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RE: (Fwd) painting problems



Sherry,

Failure to wrap is often caused by 1) operators forgeting to turn on the
electrostatic charge system and 2) improperly grounded parts.  Operators
often turn off the system to avoid Faraday effects when painting
recessed areas.  It is then very easy to forget it and to keep spraying.
 Some operators will also turn off the system because they can't produce
a good quality finish with it on.  This is quite common with panels
where after painting one side, the electrostatic charge is turned off to
paint the back side.  If the charge is kept on, then the wrap around
effect causes overspray to mar the already pained surface.  High
transfer efficiency does not always lead to less waste.

If the system is on, then improperly grounded parts should be
investigated.  A well grounded part will attract paint like a magnet.
It is very interesting to watch the coating spray out past the part and
then be drawn back in.  If the paint goes right past, then the part may
not be grounded.  Does the facility have a proactive paint rack handling
program ?  Hooks and racks should be cleaned often to remove the
build-up of paint.  The areas where electrical contact are made should
be free of grease and rust.  If paint burn-off ovens are used,
additional cleaning should be employed to remove the heat scale.  Rust
and scale can also flake off the racks and foul the paint job, resulting
in rework.

The ignition of paint filters and spray booth filters is a serious
problem most likely related to the paint resin rather that the solvent.
There are many animal and vegetable based oils that will slowly oxidize
with oxygen in the air over time.  When placed in an enclosed container,
they continue to oxidize and generate heat.  If the heat cannot be
dissipated fast enough, the material heats up and begins to smoulder.
When the can is opened, fresh oxygen is introduced and a fire starts.

Soaking the filters minimizes contact with air and the water serves as a
heat sink as the paint slowly continues to oxidize.  The downside of
this option is that it increases the amount of waste produced.  Another
way to handle this waste would be to allow the paint to dry while
maintaining a constant air flow.  The air flow would evaporate the
solvent, propmote oxidation, and keep the waste cool.  Unfortunately,
this option may not be allowed by the local air agency.  Once a
solvent-bearing waste is generated, it must be kept drummed to prevent
solvent emissions.

Hope this helps,
Mike.callahan@jacobs.com
 ----------
From: Sherry Davis
To: p2tech@great-lakes.net
Subject: (Fwd) painting problems
Date: Thursday, April 24, 1997 3:11PM


Dear P2techs,
The following request was sent to me to forward to p2tech.   We
discussed pressure reduction for the electrostatic wrap around
problem.  Any other suggestions would be appreciated.  You may post
replies to Jean Waters directly or to p2tech and I will forward.
Thanks in advance,
sherry davis




 ------- Forwarded Message Follows -------
From:          "JEAN WATERS" <jwaters@oz.oznet.ksu.edu>
Organization:  K-State Research and Extension
To:            sdavis@oz.oznet.ksu.edu
Date:          Thu, 24 Apr 1997 10:45:18 -0600
Subject:       painting problems
Reply-to:      jeansw@ksu.edu
Priority:      normal

Sherry,
	Could you please help me find answers to the following painting
questions:

1) Filter disposal.
	Two companies I visited recently soak their paint filters in water
and put them in a plastic bag before sending them to the landfill.
They claim there's no way to get the filters dry before disposal.
They have had fires in the dumpster when the filters are not soaked
in water. One company uses primarily xylene as a solvent, the other
uses primarily toluene.
	Other than getting them to switch to another paint system, do you
have any ideas for avoiding soaking the filters?  Two suggestions
I've considered are waiting until Monday morning to remove their
filters (rather than Friday afternoon) and hanging the filters from
racks outside the paint booth so they can air-dry before disposal.

2)  gun efficiency
	One company is using electrostatic guns to paint the
outside of cylinders.  The cylinders range from about 1-6 inches
in diameter.  There is alot of overspray.  They said when they
adjusted their guns to get a smaller fan they couldn't paint fast
enough.  They do paint a variety of parts.  Sometimes they paint
big pieces of equipment in addition to tubes.  My perception is
they're not getting much wrap currently.  Any ideas on how to
encourage them?  They have new, lightweight guns.  How hard is it to
adjust the fan?  Perhaps they could use a small fan for the small
tubes and adjust it bigger for the other equipment?  They also can
have 3-4 color changes per day.

Thanks for your help,
Jean


Jean S. Waters
Air Toxics Engineer
KSU Pollution Prevention Institute

jeansw@ksu.edu
913/532-6501
Sherry J. Davis
Industrial P2 Specialist
sdavis@oz.oznet.ksu.edu
133 Ward Hall,KSU
Manhattan, KS  66506-2508
913-532-6501   Fax: 913-532-6952