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Nicko

Mon Nov 15 2010, 04:18PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

Is Koptan (a Kapton clone) any good - I see various comments in other (non-HV) forums saying its fine, but has anyone compared it with the real stuff and tried it in an HV environment?

NB. Its about 5x or 10x cheaper than the Dupont offering...

Cheers

Proud Mary

Mon Nov 15 2010, 10:04PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I have bought polyimide tape from Chinese ebay sellers for use in ionisation chamber windows. I examined it with an optical microscope at x400 and found it to be mainly free of defects.

I do know that kapton enjoyed a brief heyday in avionics - brief because it was found to chafe through in cable looms.

Martin King

Tue Nov 16 2010, 10:38AM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

There's some info and some references on the use of Kapton in nuclear power stations here :-

Unlikely to affect most of us here I suspect but then you never know what some people are building in their garage !

Martin.

Finn Hammer

Tue Nov 16 2010, 05:21PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

I admit to using Kapton mainly for coolness factor, but a google search leads to people of midle east origin.
Where can I get the stuff?

Cheers, Finn Hammer

Proud Mary

Tue Nov 16 2010, 07:31PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Finn Hammer wrote ...

I admit to using Kapton mainly for coolness factor, but a google search leads to people of midle east origin.
Where can I get the stuff?

I bought good polyimide tape from ebay seller High Temp Tape Store in China, here:

Scott Fusare

Tue Nov 16 2010, 07:58PM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

Proud Mary wrote ...

I do know that kapton enjoyed a brief heyday in avionics - brief because it was found to chafe through in cable looms.

I work for an aerospace company here in the states and I can tell you unequivocally that it is still widely used in our products.

The best part is that MIL-SPEC (or our own internal requirements, not sure which) dictates that it is unusable due to age after ~1 year so it is regularly scrapped.

Proud Mary

Tue Nov 16 2010, 08:34PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

scott fusare wrote ...

Proud Mary wrote ...

I do know that kapton enjoyed a brief heyday in avionics - brief because it was found to chafe through in cable looms.

UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555

November 21, 1988

Information Notice No. 88-89: DEGRADATION OF KAPTON ELECTRICAL INSULATION

Addressees:

All holders of operating licenses or construction permits for nuclear power
reactors.

Purpose:

This information notice is being provided to alert addressees to a potentially
generic safety problem involving Kapton aromatic polyimide electrical
insulation. Kapton is used extensively in nuclear power plants as wire
insulation in con-tainment penetrations and cable entrance seals manufactured
by Conax Buffalo Corporation, and in various insulation systems in products
supplied by other vendors. Kapton is a registered trademark of E. I. du Pont
de Nemours and Company.

It is expected that recipients will review the information for applicability
to their facilities and consider actions, as appropriate, to avoid similar
problems. However, suggestions contained in this information notice do not
constitute NRC requirements; therefore, no specific action or written response
is required.

Description of Circumstances:

Problems involving Kapton insulation have been reported at nuclear power
plants and elsewhere as described below. The most significant event
identified in the nuclear industry occurred at San Onofre Unit 1.

San Onofre Nuclear Generating Station Unit 1

On June 15, 1987 Southern California Edison Company advised the NRC of a
problem involving damaged Kapton insulation on containment electrical
penetration assemblies at San Onofre Unit 1. During electrical testing of
control rod drive equipment circuits to determine if previous cooling fan
malfunctions had caused any damage, unacceptably low insulation resistances
were found on 35 circuits. In one penetration assembly alone, 11 circuits
tested below one megohm and 11 others below 100 megohms. The licensee then
visually inspected the approximately 5000 penetration leads in the plant, and
discovered nicked insulation in 52 cables covering close to 200 circuits.
Most of the defects were outside containment; 15 nicked leads were inside
containment.

8811150088
. IN 88-89
November 21, 1988
Page 2 of 5

Laboratory analysis of two damaged leads showed no signs of electrically
induced damage, and the insulation edges at the breaks were smooth (suggesting
moderate chemical attack). The damage sites were highly localized; adjacent
insulation showed no degradation. The copper conductor was oxidized
considerably.

As a short-term corrective action, the licensee replaced all safety-related
wires showing any signs of degradation or damage. Longer-term corrective
action, now partially completed, includes provision of cable tray covers;
replacement of nicked non-safety-related cables; and administrative and
procedural measures such as personnel training and written precautions
concerning unprotected Kapton-insulated wires. This event is described in
Licensee Event Report 05000205 87-008-00, dated July 10, 1987.

