[Acoustics] RE: Head cracks

Thu Aug 12 12:24:27 CDT 2004

FYI

Hi Henning:

I sent him a response (pasted below).

This is a cosmetic issue we see infrequently, but enough to know it
exists.  Dave Sulli is aware of it.  

My response:
Hi Nathan:

Ron Hippe here.  Hope all is well in Boise.

I met with our engineers regarding this.  They reviewed all the photos.
While this may look bad, the instrument will function normally with
this. It's a cosmetic issue with the urethane we cover the transducer
ceramics with.  What has happened is the urethane has shrank at the
surface slightly.  While it's not normal, it does occur on some units as
they age.  If the cracks start to propagate to the orange layer it could
possibly flood the transducer.  This is very rare, and if this happens
it is very obvious.

We recommend that whenever the unit isn't in the water that a protective
cover be used.  This is to prevent physical damage, and to prevent the
urethane from 'drying' out from exposure to UV rays.

Keep your eyes on the performance of the instrument.  It shouldn't be
affected by this condition.  

We do recommend that the instrument be returned to the factory for
reconditioning of the urethane as it ages.  We typically see them every
3-5 years depending on deployment conditions. 

If you have any additional questions do not hesitate to ask.

Regards,
Ron
-----Original Message-----
From: acoustics-bounces at simon.er.usgs.gov [mailto:acoustics-bounces at simon.er.usgs.gov]On Behalf Of Riggs, Terry
Sent: Thursday, August 12, 2004 10:55 AM
To: acoustics at simon.er.usgs.gov
Subject: [Acoustics] RE: Head cracks

The urethane will crack with excess exposure. We have had several with
the same problem after long deployments (2-3 years).  RDI recommends
having the heads checked and/or serviced every 2-3 years. Worth the time
and expense.  Terry E. Riggs 

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Subject: Acoustics Digest, Vol 13, Issue 5

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Today's Topics:

   1. ADCP Head cracking (Black, Nathan)
   2. Re: ADCP Head cracking (Victor A Levesque)

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Message: 1
Date: Thu, 12 Aug 2004 08:46:31 -0600
From: "Black, Nathan" <NBlack at idahopower.com>
Subject: [Acoustics] ADCP Head cracking
To: acoustics at simon.er.usgs.gov
	<3D72FD864A175D4193B93EC5423F574401CC3B40 at bedford.idacorp.local>
Content-Type: text/plain;  charset=iso-8859-1

Does anyone have any comments on this situation (see the message below)?

The pictures that are associated with message are post on Kelvin's FTP
site:

ftp://ftpdilurb.er.usgs.gov/pub/adcp/Files/NBlack/

Thanks for your time.

Nathan Black, EIT

Water Management Department
Idaho Power Company
(O) 208.388.2754
(C) 208.866.3786

Hi RDI techs - 

I am a fisheries technician with Idaho Power Company.  I am sending
photos of a situation which is developing on our Workhorse Rio Grande.
First of all it, seems to be working fine.  About a month ago I noticed
a cracking look developing on three of the heads of our ADCP.  The
cracks do not seem to be in the red part but more in the clear sealant
which covers the heads.  It is similar to varnish which has developed an
alligator skin effect.  It is not pealing off but looks like there may
be a problem developing.  I should also note that the cracks do not look
like water can get in them.  I am writing this e-mail to see what you
think I should do.  We would like to continue to use the unit through
our field season which concludes at the end of September.  If you feel
it is an issue which needs to be addressed sooner please let me know.
What should I do??

Jim Trainer
Idaho Power Company
P.O. Box 70
Boise, ID 83707
(208) 388-5497

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

Message: 2
Date: Thu, 12 Aug 2004 12:47:18 -0400
From: "Victor A Levesque" <levesque at usgs.gov>
Subject: Re: [Acoustics] ADCP Head cracking
To: "Black, Nathan" <NBlack at idahopower.com>
Cc: acoustics at simon.er.usgs.gov

<OF34A1E1F1.276C0E4E-ON85256EEE.005B278A-85256EEE.005C4134 at er.usgs.gov>

Content-Type: text/plain; charset="us-ascii"

Hello Nathan,

After looking at the photos, I have to ask...have you let the transducer
faces be exposed to sun light on a regular basis? Do you regularly cover
the  transducers with the yellow protective cap? How old is the unit,
and what kind of water have you used it in?

The blue plastic looks a little bleached out. I'm not a urethane expert,
but you may have sun damage. It sort of looks like there has been a
"drying out" of the urethane. The urethane (or is it polyurethane?)
faces are susceptible to sunlight damage (not sure what wavelength!).
The RDI manual even notes that you should minimize the transducer face's
exposure to sun light. If the crazing doesn't penetrate too deeply, you
could probably continue to use the ADCP (not liable for damages if I'm
wrong), but you may be looking at urethane replacement (if that's
possible) at the end of your season.

Perhaps someone at RDI would be more qualified to comment.

Good luck and let us know what you find.

Victor Levesque

U.S. Geological Survey
Center for Coastal and Watershed Studies Tampa, FL 813-975-8620
extension 167
FAX: 813-975-0839
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