.

Step-by-Step PM Procedure

1. Remove the Unit From Clinical Service

Action:

• Confirm that no patient is connected.
• Remove vaporizers or anesthetic agents from active use as needed for safe testing.
• Follow facility infection-control procedures.
• Clean and disinfect contaminated surfaces and breathing-system components before maintenance.
• Verify that all test equipment is within calibration.

Expected outcome: The machine is safe to inspect and test without exposing a patient or technician to avoidable hazards.

2. Review Configuration and Maintenance History

Action: Record:

• Exact model and serial number.
• Installed gas configuration.
• O₂ or air drive-gas configuration.
• Cylinder configuration.
• ACGO configuration.
• AGSS configuration.
• Installed vaporizers.
• O₂ sensor and gas-module configuration.
• Last annual PM date.
• Last three-year battery replacement date.
• Previous leak, calibration, alarm, or battery findings.

Expected outcome: Testing is matched to the machine’s actual configuration.

3. Replace Manufacturer-Listed Annual Components

The one-year service package is listed as P/N 0621-30-78479.

Replace the applicable components according to the unit’s configuration and service history:

• 0611-20-45600: Gas-supply inlet filter — quantity 3.
• M6M-010021---: Seal for gas-supply inlet assembly — quantity 3.
• M6M-010014---: Vaporizer-manifold seal — quantity 4.
• M6M-010031---: Seal for valve cover — quantity 2.
• M6M-010033---: Valve seal — quantity 2.
• M6M-010058---: Seal for bag arm — quantity 2.
• M6M-010038---: Seal for water-collection cup — quantity 1.
• 0601-20-78843: Sealing cushion for sodalime-canister outlet — quantity 1.
• 0601-20-78842: Sealing component for sodalime canister — quantity 1.
• M6M-010032---: Seal for sodalime-canister support — quantity 1.
• M6M-010063---: Seal for pressure-sampling connector — quantity 4.
• M6M-010006---: Seal for fresh gas and ACGO — quantity 2.
• M6M-010058---: Seal for drive gas and APL discharge — quantity 2.
• 0601-20-78848: Bellows-housing seal — quantity 1.
• 0601-10-69901: Folding bag — quantity 1.
• 0030-10-13077: Bag/mechanical-ventilation switch-axis seal — quantity 2.
• 0601-20-78840: BYPASS large sealing cushion — quantity 1.

The manual repeatedly uses the wording “as required” while also listing these components under the 12-month replacement schedule. Document each listed component not replaced and the approved reason.

Expected outcome: Applicable annual wear components and seals are renewed and correctly installed.

4. Perform the System Inspection

Action: Confirm that:

• The machine has no visible damage.
• All components are correctly attached.
• The breathing circuit is correctly assembled.
• Breathing tubes are undamaged.
• Vaporizers are correctly installed, locked, and interlocked.
• Pipeline and cylinder connections are correct.
• Cylinder valves remain closed when pipeline supplies are being used.
• Gas-pressure gauges are intact and readable.
• Casters are secure.
• Brakes prevent movement.
• The breathing-system assembly is locked in position.
• The power cord and plug are undamaged.
• AC and battery indicators operate.
• The system switch operates correctly.
• Shelves, drawers, rails, and accessory mounts are secure.

Expected outcome: The machine is complete, stable, correctly assembled, and free of visible safety defects.

5. Test Pipeline Gas Supplies

Action:

• Disconnect pipeline supplies and close cylinder valves.
• Bleed residual pressure until the gauges return to zero.
• Confirm each gauge returns to zero.
• Connect the O₂ pipeline.
• Turn the system on and set the flow controls to midrange.
• Confirm O₂ pipeline pressure is 280–600 kPa.
• Confirm unrelated gas gauges remain at zero.
• Disconnect O₂ and verify the appropriate supply alarms occur as pressure falls.
• Connect the remaining pipeline supplies individually.
• Confirm each connected pipeline pressure is 280–600 kPa.

Expected outcome: Gauges zero correctly, gas-specific connections are correct, pipeline pressures are within range, and low-supply alarms operate.