The licensee attributed the damage primarily to physical damage (cuts, punc-
tures, abrasions) to exposed Kapton insulation, mainly during installation of
the replacement penetration assemblies in 1985-86. Some damage was attributed
to subsequent stepping on the wires and placing or dropping objects on them.
Once the Kapton insulation was penetrated, condensation of marine air on the
outside containment pigtails provided a conductive path that lowered
insulation resistances. The extensive replacement of containment electrical
penetration assemblies such as occurred at San Onofre Unit 1 is uncommon, and
it contributed to the exposure of unprotected Kapton leads to mechanical
damage. Exposure of the Kapton leads to an outside marine atmosphere is also
unusual.

Other Kapton Concerns

(1) Information Notice 87-08 (reference 1) describes 1986 failures of
motorized valve operators because wires insulated with Kapton/Teflon and
Nomex short-circuited. The Kapton/Teflon was a 0.0012-inch tape
overlapped 50-percent. These wires were subjected to abrasion damage
during wiring of the valve operators.

(2) Information Notice 87-16 (reference 2) describes 1987 degradation of
Kapton diaphragms in pressure switches caused by chemical attack by
ammonia con-tained in the process fluid.

(3) In 1984 Gulf States Utilities filed a 10 CFR 50.55(e) report concerning a
short circuit between two Kapton-insulated wires from Conax penetration
assemblies at River Bend Station Unit 1. The condition occurred during
plant construction, and inspection showed 15 of 201 conductors to have
nicked or otherwise damaged insulation. Investigation showed that degra-
dation was generally attributable to scuffs, gashes, and related damage
aggravated by the presence of water.

(4) In several instances anomalies have occurred during qualification type
testing of Kapton-insulated pigtail wires on Conax products or on other
equipment such as transmitters that had cable entrances sealed by Conax
seals. The anomalies have been attributed to handling and stresses not
typical of plant installations; e.g., shipment from a radiation test
facility to a steam test facility. Only a few wires showed degradation
in each instance, whereas multiple wires not subject to abnormal handling
have successfully completed type test sequences.

. IN 88-89
November 21, 1988
Page 3 of 5

(5) In response to Information Notices 87-08 and 87-16, du Pont wrote to the
NRC to caution that when Kapton is used in nuclear power plants where
environmental qualification is required, engineered designs which protect
Kapton from direct exposure to loss of coolant accident sprays are
required. This is because Kapton tends to degrade when exposed to high
temperature steam or to certain volatile chemicals such as sodium
hydroxide.

(6) The Naval Research Laboratory (NRL) has published or presented several
papers (references 3, 4) describing failures of Kapton-insulated wires
during laboratory testing. The Navy has carefully examined potential
problems with Naval aircraft service. As a result, The Navy intends to
stop buying aircraft using Kapton-insulated wire, and the other military
services are studying possible implementation of restrictions.

The NRL work, in conjunction with other available information, shows that
Kapton wire insulation is subject to damage by four mechanisms:

Ã¸ Mechanical nicking or gouging can expose a wire conductor. Low in-
sulation resistance can occur if an electrical path to an adjacent
metallic conductor is formed by either a conductive solution or
direct metal-to-metal contact. The San Onofre Unit 1 event is of
this type.

Ã¸ Direct chemical attack by strong alkaline solution can dissolve
Kapton. This process would be of concern only if Kapton were
installed contrary to Conax installation instructions in plants with
sodium hydroxide spray, so that the Kapton was either exposed to
prolonged direct spray impingement or prolonged soaking in spray
solution.

Ã¸ Bullets or projectiles can damage energized wire bundles. This is
not likely in commercial power plants, and related safety concerns
are minimal because of the redundancy and separation used for
safety-related equipment.

Ã¸ A complex hydrolytic Kapton degradation process has been identified
with synergistic, non-linear dependence on temperature, moisture,
and mechanical strain. Test data from 60 degrees Celsius upward
show a reciprocal logarithmic temperature dependence. du Pont
(reference 5) has suggested a fifth-power humidity dependence. Wolf
(reference 6) reported a strong dependence on strain and postulated
a minimum strain of 3 to 4 percent below which degradation does not
occur. The process is almost fully reversible provided that actual
cracking has not occurred. Review of commercial nuclear power plant
applications indicates that this mechanism is not significant for
either normal or accident conditions; operating experience and type
test results support this conclusion. However, violation of minimum
bend radius requirements specified by Conax and Rosemount for their
wires, combined with significant moisture exposure and elevated
temperatures, could produce this type of damage.

