What is a cable pass through?

A cable pass through, also known as a cable gland, is a device that allows cables to pass through panels, walls, or enclosures while also sealing the entry point from water, dust, chemicals and other environmental contaminants. Cable pass throughs are an important part of infrastructure cabling as they protect connections and sensitive equipment from damage.

What are the Main Functions of a Cable Pass Through?

There are three core functions of a cable pass through:

• Sealing – Cable pass throughs seal the entry point of cables into an enclosure to prevent water, dust, insects and other contaminants from getting in. This protects sensitive electronics and connections inside the enclosure.
• Strain Relief – They provide strain relief on cables so that if they are pulled or moved, the stress is absorbed by the cable gland and not transmitted to electrical connections. This prevents cables from becoming loose or disconnected.
• Retention – Cable glands firmly grip cables to prevent them from slipping out due to vibrations or other movements. This provides a secure, fixed installation.

In summary, cable glands form a tight seal around cables, protect connections from stress and securely retain the cables to avoid slippage. Their primary purpose is to protect electrical systems and infrastructure from environmental damage and disruption.

What are the Different Types of Cable Pass Throughs?

There are several different types of cable pass throughs designed for different applications and cable types:

Conduit Bodies

Conduit bodies are tubular fittings used to connect runs of conduit and provide a junction point for pulling wires. They have threaded openings allowing conduit to be joined. Conduit bodies can have multiple openings and provide bend radius control in conduit runs.

Cord Grips

Cord grips are a basic type of cable gland used for light duty applications. They are made of plastics or rubber and have a clamping mechanism to seal around the cable jacket and retain the cord. They provide minimal strain relief.

Armored Cable Glands

Armored cable glands secure and seal armored cables which are wrapped in a metal braid or steel wire. The gland clamps directly on the armored part of the cable for mechanical and electrical continuity.

Metal or Plastic Glands

Metal cable glands are heavy duty devices made from brass, aluminum or stainless steel. They can have threaded openings to connect conduit systems and provide excellent strain relief. Plastic glands are lighter but still robust for industrial uses.

Explosion Proof Glands

Explosion proof cable glands are specifically designed to prevent flames or explosions from propagating through the cable opening. They are required for cabling in hazardous locations and meet certain safety standards.

EMI/RFI Shielded Glands

Shielded cable glands contain conductive mesh or metal components to prevent electromagnetic interference (EMI) and radio frequency interference (RFI). They block stray signals and ensure electronic noise does not pass through the opening.

What Materials are Used to Make Cable Glands?

Cable glands are made from materials that can withstand industrial environments, chemicals, extreme temperatures and corrosion. Common materials include:

• Brass – Brass is corrosion resistant but expensive. It is used for high quality glands.
• Stainless Steel – Stainless provides excellent corrosion resistance for harsh environments like chemical and marine applications.
• Aluminum – Lightweight but durable aluminum is good for general industrial use.
• Plastic – Plastic is inexpensive but suitable only for light duty applications indoors.
• Rubber – Rubber glands provide flexibility for a tight fit around cables.

Metal glands generally provide the best mechanical performance and durability. Engineers select gland materials suited to specific application requirements.

How are Cable Glands Installed?

Cable glands are installed using the following basic process:

1. The entry hole is drilled in the panel or enclosure to the size required for the gland fitting.
2. A knockout punch may be used to remove material if an existing hole is too small.
3. The gland is inserted into the hole from outside the enclosure and fastened into place using a locking nut or threads.
4. A compression ring inside the gland is loosened, the cable is fed through the gland opening, then the ring is tightened around the cable jacket to seal it.
5. Further tightening of gland compression provides cable retention and strain relief.
6. For watertight sealing, the inner gland seal is tightened against the cable before the final outer locking nut is turned to prevent loosening.

The installation instructions provided by the gland manufacturer should always be followed, especially for achieving proper sealing. Using the right tools, the process can be performed simply in-situ without dismantling equipment.

Why are Cable Glands Important for Safety?

Properly installed high quality cable glands are vital for safety. Here are some of the key risks if cable openings are not properly sealed and retained:

• Fire propagation – Flames can spread more easily between areas through unsealed openings.
• Gas leaks – Dangerous chemicals or gases can leak through the gaps.
• Arc flash hazards – Exposed live conductors increase risk of arc flash.
• Electrocution – Water ingress raises risk of electric shock.
• Contamination – Dust buildup can impair equipment cooling or clog machinery.
• Rodent damage – Pests gnawing on cables create fire risk.

Shortcuts like using tape or caulk around cables does not provide proper sealing or strain relief. Investing in high-quality cable glands that are properly installed reduces risks and prevents catastrophic failures.

What are the Factors to Consider When Selecting a Cable Gland?

Choosing the right cable gland involves considering the following factors:

• Cable diameter – Inner seal diameter must match cable size.
• Cable type – Specific glands for armored cable, braided, etc.
• Temperature – Heat resistance capabilities.
• Number of cables – Multi cable glands available.
• Sealing – IP dust/water ingress rating.
• Material – Environmental resistance requirements.
• EMI shielding – Whether EMI protection is needed.
• Hazards present – Explosion proof rating for the zone.

Choosing the most suitable gland that meets the ratings and design needs is essential to safe performance. Consulting gland manufacturer specifications ensures proper selection.

What are the Steps Involved in Maintaining Cable Glands?

Regular inspection and maintenance ensures cable glands provide ongoing protection. The main maintenance steps are:

1. Check for signs of damage like cracks or deterioration and replace damaged glands.
2. Verify tightness of gland compression to avoid leaks.
3. Confirm adequate strain relief by trying to rock or twist cables.
4. Check for cable jacket wear or tears and loose connections.
5. Clean dust and debris buildup; inspect for corrosion.
6. Lubricate threads and sealing surfaces if needed.
7. Test sample glands for proper sealing using pressure or dye testing.
8. Confirm tightness of lock nuts and external gland body.
9. Verify grounding connections are intact.
10. Document all inspection and maintenance performed.

A proactive maintenance approach identifies issues before failures occur and protects system reliability.

What are Some Common Problems with Cable Glands?

Some common cable gland problems that occur are:

• Corrosion – Environmental corrosion can degrade gland body and compression parts.
• Leaking seals – Hardened or damaged seals allows dust or moisture ingress.
• Loose connections – Vibration can loosen gland compression and retention.
• Pests – Rodents or insects building nests inside the gland opening.
• Blocked threads – Debris buildup jams threads so the gland cannot be tightened.
• Insufficient strain relief – Allows cables to be pulled loose from connections.
• Incorrect sizing – Wrong inner diameter allows leakage around cable.

Checking for these types of deficiencies and replacing damaged glands helps prevent bigger problems from occurring.

Conclusion

Cable glands are a crucial component in any infrastructure cabling project to protect connections, prevent leaks, avoid EMI issues and reduce safety risks. Selecting the proper cable gland type and size for the application and carrying out competent installation is key. Maintenance should include routine inspections and replacing any damaged glands. Investing in high quality cable pass throughs from reputable manufacturers ultimately saves money by preventing expensive system failures and downtime.