6. Test Cylinder Supplies

Skip this step when cylinders are not configured.

Cylinder Pressure

Action:

• Open each cylinder slowly.
• Confirm sufficient cylinder pressure.
• Close the cylinder valves after inspection.

Expected outcome: Each installed reserve cylinder contains sufficient gas.

High-Pressure Leak Test

Action:

• Turn the system off.
• Close the auxiliary O₂ flowmeter when configured.
• Open the cylinder valve and record pressure.
• Close the valve.
• Record pressure after one minute.

Pass criteria:

• Drive-gas cylinder pressure drop is not more than 5,000 kPa.
• Non-drive-gas cylinder pressure drop is not more than 690 kPa.

Replace the cylinder gasket and repeat the test when excessive loss is found.

Expected outcome: No unacceptable cylinder-side high-pressure leak is present.

7. Test the Flow-Control System

Action:

• Confirm all flow controls move smoothly.
• Confirm the electronic flow display operates normally.
• Confirm the total-flow tube float moves freely.
• Test each available gas through its operating range.
• Verify that the O₂/N₂O proportioning system prevents a hypoxic mixture.

For units using the O₂ sensor, measured oxygen concentration must remain at least 25% throughout the O₂/N₂O linkage test.

For units tested without the O₂ sensor, verify the manufacturer-listed minimum O₂ flows:

• N₂O at 0.6 L/min: O₂ must be at least 0.2 L/min.
• N₂O at 1.5 L/min: O₂ must be at least 0.5 L/min.
• N₂O at 3.0 L/min: O₂ must be at least 1.0 L/min.
• N₂O at 7.5 L/min: O₂ must be at least 2.5 L/min.

Expected outcome: Gas controls, displays, floats, and the O₂/N₂O linkage operate normally.

8. Test the Vaporizer Mounting and Back Pressure

Use only vaporizers compatible with the installed manifold.

Action:

• Confirm each vaporizer is properly mounted and locked.
• Confirm the interlock prevents simultaneous activation of two vaporizers.
• Set O₂ flow to 6 L/min.
• Confirm the flow remains stable.
• Adjust the vaporizer from 0% to 1%.
• Repeat for each installed vaporizer.

Pass criterion: O₂ flow does not decrease by more than 1 L/min over the tested vaporizer range.

Use approved scavenging or collection during this test.

Expected outcome: Vaporizer mounting, interlock, and machine back pressure are acceptable.

9. Test the O₂ Flush

Mechanical Ventilation Position

Action:

• Occlude the patient connection.
• Completely collapse the bellows.
• Press and hold the O₂ flush.
• Repeat at least twice.

Pass criterion: Bellows fully inflate within 1–3 seconds.

Manual Ventilation Position

Action:

• Connect a 1 L or 3 L bag.
• Set the APL valve to 75 cmH₂O.
• Collapse the bag.
• Press and hold the O₂ flush.
• Repeat at least twice.

Pass criteria:

• 1 L bag fully inflates within 1–3 seconds.
• 3 L bag fully inflates within 3–6 seconds.

Expected outcome: O₂ flush flow is adequate and the pushbutton returns normally.

10. Inspect Breathing-System Components

Action: Check:

• Inspiratory and expiratory valve discs.
• Bellows and bellows housing.
• Folding bag.
• Manual bag.
• Bag arm.
• APL valve.
• Bag/mechanical-ventilation selector.
• Absorber canister and seals.
• Water-collection cup.
• Flow sensors.
• Patient connections.
• Breathing tubes.
• Circuit adapter.
• O₂ sensor connection.
• Visible contamination, cracks, deformation, looseness, or missing components.

Confirm that the inspiratory valve opens during inspiration and closes at expiration. Confirm that the expiratory valve opens during expiration and closes at inspiration.

Expected outcome: The breathing system is correctly assembled, clean, undamaged, and mechanically functional.

11. Perform the Bellows Test

Action:

• Place the machine in Standby.
• Select mechanical ventilation.
• Set fresh-gas controls to minimum.
• Occlude the patient connection.
• Use the O₂ flush to raise the folding bag fully.

