I. Air Source System Maintenance: Foundation of Stable Control
The air source powers the control box's energy conversion and requires dry, clean conditions:
- Triple-unit maintenance:
- Drain accumulated water from the air filter-regulator-lubricator daily; maintain oil levels in the lubricator's cup above 2/3 to ensure adequate pneumatic component lubrication.
- Line sealing:
- Use soap water to inspect gas line connectors (e.g., M16×1.5 quick couplings) for leaks monthly. Leaks cause valve positioning errors or pressure feedback anomalies.
- Pressure regulator calibration:
- Input air pressure must stabilize at 0.35 MPa. Deviations risk distorting pressure transmitter signals.
II. Hydraulic System Servicing: Lifeline of Power Output
Hydraulic oil quality and accumulator conditions determine response reliability:
- Oil management and replacement:
- Replace #10 aviation hydraulic oil every six months; simultaneously clean the oil tank and filters (filtration precision ≤25μm).
- Check oil levels weekly via the sight glass and refill to the 2/3 mark to prevent pump dry-running.
- Accumulator maintenance:
- Verify nitrogen pre-charge pressure every six months (1 MPa). Insufficient pressure causes frequent pneumatic pump cycling or emergency valve failure.
- Pneumatic pump debugging:
- Adjust regulator T2 to maintain system oil pressure at 3 MPa (max 4 MPa). Confirm the relief valve activates automatically during overpressure events.
III. Instrument and Transmitter Calibration: Key to Precision Monitoring
Inaccurate instruments may mask downhole risks:
- Valve position transmitter calibration:
- Coarse adjustment: Loosen mounting bolts and reposition the transmitter to zero the position gauge when the choke valve is fully closed.
- Fine adjustment: Rotate the sleeve to modify spring tension, correcting deviations within ±5%.
- Pressure transmitter correction:
- If standpipe/casing pressure readings are low, tighten the valve seat clockwise; if high, loosen counterclockwise. Calibrate against manifold direct-read gauges.
IV. External Line and Valve Maintenance: Eliminating Erosion Risks
Choke manifold and valve reliability depend on hardware integrity:
- Line connection checks:
- Inspect hydraulic control line seals (M22×1.5 quick couplings) monthly for aging to prevent oil leaks.
- Choke valve operation protocols:
- Personnel must stand beside valves during manual adjustments to avoid high-pressure fluid ejection.
- Cycle valves weekly to prevent mud solidification-induced jamming.
- Flat valve operation rule:
- After closing, rotate handwheels back 1/4~1/2 turn to prevent thermal expansion-induced seal failure or restart failure.
V. Critical Maintenance Cycles and Checklist
Table: Core Maintenance Schedule for Choke Manifold Control Panels
| Maintenance Category | Frequency | Operation Content | Acceptance Criteria |
| F.R.L Unit | Daily Drain | Drain the accumulated water from the water filter and check the oil level in the oil mist lubricator | The liquid level in the oil cup is ≥2/3, and there is no standing water |
| Hydraulic oil status | Weekly | Inspect oil level/contamination | Oil clear, foam-free, level compliant |
| Instrument calibration | Monthly | Calibrate position/pressure transmitters | Display error ≤1% |
| Accumulator inspection | Every 6 months | Test nitrogen pre-charge pressure | Pressure stable at 1 MPa |
| Hydraulic oil replacement | Every 6 months | Replace oil, clean tank/filters | Oil meets #10 aviation hydraulic standard |
Maintenance Equals Safety
In an ultra-deep well project in eastern Sichuan, insufficient accumulator nitrogen pressure delayed valve closure, causing wellhead casing pressure to surge toward critical levels. Post-incident analysis revealed skipped biannual inspections. The crisis was only resolved by activating the manual pump-underscoring that control box maintenance is not an expense but an investment in well-control barriers. When every coupling seals reliably, every instrument reads accurately, and every drop of hydraulic oil remains pure, well control safety transforms from procedure to practice.
Pro Tip: Drilling teams can implement a maintenance red-tag system-applying expiration tags to critical components like accumulators and triple-units. Uninspected items trigger visual alerts, enabling real-time oversight.