Non-Magnetic Measurement Sub Housings for MWD/LWD in Directional Drilling
Non-magnetic measurement sub housings are precision-engineered sleeves that encase MWD (Measurement-While-Drilling) or LWD (Logging-While-Drilling) probe assemblies in directional drilling operations. Their primary function is to provide a magnetically neutral environment around the probe, ensuring the local magnetic field closely matches the earth’s natural geomagnetic field—enabling accurate determination of borehole azimuth and inclination.
These housings are installed directly adjacent to the probe section and must maintain structural integrity under high torsion, tension, and internal pressure while introducing zero magnetic interference to sensitive downhole sensors.
Key Technical Properties
l Relative permeability (μr): ≤ 1.005 — verified by third-party test reports
l Non-sparking: Safe for use in gassy or explosive underground environments
l High strength: Tensile strength ≥ 1035 MPa, yield strength ≥ 965 MPa
l Excellent ductility: Elongation significantly exceeds beryllium copper alloys
l Corrosion resistance: Suitable for high-H₂S, acidic downhole conditions
Technical Specifications
|
Specification |
Value |
|
Material |
High-strength austenitic non-magnetic steel (P650 grade) |
|
Outer Diameter Options |
70 mm, 76 mm, 89 mm, 91 mm |
|
Wall Thickness |
Precision-machined for uniformity (±0.1 mm tolerance) |
|
Relative Permeability (μr) |
≤ 1.005 |
|
Tensile Strength |
≥ 1035 MPa (Typical: 1165 MPa) |
|
Yield Strength |
≥ 965 MPa (Typical: 1046 MPa) |
|
Certification |
MA Certified (mining) / API-compliant documentation available |
Note on Material Grades:
Standard housings are manufactured from P650-grade non-magnetic steel to ensure minimal magnetic signature and high mechanical reliability. For cost-sensitive applications with moderate loads, P550-grade alternatives are available upon request.
Design & Application Considerations
Designed with uniform wall thickness to prevent eddy current distortion and signal attenuation
Compatible with standard MWD probe diameters and thread connections (API Regular, FH, or custom)
Typically installed between two sections of non-magnetic drill pipe to create a continuous low-permeability zone around the probe
As an OEM supplier for national coal mine safety programs, our non-magnetic measurement sub housings have been deployed in hundreds of directional gas drainage boreholes, where signal fidelity directly impacts drilling accuracy and safety. Each batch includes full material traceability and optional third-party permeability verification (SGS/BV).