Introduction to Cable Gland Size Chart

A Cable gland size chart is a practical reference used to match thread type, thread size, and cable outer diameter to the correct gland model. Cable glands follow several international standards — Metric (M), PG, NPT, and BSP/G — and the chart simplifies selection, helping engineers and installers eliminate guesswork.

Proper sizing ensures a secure mechanical hold, reliable sealing (IP ratings), strain relief, and long-term durability. Incorrect sizing can cause leaks, cable damage, loss of ingress protection, and potential electrical faults.

Why Cable Gland Sizing Matters in Industrial Applications

In critical sectors such as oil & gas, marine, manufacturing, and automation, precise gland sizing is essential. Mistakes in sizing can lead to cable slippage, moisture ingress, contamination, and in hazardous-area applications, a loss of explosion-proof integrity.

Understanding Thread Types in Cable Glands

Understanding thread standards is necessary when using a Cable gland size chart. Common series include Metric (M), PG, NPT (tapered), and G/BSP (parallel).

Metric Threads (M-Series)

Metric threads are the most commonly used worldwide. Typical sizes run from M12 through M63, with M16, M20, M25, M32 being frequent choices for control and power cabling.

PG Threads

PG is a German legacy standard. PG threads (PG7–PG48) have a different form factor and are still encountered in older equipment or regional installations.

NPT Threads

NPT (National Pipe Taper) is common in North America. Because NPT is tapered, sealing behavior differs from parallel-threaded glands and may rely on thread engagement or sealant.

G / BSP Threads

BSP (British Standard Pipe) parallel threads (often labeled G) are used across industrial and offshore equipment. They require correct sealing methods for best IP performance.

Core Elements of a Cable Gland Size Chart

An effective sizing chart includes the following fields:

• Thread Diameter: The nominal gland thread (e.g., M20, PG16, 1/2" NPT).
• Cable Outer Diameter (OD): Range the gland will clamp and seal around.
• Clamping Range: Minimum and maximum cable OD for reliable sealing.
• Ingress Protection Level (IP): Typical ratings the gland supports.
• Material & Application Notes: Suggested materials (brass, stainless steel, nylon) for environments.

Comprehensive Cable Gland Size Chart

The tables below present common industry reference ranges for Metric, PG, NPT, and BSP/G series. Use manufacturer datasheets to confirm exact clamping ranges for a specific product.

Metric Cable Gland Size Chart

PG Cable Gland Size Chart

NPT Cable Gland Size Chart

G / BSP Cable Gland Size Chart

How to Choose the Right Cable Gland Size

Follow these steps to select the proper gland:

1. Measure the cable outer diameter (OD): Use a calibrated vernier caliper and measure over the cable jacket (keep measurements to two decimal places where possible).
2. Match the OD to the clamping range: The cable OD should fall within the gland’s specified clamping range — ideally near the mid-point of that range for best seal performance.
3. Select the thread type: Use the thread series required by the enclosure or equipment (Metric is commonly the default).
4. Confirm IP and environmental requirements: Choose glands rated for the environment (e.g., IP68 for permanent submersion or IP69K for high-pressure washdown).

When in doubt, consult the manufacturer’s datasheet for the specific gland model. Manufacturer tolerances and seal designs vary.

Common Sizing Mistakes & How to Avoid Them

• Using a gland that is too tight: Can damage cable jackets during installation and affect conductor insulation.
• Oversizing “just in case”: Leads to poor sealing and reduced ingress protection.
• Ignoring armor or braid: Armored cables require appropriate armored glands with dedicated sealing for the armor.
• Mismatching thread standards: Do not force different thread standards together; use proper adapters if required.

Application-Based Cable Gland Sizing Examples

Electrical Control Panels

Typical gland sizes for control panels range from M16 への M25, depending on cable bundles and IP requirements.

Oil & Gas Explosion-Proof Installations

Explosive/hazardous-area installations frequently use metallic glands (brass or stainless steel) with size choices such as M20 への M32. Select glands certified for the required hazardous-area class (e.g., Ex d).

Outdoor Waterproof Enclosures

Outdoor enclosures needing submersion or high ingress protection often use IP68 rated glands. Sizes like M20 そして M25 are common for typical power and signal entries.

Material Selection Based on Size & Environment

Material matters as much as size when environmental conditions are harsh.

• Brass: Good mechanical strength and common for control installations.
• Stainless Steel (316): Preferred for marine, offshore, and corrosive sites.
• Nylon / Plastic: Lightweight and cost-effective for non-critical indoor uses; may not be suitable for high temperatures or corrosive environments.

Advanced Sizing Considerations

EMC/EMI Shielding

When cable screening/shielding is required for EMC performance, use metal glands with an integrated EMC clamp or a separate EMC earthing kit.

Multiple Cable Entry Glands

For enclosures with bundled cable entries, use multi-hole plates, grommets, or modular multi-gland solutions sized to the combined cable diameters and required IP rating.

High-Temperature Applications

Select seal materials rated for the expected operating temperature (e.g., silicone or Viton seals for elevated temperatures) and confirm thermal expansion effects on clamping ranges.

よくある質問

1. How do I know which size cable gland to choose?

Measure the cable outer diameter (OD), consult a reliable Cable gland size chart, and select a gland whose clamping range includes your cable OD. Confirm thread type and IP rating.

2. Is Metric better than PG or NPT?

Metric (M series) is the global standard in many industries and provides consistent sizing ranges. PG and NPT may be required for legacy equipment or region-specific installations.

3. Can I use one size larger “just in case”?

No. Oversizing a gland can compromise sealing effectiveness and reduce the gland’s IP rating. Always match the cable OD to the specified clamping range.

4. What happens if the cable OD is too small?

If the cable OD is below the gland’s minimum clamping range, the gland will not form a proper seal and ingress protection will be compromised.

5. Can I mix thread types?

Threads are not interchangeable without adapters. Use the appropriate thread type for the enclosure or use a certified adapter designed for the intended application.

6. Where can I find engineering-approved charts?

Consult manufacturer datasheets and engineering catalogs from reputable suppliers such as LAPP or other certified manufacturers for model-specific clamping ranges and performance data.

結論

A precise Cable gland size chart is a fundamental tool for safe, reliable, and code-compliant cable installations. By measuring cable OD accurately, matching the clamping range, selecting the correct thread type, and verifying material and IP requirements, engineers and installers can avoid common pitfalls and ensure long-lasting, high-integrity connections across any industrial environment.

For product-specific charts and model data, always consult manufacturer datasheets.