where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

KARL DEUTSCH
INSTRUMENTS AND SYSTEMS FOR NON-DESTRUCTIVE TESTING OF MATERIALS.

563 views
Technical Discussions
Patrick Huttenhuis
Patrick Huttenhuis
09:19 Jan-09-2003
NDT's for middle voltage cables

A client of us, a producer of middle voltage cables (up to 50 kV) has problems during the extrusion process. During the extrusion process once in a while there arise small bubbles (1-3 mm) in the isolating poly-ethylene layer. It is believed that this bubbles will result in undesirable voltage breakdown.
The cable consists of a 12-22 mm aluminium pipe. Around this pipe a three layer polymer is constructed during one extrusion step. The three layers are:

- a black (carbon) PE layer of appr. 0.5 mm
- a white PE layer of appr. 5 mm. In this layer the bubbles have been seen,
a black (carbon) PE layer of appr. 0.5 mm

After the extrusion the cable is vulcanised and cooled.

Do you know if there are non-destructieve methods (preferable online) which can indicate the bubbles in the polymer layer. If yes, what kind of methods are available, what are the conditions and advantage / disadvantages of the methods. The production speed of the cable is betwen 8 and 30 m/min.

Thank you in advance for your advice.

Kind Regards,

Patrick Huttenhuis
Procede Twente B.V.
patrick.huttenhuis@procede.nl


    
 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 293

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
293
09:45 Jan-09-2003
Re: NDT's for middle voltage cables
: A client of us, a producer of middle voltage cables (up to 50 kV) has problems during the extrusion process. During the extrusion process once in a while there arise small bubbles (1-3 mm) in the isolating poly-ethylene layer. It is believed that this bubbles will result in undesirable voltage breakdown.
: The cable consists of a 12-22 mm aluminium pipe. Around this pipe a three layer polymer is constructed during one extrusion step. The three layers are:
:
: - a black (carbon) PE layer of appr. 0.5 mm
: - a white PE layer of appr. 5 mm. In this layer the bubbles have been seen,
: a black (carbon) PE layer of appr. 0.5 mm
:
: After the extrusion the cable is vulcanised and cooled.
:
: Do you know if there are non-destructieve methods (preferable online) which can indicate the bubbles in the polymer layer. If yes, what kind of methods are available, what are the conditions and advantage / disadvantages of the methods. The production speed of the cable is betwen 8 and 30 m/min.
:
: Thank you in advance for your advice.
.
: Kind Regards,
.
: Patrick Huttenhuis
: Procede Twente B.V.
: patrick.huttenhuis@procede.nl
.

Dear Partick,
Sounds as if an Electronics solution rather than an NDT solution may be able to detect these bubbles.
I suggest that you speak with some electronics experts.
My thoughts are that the bubbles inside the 5 mm layer will affect the effective dielectric constant, and looking at the electrical capacity between the aluminium pipe and a separate electrode on the outside of the wrapped cable may provide a solution.
The thicknesses however may be fairly high to have a measurable effect.

Veel succes met de toepassing.
I wish you success with the application.

Godfrey Hands


    
 
 
Jörg Collrep
Jörg Collrep
00:02 Jan-09-2003
Re: NDT's for middle voltage cables
Dear Patrick,
this kind of defects could easily be detected by shearography but not within the production speed as we need some time ( 3 - 5 sec )to excite the cable with a very low thermal or vacuum excitation and acquire an image under loaded and unloaded condition. If you would like to know more about the technique pls reply to me directly.
Thanks
Jörg Collrep
Steinbichler Optotechnik GmbH
www.steinbichler.de


: A client of us, a producer of middle voltage cables (up to 50 kV) has problems during the extrusion process. During the extrusion process once in a while there arise small bubbles (1-3 mm) in the isolating poly-ethylene layer. It is believed that this bubbles will result in undesirable voltage breakdown.
: The cable consists of a 12-22 mm aluminium pipe. Around this pipe a three layer polymer is constructed during one extrusion step. The three layers are:
:
: - a black (carbon) PE layer of appr. 0.5 mm
: - a white PE layer of appr. 5 mm. In this layer the bubbles have been seen,
: a black (carbon) PE layer of appr. 0.5 mm
:
: After the extrusion the cable is vulcanised and cooled.
:
: Do you know if there are non-destructieve methods (preferable online) which can indicate the bubbles in the polymer layer. If yes, what kind of methods are available, what are the conditions and advantage / disadvantages of the methods. The production speed of the cable is betwen 8 and 30 m/min.
:
: Thank you in advance for your advice.
.
: Kind Regards,
.
: Patrick Huttenhuis
: Procede Twente B.V.
: patrick.huttenhuis@procede.nl
.



    
 
 

Product Spotlight

X-ray CT aids research into defect formation in AM parts

X-ray CT is used to research how additive manufacturing process parameters influence defect format
...
ion in AM parts.
>

Panther

M2M PANTHER is a phased-array equipment designed for both desktop and industrial applications, offer
...
ing unparalleled performance in a compact unit. It combines the speed required for industrial integrated Phased-Array Ultrasound (PAUT) solutions, with the most complete set of total focusing method (TFM) imaging techniques, making it the ultimate tool for R&D and procedure qualification.
>

NDTkit RT

NDTkit RT, TESTIA's Digital Radiography software The NDTkit product line software for X-ray analysi
...
s. NDTkit RT is a software benefiting from the Ultis kernel which is dedicated to radiographic image analysis. It offers a set of tools and filtering processes to assist RT operators in finding relevant flaws.
>

Conformable wedge transducer

The conformability is obtained with a flexible membrane filled with water between the transducer and
...
the inspected component. The coupling between the membrane and the component requires a small quantity of water or couplant. The conformable wedge combines the acoustic performance of immersion technique with good coupling and low attenuation.
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window