Pass criteria:

• Airway pressure does not exceed 15 cmH₂O during filling.
• The folding bag does not fall after filling.

Expected outcome: The bellows assembly does not show an obvious leak.

12. Perform the Mechanical-Ventilation Leak Test

Action:

• Place the system in Standby.
• Connect the breathing-circuit Y-piece to the leak-test plug.
• Set O₂ flow to approximately 0.15–0.2 L/min.
• Fill the bellows.
• Select mechanical ventilation.
• Start the machine’s breathing-system leak test.
• Allow the test to complete.

Pass criterion: The machine displays that the test passed, indicating leakage is within approximately 0.15–0.2 L/min.

Expected outcome: Bellows, drive-gas circuit, absorber, tubing, flow sensors, and connectors have acceptable airtightness.

13. Perform the Manual-Ventilation Leak Test

Action:

• Place the machine in Standby.
• Select manual ventilation.
• Install the manual bag.
• Close the APL valve to 75 cmH₂O.
• Set O₂ flow to 0.15–0.2 L/min.
• Occlude the patient connection.
• Use the O₂ flush to raise circuit pressure to approximately 30 cmH₂O.
• Release the flush and observe the pressure gauge.

Pass criterion: No meaningful pressure decrease indicating a breathing-system leak.

Expected outcome: The manual circuit, APL valve, check valves, absorber, tubing, sensors, and connections are leak-free.

14. Test the APL Valve

Action:

• Set the APL valve to 30 cmH₂O.
• Inflate the manual bag with the patient circuit occluded.
• Observe the airway-pressure gauge.
• Set the APL valve to MIN.
• Set O₂ flow to 3 L/min with other gases off.
• Press the O₂ flush.
• Return O₂ flow to minimum.

Pass criteria:

• At the 30 cmH₂O setting, the gauge reads 20–40 cmH₂O.
• At MIN with O₂ at 3 L/min, pressure is less than 5 cmH₂O.
• During O₂ flush at MIN, pressure does not exceed 10 cmH₂O.
• With O₂ returned to minimum, pressure does not fall below 0 cmH₂O.

Adjust APL-valve accuracy according to the service manual when outside limits.

Expected outcome: The APL valve regulates and relieves pressure correctly.

15. Test the ACGO Pressure-Relief Valve

Perform only when ACGO is configured and the required fixture and measurement equipment are available.

Pass criterion: Pressure at valve opening is 100–125 cmH₂O.

The service manual identifies pressure-relief valve assembly P/N 0621-30-69662 when replacement is necessary.

Expected outcome: The ACGO pressure-relief valve opens within the manufacturer-listed range.

16. Test Mechanical Ventilation

Connect a 2 L bag as a test lung.

Volume-Controlled Ventilation

Test the following manufacturer-listed combinations using fresh gas of approximately 0.5 L/min:

• 300 mL at 15 BPM.
• 600 mL at 15 BPM.
• 900 mL at 15 BPM.
• 1,200 mL at 15 BPM.

Pass criteria:

• Displayed exhaled tidal volume is within ±10% of the set tidal volume.
• The bellows returns to the top during each breath.
• Displayed peak pressure agrees with the airway-pressure gauge within 2 cmH₂O.
• Waveforms are normal.
• No technical alarm occurs.

Pressure-Controlled Ventilation

Perform only when PCV is configured.

Manufacturer-listed test settings:

• Pinsp 10 cmH₂O, 15 BPM, PEEP off.
• Pinsp 15 cmH₂O, 12 BPM, PEEP 5 cmH₂O.
• Pinsp 20 cmH₂O, 10 BPM, PEEP 8 cmH₂O.

Pass criteria:

• Displayed Ppeak is within ±2 cmH₂O of the Pinsp setting.
• Displayed Ppeak agrees with the gauge within 2 cmH₂O.
• Displayed PEEP agrees with the gauge within 1 cmH₂O.
• The bellows returns to the top.
• Waveforms are normal.
• No technical alarm occurs.

