Introduction

In the power industry, equipment reliability is a top priority. Even small amounts of moisture or contamination can lead to short circuits, corrosion, and insulation damage, resulting in costly downtime and potential system failures. One of the most effective ways to protect electrical infrastructure is through the use of butyl sealants – modern sealing solutions widely used in transformers, switchgear, and control cabinets.

This article explains what butyl sealants are, how they work, where they are used, and why they are essential for electrical systems.

What Are Butyl Sealants?

Butyl sealants are flexible materials made from butyl rubber (IIR) – a synthetic polymer known for its exceptionally low permeability to gases and water vapor.
They are available as tapes, cords, sealant masses, or pastes, which due to their tacky and plastic nature, easily conform to different surfaces.

Key features of butyl rubber include:

• Excellent resistance to moisture and air,

• Chemical stability when exposed to oils, greases, acids, and alkalis,

• Elasticity over a wide temperature range (–40°C to +100°C),

• Long-term durability with no hardening or cracking over time.

Why Use Butyl in Electrical Systems?

Transformers and switchgear contain many points where moisture and air can penetrate. Condensation inside the equipment can cause oxidation of contacts, metal corrosion, and degradation of insulating oils.
Effective sealing materials must therefore:

• maintain long-term tightness,

• resist temperature fluctuations and vibrations,

• require little to no maintenance.

Unlike silicone or acrylic sealants, butyl sealants do not dry out, shrink, or lose elasticity—ensuring lasting protection even after many years of service.

Applications of Butyl Sealants in Transformers and Switchgear

1. Cable Entry Sealing

In transformers and cable switchgear, the areas where cables pass through enclosures or foundations are particularly prone to moisture ingress.
Butyl tapes and sealing masses are used to fill and protect these critical points, preventing:

• groundwater infiltration,

• vapor condensation,

• corrosion at metal joints.

➡️ Example:
In underground low-voltage switchgear, butyl tape is applied between the cable duct and the protective conduit to stop capillary water and dust from entering the system.

2. Transformer Cover and Housing Sealing

In hermetically sealed and oil-filled transformers, butyl sealants are used to seal covers, flanges, filling caps, and valves, preventing:

• ingress of air and moisture,

• leakage at screw or flange connections,

• degradation of transformer oil.

➡️ Example:
During transformer maintenance, butyl tape is applied to the edges of the tank cover to maintain full sealing even after multiple openings.

3. Switchgear and Control Cabinet Sealing

Outdoor switchgear and control cabinets must withstand rain, dust, and temperature changes.
Butyl sealants are used as:

• gaskets for doors and panels,

• fillers for joints between enclosure components,

• protection for screw and rivet connections.

➡️ Example:
In outdoor switchgear originally rated IP54, applying butyl tape around door edges can increase sealing performance up to IP66, ensuring protection against water and dust.

4. Metal–Concrete Joint Sealing

In transformer substations, metal structures are often anchored in concrete foundations.
Because of the different thermal expansion of steel and concrete, microgaps can form, allowing moisture to penetrate.
Butyl cords or tapes effectively eliminate these leaks by creating a durable water- and gas-tight barrier.

➡️ Example:
When installing foundation cable entries, butyl sealant is applied between the metal flange and concrete slab to ensure long-term tightness of the connection.

Advantages of Butyl Sealants

• ✅ Excellent adhesion to metal, concrete, glass, and plastics

• ✅ No need for primers or additional adhesives

• ✅ Long-term flexibility and resistance to aging

• ✅ UV-, oil-, and chemical-resistant

• ✅ Can be applied in any weather conditions

• ✅ Easy to remove or replace when needed

Butyl Sealants in Practice – Industrial Applications