Enhancing Safety and Performance-The Dielectric Flange Bolt Kit

A dielectric flange bolt kit isolates a flanged joint so cathodic protection current stays on the pipe instead of crossing to the other side. A 6-inch 150 lb set pairs a Gylon 3500 gasket with bolt sleeves and isolating washers, and it seats the same way as our flange gaskets.

What the Dielectric Bolt Kit Is

The kit replaces standard gasket and bolting with an insulating set: a dielectric gasket (here Garlock Gylon 3500, a PTFE-based sheet) seals and insulates the faces, sleeves line each bolt hole, and washers isolate the bolt heads and nuts. Installed, the two flanges are electrically separated while the joint stays pressure-tight.

• Dielectric gasket — Gylon 3500 PTFE-based sheet seals and insulates the faces.
• Bolt sleeves — plastic liners stop current travelling through the bolts.
• Isolating washers — cover both the bolt head and nut sides.
• Retaining ring — centres the gasket and keeps it from blowing inward.

Why Electrical Isolation Matters

Stray current and cathodic protection systems can push electrons across a flanged joint, wasting protection energy and driving galvanic corrosion where current leaves the metal. An insulated joint keeps the protection on the intended structure and stops the bolted connection from becoming the weak point. It also reduces interference with nearby instrumentation.

Key Benefits

• Keeps cathodic protection current on the protected structure.
• Stops galvanic corrosion at dissimilar-metal joints.
• Reduces stray-current interference with instrumentation.
• Gylon 3500 gasket adds broad chemical resistance to the insulation.

Where They Are Used

Dielectric bolt kits go on buried and above-ground pipelines, tank farms, refinery and pump stations, and power-plant water and fuel lines — anywhere protection systems run or stray currents appear. The 6-inch 150 lb size is a common branch and station size.

In the Joint

The insulating gasket sits between the faces, sleeves line the bolt holes and washers isolate the fasteners, so the only path across the joint is the fluid; the pipe flanges carry the mechanical load. Torque evenly in a cross pattern and never mix isolating parts with plain hardware.

Installation and Care

Clean the faces, fit the gasket centred, push the sleeves in fully and stack washers correctly on both sides of each bolt. Torque in stages and cross-pattern to the gasket maker's value — over-torque splits sleeves and destroys isolation. Test with a megger across the joint after assembly and at turnaround, and replace any sleeve or washer that is cut, crushed or missing.

Frequently Asked Questions

How do I verify the isolation after install?

Measure resistance across the joint with a megger or ohmmeter; a good insulated joint reads high resistance, typically in the megohm range. Low readings mean a damaged sleeve, washer or gasket.

Can the kit handle sour or chemical service?

Choose the gasket sheet for the media — Gylon 3500 covers many chemicals; for sour service confirm the grade against NACE requirements and the fluid's compatibility data.

What sizes and pressure classes exist?

Kits are built for standard ASME B16.5 sizes and classes; 6-inch 150 lb is a common station size, and other sizes follow the same sleeve-and-washer principle.