Merit Partnership Pollution Prevention Project for Metal Finishers
^Reducing Dragout With Spray Rinses^jgjy
The Merit Partnership is a joint venture between U.S. Envi-
ronmental Protection Agency (EPA) Region 9, state and local
regulatory agencies, private sector industries, and community
representatives. The partnership was created to promote pol-
lution prevention (P2), identify P2 technology needs, and ac-
celerate P2 technology transfer within various industries in
southern California. One of these industries is metal finish-
ing, which is represented in the Merit Partnership by the Metal
Finishing Association of Southern California (MFASC). To-
gether, MFASC, EPA Region 9, and the California Manufac-
turing Technology Center (CMTC) established the Merit Part-
nership P2 Project for Metal Finishers. This project involves
implementing P2 techniques and technologies at metal finish-
ing facilities in southern California and documenting and
sharing results. Technical support for this project is provided
by Tetra Tech EM Inc. (formerly PRC Environmental
Mangement, Inc.). The project is funded by the Environmen-
tal Technology Initiative and EPA Region 9 and is implemented,
in part, through CMTC by the National Institute of Stan-
dards and Technology.
This fact sheet summarizes the benefits of installing spray rinses
on electroplating lines, including reduced dragout and better
rinsing; the components of spray rinses; and some consider-
ations for designing them. In addition, this fact sheet de-
scribes a spray rinse case study conducted at a decorative nickel
and chrome electroplating facility in southern California.
WHY USE SPRAY RINSES?
Using spray nozzles as part of a rinse system can significantly
reduce (1) dragout of expensive and hazardous process chemi-
Benefits of Spray Rinses
~ Less raw material wasted because of reduced dragout
~ Less contamination of process baths by dragin
~ Lower rinse water flow rates required in running rinses
~ More efficient, higher quality rinsing
Installing well designed spray rinses can have an immedi-
ate and significant effect on your bottom line.
cals and (2) the amount of rinse water needed. When used on
parts over plating and dragout tanks, spray rinses provide a
method to recover concentrated process chemicals for reuse.
By reducing dragout, spray rinses allow immersion-type rinse
tanks to operate at lower flow rates or even as static rinses.
Also, spray rinses use rinse water more efficiently than stag-
nant and running rinses. Spray rinse applications in electro-
plating lines (both hand-operated and automatic conveyer and
hoist systems) include use over plating tanks, dragout tanks,
and rinse tanks. The ideal spray rinse application permits
dragout reduction and reuse and improves rinse performance.
CONES, FANS, AND MISTS
Nozzles are the key components of spray rinses and are com-
mercially available with a wide range of flow rates and several
spray patterns. Common suppliers of nozzles are manufactur-
ers of industrial nozzles and suppliers of plumbing and irriga-
tion equipment. For applications over plating and dragout
tanks where minimizing flow rate is critical, nozzles with flow
rates ranging from 0.04 to 1.0 gallon per minute (gpm) are
used in groups to provide coverage and are operated intermit-
tently to minimize water use. Nozzles with flow rates ranging
from 1.0 to 10 gpm are typically used for applications where
minimizing flow rate is not so critical. The two types of nozzles
Figure 1. Cone, Fan, and Fine Sprays
available are hydraulic nozzles, which spray water only, and
air-atomized nozzles, which use both water and air. Available
nozzle spray patterns include full cone, hollow cone, flat fan,
and fine spray like mists and fogs. Hydraulic spray rinses
with full cone, flat fan, and fine spray patterns (see Figure 1)
are adequate for most applications on electroplating lines. Air-
atomized nozzles can be used where compressed air is avail-
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JANUARY 1997
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Determining Net Flow Rate
of Spray Rinses Over Plating Tanks
To avoid overflow of plating tanks, the net flow rate of the
spray rinses should not exceed the evaporation rate of the
plating solution.
Net Flow Rate < Evaporation Rate
Net Flow Rate = (No. of nozzles) • (nozzle flow rate)
' ( % of time nozzle sprays)
Evaporation Rate: Vari-
ous plating handbooks
provide graphs and tables
for evaporation rates as a
function of temperature.
However, direct measure-
ment of evaporation rate
by recording volume of
make up water added or
the increase in freeboard
over time is preferable.
Source: Electroplating Engineer-
ing Handbook, Durney, 1984
a
hJ
4-
0 100 120 140 160 180 200 220
TEMPERATURE °F
Pick the Best Switches for the Application
Lever: Mechanically switched on and off by passing equip-
ment such as hoists, conveyors, and racks; well suited to
automated lines
Pressure Contact: A plastic-coated, pressure-sensitive strip
switch that can be used on hang bars; good for racks manu-
ally placed on a hang bar over plating and dragout tanks
Trigger: Hand-held spray gun with trigger; allows focused
rinsing
Foot Pedal: Installed with sprays on hand-racked lines;
ideal for brief rinses over a dragout tank while operator
holds racks
able to increase the rinsing effectiveness of the spray by gener-
ating a mist or fog. Other nozzle specifications important to
designing spray rinses are the angle and length of the spray
pattern, which determine the number and spacing of the
nozzles. Specifying a nozzle spray angle can help to achieve
complete coverage or overlapping patterns from adjacent
nozzles.
