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 -

575 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


    
 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 298

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
298
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


    
 
 Reply 
 
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
.



    
 
 Reply 
 

Product Spotlight

TOPAZ® 64: Fully Integrated Portable 64 Channel PAUT Instrument with FMC & TFM

Introducing TOPAZ64, the industry’s most intelligent fully integrated, portable 64-channel phased
...
array ultrasound (UT) instrument. TOPAZ64 combines code-compliant phased array UT with the industry’s most advanced full matrix capture (FMC) and total focusing method (TFM) capabilities. Featuring the highest acquisition frequency in its class, high resolution FMC and a 12” multi-touchscreen, users can easily visualize even the smallest flaws. TOPAZ64 can generate a bipolar pulse that provides more acoustic energy versus previous models for punching through thick components. The result is a portable tool that delivers increased inspection coverage, more accurate signals, and the ability to handle all UT inspections in one package. TOPAZ64 is ideal for challenging applications in transportation, oil and gas, manufacturing and power generation.
>

UCI Hardness Tester NOVOTEST T-U2

UCI hardness tester NOVOTEST T-U2 is is used for non-destructive hardness testing of: metals and
...
alloys by scales of hardness: Rockwell (HRC), Brinell (HB), Vickers (HV); non-ferrous metals, alloys of iron etc., and using five additional scales for calibration; with tensile strength (Rm) scale determines the tensile strength of carbon steel pearlitic products by automatic recalculation from Brinell (HB) hardness scale.
>

Varex Imaging Large Field of View (FOV) Digital Detector Arrays (DDAs)

A larger FOV DDA can reduce the space and volume of the X-ray inspection system on the factory floor
...
, enable faster scanning times, better throughput and better resolution images at a lower dose. Customers can also save time and money. With these benefits in mind, Varex Imaging has designed a family of large FOV detectors (4343HE, XRD 1611, 4343DX-I, 4343CT) for our industrial imaging customers.
>

iProbe - USB Phased Array Probe

Turn your PC, Laptop or Tablet into a powerful 32:64 Phased Array system with our USB powered Phas
...
ed Array iProbe and inspection software package. Perform affordable weld inspection and corrosion mapping inspections with this powerful but small system. The probe has a 100V pulser, 8K PRF, dual axis encoder input and achieves outstanding signal quality.
>

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