United States
                         Environmental Protection
                                    Risk Reduction
                                    Engineering Laboratory
                                    Cincinnati OH 45268
                         Research and Development
                                    EPA/600/S-92/016 May 1992
               Waste Minimization Assessment for a Manufacturer of
                         Permanent-Magnet DC Electric  Motors

                                  F. William Kirsch and Gwen P. Looby*
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small- and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. Waste Minimization Assessment Cen-
ters (WMACs) were established at selected universities and
procedures were adapted from the EPA Waste Minimization
Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).
The WMAC team at the University of Tennessee performed an
assessment at a plant manufacturing permanent-magnet DC
electric motors—approximately 12 million motors and repair
parts per yr. The armatures  and stators are  manufactured
separately  and  then assembled into complete  motor units.
After assembly, the  motors are appropriately masked and
painted according to customer specifications. The team's re-
port, detailing findings 'and recommendations, indicated that
the majority of waste was generated in the armature assembly
line  but that the greatest savings could be obtained by install-
ing an electrostatic powder coating system to reduce the gen-
eration of waste paint solids (93%) and to eliminate the gen-
eration of waste paint liquids.

This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, OH, to announce key findings of an ongoing research
project that  is fully documented in a separate report of the
same title, which is available from the authors.


The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
'University City Science Center, Philadelphia, PA 19104.
                         additional stress on the environment. One solution to the prob-
                         lem of waste is to reduce or eliminate the waste at its source.

                         University City Science Center (Philadelphia, PA) has'begun a
                         pilot project to assist small- and medium-size manufacturers
                         who want to minimize their formation of waste but who lack the
                         in-house expertise to do so. Under agreement with EPA's Risk
                         Reduction Engineering  Laboratory, the Science Center has
                         established three WMACs. This assessment was done by
                         engineering faculty and  students  at the University of
                         Tennessee's (Knoxville) WMAC. The assessment teams have
                         considerable direct experience With process operations in manu-
                         facturing plants and also have the knowledge and skills needed
                         to minimize waste generation.

                         The waste minimization assessments are done for small- and
                         medium-size manufacturers at no out-of-pocket cost to the
                         client. To  qualify for the assessment, each client must fall
                         within Standard Industrial Classification Code 20-39, have gross
                         annual sales not exceeding $50 million, employ no more than
                         500 persons, and lack in-house expertise in  waste minimiza-

                         The potential benefits of the pilot project include minimization
                         of the amount of waste generated by manufacturers, reduced
                         waste treatment and disposal costs for participating plants,
                         valuable experience for graduate and undergraduate students
                         who participate in the program,  and  a cleaner environment
                         without more regulations and higher costs for manufacturers.

                         Methodology of Assessments
                         The waste minimization assessments require several site visits
                         to each client served. In general, the WMACs follow the proce-
                         dures outlined in the  EPA Waste Minimization Opportunity
                         Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC
                                                   ug>  Printed on Recycled Paper

 staff locates the sources of waste in the plant and identifies the
 current disposal or treatment methods and their associated
 costs. They then identify and analyze a variety of ways to
 reduce or eliminate the waste. Specific measures to achieve
 that goal are recommended and the essential supporting tech-
 nological and economic information is  developed.  Finally, a
 confidential report detailing the WMAC's findings and recom-
 mendations (including cost savings,' implementation costs, and
 payback times) is prepared for each client.

 Plant Background
 The plant produces permanent-magnet DC electric motors for
 general use. The plant operates 6,860 hr/yr to produce ap-
 proximately 13 million motors and parts.

 Manufacturing Process
 Raw materials for  the manufacture of the motors and parts
 Include Iron and aluminum castings, steel tubing and shafting,
 copper wire, copper commutators, steel laminations, purchased
 fans, poles, epoxy coating, varnish, adhesive, and cleaning
 chemicals. The two separate parts of the product (the armature
 and the stator) are manufactured separately  and  then as-
 sembled into complete motor units.  An abbreviated process
 flow diagram is illustrated in Figure 1.

 The following steps are involved in making the motors:

 Armature Assembly
 Assembly of the armatures begins with the cutting and machin-
 ing of steel shafts. A semi-synthetic metal working fluid or
 coolant is used in the machining area to cool the grinders and
 lathes; spent coolant is disposed of offsite as hazardous waste.
 Metal scrap is hauled offsite by a metal reclaimer.

 Approximately 2% of the shafts are then taken to the painting
 area to be coated with a "black oxide" paint while the remaining
 98% receive no  coating. The painting  process is described in
 detail. Next, all shafts are transported to a subassembly area
 where steel laminations are  stacked  (the height will vary ac-
 cording to motor design) and pressed onto a shaft. Assembled
 armatures are then  preheated in a laminating oven. After pre-
 heating, each part  Is manually dipped into a 200-gal epoxy
 powder dip tank  and allowed to cool. An exhaust hood collects
 released epoxy dust that is ducted  to a collection bag filter for
 periodic disposal offsite as  hazardous waste. This powder
 becomes waste after collecting moisture from the atmosphere.