DESIGN CONSIDERATIONS FOR SPRAY RINSES
Components for spray rinses include filters, switches (electri-
cal or mechanical) to turn the nozzles on and off, and check
valves (see Figure 2).
Filters: Rust and dirt particles from aging metal supply lines
can prevent check valves from opening and sealing properly
and can cause nozzle spray patterns to deteriorate. Adding a
filter to the water supply line is necessary to prevent clogging
of the small orifices in check valves and nozzles.
Switches: Switches (operated manually or with timers) can be
used to shut off flow when spray rinses are not needed. Using
switches ensures that the resulting rinse solution is low in
volume, is highly concentrated, and is therefore easier to re-
turn to the plating tank.
Check Valves: In spray rinses with nozzles that operate inter-
mittently or on a timer, check valves offer two distinct advan-
tages: (1) they prevent water in the supply line from draining
into the tank when the switch closes, and (2) they maintain
line pressure so that the spray pattern develops quickly when
the water is turned on. These advantages are significant for
spray rinses in-
stalled over plat-
ing tanks and
for stagnant
rinse tanks
where overflow
is a possibility.
CASE STUDY: ALL AMERICAN SPRAY RINSES
The Merit Partnership sponsored a P2 project that involved
installing and evaluating spray rinses at the All American Manu-
facturing (All American) facility in Los Angeles, California.
The All American facility performs job shop and captive shop
work, including both metal stamping and forming operations,
and it electroplates decorative nickel and chrome onto plumb-
ing fixtures. The facility covers about 20,000 square feet, of
which 5,000 square feet is dedicated to metal finishing. All
WATER SUPPLY
O
ON
B
OFF
o
SPRAY
NOZZLE
EMZZE^
CHECK VALVE
FILTER
SWITCH
Tips for Check Valves
~ Buy check valves that allow adjust-
ment of nozzle actuating pressure
~ Use one check valve per nozzle
~ Place check valve close to nozzle
Figure 2. Components of Spray Rinses
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Three Spray Rinse Applications at AH American
Nickel Plating Tanks (2)
Nickel Dragout Tanks (2)
Chrome Plating Tank
Nozzles/Tank
8
8
6
Nozzle Spray Pattern
Flat Fan (Hydraulic)
Flat Fan (Air-Atomized)
Misting (Hydraulic)
Nozzle Material
Stainless Steel
Brass
Plastic
Flow Rate/Nozzle
0.3 gpm
0.4 gpm
0.04 gpm
Net Flow Rate/Tank
0.12 gpm
0.27 gpm
0.12 gpm
(8 nozzles, at 0.3 gpm for
(8 nozzles at 0.4 gpm for
(6 nozzles at 0.04 gpm for
3 seconds per minute)
5 seconds per minute)
30 seconds per minute)
American employs about 10 workers in the electroplating de-
partment for one shift per day. The plating line consists of
two parallel nickel plating lines with an automated hoist fol-
lowed by a single chrome plating line that is first hand- and
then conveyor-operated. The rinse system for each line origi-
nally consisted of an immersion-type dragout tank and a series
of stagnant and running rinse tanks. The primary objective of
the P2 project for All American was to reduce dragout loss
and enhance dragout recovery by adding several spray rinses
to the existing rinse systems. By first reducing dragout, All
American can reduce water use and consider chemical recov-
ery technologies that move the operation toward its goal of
zero discharge.
Three spray rinses are installed at the facility: one over a pair
of nickel plating tanks, one over a pair of empty nickel dragout
tanks, and one over the chrome plating tank. Nozzle material
is selected based on the corrosiveness of each installation. An
adjustable check valve is installed immediately upstream of
each nozzle to prevent draining of water and to maintain line
pressure. The net flow rate from the spray rinses over the
nickel plating tanks is selected so as not to exceed the evapora-
tion rate of the tanks
and to minimize
evaporator use before
dragout is returned to
the plating tanks.
Nickel Plating Line
Spray Rinses: Both
spray rinses on the
nickel plating lines
are actuated by
switches tripped by
the up-and-down
movement of the
hoist. Each tank
has eight nozzles
mounted around the
lip of the tank and
directed slightly
downward so that the
combined dragout
and rinse water drop into the tanks and overspray is mini-
mized. The spray rinses on each tank turn on separately once
per cycle: the spray rinses over the plating tanks turn on as the
racks are withdrawn from the tanks, and the spray rinse over
the nickel dragout tanks (see Figure 3) turns on as the racks are
lowered into the tanks.
