The Problem

Corrosion at pipe supports is one of the leading causes of process piping failures. It is the beam supports and saddle clamps that have historically caused the majority of problems. These have the following undesirable features in common:

• Crevices – the formation of a crevice at the pipe surface.
• Water Entrapment – water is trapped and held in contact with the pipe surface.
• Poor Inspectability and Maintainability – virtually impossible to paint or otherwise maintain; visual and/or NDT inspection are often difficult.
• Galvanic Couples – even when both the pipe and support are steel, the metallurgical differences can still provide enough potential difference to drive a corrosion cell.

The Corrosion Mechanism:

1. Water is trapped.
2. The paint system fails (atmospheric coatings soften in immersion service).
3. Corrosion is initiated.
4. Corrosion undercuts paint film.
5. Crevice corrosion starts.
6. Pipe fails.

Nu-Bolt™ and I-Rod® have been specified on thousands of offshore production platforms since 1987. They simply and economically address the root cause of crevice corrosion by:

• Eliminating crevices.
• Eliminating water entrapment.
• Eliminating metal-to-metal contact.
• Allowing for ease of inspection and maintenance.
• Providing complete support to the piping system.

Designed by corrosion engineers, Nu-Bolt™ is a standard pipe U-Bolt modified with a variety of corrosion resistant treatments to provide reliable, long-term service in severe operating environments associated with offshore oil & gas production and coastal process facilities.

Type 316 alloy stainless steel is used as the structural metal. This is a molybdenum-bearing grade steel which gives the better overall corrosion resistance properties than Type 304 and higher creep strength at elevated temperatures. Type 316 resists chloride attack, and is ideal for use in marine atmospheres and other corrosive environments.

Polyshrink is applied over the shank of the U-Bolt to protect the paint system during installation. Polyshrink is not designed to protect the U-Bolt. The material is a crosslinked, high compressive strength, UV-stable polyolefin, and is good for continuous operation up to 230°F (110°C).

Standard, stocked U-Bolt coatings:

• Hot Dip Galvanize – suitable for moderately aggressive areas.
• SermaGard® – an aluminum-ceramic coating offering superior corrosion resistance in aggressive environments.

I-Rod®

I-Rod® is a high-strength thermoplastic rod in a half round configuration. I-Rod is inserted so the round surface interfaces with the pipe.

The half round profile:

• Minimizes contact crevice, and thus eliminates moisture retention.
• Provides a standoff between the pipe and support, and thus:
  - Insulates electrically.
  - Improves maintainability.
  - Improves inspectability.

The high-strength thermoplastic material also:

• Provides excellent compressive strength.
• Is UV stable.
• Has a low friction coefficient, which assists in pipe fitting when used as a beam dressing, and reduces coating damage during new construction.

When used independently as a beam dressing, I-Rod® is typically supplied in 5’ and 10’ lengths.

I-Rod Specifications (Standard High Impact Thermoplastic)
 

To assist our customers, we have put together answers to the most frequently asked questions regarding I-Rod pipe support systems.

The photos below were recorded during a routine topside inspection of an offshore structure that was installed in 1989. This was the first offshore structure where the I-Rod system was specified for new construction. The total added cost of this system was less than $10,000. The photos demonstrate the success of the system, which has subsequently been used on thousands of offshore structures.