The Complete Guide to Duct Sealing Blanking Plugs for Empty Ducts

When installing ducting systems for power cables, fibre optic networks, utilities, or telecoms, it’s common to have empty or spare ducts left unused until future expansion.

These ducts must still be sealed to prevent serious problems, including:

- Water ingress and flooding
- Gas leakage or infiltration (methane, radon, hydrogen sulphide, hydrocarbons)
- Entry of dirt, debris, or rodents
- Pressure loss in pressurised systems
- Corrosion and long-term damage

This is where duct sealing blanking plugs (sometimes called mechanical duct plugs or empty duct seals) play a critical role.

What Are Duct Sealing Blanking Plugs?

A blanking plug is a removable and reusable seal designed to close off unused ducts. Instead of leaving a duct exposed, the plug expands inside the duct wall to create a gas-tight and water-tight barrier.

High-quality plugs protect infrastructure while allowing ducts to remain accessible for future cable installations.

Types of Duct Plugs on the Market

1. Rubber Expansion Duct Plugs

- How they work: A rubber gasket expands inside the duct when compressed with a nut or plate system.
- Pros: Lightweight, reusable, corrosion-free, quick to install, cost-effective.
- Cons: Limited to low pressures (typically ≤ 0.5 bar). Rubber can degrade under UV or chemical exposure.
- Best for: General electrical, telecom, and low-pressure duct sealing.

2. Metal Blanking Plugs

- How they work: Solid steel or aluminium caps fixed over the duct.
- Pros: Strong, rigid, durable if stainless steel is used.
- Cons: Expensive, prone to corrosion if low-grade metals are used, heavy, not easily reusable, difficult to seal gas-tight.
- Best for: Permanent structural closures, but rarely ideal for reusable sealing.

3. Advanced Mechanical Duct Seals

- How they work: Multiple sealing rings with stainless steel compression plates and torque-controlled nuts.
- Pros: High pressure resistance (up to 8.0 bar), corrosion-resistant, gas-tight, reusable, long service life.
- Cons: Higher initial cost, requires correct torque installation.
- Best for: Critical infrastructure, water utilities, underground ducts, or high-pressure environments.

Choosing the Right Blanking Plug

When selecting a duct sealing system, consider:
- Pressure resistance required (0.5 bar vs multi-bar)
- Corrosion resistance (rubber vs stainless steel)
- Ease of installation and removal
- Future reusability
- Budget vs risk profile

Our Recommended Solutions

At AC Cable Solutions, we supply a complete range of mechanical duct plugs designed to suit different applications.

Duct Plugs – Reusable Rubber Expansion Plugs (Up to 0.5 bar)

• Pressure-tight up to 0.5 bar
• Quick installation with hand tools
• Lightweight and reusable
• Ideal for telecom, fibre optic, electrical, and spare cable ducts
• Available in multiple duct sizes

Perfect for everyday sealing requirements where ducts are not subject to high pressure.

View Product: https://accablesolutions.com/collections/mechanical-duct-systems/products/ductplug-reusable-rubber-expansion-plug-for-pipe-sealing

Kraso Blank Seals – Heavy Duty Stainless Steel Duct Sealing (Up to 8.0 bar)

• Manufactured from high-grade stainless steel
• Sealing performance up to 8.0 bar
• Resistant to gas, water, vapour, and hydrocarbons
• Torque control nut ensures correct installation every time
• Standard sizes available: 80, 100, 125, 150, 200, 250, 300, 350, 400, 500 mm
• Custom sizes manufactured to order

The ultimate choice for pressurised ducts, underground installations, and demanding water utility or industrial applications.

View Product: https://accablesolutions.com/collections/mechanical-duct-systems/products/kraso-blank-empty-mechanical-duct-sealing-system

Why Not Low-Grade Metal Plugs?

Some cheaper plugs on the market use low-quality metals that:
- Corrode quickly when exposed to moisture
- Fail to provide a reliable gas-tight seal
- Require frequent replacement
- Offer poor long-term value despite higher upfront cost

In comparison, our duct plugs and Kraso seals are engineered for durability, reusability, and proven sealing performance.

Conclusion

Whether you’re sealing an empty duct temporarily or protecting critical infrastructure long-term, choosing the right blanking plug is essential.

- For general duct sealing up to 0.5 bar → choose our Duct Plugs.
- For high-pressure environments up to 8.0 bar → choose Kraso Blank Seals.

Both solutions provide reusable, corrosion-resistant, gas-tight and water-tight sealing that you can trust.

👉 Explore our full range of duct sealing systems and request a quotation today.