. IN 88-89
November 21, 1988
Page 4 of 5

du Pont has several publications describing Kapton and its use. These may be
obtained by contacting:

Mr. Paul Wyche
E. I. du Pont Nemours and Company, Inc.
External Affairs Department N-2526
Wilmington, Delaware 19898
Phone: (302) 774-1942

Conax Seals

The major safety-related use of Kapton in commercial nuclear power plants is
in Conax products: containment electrical penetration assemblies, penetration
replacement adapter module assemblies, electrical conductor seal assemblies
(ECSAs), PL-type gland seals, and resistance temperature detector assemblies.
Conax uses Kapton-insulated wire constructed of two wraps of type FN Kapton
film, spiral wrapped in opposite directions. Since the film consists of 0.001
inch of Kapton sandwiched between two 0.0005-inch layers of Teflon (a du Pont
trademark for FEP fluorocarbon), and each wrap is overlapped 50-percent, the
total insulation thickness is 0.008 inch. The MIL-W-81381/11 wire used by the
Navy is similar except that it has a 0.002-inch dispersed Kapton topcoat.

For seal assemblies, Conax supplies a heat-shrinkable polyolefin jacket to me-
chanically protect Kapton insulation. In addition, installation manuals
caution against mechanical damage and protective conduit is also specified.
Penetration assemblies are supplied with a junction box which encloses Kapton
leads. Most other vendors using Kapton-insulated leads in safety-related
applications provide covers or enclosures (for example, Rosemount seals and
Target Rock and Valcor solenoid valves).

Discussion:

Despite the plant-specific aspects of the San Onofre Unit 1 event, the generic
lesson is that the performance of numerous Kapton-insulated wires degraded
considerably after only one year in a quite mild environment. Mechanical
damage to Kapton insulation combined with exposure to condensation of moist
salty air produced unacceptable degradation of the electrical insulation
properties.

Although Kapton-insulated pigtails have successfully completed several
accident qualification type tests, the test specimens are believed to have
been free from nicks in the insulation; further, test anomalies occurred in
some cases in which the pigtails were subjected to abnormal handling. The
lesson is that preaccident damage can lead to failure of Kapton-insulated
wires during or after accidents.

Addressees are alerted that the following conditions may breach the integrity
of Kapton insulation, leading to possible failures under either normal or
accident conditions:

(1) Mechanical damage such as nicks, cuts, abrasion, or sharp bending
combined with exposure to moisture.

(2) Prolonged contact with alkaline solutions.
. IN 88-89
November 21, 1988
Page 5 of 5

Addressees are also reminded that excessive handling of wiring is undesirable.
In view of the industry's generally good operating experience with Kapton,
addressees may elect to take actions in response to the information in this
notice by beginning with review of procedures and designs to determine whether
the conditions cited above may exist. Caution with any future maintenance or
installation activity involving Kapton is important.

Virtually all commercial nuclear power plants contain Kapton-insulated wires
in safety and non-safety-related applications, with Conax products used most
extensively. Such components as containment electrical penetration assemblies
and cable entrance seals are commonly used in Class 1E circuits and in
applications requiring qualification to 10 CFR 50.49. Failure of Kapton
insulation during either normal plant operation or accident conditions could
render associated equipment inoperable.

No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact listed below or the Regional Administrator of the appropriate regional
office.

Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation

Technical Contact: Richard C. Wilson, NRR
(301) 492-0997

Attachments: 1. References
2. List of Recently Issued NRC Information Notices
. Attachment 1
IN 88-89
November 21, 1988

REFERENCES

1. Information Notice No. 87-08: "Degraded Motor Leads in Limitorque dc
Motor Operators," February 4, 1987.

2. Information Notice No. 87-16: "Degradation of Static "O" Ring
Pressure Switches," April 2, 1987.

3. F. J. Campbell, "Temperature Dependence of Hydrolysis of Polyimide Wire
Insulation," IEEE Transactions on Electrical Insulation, Vol. EI-20 No.
1, February 1985.

4. A. M. Bruning, "Predictive Life Measurements of Naval Aircraft Wiring,"
Proceedings: Workshop on Power Plant Cable Condition Monitoring, EPRI
EL/NP/CS-5914SR, July 1988.

5. J. O. Punderson and J. F. Heacock, "Polyimide Film Insulation for
Aerospace Wire and Cable: Why Long-Term Performance Exceeds Some Limited
Laboratory Projections, " presented at the 34th International Wire and
Cable Symposium, Cherry Hill, NJ, November 19-21, 1985 (available from du
Pont).

