wire drawing?

[Dean A]

can anyone give a good definition of wire drawing? I keep hearing about
it re: valves under "high pressure" diffs that are run for long periods
just slightly off seat. what constitutes "high pressure" diff?
I'm working on a chilled water spray system with relatively low total
flow (2-3 gpm) at 110psi with small needle valves set slightly open at
the end of each of 11 spraybars to allow some flow thru the components
back to the open reservior. here's a pic of one of the needle valves:
<http://members.home.net/drit1/pinvalve.jpg>
is this wire drawing, or attack of the brass by a chemical in the
water. the rest of the system is stainless or plastic - these valves
were added after the initial installation. I'm suspicious of whatever
chemical they add to the water causing this damage but don't want to
rule out "wire drawing"

[zero]

"Dean A" <drit1...@homey.invalid.com> wrote in message news:3BDC3FBF...@homey.invalid.com...

> can anyone give a good definition of wire drawing? I keep hearing about
> it re: valves under "high pressure" diffs that are run for long periods
> just slightly off seat. what constitutes "high pressure" diff?
> I'm working on a chilled water spray system with relatively low total
> flow (2-3 gpm) at 110psi with small needle valves set slightly open at
> the end of each of 11 spraybars to allow some flow thru the components
> back to the open reservior. here's a pic of one of the needle valves:
> <http://members.home.net/drit1/pinvalve.jpg>
> is this wire drawing, or attack of the brass by a chemical in the
> water.

That's NOT wire draw! (IMHO)
Try a stainless needle/seat valve. I'd find out what's in the water
first before spec'ing a valve. (ph, hardness, etc.)
Someone else can comment on wire draw cuts and
things that eat bronze for lunch.

[Ken Hartsell]

Looks like cavitation damage to me. Info from a study is at
http://www.sciencescope.org/jst/jst98/resumes/pouvreau.html. There
are many pictures of cavitation at
http://www.fb-chemie.uni-rostock.de/ess/sonochem_image.htm. Just
found these two links by searching google for cavitation.

I've seen cavitation damage on pump intakes and it looked like your
nozzle with localized erosion/pitting damage. Sometimes the
cavitation can be heard (sounded like gravel going through the pump)
if the ambient noise is not too high.

Dean A <drit1...@homey.invalid.com> wrote in message news:<3BDC3FBF...@homey.invalid.com>...

[Dave & Nicole Herrington]

First thing that got my attention "system piped in plastic and stainless"
and "needle valve." I smell chemical all the way.....

Wire drawing - "restriction of area for a flowing fluid causing a loss in
pressure by friction without loss of heat or performance of work; also
called throttling"

If that were the case I think you would see patterns that look more like
erosion or "channeling".

Might want to check some of your stainless - if it is chemical - stainless
is just as likely to be pitted (depending on the type of chemical) or
eroded.

Dave

[brian.doherty]

Dean,

It doesn't look like wire drawing to me, especially as it is not just at the
closing surface of the valve plug/pin. It looks more like chemical attack;
in fact, it is similar (although the craters are a bit more rounded) to the
dezincification of brass, as found if unsuitable brasses are used with sea
water).

Regards,

Brian

Dean A <drit1...@homey.invalid.com> wrote in message
news:3BDC3FBF...@homey.invalid.com...

[Dean A]

thanks for your replies. they've bought stainless needle valves - we'll see
what happens to them. the existing stainless parts (that I've seen - pump
casings & impellers, other valves, reservoir - look untouched by the additive)

[J. S. Nunes]

If the stainless doesn't work, next step is monnel or inconnel....both very
pricey

"Dean A" <drit1...@homey.invalid.com> wrote in message

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