Crossover Sub (Protection Sub) is a short heavy-duty tubular component used in Horizontal Directional Drilling (HDD) drill string. It is also known as Saver Sub in drilling industry.
It is installed between rotary head / drill pipe and downhole tools. Its two ends are machined with different thread connections to adapt mismatched thread sizes/types between drill string components.
Main function
1. Transfer torque, axial pull and mud circulation during pilot bore and pullback.
2. Protect expensive drill pipe, rotary head and downhole tools: Concentrate thread wear onto this replaceable short sub, so that costly main drill string threads avoid frequent damage.
3. Bridge incompatible API or HDD proprietary thread connections in BHA.
Manufactured from forged alloy steel, quenched & tempered. Thread surface treatment: phosphating / copper plating for anti-galling. Designed and inspected per API 7-1 & DS-1 standards.
Main Technical Parameters
| Item | Specification |
| Product Name | HDD Crossover Sub / Protection Sub / Saver Sub |
| Material | AISI 4145H Modified Alloy Steel, Forged |
| Heat Treatment | Quenched & Tempered |
| Thread Standard | API Reg / NC / IF / FH or Custom HDD Thread |
| Thread Surface | Phosphating / Copper Plating |
| Working Function | Torque transmission, pull load transfer, mud passage, thread protection |
| OD (Outer Diameter) | Customized (e.g. 89mm, 102mm, 127mm, 140mm, 168mm) |
| ID (Inner Bore Diameter) | Customized based on mud flow requirement |
| Overall Length | 300~800 mm (custom) |
| Rated Torque | Matched to thread connection (the weaker thread governs rating) |
| Rated Tensile Load | According to body & thread strength |
| Test & Inspection | MPI Magnetic Particle Inspection, UT Ultrasonic Test, Thread Gauging |
| Compliance | API 7-1, DS-1 |
Common thread combinations for HDD:
– 3-1/2 Reg × NC38
– NC38 × NC50
– NC50 × 4-1/2 Reg
– Custom HDD machine proprietary threads (Vermeer, Ditch Witch etc.)
Product Photo
