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cLeaningtimes Busting Some Metal Cleaning Myths

R e a d e r s are likely familiar with "MythBusters," a popular pro-

gram shown on the Discovery Channel in which tech-savvy investigators explore, analyze, test, and evaluate urban legends, popular beliefs, and Internet rumors. The show I remember best addressed the myth that the quacking of a duck produces no echoL

While we don't have testing facilities like the MythBusters' to support this month's column, we'll consider five cir- cumstances in which there is a widely held opinion among cleaning profes- sionals-perhaps even a myth. We'll used publicly available data to evaluate the veracity of these myths, and draw a conclusion about their veracity.

that the supplier reserves the right to pri- vately negotiate a discount from "retail" pricing with every customer, based on the customer's individual situation.

merly known as Chemical Marketing Reporter, http://www.icispricing.com/) are useful, but most finishers don't use enough mineral spirits to justify the cost of the subscription.

Recently, however, I discovered a pub- licly accessible source of prices of formu- lated cleaning agents-not commodity

TABLE h DEGREASER PRICES FROH DLA

['via ME SUPPLIER PA CKAGE PRICE*

X (:ALII~ ER IN IAND GALLON S499.34

INTEGRATED ATTAC K C H FM ISTI RES GALLON S675.51

BIO T 2ouA BIOCHEM SYSTEMS GALLON 51,856,57

OS-10 Dow-C ORNING PINT S 14.57

VERTREL XF DUPONT GALLON S I, 155.58

~NO TE THAT THESE ARE NO Y "RETAIL"PRICE#, [HEY REPRESENT CO#T5 TO L/,S,

COVERNMENTAGENcTE# F©R TRANSFER FROM THE [)EFENCE SUPPLY ~ENTER

{R/(-HMONe;. MYTH #1: PRICES ARE CONFIDENTIAL I have believed-and have probably helped spread-this myth throughout my consulting career. The basic idea is

TITAN ........ ~ t T ~ R ~ , t , 0 N ~ ' , ~ !i',

Hating and Chrome Specialists

~ h r o m i c A c i c

Chromic AcM Rake Fume Suppressants Chromic Acid Crystal Btightsners Insoluble Lead Anodes Testing and Support

t / l e t a l s / A n o d e ~ Cobalt Copper Brass Bronze

Nickel cro~s a J , d ~ Zinc B e c ~ c ~ m s

Ball~ ilat~b N ~ g ~ s Tin ~ a~ o ~ MORE m~s, i , ~ ~

" u s t o m S o l u t i o n - ' FaSt Sel rv~e Custom Alloys

Mild Custom Anodes O ~ l ~ Custom Baskets

Custom Blends S i l v e r A n o d e s

a n d C h e m i c a l s

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While that "right" seems to make sense in theory, its practical application has always seemed less sensible, in that throughout the industry "retail" prices have traditionally been assumed to be confidential.

I'm currently writing a book cover- ing the technology of cleaning solvents. In preparing that book, every supplier I've asked about "retail" pricing has either: • Said that pricing information is con-

fidentia|; • Said they didn't want pricing infor-

mation published and wouldn't reply with specific information;

• Said pricing was currently being re- evaluated; or

• Provided a range of numbers that revealed little value.

Users can learn about pricing of com- modity chemicals that are useful as clean- ing agents, such as acetone, mineral spir- its, isopropanol, soy-based solvents, or heptane. Subscription services, such as ICIS Chemical Business Americas (for-

solvents. That source is a catalog pub- lished for U.S. Military bases by the Defense Logistics Agency (DLA): the DLA Environmental Products Catalog- FY 07, which can be downloaded as a PDF from the Internet (http://www.dscr.dla.mil/).

Products included are hydrocarbon-, aqueous-, semi-aqueous-, and solvent- based degreasing products. A few exam- ples of specific prices for products of various types are shown in Table I.

Certainly, the DLA has negotiated contracts based on use volumes not pertinent to individual finishing job shops. You should expect to pay more, though the U.S. government has been known, in years past, to pay $600 for hammers and toilet seats.

The DLA catalog busts the myth that all pricing information is confidential.

