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Crossover Sub (XO Sub)
Crossover Sub (XO Sub) is used to connect two different thread types or sizes in a drill string or BHA. It provides a reliable transition for drilling operations, workover, and tool string compatibility.
Category:
Handling & Hoisting
The Crossover Sub (XO Sub)(Cross Over Sub / Cross-over Sub) is a critical connection component used in the drill string or BHA to connect two different thread types, sizes, or connection standards.
It is commonly applied when transitioning between drill pipe, drill collars, subs, downhole tools, or surface equipment, ensuring reliable make-up, structural integrity, and compatibility across the string.
- Drill Pipe to Drill Collar crossover subs
- BHA tool connection crossover subs
- API standard connections (REG / IF / FH, etc.)
- NC connections (NC26 / NC31 / NC38 / NC46 / NC50, etc.)
- Premium thread equivalents available upon request
- Special shoulder / stress-relief designs for demanding drilling conditions
- Reliable crossover between different thread sizes and types
- High-strength design for torque, tension, and cyclic loading
- Precision machined threads for stable make-up and break-out
- Optional stress-relief groove and optimized shoulder profile
- Suitable for drilling, workover, and downhole tool strings
- Connecting drill pipe to drill collar or BHA components
- Transition between different API connection standards
- Tool string compatibility for directional drilling and conventional drilling
- Workover strings and servicing operations where mixed connections exist
XO Subs are customized based on the required connection transition. Below is the typical RFQ parameter list and common configuration logic.
| Parameter | Typical Options | Notes |
|---|---|---|
| Connection A (Pin/Box) | REG / IF / FH / NC / Premium | Specify pin or box and exact thread designation |
| Connection B (Pin/Box) | REG / IF / FH / NC / Premium | Define the required crossover direction clearly |
| OD / Length | Per BHA / string requirement | May follow drill collar or tool OD envelope |
| Material | AISI 4145H Mod / per project | Heat-treated alloy steel commonly used |
| Optional Design | Stress-relief groove / hardbanding | Selected based on load and wear conditions |
- Raw material certificates (MTC) available
- Heat treatment records upon request
- Dimensional inspection for threads and shoulders
- MPI / UT inspection available per project requirement
- Final inspection and packing records before delivery
- Connection A: thread type + size + pin/box (e.g., NC38 Pin)
- Connection B: thread type + size + pin/box (e.g., 4 1/2" IF Box)
- Application position: drill pipe / drill collar / BHA / surface equipment
- OD and length limitation (if any)
- Quantity and required delivery schedule
- Any special requirements: stress-relief groove, coating, inspection level
Unionlever OFS supplies Crossover Subs (XO Subs) with clear connection mapping and engineering-friendly RFQ logic, helping customers avoid common ordering mistakes in mixed-string operations.
We support customization, trial orders, and project-based inspection requirements, ensuring the crossover solution matches your drilling string configuration from the first RFQ.
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sales@unionleverofs.com
ofs@unionlever.com
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Unionlever Oilfield Equipment Co., Limited
A Member of
Unionlever International Group Limited
(Established Since 2010)
"To be a globally trusted leader in oilfield equipment and integrated supply solutions."
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