회사 소식 Common Nozzle Sizes for Drag Bits and Application References

Drag bits are cost-effective core tools for soft formation drilling, widely used in scenarios such as water well drilling, shallow mine stripping, and oil & gas well surface drilling. Their nozzles (also known as "water eyes") are key components ensuring drilling efficiency. The core functions of nozzles include injecting drilling fluid to cool the drag bit’s cutting edges, flush cuttings, and prevent bit sticking. The rationality of nozzle size (primarily inner diameter, outer diameter, and connection method) directly affects operational performance: a too-small size leads to insufficient drilling fluid flow, causing cuttings accumulation and overheating wear of cutting edges; a too-large size results in pressure loss, weakening flushing force. This article uses plain language and clear tables to sort out common nozzle size specifications, selection criteria, and typical application scenarios for drag bits, helping industry practitioners quickly match bit models with nozzle sizes and improve the stability and economy of soft formation drilling.

Before exploring sizes, let’s briefly sort out the core value of nozzles to understand "why size selection cannot be ignored":

1. Cooling Cutting Edges: The cutting edges of drag bits are mostly inlaid with tungsten carbide cemented carbide strips. During drilling, friction with soft formations (such as clay and loose sandstone) generates significant heat. High-pressure drilling fluid precisely cools the edge through nozzles, preventing tungsten carbide strips from falling off or wearing due to overheating;
2. Efficient Cuttings Removal: Soft formation cuttings are prone to loose accumulation. High-speed injected drilling fluid can quickly flush cuttings from the bit working surface to the ground, avoiding repeated crushing of cuttings or bit sticking;
3. Protecting the Bit Body: The fluid film formed by drilling fluid reduces abrasive damage to the bit body from cuttings, while preventing clay from adhering to the bit, reducing drilling resistance.

The mainstream material of drag bit nozzles is tungsten carbide cemented carbide (some entry-level products use cemented carbide inserts), featuring ultra-high hardness (HRA≥89), wear resistance, and erosion resistance. It can withstand drilling fluid pressure of 10-30MPa, with a service life 4-8 times that of ordinary metal nozzles, perfectly adapting to the high-frequency operational needs of drag bits in soft formations.

Nozzle size marking for drag bits is centered on "inner diameter (imperial/metric) + connection method". The outer diameter and length need to match the nozzle mounting holes of the bit (complying with industry general standards or manufacturer-customized specifications). Below are the most commonly used size specifications in the industry, covering the adaptation needs of mainstream 4-14 inch drag bits, with a particular focus on balancing flow and pressure in soft formation drilling:

1. Size marking logic: The industry prioritizes imperial units (inches) to align with international general specifications for drag bits. Metric units are for conversion reference, facilitating use in non-imperial unit regions;
2. Connection method: Threaded connections are absolutely mainstream (accounting for over 98%). Among them, NC46 and NC50 adapt to small-to-medium drag bits, while NC60 adapts to large bits. Threaded connections are easy to install and have strong sealing, requiring no complex tools;
3. Non-standard sizes: For micro drag bits (≤4 inches) or special scenarios (such as precise pressure-controlled drilling), non-standard nozzles with inner diameters of 4-5mm (corresponding to 3/32"-4/32") can be customized to meet personalized needs.

Selecting drag bit nozzle sizes requires no complex calculations. Focus on the following 3 points for quick demand matching:

Nozzle size is positively correlated with bit diameter: the larger the bit diameter, the greater the required drilling fluid coverage area and flow, and the larger the corresponding nozzle inner diameter. For example: An 8½-inch (215.9mm) drag bit is usually paired with a nozzle with an inner diameter of 11/32"-13/32". Using a small 9/32" nozzle will result in insufficient drilling fluid coverage of all cutting edges, with cuttings accumulating in the middle of the bit, causing sticking.

Drag bits are only suitable for soft formations. Different soft formations have slightly different requirements for nozzle sizes:

• Extremely soft formations (such as silt and clay layers): Cuttings are highly fluid and need to be discharged quickly with large flow. A slightly larger nozzle can be selected (e.g., 13/32" instead of 11/32") to avoid clay adhesion;
• Loose sand layers: Cuttings have large particles and require sufficient flushing force. It is recommended to select a medium-to-large size (e.g., 11/32"-13/32") to balance flow and pressure;
• Soft formations with a small amount of fine gravel: Enhanced drilling fluid impact force is required. Prioritize a medium size (e.g., 11/32") to avoid insufficient pressure caused by large nozzles, which cannot disperse gravel.

Nozzle size must match the rated flow rate and pressure of the drilling pump:

• Large drilling pump flow rate (≥20L/s): Select a large-sized nozzle (e.g., 13/32"-15/32") to avoid excessive system pressure due to flow restriction, which may damage the bit or pipeline;
• Low drilling pump pressure (≤15MPa): Select a medium-sized nozzle (e.g., 9/32"-11/32") to ensure sufficient flushing force of drilling fluid and avoid cuttings accumulation;
• Industry experience formula: Nozzle inner diameter (inch) ≈ Bit diameter (inch) * 0.03-0.06 (e.g., 10¾-inch bit * 0.05 ≈ 11/32-inch nozzle).

1. Size Consistency: Multiple nozzles (usually 2-4) on the same drag bit must be of the same size to avoid unbalanced force on cutting edges, bit wear, or trajectory deviation due to uneven flow;
2. Material Adaptation: Prioritize tungsten carbide cemented carbide nozzles, especially in formations containing fine gravel, to avoid frequent replacement of ordinary metal nozzles due to rapid wear, which affects operational efficiency;
3. Installation Inspection: Clean debris (such as sand and oil) from the nozzle inner diameter before installation, check thread sealing, and test drilling fluid pressure after installation (fluctuation ≤3MPa is normal);
4. Regular Replacement: When the nozzle inner diameter wears more than 15% of the original size (e.g., a 11/32" nozzle with a worn inner diameter ≥9.5mm), or erosion pits/cracks appear, replace it in a timely manner to avoid affecting cooling and cuttings removal effects.

Selecting drag bit nozzle sizes requires no complex professional knowledge. The core is to match "bit diameter + formation characteristics + drilling fluid parameters": choose large sizes for extremely soft formations and large bits, medium sizes for soft formations with a small amount of gravel, and small sizes for small bits and low-flow scenarios. The common size table compiled in this article can be directly used as a quick reference for purchasing and replacing nozzles, covering over 90% of soft formation drilling scenarios.

As a tungsten carbide industry practitioner, we can provide full-specification drag bit nozzles (from 7/32" to 15/32" and non-standard customization), made of high-end YG6/YG8 tungsten carbide to ensure ultra-high wear resistance and erosion resistance. If you need to recommend precise sizes based on specific drag bit models, drilling formations, or equipment parameters, please contact us for customized solutions to help improve soft formation drilling efficiency and reduce operation and maintenance costs.