Non-Magnetic Cable-Pass-Through Check Valves for MWD Telemetry in Directional Drilling
Non-magnetic cable-pass-through check valves are specialized downhole components used in long-reach directional drilling systems, particularly where real-time MWD/LWD telemetry is required via a central electrical cable running through the drill string.
These valves serve three critical functions:
1. Prevent backflow of drilling fluid when pumps are off, protecting downhole tools from pressure surges;
2. Transmit hydraulic power to bottom-hole motors during operation;
3. Enable uninterrupted electrical signal transmission through a sealed central bore, supporting continuous data feedback from MWD probes.
Constructed entirely from non-magnetic materials (μr ≤ 1.005), they eliminate magnetic interference that could distort azimuth measurements—essential for accurate borehole navigation in coalbed methane or horizontal wells.
Key Technical Properties
l Relative permeability (μr): ≤ 1.005 — verified by third-party test reports
l Integrated central cable channel: Sealed against 12 MPa pressure while maintaining low electrical resistance
l High mechanical strength: Tensile strength ≥ 1035 MPa, yield strength ≥ 965 MPa
l Excellent toughness: Meets or exceeds 135 ksi steel grade ductility standards
l Leak-tight sealing: Stable signal transmission at operating pressures up to 12 MPa
Technical Specifications
|
Specification |
Value |
|
Material |
High-strength austenitic non-magnetic steel (P650 grade) |
|
Pressure Rating |
≥ 12 MPa |
|
Conductor Resistance |
< 0.5 Ω/km |
|
Insulation Resistance |
≥ 10 MΩ |
|
Tensile Strength |
≥ 1035 MPa |
|
Yield Strength |
≥ 965 MPa |
|
Magnetic Permeability (μr) |
≤ 1.005 |
|
Body Construction |
Monobloc forged design with full heat treatment |
|
Certification |
MA Certified (mining applications) |
Note on Material Grade:
The valve body is machined from P650-grade non-magnetic steel to ensure structural integrity under cyclic pressure loads while maintaining minimal magnetic signature. This material is standard for high-reliability MWD-compatible downhole tools.
Application & Integration
Designed for use with center-cable drill strings in 1,000+ meter directional boreholes
Installed above the mud motor and below the MWD sub to isolate pressure zones while preserving telemetry continuity
Compatible with standard API thread connections (Regular, FH) or custom mining interfaces
As an OEM supplier for national mine safety programs, our non-magnetic cable-pass-through check valves have been deployed in hundreds of gas drainage projects, where reliable signal transmission directly impacts drilling control and outburst prevention. Each unit undergoes hydrostatic testing and includes optional third-party verification (SGS/BV) upon request.