 Next, the epoxied shafts with lamination  are put onto a coil-
 winding machine on which  copper wire is manually wound onto
 the epoxy-coatod unit and fitted  between the "fins" of  the
 lamination. Wood or paper insulators are manually tapped
 between each "fin" and then copper commutators are applied
 to the end of each shaft and wire terminators are connected to
the copper  commutators.  The armatures are then  manually
 loaded into an oven in which varnish is applied over wires at
 both ends of the  lamination and drying occurs. Surface varnish
 and epoxy along with some lamination metal is then ground off
to meet specifications.  Small amounts of this waste varnish/
 epoxy powder are disposed of in the municipal trash. In addi-
tion, varnish that becomes too thick for proper  application is
shipped offsite as a hazardous waste.

 Finally,  pre-purchased  fan components are preheated in an
eloctrfc oven and manually dropped down onto shafts. The part
 is allowed to air cool to produce a tight fit. From the sub-
 assembly area, finished armatures are transported to the fin-
 ished goods stock room to await final assembly.

 Stator Assembly                ',
 Stator assembly begins with machining of steel tubing. After
 machining,  parts  are transferred to the cleaning area where
 they are  manually  conveyed and dipped in a  series  of five
 tanks to prepare the surface for adhesive fastening of magnetic
 poles. The first tank is a caustic-solution bath.  Secondly, the
 parts are dipped in  a rinse tank after which they are immersed
 in  a phpsphating tank. Another rinse tank follows  the
 phosphating tank and finally the  parts are dipped in a sealing
 tank that contains sodium nitrate. Solutions from tanks #1 and
 #3 are dumped every 6 wk.  Sludge from those tanks is shov-
 eled out of the tank bottoms and shipped offsite as  hazardous
 waste;  wastewater from the tanks  flows to the septic tank
 where the acidic water from tank #3 neutralizes the caustic
 water from tank #1. The water streams from rinse tanks #2 and
 #4 are combined for neutralization and pumped to the  sewer.
 From the septic tank, the wastewater is pumped to the sewer.

 The machined and cleaned tubing lengths are then transported
 to the adjacent pole area where they are manually wiped clean
 with an acetone-wetted cloth. On  an  annual basis, 75% of
 these cloths are shipped offsite, washed, and brought back to
 the plant for reuse. The remaining 25% of the rags are too torn
 or thin for reuse and are shipped offsite for incineration. Next,
 the pole pieces with adhesive applied are manually applied to
 the inside surface of each unit and held in place with clamps.
 The adhesive is cured by baking the stator units in one  of four
 curing ovens. Next, the stator units are taken to another subas-
 sembly area where the poles are  magnetized  and then the
 units are transferred to final assembly.

 In final assembly, armatures are placed inside the stators and
 iron castings with bearings are positioned on the end  of the
 stators to form the complete  motors. Upits may then be trans-
 ported to the painting area, if required.

 About 2% of this plant's products arei  painted black for cos-
 metic purposes. Parts to  be painted are manually removed
 from final assembly and placed on a conveyor system.  These
 parts are conveyed through a water curtain spray paint  booth
 and are manually spray-painted with  solvent-based flat black
 paint. Paint overspray is captured in the water curtain  and is
 precipitated out with the use  of a chelating agent. Waste paint
 sludge from this operation is periodically removed  from the
 booth and shipped offsite as hazardous waste. In addition,
 some paint is skimmed off the top of the water and  added to
 the paint sludge. Water from the water  curtain sump that has
 become too contaminated with paint is shipped offsite as waste
 paint liquids.

 Approximately 3% of the painted products are conveyed through
 an "air-dry" spray paint booth to which gloss  black painHs
 added. Used air filters are removed from this booth and  added
to the paint solids waste barrels.

 Each paint booth has one spray gun; in use. The guns are
 cleaned periodically with  solvent; spent solvent is shipped
offsite as a hazardous waste.

 Finally the product pieces are air-dried, packaged, and shipped.

                             Armature Assembly

                             Epoxy Coating
                             Varnish Coating
                             Fan Addition
                   Waste Epoxy
                   Waste Varnish
             Stator Assembly

             5-Stage Surface Prep
             Acetone Cleaning
             Poles Glued in
             Pole Magnetization
                                                    Spent Coolant
                                                    Scrap Metal
                                                Final Assembly
                                                  - castings added
                  Acetone Contaminated Rags
                  Surface Prep Liquid
                     Water and Sludge
                                                       Paint Line
                  Waste Paint Liquids
                  Waste Paint Solids
                  Waste Solvent
                                              Packaged and
 Figure 1. Abbreviated Process Flow Diagram.
Existing Waste Management Practices
  • A  coolant  recovery system recovers almost all  of  the
    coolant for reuse in the machining tools.