6. C. J. Wolf, D. L. Fanter, and R. S. Soloman, "Environmental Degradation
of Aromatic Polyimide-Insulated Electrical Wire," IEEE Transactions on
Electrical Insulation, Vol. EI-19 No. 4, August 1984.
. Attachment 2
IN 88-89
November 21, 1988
Page 1 of 1

----------------------------------------------- -------------------------------------------------- -------------------------------------------------- ------------------

Concerns About Kapton Wiring Raised Two Decades Ago

Kapton (aromatic polyimide) is the dominant form of general purpose wire insulation on a number of aircraft in service, notably the Swissair MD-11 that crashed Sept. 2, and also including the DC-10, MD-80, 727, 737 (current generation), 747-100/200/300, and the 767. It has a long and controversial history, and the industry has since opted for improved insulation types, such as Teflon-coated Kapton (see ASW, Sept. 21).

However, thousands of miles of Kapton wire are found in older jetliners still in service. One wire and cable expert believes the FAA should require improved wiring types (such as TKT) for all repair replacement wiring and for wiring included in modification kits. Below, a letter sent two decades ago from TWA's director of electronics engineering to Boeing, saying the airline did not want to receive any more new jets outfitted with Kapton wiring:

June 30, 1977

Mr. Jack Miller

727 Customer Engineering, Boeing Commercial Airplane Co. Seattle, Washington 98241 Subject: General Purpose Airframe Electrical Wire

Dear Jack:

An informal meeting of Boeing and TWA wire specialists was held at Renton on June 21, 1977. It was learned from this discussion that Kapton insulated wire is the prime candidate as a replacement for PVC/Nylon general purpose airframe on the B727.

We are concerned about such an application because of our experience with Kapton insulated wire on the L-1011. As brought out in the meeting, wire failures are not excessive in terms of absolute numbers, but the mode of failure has put some of our aircraft out of service for one to three days, and in one case triggered extensive fire damage...

We have found that a wire-to-wire or wire-to-ground short circuit can occur if the insulation is nicked or pinched, because Kapton insulation inherently allows the surface damage to propagate to the conductor. When an arc is struck, the tough, high-temperature insulation material does not flow, causing the molten copper to spew out of the small fault in the insulation and damage the insulation of adjacent wires. The damage and short circuits progress successively through the bundle until all or most of the bundle are severed.

Also...Kapton wire will further aggravate the problems of bent and pushed back contacts and moisture contamination experienced with...connectors. The most extensive application of Kapton wire has been on the L-1011 which uses MIL-C-83723 Type III connectors that feature closed entry contacts and improved moisture seals. This connector is more forgiving when confronted with the springiness and spiral wrap of Kapton wires, which tend to splay the contacts and reduce moisture seal effectiveness. Despite the efforts of TWA and other airlines to switch to MIL-C-83723 connectors, the B727 still incorporates MIL-C-26500 connectors in the basic design.

Another potential problem we foresee is one that could result from attempting to bring down the cost of Kapton insulated wire to make it competitive with other wire constructions. We understand that wire manufacturers now claim to have a method to process the wire that will permit tin coated conductors to be used. Silver or nickel coated conductor is presently used because of the high temperature required to fuse the Kapton/FEP film wrap. Kapton insulated wire would be highly vulnerable to conductor strand blocking if tin coated conductors are used. This blocking would result in insidious problems of conductor breakage to plague the airlines.

Because of Kapton's notch sensitivity and other minus factors such as springiness, delamination, difficulty in stripping and cost, we will strongly object to any proposed use of this wire on future TWA aircraft.

Very truly yours, W.B. Clark Director - Electronics Engineering

COPYRIGHT 1998 Access Intelligence, LLC

Nicko

Tue Nov 16 2010, 09:22PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

From what I'm now reading, Kapton is "not a good plan".

I was looking for an insulator between windings on an HV transformer...

Cheers

Scott Fusare

Wed Nov 17 2010, 09:41AM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

Interesting, but it does not change the fact that material is still used in the aerospace community. I'll ask around and see what the story is from our end.

Martin King

Wed Nov 17 2010, 02:41PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

I can't remember where, but I saw a video of a Kapton wiring fire in a Lab based controlled experiment YEARS ago. Best I can find on the WEB is

but I saw it before 2008. The videos on this link don't work for me but that may be because I'm UK based? If they work for anyone else let me know.

Martin.

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