MYTH #2: LOWER EXPOSURE LIMIT = MORE HAZARD The eight-hour exposure l imit recom- mended by the ACGIH 2 for benzene is

July/August 20071 metatfinishing 194 www.meta[finishing.com

deaningtimes TABLE Ih EXPOSURE LIMITS, A N D C O N S E Q U E N C E S

CHEMICAL EXPOSURE LIPIIT, PPI~ RISK BEING PROTECTED BENZENE (J,5 HUMAN CARCINOGEN

REVERSI B LE ACUTE NASAL AND D BE 1 '5

SKIN IRRITATION

LACTIC ESTERS 1,5 TO 5 REVERSI B LE ACUTE NASAL

IRRITATION

N-PB 10 (_~HRONIC REPRODUCTIVE HARM

ACETONE 75(-) MORE CONCERN ABOUT

FLAMMABILITY

0.5 ppm. Benzene is a known human carcinogen. That limit for n-propyl bro- mide (n-PB) is 10 ppm; Stoddard sol- vent is 100 ppm; acetone is 750 ppm. The equivalent for esters o f dibasic acids (DBE 3) is 1.S ppm, and for esters of lactic acid, between 1.5 and 5 ppm.

This information supports the belief (myth) that DBE must be another human carcinogen or at least a suspect human carcinogen, and use of acetone must be without toxic risk.

From Table II, it's clear that exposure limits protect against both acute (short term) and chronic (long term) experience with hazards. Scientists who formulate exposure limits set them at levels that will protect a human without con- straints or pre-existing debilitation in a daily eight-hour exposure to a recog- nized hazard.

Identification o f that exposure limit is ACGIH's only charter in this pro- gram. Comparison to other hazards manifested by other chemicals does not matter. In other words, benzene and

DBE have similar exposure limits to mitigate two different risks: cancer and an itchy nose. But acetone is nearly without toxic risk!

This busts the myth that the level of expo- sure limit is related to the level of hazard being prevented.

MYTH #3: THE PUMP CAN MAKE A DIFFERENCE IN AQUEOUS CLEANING SYSTEMS Successful application o f an aqueous cleaning technology to a surface, using suitable hydraulic force, produces a mix- ture of soil in water. The mixture may be an emulsion or a two-phase brew.

The next stage of operation is to sep- arate the small volume of soil from the large volume of water. This is typically done using gravitational or centrifugal force and some sort o f skimmer or other oil-collection device. Particle (droplet) size o f the soil/oil material is the variable most significantly affecting performance of the separator. Ease o f separation is often a function of the square o f the droplet size.

This is where pump design can be significant. The vanes o f a centrifugal pump, rotating at 3,600 revolutions per minute, will chop large droplets into small ones, thus making the oil separa-

Clean and Dry-

nPB Cleaning So ents

Tel. (800) 696-9520, www.Solvon.com

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www.meta[finishing.com July/August 20071 meta|finishing 195

cleaningtimes TABLE IIh FLASH P O I N T A N D F L A H H A B I L I T Y RESULTS

FLASH POINT °F SOLVENT UEL LEL, voL%

N-Pr<or'YL BROMIDE 4.6, 1 }ig

MHHYLENE NONE~ CHLORIDE 1 ~ I (~), 2 } ,(Z )

TRICHLOROETI--'IYLENE 7''OJ 1 1 .O

tion job much more difficult. A low- cost, compressed-air-driven piston pump is often a better choice because it accomplishes transfer of the oil-water mixture without changing the droplet size. One drawback to these pumps is their noise level.

This confirms the myth that the design of a water transfer purnp can affect performance of an aqueous cleaning system.

MYTH #4: NO FLASH POINT = NO FIRE Many users believe that the flash point test is the definitive evaluation o f whether or not a chemical can be ignit- ed (catch fire).

But there are at least four measures o f ignition potential in common use: • Flash point (ASTM D56), • Flammability limits (ASTM WK5917) • Autoignition point (ASTM E659-78) • Fire point (ASTM D1310-01)

The latter two are seldom used to characterize cleaning chemicals because: (1) temperatures at which a chemical

self-ignites aren't found in practice, and (2) no safety regulations depend upon values of fire point as they do with val- ues of flash point.