Expected outcome: The ventilator delivers and measures volume and pressure within the manufacturer-listed tolerances.

17. Test Alarms

Use the manual’s test setup unless facility policy provides a validated equivalent.

Verify operation and cancellation of:

• Low FiO₂ alarm when O₂ monitoring is configured.
• High FiO₂ alarm.
• Low minute-volume alarm.
• Apnea alarm.
• Sustained-airway-pressure alarm.
• High airway-pressure alarm.
• Low airway-pressure alarm.
• O₂ supply-failure alarm.
• Drive-gas-pressure-low alarm.
• Battery-in-use notification.

Expected outcome: Each alarm activates under the simulated condition and clears when the condition is corrected.

18. Inspect the AGSS

Action:

• Confirm the float rises above the MIN indication with adequate scavenging.
• Confirm the float moves freely on its guide.
• Inspect the filter screen for blockage.
• Inspect the transfer tube, receiving hose, fittings, O-rings, nylon pads, and seals.
• Confirm pressure-compensation openings are unobstructed.
• Confirm the facility disposal system provides suitable flow.

The manual identifies an AGSS disposal-system range of approximately 50–80 L/min.

Expected outcome: Waste-gas transfer and receiving components are intact, unobstructed, and functional.

19. Test AC and Battery Operation

Action:

• Connect AC power.
• Confirm the AC and battery indicators illuminate.
• Turn on the machine.
• Disconnect AC power.
• Confirm the machine remains operating and displays the battery-use message.
• Confirm the AC indicator turns off and the battery indicator flashes.
• Restore AC power.
• Confirm the message clears and charging indications return.

Expected outcome: The machine transfers between AC and battery operation without unintended shutdown.

Review the three-year battery replacement schedule and replace applicable batteries when due.

20. Check Sensor Zero Points

Access the manufacturer diagnostic display with the system in Standby, fresh gas off, and the patient connection open to atmosphere.

Manufacturer-listed ranges:

• Airway-pressure sensor A/D value: 400–800.
• PEEP-pressure sensor A/D value: 400–800.
• Inspiratory flow-sensor A/D value: 200–1,000.
• Expiratory flow-sensor A/D value: 200–1,000.
• Ventilator flow-sensor A/D value: 200–1,000.

Expected outcome: Actual measured pressure and flow values read zero, and A/D values are within the listed ranges.

The manual states that an out-of-range zero point cannot be corrected through calibration and may indicate that the monitor board must be replaced.

21. Verify Flow-Sensor Accuracy and Calibrate

Using a calibrated flow reference, verify the sensors at approximately:

• 3 ±0.5 L/min.
• 10 ±1 L/min.
• 20 ±1 L/min.
• 30 ±2 L/min.
• 60 ±3 L/min.

Pass criterion: Each machine flow-sensor reading agrees with the calibrated reference within 1 L/min or 5% of the reference reading, whichever is greater.

Perform the applicable manufacturer flow calibration when:

• Tidal-volume measurement deviation exceeds 10%.
• A flow sensor has been replaced.
• The monitor board, expiratory-valve assembly, or three-way valve assembly has been replaced.
• Accuracy verification fails.

Expected outcome: Flow sensors meet manufacturer-listed accuracy and calibration completes successfully.

22. Verify Pressure-Sensor Accuracy and Calibrate

Using a calibrated pressure reference, verify at approximately:

• 5 ±1 cmH₂O.
• 20 ±1 cmH₂O.
• 50 ±1 cmH₂O.
• 70 ±2 cmH₂O.
• 90 ±2 cmH₂O.

Pass criterion: Airway and PEEP pressure readings agree with the reference within 1 cmH₂O or 2% of the reference reading, whichever is greater.

Perform pressure calibration after replacement of the monitor board, expiratory-valve assembly, or three-way valve assembly, or when the accuracy criterion is not met.

Expected outcome: Pressure sensors meet manufacturer-listed accuracy.

23. Verify Electronic Flowmeter Accuracy

Using an appropriate calibrated gas-flow reference:

• Verify O₂ and air at approximately 3, 5, and 8 L/min.
• Verify N₂O according to the manual’s O₂-offset method.

