Setting the Record Straight on Laundries
C.W. Berndt
President
C.W. Berndt Associates, Ltd.
Highland Park, IL
To the Editor:
Congratulations on an excellent presentation (“How to Choose a Cleanroom Laundry,” CleanRooms, Jan. 1996, p. 12) that clearly emphasizes knowledgeability, professionalism, quality, controls, testing and service excellence in a cleanroom laundry`s approach to its customers. I have always preached an informed and partnered approach to user/cleanroom laundry relationships.
There are a few observations about the article that I would like to make:
Joe Rauchet (AT&T Microelectronics), David Hope (Intel), Roger Dienter (Analog Devices), and Dale Malzie (Alcatel) all represent excellent approaches to how the user/cleanroom laundry relationship should be structured. Others would do well to follow their lead in establishing similar relationships with their cleanroom laundries.
Concerning Joe Rauchet`s anti stats, one potential use is in the final rinse of the wash process viz., to reduce the propensity for particle redeposition onto the garments. Realizing that the consensus is that less than 5 percent of defects are attributable to human operators, this is only true if an informed approach to a cleanroom garment program is actually taken. This means (based on intended use) the right fabric, right garment design, right garment construction, properly controlled laundering, correct wearing, proper garment storage, sufficient change frequencies, etc. If this is not the case (and it isn`t many times), the five percent figure is probably a lot higher.
HEPA-retrofitted dryers should almost always be steam powered. Gas and such will run a high risk of “burning” garments.
Cleanroom laundries (the bigger ones) may give the impression that they “operate entirely separate from the big industrial laundries…” however, many times, behind the scenes corporate requirements, demands and lack of really understanding the cleanroom laundry`s different needs, do not allow for truly operating separately. This corporate industrial laundry mentality or way of doing things can impact negatively on the cleanroom laundry hence its performance effectiveness in serving the user.
Your reference to “IES-RP-CC0003-87T” is not appropriate. IES-RP-CC003-87-T is a 1987 vintage of a “temporary” document that has been superseded by IES-RP-CC003.2.
The annotated procedure of ASTM F51-68 (R89) Alternate Method doesn`t seem to parallel that shown in IES-RP-CC003.2. This Recommended Practice specifies membrane filters to be 0.45 µM, 28 L (1.0 cfm) airflow at 10 cm w.g. (4 in. w.g.), garment fabric vacuumed within the area of the support grid (1 ft2 or 0.093 m2) using 10 overlapping strokes, etc. You mention 20 liters per minute, 0.8 µM membranes and 1 minute of vacuuming.
The Helmke Tumble Test or correctly called the H-Y Drum Test (Helmke-Yiech)1-see below provides cleanliness classification only of 0.5 µM and larger particles.
ASTM F51-68 is a good test which has a great deal of application for measuring 5 µM and greater particles plus fibers for the pharmaceutical industry. This is hardly a limited application “to satisfy statistical test requirements or specific customer requests.” I would argue about the tedious and laborious aspects of the test if properly set up and part of a well thought out sampling/testing plan.
“Relatively fail-safe” isn`t a descriptor I would use for describing Helmke test.
[1] Dick Yiech–retired from AT&T (Western Electric)–was the co-orginator of the Helmke Tumble Test along with Dr. George Helmke of Bell Labs (also retired). George used a 5-gallon container on a jar roller with angle irons welded in. Dick took the original design, which was too small, and perfected it including test surface area to classification relationships and developed what is today known as the H-Y (Helmke-Yiech Drum Test). The whole thing started with a memo from someone at AT&T suggesting manual rotation of a garment inside its plastic bag and measuring particles with a tube connected to a particle counter and inserted into the cut-off corner of the plastic bag.