and unloading a machine is part of the cycle. Water-based
machines often cycle quickly when cleaning large, simple
shapes; vapour systems are faster when cleaning tight spaces
and components with many voids.
Throughput affects operating expenses dramatically. For
example, DuPont reports that in a small, modern vapor
degreaser “normal” solvent losses are about 0.118 lbs. per square
foot of vapor area per hour of operation, or roughly one pound
per day (larger and more efficient machines have still lower
loss rates). In stand-by mode, this drops 75%. To compute total
cleaning costs, engineers will need a fairly accurate estimate of
the throughput requirements placed on the systems.
The front nine: One-time costs
To calculate and compare total cleaning costs, all of the costs
for each system need to be re-calibrated into one standard
unit of measure, the total cost per part cleaned. That’s easy to
track for consumables like solvent and electricity, but often the
initial acquisition costs are ignored (refer to the checklist for
other fixed costs to consider).
Up-front capital costs include the actual cost of the
machine, freight, site preparation and set-up costs. Most engineers also include building renovations, ventilation enhancements, electrical upgrades and water-treatment subsystems
required to support the new system. These expenses can be
as costly as the cleaning machine itself, so be sure to include
your facilities manager, your health and safety people, your
environmental people and your fire safety team as well as the
production people in developing these plans.
Engineers should include the cost of the funds that will be
tied up in the machinery. With a spreadsheet, it’s easy to use
the “payment” (PMT) financial function to estimate the cost-per-month of the equipment, which can easily be converted
into a cost-per-part.
Another consideration is the actual cost of the space
required by the cleaning machine and the support systems it
requires. The “floor space requirement” usually is described as
a multiple of the physical size of the machine.
It has been my experience that aqueous and semi-aqueous
systems require more floor space than solvent-based systems.
Aqueous systems require water-treatment facilities which can
be as large as the cleaners themselves. Aqueous systems also
have slower cycle times, so more space is needed for work-in-progress, supplies, conveyor systems and access aisles.
For example, I have seen a 30-foot aqueous cleaner which
had a 200 sq. ft. footprint in the factory. But the system tied-
up 1,400 square feet of floor space with ancillary systems: a 7X
floor space factor. For vapor systems, a 4X factor would be a
To estimate floor space costs, call your financial people and ask
them for the “fully-loaded per-foot costs” for the space in which
you are interested. This usually will be expressed as a triple-net
rent per square foot. Included this number should be the cost of
the space itself, plus heating, cooling and lighting costs, and some
portion of the cost of shared facilities, like the lavatories.
The back nine: Operating costs
Once the throughput has been defined, it is relatively easy to
compute operating costs. Normally the equipment manufacturers will provide rule of thumb guidelines for typical installations. Direct operating costs include the cost of lost solvent,
the cost of the electricity and the cost of consumables (e.g.,
saponifiers, filters, etc.) which are required by the system.
‘Drag-out’ is a special operating cost, and this is one of
the few areas where the cost of the solvent comes into play.
Drag-out is the loss of solvent due to being trapped in, on
and around the clean parts as they move through the cleaning
system. High-boiling solvents like water and hydrocarbons are
prone to high drag-out losses but the chemicals are relatively
cheap. Low-boiling solvents can minimise drag-out but—since
these solvents are pricey—even small losses can be alarmingly
Look for optional equipment which helps eliminate drag-out
losses. Newer vapor degreasers use extra refrigeration, superheat
and hoists to reduce drag-out losses and save money. Aqueous
systems have similar money-saving options such as air-knives
and extra drying chambers which cut solvent losses but add to
the electric bill. It’s sad but true: there is no free lunch.
A good vendor should be able to document incremental
operating costs and drag-out losses on a feature-by-feature
basis. Furthermore, they should be able to highlight specific environments (e.g., types of contamination, cycle times)
which optimize the usefulness of each feature. With this data,
it becomes simple for a savvy engineer to add these costs to the
Labor is the dirty secret of cleaning and should be handled
separately from the other operating costs. Many companies
feel their automated cleaning processes are under control. But
inspection reveals they often have technicians performing auxiliary inspections, hand-spraying, re-cleaning, and drying the
September 2014 • www.cemag.us