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Dielectric Pipe Support System
Eliminate corrosion problems at pipe supports
with the
Nu-Bolt™ and I-Rod® dielectric pipe support systems.
 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:
- Water is trapped.
- The paint system fails
(atmospheric coatings soften in immersion service).
- Corrosion is initiated.
- Corrosion undercuts paint
film.
- Crevice corrosion starts.
- Pipe fails.
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The
Solution 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.
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Nu-Bolt™
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.
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| Nu-Bolt Pipe Bolt
Dimensions
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I-Rod® Technical Specifications
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Property Value |
ASTM Test |
Value |
| Density, 73°F |
D792 |
1.41 |
| Tensile Strength,
73°F |
D638 |
9,800 psi |
| Tensile Modulus
of Elasticity, 73°F |
D638 |
440,000
psi |
| Elongation at
Break, 73°F |
D638 |
30-60 % |
| Flexural Modulus
of Elasticity, 73°F |
D790 |
455,000
psi |
| Flexural
Strength, 73°F |
D790 |
13,800
psi |
| Compressive
Strength, 10% Deform., 73°F |
D695 |
16,000
psi |
| Coefficient of
Friction (Dry vs. Steel), Dynamic |
PTM 55007 |
0.25 |
| IZOD Impact
(notched), 73°F |
D256 |
1.5
ft-lbs/in per notch |
| Hardness,
Rockwell, 73°F |
D785 |
119-122 |
| Deformation under
Load |
D621 |
1.0% |
| Melting Point |
D3418 |
329°F |
| Coefficient of
Linear Expansion |
E831 |
5.8 x 10-5
in/in/°F |
| Continuous
Service Temperature |
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194°F |
| Heat Deflection
Temperature, 264 psi |
D648 |
220°F |
| Flammability
Rating |
VL94 |
HB |
| Volume
Resistivity |
D257 |
1.0 x 1015
Ohm cm |
| Dielectric
Strength, Short Term |
D149 |
420 V/mm |
I-Rod® Pipe Support FAQ
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| Q:
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What is the difference between
I-Rod pipe support and a Nu-Bolt? |
| A: |
I-Rod thermoplastic is the white,
half-round rod that we use for all types of pipe supports. This is
why we called the brand I-Rod. A Nu-Bolt™ assembly is simply one
form of an I Rod pipe support. The Nu-Bolt is comprised of one
(1) piece of I-Rod, fitted on a coated U-bolt, with 4 nuts. |
| Q: |
Is I-Rod made of Teflon®? |
| A: |
No. I-Rod is a high-impact
thermoplastic material. Teflon would not function due to lack of
compressive strength. |
| Q: |
Is the material on a Nu-Bolt™
Neoprene? |
| A: |
No. It is a cross-linked,
heat-shrinkable polyolefin material. Neoprene would have to be
vulcanized to stick to the U-Bolt. It would deform too much and
cause problems with moisture retention. The purpose of the
heat-shrink is to minimize damage to the pipe coating during
installation. |
| Q: |
What is the maximum piping
temperature that I can use I-Rod on? |
| A: |
Normally, crevice corrosion is not a problem
at temperatures above 90°C (194°F) because the water simply
evaporates. This is therefore the upper recommended continuous
service temperature. The material will, however, perform up to 120°C
(250°F), but may experience some slight deformation at the contact
area. There is a High Temperature version of I-Rod available for
extreme heat, please contact us if you have questions about this HT
material. |
| Q: |
Does the I-Rod create a stress
raising point on the pipe? |
| A: |
No, not if the piping is correctly
supported along its length. If there is noticeable sagging between
support points, then the pipe is being overstressed and inadequately
supported. Note: I-Rod has been used on hundreds of thousands of
pipe supports since 1989, and we have never seen a
problem. |
| Q: |
How do I know I’m buying I-Rod
and not some inferior copy? |
| A: |
Every shipment of I-Rod is
traceable and is sent with a certificate of authenticity. I-Rod is
distinctly marked as such. |
| Q: |
How can I secure the I-Rod to
the beam? Is there an epoxy glue I can use? |
| A: |
Our double-sided tape usually works
well for initial fastening. Otherwise, I-Rod should be mechanically
fastened to the beam. We do not recommend any type of adhesive or
sealant. |
| Q: |
What is
I-Liner™? |
| A: |
I-Liner is a new product used to
line saddle clamp style supports. It is comprised of a base
material, slotted and filled with multiple pieces of I-Rod. It is
designed to prevent crevice corrosion at then more substantial
weight bearing supports. It is available it in sheets (which can
then be cut to length), or pre-installed in Grinnell clamps. |
A Case Study of
13 Years of Offshore Exposure
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.
Installed Nu Bolts -
No crevice corrosion.
Fuel gas line, always
wet. Green coloration is mold. The beam paint
system has failed, but there is not corrosion at pipe support.
I-Rod installed under
pig launch/receive barrel, bolted to support beams.
I-Rod was found
particularly effective on small diameter, screwed piping,
which typically has the highest maintenance cost per square foot.
I-Rod were also found
effective on the largest diameter piping
of the offshore structure.
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