Email: sales@unikelly.com WhatsApp: +86 19108462246
Email: sales@unikelly.com WhatsApp: +86 19108462246
To customize a Kelly bar for a rotary drilling rig, you should provide the rig brand and model, required drilling depth, Kelly bar type, diameter, number of sections, section lengths, maximum rotary torque, and connection dimensions. Information about ground conditions and drilling tools is also important for determining the appropriate design. If you do not have complete technical drawings, the original Kelly bar, equipment specifications, and clear photographs can help the manufacturer evaluate your requirements and develop a suitable customized solution.
A Kelly bar is a telescopic drilling component that transfers torque and crowd force from a rotary drilling rig to the drilling tool. Its dimensions, structural design, and connection configuration must match the drilling rig and the project's operating requirements.
Unlike standard equipment accessories, a customized Kelly bar cannot be designed based on its outside diameter alone. Even two rotary drilling rigs from the same manufacturer may require different Kelly bar configurations because of differences in rotary drives, machine versions, torque requirements, and connection structures.
Providing accurate technical information before production helps the manufacturer:
Confirm compatibility with your rotary drilling rig.
Determine the appropriate Kelly bar diameter and section configuration.
Evaluate torque and axial load requirements.
Design suitable upper and lower connections.
Calculate the required telescopic length and drilling depth.
Reduce dimensional errors and unnecessary modifications during installation.
The more complete the technical information, the easier it is to develop a Kelly bar that meets your equipment and project requirements.
The first and most important information is your rotary drilling rig's brand and exact model.
Common rotary drilling rig brands include Bauer, Soilmec, Liebherr, SANY, XCMG, Zoomlion, and IMT.
However, providing only the brand name is usually insufficient. Different models and production versions may have different rotary drive configurations, Kelly bar guide dimensions, and connection arrangements.
For example, a Kelly bar designed for a Bauer BG30 should not automatically be assumed suitable for a Bauer BG36.
Please provide:
Rig manufacturer and brand.
Exact machine model.
Machine production year or version, if available.
Rotary drive model, if known.
Original Kelly bar model or part number, if available.
If you are unsure about the exact technical configuration, a photograph of the complete drilling rig and its rotary drive can help with the initial assessment.
The next step is to determine which type of Kelly bar is suitable for your application.
The two main types are Friction Kelly Bars and Interlocking Kelly Bars. They use different torque-transmission mechanisms and are designed for different drilling requirements.
Friction Kelly Bar
A Friction Kelly Bar transfers torque through friction between its telescopic sections. It is commonly used for drilling in silt, clay, and less dense sand and gravel.
It is often selected for general foundation drilling applications where the required torque can be transmitted within the bar's rated operating capacity.
Interlocking Kelly Bar
An Interlocking Kelly Bar uses mechanical locking features between telescopic sections to transmit torque. This structure provides positive mechanical torque transmission and is generally preferred for more demanding drilling conditions, including dense sand, gravel, and rock formations.
When selecting a type, consider:
Ground conditions.
Maximum rotary torque.
Required drilling depth.
Drilling tool type.
Operating requirements of the rotary drilling rig.
If you are not sure which type is appropriate, provide your project information and rig specifications. The manufacturer can help evaluate the suitable configuration.
Diameter and section configuration are essential dimensions in customized Kelly bar manufacturing.
The Kelly bar diameter affects the telescopic structure, compatibility with the rotary drilling rig, and the structural design of each section.
The number of sections determines the telescopic configuration and contributes to the achievable drilling depth.
For reference, UNIKELLY offers the following product configurations:
| Kelly Bar Type | Diameter Range | Available Sections |
| Friction Kelly Bar | 355–630 mm | 3–6 sections |
| Interlocking Kelly Bar | 355–930 mm | 3–5 sections |
These are product range references rather than universal specifications for every drilling rig.
When requesting a customized Kelly bar, provide the following information if available:
Outer diameter of the Kelly bar.
Diameter of each telescopic section.
Number of sections.
Individual section lengths.
Wall thickness, if known.
Existing technical drawings or dimensional records.
If you do not know the exact dimensions, the rig model and original Kelly bar photographs can be used as a starting point for further evaluation.
The required drilling depth is another key factor in determining the Kelly bar configuration.
For example, a project requiring a maximum borehole depth of 50 meters may need a different telescopic arrangement from one requiring 80 or 100 meters.
However, the total length of a Kelly bar is not necessarily equal to its achievable drilling depth.
The actual drilling depth depends on several factors:
Length of each telescopic section.
Number of sections.
Overlap between adjacent sections.
Available extension stroke.
Rotary drilling rig mast height.
Drilling tool and connection length.
Overall machine configuration.
When requesting a customized Kelly bar, specify your maximum required drilling depth and, if possible, the original Kelly bar's extended and retracted lengths.
This information helps the manufacturer evaluate the appropriate section arrangement without compromising the rig's operating limitations.
A Kelly bar must withstand the mechanical loads generated during drilling.
The rotary drive produces torque, which is transferred through the Kelly bar to the drilling tool. At the same time, the crowd system applies downward force to facilitate drilling.
These loads directly influence the structural design and material requirements of the Kelly bar.
Please provide:
Maximum rotary torque: The maximum torque output of your rotary drilling rig, usually specified in kNm.
Crowd force: The maximum crowd force generated by the rig's crowd system, if available.
Operating requirements: The typical torque and drilling loads expected during your project.
The manufacturer can use these parameters to evaluate the required structural capacity and torque-transmission design.