Pass criterion: Electronic flowmeter indication agrees with the reference within 10% of the reference reading.

Calibrate when the electronic flowmeter board or throttling device has been replaced or when accuracy is outside the manufacturer-listed limit.

Expected outcome: Electronic gas-flow displays meet manufacturer-listed accuracy.

24. Calibrate the O₂ Sensor

Perform when the O₂ sensor is configured.

Calibrate at:

• Room air, approximately 21% O₂.
• Pure oxygen, approximately 100% O₂.

Calibration is manufacturer-listed after O₂ sensor or monitor-board replacement, or when measured oxygen concentration deviates by more than 3% in both room air and pure oxygen.

Expected outcome: O₂ calibration completes and the displayed value is appropriate in room air and oxygen.

25. Perform the Low-Pressure Pneumatic Leak Test

Perform the manufacturer low-pressure pipeline leak test referenced in the annual maintenance checklist.

Document:

• Test setup.
• Test pressure or flow.
• Observed leakage.
• Pass/fail result.
• Any repaired connection, tube, valve, seal, or manifold.

Expected outcome: The low-pressure pneumatic system has no leak exceeding the manufacturer’s test criteria.

26. Complete Final Checkout

Action:

• Reinstall all panels and covers.
• Restore all tubing and electrical connections.
• Remove all test plugs and test fixtures.
• Confirm the patient circuit is unobstructed.
• Confirm cylinder valves are closed unless facility procedure requires otherwise.
• Restore alarm limits and user settings.
• Confirm vaporizers are locked and off.
• Confirm brakes, drawers, shelves, lights, and accessories are secure.
• Run the machine’s normal pre-use or checkout sequence.
• Verify no unresolved technical alarms remain.
• Affix the PM label according to facility policy.

Expected outcome: The machine is fully assembled, configured, and ready for clinical pre-use checkout.

Electrical Safety Testing

The Mindray service manual specifies leakage current not greater than 500 µA and protective-earth impedance from the power-cord grounding terminal to exposed metal less than 0.2 Ω.

Ground Resistance

Ground resistance measured in ohms, manufacturer limit <0.2 Ω:

Result =

Pass / Fail =

Leakage Current

Touch/chassis leakage measured in microamps:

Facility limit used = 500 µA

Result =

Pass / Fail =

Document the electrical-safety analyzer, asset number, calibration due date, test standard or mode, applied-parts configuration, and power-cord condition according to facility policy.

Pass / Fail Criteria

PM Pass Criteria

• Annual manufacturer-listed inspection and testing completed.
• Applicable annual replacement components replaced or disposition documented.
• Three-year battery status reviewed.
• Pipeline and cylinder tests pass.
• No unacceptable pneumatic or breathing-system leaks remain.
• Ventilator volume and pressure accuracy meet the listed tolerances.
• O₂/N₂O linkage operates correctly.
• Alarm functions pass.
• APL valve, O₂ flush, AGSS, and power-transfer tests pass.
• Required calibrations complete successfully.
• Ground resistance is less than 0.2 Ω.
• Leakage current does not exceed 500 µA.
• No unresolved technical alarms or unsafe physical defects remain.

Remove From Service Criteria

Remove the machine from service when any of the following remains unresolved:

• Failed breathing-system or pneumatic leak test.
• Incorrect gas connection, pressure, or flow.
• Failed O₂/N₂O proportioning protection.
• Failed ventilator volume or pressure accuracy.
• Failed O₂, flow, or pressure calibration.
• Failed alarm.
• Failed APL valve or pressure-relief valve test.
• Failed AGSS function.
• Failed AC-to-battery transfer.
• Ground resistance or leakage current outside manufacturer limits.
• Damaged breathing-system component, tubing, power cord, connector, caster, brake, vaporizer mount, or gas fitting.
• A test plug or obstruction cannot be positively accounted for.
• Unresolved technical alarm.
• Required post-service testing cannot be completed.

Use the manufacturer service manual, facility policy, and approved AEM program to determine the final PM interval and return-to-service requirements.