Chrome Plating Tank Spray Rinse: Six fine spray misting
nozzles are installed above a hang bar over the chrome plating
tank (see Figure 4); one nozzle is used for each rack position
on the hang bar. A compressed air vibrator is also attached to
the hang bar in order to enhance droplet formation. The nozzles
are angled about 45 degrees toward the splash guard at the rear
of the tank. The nozzles are actuated by two pressure-sensitive
contact switches installed along the top of the hang bar. Each
switch controls three nozzles and is actuated by the weight of
the racks on the hang bar.
Operation and Maintenance: Maintenance of the spray rinses
includes periodically removing the nozzles from the nozzle
bodies and washing away any obstructions from the nozzle
interiors with water or compressed air. The filters used at All
American are canister-
type filters with no fil-
ter elements and need
to be periodically un-
screwed and rinsed.
Before the filters were
installed, many of the
check valves became
clogged and did not
open and shut quickly
and completely. With
the filters in place,
these problems have
not recurred.
CASE STUDY
COSTS
The total cost for all
three spray rinse appli-
cations was $4,890. In-
Figure 3. Spray Rinses on
Nickel Dragout Tank
Figure 4. Misting Nozzles over
Chrome Plating Tank
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All American Spray Rinse Costs
Nozzles
Two Nickel Plating Tanks
$800
Two Nickel Dragout Tanks
480
Chrome Plating Tank
60
Check Valves
100
Piping
650
Pressure Reducers and Filters
600
Switches
600
Installation
1,600
Total
$4,890
stallation of the spray rinses was performed by All American
staff, and operation and maintenance are performed as part of
the staff s daily inspection routine.
Nozzle costs vary widely (from $2 to $70 per nozzle) depend-
ing on the material used and the supplier. Generally, indus-
trial spray nozzle manufacturers provide higher quality at a
higher cost and offer nozzles made of a variety of materials
with precise spray patterns and flow rates; plumbing and irri-
gation equipment suppliers provide less expensive, plastic
nozzles and less selection of nozzle operating parameters.
CASE STUDY RESULTS
After installation of the spray rinses and several weeks of sys-
tem shakedown and fine tuning, a series of tests were per-
formed under controlled plating and production conditions
with and without the three spray rinses operating. As parts
were plated, the conductivity (which can be related to the con-
centration of plating solution) of the rinse water was mea-
sured in a stagnant rinse tank immediately following the tanks
with spray rinses.
During the tests, the spray rinses over the nickel plating and
dragout tanks together reduced dragout from the nickel plat-
ing lines by 58 percent compared to dragout from the lines
operating with no spray rinses (see Figure 5). The spray rinse
over the chrome plating tank reduced dragout by 64 percent
compared to the system operating with no spray rinse.
$600
$500
$400 --
$300 --
$200
$100
$0
$528
~ Sprays On
~ Sprays Off
$315
$215
$115
Nckd Solution Chrorre Solution
Monthly Dragout Costs
Figure 6. Monthly Cost Savings Due to Dragout
Reduction
Spray Rinse Results
Without With
Spravs Sprays
Nickel Solution Dragout 50.0 gal/mo 20.8 gal/mo
Chrome Solution Dragout 63.1 gal/mo 23.0 gal/mo
Rinse Water* 380,000 gal/mo 152,600 gal/mo
Total Cost Savings = $8,376/year
Total Cost = $4,890
Payback Period = 0.6 year
* Estimated based on dragout reduction
Monthly
Savings
$313
$200
$185
Data from the tests demonstrate that the addition of the spray
rinses to the existing rinsing scheme at the All American facil-
ity dramatically reduced the dragout from both the nickel and
chrome plating lines (see Figure 6). Based on the savings asso-
ciated with recovery and reuse of the nickel and chrome plat-
ing solutions and the corresponding rinse water reduction
possible, the payback period for the rinses installed is 0.6 year.
Although All American does not treat its wastewater before
discharge, facilities performing on-site treatment would experi-
ence additional savings of the treatment chemical, sludge dis-
posal, and operating costs associated with treatment systems.
Industry average costs for treatment of wastewater from elec-
troplating operations are about $12 per 1,000 gallons.
For more information on spray rinses, the Merit Partner-
ship, or the All American case study, please contact the
following individuals:
Laura Bloch (EPA Region 9) at (415) 744-2279
John Siemalc (CMTC) at (310) 263-3097
Dan Cunningham (MFASC) at (818) 986-8393
John Norton (All American) at (213) 581-6293
Figure 5. Sprays Reduce Nickel Dragout by 58%
Assistance for this fact sheet was provided by
Tetra Tech EM Inc.
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