It is important to distinguish between the maximum torque generated by the drilling rig and the allowable torque of the Kelly bar. The customized Kelly bar must be designed according to its intended operating loads and engineering limits.
If you cannot provide the Kelly bar's required torque capacity, the exact rig model and its technical specifications are useful starting points.
Connection compatibility is one of the most important considerations in custom Kelly bar manufacturing.
The upper connection connects the Kelly bar to the rotary drive, while the lower connection attaches it to the drilling tool or adapter.
An incorrect connection design may prevent installation even if the Kelly bar's diameter, length, and number of sections are correct.
The manufacturer may need the following information:
| Connection | Important Information |
| Upper Connection | Rotary drive interface, dimensions, bolt-hole positions, and connection structure |
| Lower Connection | Drilling tool or adapter interface, dimensions, and locking arrangement |
| Special Requirements | Customized adapters, connection changes, or existing machine-specific designs |
If possible, provide original connection drawings or clear photographs of both ends of the existing Kelly bar.
For replacement projects, the connection dimensions should be verified against the original equipment design rather than estimated from photographs alone.
Although the Kelly bar is connected directly to the drilling rig, its design must also suit the actual drilling application.
Different geological conditions generate different drilling resistance and operating loads.
For example:
Clay and silt generally involve different drilling resistance from dense gravel.
Hard rock drilling may require higher torque and more demanding tool configurations.
Mixed ground conditions can create changing loads during drilling.
The drilling tool also affects the loads transmitted through the Kelly bar.
Common drilling tools include soil buckets, drilling augers, core barrels, and other specialized foundation drilling tools.
To help determine the appropriate configuration, provide:
Main ground conditions.
Maximum pile diameter.
Required drilling depth.
Drilling tool type.
Whether the project involves rock or mixed ground conditions.
This information helps the manufacturer evaluate whether the proposed Kelly bar structure and torque capacity are suitable for the actual application.
Yes. A lack of original technical drawings does not necessarily prevent Kelly bar customization.
Many customers need replacement Kelly bars for existing rotary drilling rigs but do not have complete engineering drawings.
In this situation, several types of reference information can help:
Option 1: Original Kelly Bar
If the existing Kelly bar is still available, its dimensions and connection structures can be inspected. However, worn or deformed components should not be used as the only reference for manufacturing dimensions.
Option 2: Equipment Technical Specifications
The drilling rig's original manual, technical data sheet, and rotary drive specifications can provide important reference information.
Option 3: Photographs and Measurements
Clear photographs of the complete Kelly bar, individual sections, upper connection, lower connection, and drive keys can help the manufacturer understand its structure.
Option 4: Existing Product Drawings
If you have previous purchase drawings, supplier specifications, or inspection records, these can be useful for confirming the original configuration.
A combination of machine information, dimensional measurements, and photographs is often more useful than any single reference.
Before production, critical dimensions and interfaces should be verified through an appropriate technical review.
To make the quotation and technical evaluation process more efficient, prepare the following information before contacting a Kelly bar manufacturer.
| Information | Required Details |
| Rig Brand | Bauer, Soilmec, Liebherr, SANY, etc. |
| Rig Model | Exact machine model and version |
| Kelly Bar Type | Friction or Interlocking |
| Outer Diameter | Required diameter in mm |
| Number of Sections | 3, 4, 5, 6, etc. |
| Section Length | Individual section lengths, if available |
| Required Drilling Depth | Maximum borehole depth in meters |
| Maximum Torque | Rotary drive torque in kNm |
| Crowd Force | Maximum crowd force, if available |
| Upper Connection | Rotary drive connection dimensions |
| Lower Connection | Drilling tool or adapter connection |
| Ground Conditions | Clay, silt, sand, gravel, rock, or mixed formations |
| Drilling Tool | Soil bucket, auger, core barrel, etc. |
| Reference Materials | Technical drawings, photographs, or original Kelly bar |
You do not need to have every parameter available before making an inquiry. Start with the rig brand and model, required drilling depth, and any existing Kelly bar information. The remaining technical details can be confirmed during the engineering assessment.
UNIKELLY specializes in Friction Kelly Bars and Interlocking Kelly Bars for major rotary drilling rig brands, including Bauer, Soilmec, Liebherr, and SANY.
Different drilling rigs and foundation projects may require different Kelly bar configurations. UNIKELLY can evaluate customized solutions based on your machine specifications and operating requirements.
Customization can cover:
Kelly bar diameter and telescopic section dimensions.
Number of sections and individual section lengths.
Overall length and drilling depth requirements.
Torque-transmission structure.
Upper and lower connection configurations.
Machine-specific compatibility requirements.
Whether you need a new Kelly bar for a drilling project or a replacement for an existing rotary drilling rig, providing accurate technical information is the first step toward selecting the right solution.
Customizing a Kelly bar requires a clear understanding of the rotary drilling rig, operating loads, telescopic dimensions, connection interfaces, and project conditions.
The most important information includes the rig brand and model, Kelly bar type, diameter, number of sections, required drilling depth, maximum torque, and connection dimensions. Ground conditions and drilling tool specifications also help determine the appropriate design.
If you do not have complete technical drawings, you can still start with your rig model, existing Kelly bar photographs, and basic project requirements.
Contact UNIKELLY to discuss your customized Kelly bar requirements. Send us your equipment information and technical references, and our team can help evaluate a suitable Friction Kelly Bar or Interlocking Kelly Bar solution for your rotary drilling rig.