Flash point and lower and upper flammabili ty limits (LEL and UEL respectively) do measure ignition potential. But they simulate use in dif- ferent environments. The former repre- sents liquid use in a open tank (TAG open cup) or a closed storage tank (TAG closed cup), and the latter repre- sents a vapor cloud. In a flash point tester, a few cc of liquid are heated below an ignition source; in a flamma- bility tester, five liters of vapor at 25 °C are present with a high-energy ignition s o u r c e .

In other words, as in industrial

applications, a fire can be started in more than one way. Some test exam- ples are in Table III.

Certainly, a chemical cannot mani- fest a result in the flash point test but does so in a flammability test.

Ignition in a flammability tester, but not in a flash point tester, busts the myth that a flash point test is the definitive proof of poten- tial for fire.

MYTH #5: LOW EVAPORATION = LOW VOC A prominent solvent cleaning product is portrayed in its MSDS as a"...Hydro-treat- ed hydrocarbon compound. Non-photo- chemically reactive."

The supplier's representative notes that "...it is not VOC exempt, even

Remember when...

- "Customer Service" really meant Customer Service?

- You didn't need a minimum order?

- Your supplier formulated products for your needs?

- Your lab results were timely, free and meant something?

- A real person answered the phone?

Call us old fashioned, but at Benchmark Products we still remember when

...because we do it everyday. See us at SUR/FIN 2007 PO Box 68809 Indianapolis, iN 46268 Booth #707 Phone: 800-428-0719 Fax: 317-872-0248

info@benchmark-products.com www.benchrnark-products.com

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P~TS

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July/August 20071 metalfinishing 196 www.meta[finishing.com

deaningtimes though the vapor pressure is under 1 mm Hg."

The U.S. EPA's standard for negligi- ble photochemical reactivity is that the maximum incremental reactivity (MIR) parameter is less than that of ethane, or 0.31. Evaporation rate or vapor pres- sure do not appear in that specification for being non-photochemically reac- tive 5.

This supplier's product description does not appear on the U.S. EPA's list of VOC-exempt chemicals. The claim "non-photochemically reactive" appears to be without basis.

Study of the U.S. EPA's policies busts the myth that evaporation has anything to do with VOC exemption in the U.S.

This column has been an attempt to communicate the importance of facts in managing cleaning technology, or any effort, for that matter. If readers have

busted myths about use of cleaning technology, or want to inquire whether a situation is a myth or fact, please contact the au thor -o r MythBusters.

REFERENCES 1. The answer is YES, but the echo

can't be detected because its sound signature is nearly identical to that of the original sound. "MythBusters" uses the word "swal- lowed" to describe the fate of the sound echo.

2. American Congress o f Government Hygienists (ACGIH) is the "referee" or "last resort" organization setting exposure limits.

3. These solvents, such as dimethyl adi- pate, are very useful for cleaning polymeric residues.

4. Not all experiments support the outcome above. There are legiti- mate, published scientific studies that support the contention that these solvents have flash point val-

ues of 75°F, -25°F, and 90°F from top to bot tom in Table II. The rea- son for this discontinuity is that these solvents contain both fuel (hydrogen and carbon atoms) and a fire suppressant (the halogen atom).

5. Note that the situation is reversed in Europe. Vapor pressure is all that matters. Exemption is generally pro- vided if the vapor chemical pressure is less than 0.075 mm Hg. In Europe, MIR and atmospheric reac- tivity have no "cred."

John B. Durkee, II, PhD, PE, is a consultant in metal and critical cleaning,. Contact him in Hunt, Texas, at jdurkee@precisioncleaning.com, (830) 238-7610; Fax (612) 677-3170; or (830) 4S9-SSSS (cellular). Durkee is the author of the recently published book, "Industrial Cleaning Processes and Technology," (ISBN 0-0804.48887) by Elsevier Management.

Ullra-Kool Inc. is celebcaUng its 22nd

year as a leader in Vapor Degreaser Design.

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From our small bench top to our most popular enclosed and automated cleaning systems

we can provide you with the personal touch to meet your cleaning needs.

You can reach us at 1-888-294-6812 Email: info@ultra-kool.com

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