[ RadSafe ] Arresters, spark gaps for Rich Wagner

NiagaraNet at aol.com NiagaraNet at aol.com
Wed Apr 28 20:54:00 CDT 2010

Please post and thnx.

Here you go Richard.
Lou Ricciuti
Re:Original Message--
For the behalf of Richard Wagner,
Subject: Help with Westinghouse SV type arrestor

Found a few  Westinghouse lightening arrestors that read about 400 uR/hr
on an ion  chamber and maximally 2000 cpm on a 44-9 G-M.
Any idea about what isotope  may be inside of them?
Picture  Links:
_http://tinypic.com/r/zxp2xx/5_ (http://tinypic.com/r/zxp2xx/5) 
Here's some information that I've obtained from :
Joe Osterhout Consulting
In a message dated 4/28/2010 8:44:08 A.M. Eastern Daylight Time,  
joeosterhout at att.net  writes:

It was most likely manufactured before 1970 to have the brown  porcelain. 
That size porcelain would house anything from 3 to about 18  kV.
The name tag which contains full identification is mounted on the  ground 
end casting if W, but this one looks like the nametag is on the  separate 
angle bracket at the base.
Don't attempt to read the nametag while energized except possibly by a  
mirror on an insulated stick.
If W and before 1970, it is either type SV (1950 - 60) SVT (1960 - about  
69) or CPL (1969 - about 1980).
SV was passive spark gap, SVT and CPL active (current limiting) spark  gap.
It is not likely modern solid state technology.

OK, so you have a 5 kV type SV arrester.
They contain a series of spark gaps made of formed brass plates with  ring 
shaped resistor spacers and silicone carbide nonlinear resistors in  series 
with the spark gaps.
The spark gaps are insulating at normal system voltage, then when  voltage 
approaches a dangerously high level - like due to lightning, the  gaps 
spark, conducting the lightning current to ground.  After the  lightning current 
has passed (typically 10,000 A or less with duration of 40  microseconds or 
less), the current due to power system voltage is limited to  100 A or so by 
the silicone carbide resistors - allowing the spark gaps to  stop 
conducting following the next natural power system voltage zero point -  returning to 
the original insulating state and ready to perform again at  some future 
Depending on age of the arrester - not seen on your nameplate photo -  the 
arrester may contain radium salts painted unto the spark gap pates (pre  
1960) or if not, then perhaps what you have is something in the porcelain  
I suggest that you hold a cheap radio tuned to about 1000 AM within  10 
feet of the arrester.  If there is radio noise, the arrester is in  danger of 
failing and should be  replaced.



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