Waste Minimization Opportunities
The waste currently generated by the plant, the source of the
waste,  the quantity of the waste, and the annual treatment and
disposal costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC recommended for the plant. The minimization opportu-
nity, the waste in question, the possible waste reduction and
associated savings, and the implementation cost along with
the payback time are also shown in Table 2. The quantities of
waste currently  generated  by the plant and  possible waste
reduction depend upon the production level of the plant. All
values should be considered in that context.
It should be noted that the economic savings of  the WMOs
usually  address only the raw material  cost  avoidance and
reduction of present and future costs associated  with waste
treatment and disposal. Other savings not quantifiable by this
study include a wide variety of possible future costs related to
changing emissions standards, liability, and employee health. It
should also be noted that the savings given  for each WMO
reflect the savings achievable when implementing  each WMO
independently and do not reflect duplication of savings that will
result when WMOs are implemented in a package.

Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team,  five additional measures were considered.
These measures were not completely analyzed because of
Insufficient data or minimal savings as indicated below. They
were brought to the plant's attention for future reference,' how-
ever, since these approaches to waste reduction may increase
In attractiveness with changing plant conditions.

  •  Install drag-out boards on the tanks in the five-step clean-
     ing operation to drain tank solutions back into the tanks.

  *  Collect the solvent used for cleaning the paint spray guns
     for reuse. Currently, the solvent becomes part of the liquid
     paint wastes.
                                    •  Use a detergent or a water-based solvent rather than the
                                      currently used solvent to clean dirty metallic raw material
                                      to reduce the costs associated with handling and removing
                                      the waste currently associated with this cleaning process.

                                    •  Convert the current varnish spray system to a more effi-
                                      cient robotic dip system.

                                    •  Install an automatic metering system to reduce the amount
                                      of excess adhesive  used  in attaching  the poles to the
                                      inside surface of the stators.

                                  This research brief summarizes a part of the work done under
                                  Cooperative Agreement No. CR-814903 by the University City
                                  Science Center under the sponsorship of the U.S. Environmen-
                                  tal Protection Agency. The EPA Project Officer is  Emma Lou
                                  George.                              '
Tablt 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Annual Quantity
   Annual Waste
Management Cost, $

Waste coolant

Thickened varnish

Waste epoxy powder

Znc phosphate/caustic

Waste sealant

Waste adbasiva

Spent solvent

Paint solids (Including plastic
shoots, filters, and precipi-
tated pa/nt from the paint
booth water curtain)

Westa paint liquids
(water from the paint
booth water curtain that is
too contaminated to be
Cutting and machining of steel shafts                  1-1/2 truck loads
Metal scrap is hauled offsite by a metal reclaimer

Cooling of the grinders and lathes in the machining area        17,600 Ib

Application of varnish to armature assemblies                    920 Ib

Application of epoxy powder to armature assemblies             5,175 Ib

Five-stage washer in stator assembly line                      3,520 Ib

Five-stage washer in stator assembly line                            *

Adhesive application to the poles in the stator assembly line        30 Ib

Cleaning of paint spray guns                                2,640 Ib

Spray paint booth                                         7,920 Ib

Water curtain in the spray paint booth                         8,840 Ib









'Quantity and cost unknown.

Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
                                                                Annual Waste Reduction
        Net Annual   Implementation   Payback
         Savings          Cost         Years
Paint solids
Paint liquids
Paint solids
Paint liquids
Paint solids
Paint liquids
Waste epoxy
Zinc phosphate/
caustic sludge
Waste sealant
Waste adhesive
Install an electrostatic powder               7,392 Ib
coating system to replace the               8,840 Ib
water curtain spray paint booth.
Retain the gloss paint booth;
because of its limited use, a change
is not recommended.

Replace the compressed air paint           3,960 Ib
spray guns with air-assisted airless          4,420 Ib
paint spray guns.  Paint overspray will
be reduced as a result of increased
paint adhesion to  the product

Use the currently inactive electro-           3,696 Ib
static spray paint booth to replace           4,420 Ib
the water curtain spray paint booth.
Reduced raw material costs and
waste generation  will result  from using
the system. Retrain plant personnel in
proper operating techniques.

Recycle spent epoxy powder. Install         4,658 Ib
an air-tight collection system to permit

Discontinue the use of the pole              3,520 Ib
adhesive and utilize a mechanical
means of attaching the poles to the              *
inside surfaces of the stators. Imple-           30 Ib
mentation of this WMO would
eliminate the need for the five-stage
washer in the stator assembly line.
$10,2301*      $78,440
   5,850'       15,440
   9,970'        7,000

  14,470'        6,480
 31,760'*      110,880
'Includes raw material cost savings.
'Total cost savings have been reduced by the cost of new material required.
                                                                              •&U.S. GOVERNMENT PRINTING OFFICE! I99Z - 648-080/40Z58



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