Machinery Lubrication magazine published by Noria Corporation
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are a repository of data spanning weeks, months or even years. This is not representative of the current conditions, including the health of the oil, the contaminant level of the oil and the active rate of machine wear. The obvious solution is to use the live-zone sampling technique. If this is not possible, the sample documentation or label must disclose that the bottle contains a cold or dormant fluid sample. This will be taken into account by the analyst when the data is interpreted. Not all tests are influenced by dormant fluid samples. Figure 5 shows the properties of highest and lowest risk. Particle Settling in Bottles and glassware I've toured a large number of oil analysis labs in my career, including several in the last couple of years. From my observations, the vast majority of these labs seem to downplay the importance of proper sample agitation or have the misconception that their in-house method is adequate. In fact, proper agitation is seen, but it is rare. Standards such as ASTM D7647 and ISO 11500, which provide guidance on the proper use of particle counters, clearly empha- size the importance of agitation. For example, the following is from ASTM D7647: "Homogenize the incoming sample by shaking the sample container and its contents in the mechanical shaker. For samples 200 mL or less, shake for one minute. For samples 200 mL or larger, shake for three minutes." Several years ago I supervised a very basic study on sample agitation. Four identical samples were prepared using a standardized test dust (mostly silica) as the contaminant. To obtain a baseline, one of the four samples was analyzed using a freshly calibrated particle counter (control sample). The results showed 1,658 particles greater than 10 microns per milliliter (see Figure 6). The remaining three samples were then allowed to rest overnight. The following day, Sample 1 was analyzed without agitation. The results showed 29 parti- cles or less than 2 percent of the particle count found in the control sample. Sample 2 was analyzed after five minutes of vigorous hand agitation. This produced 1,287 particles or 78 percent of the control sample. Finally, Sample 3 was analyzed after five minutes in a paint shaker. The results were nearly identical to the control sample. The importance of agitation was stressed in a National Fluid Power Association report jointly authored by Caterpillar Inc., Hiac/ Royco and Butler Machinery. The report stated that "the sample extracted from the sample bottle for analysis must be representa- tive of the whole bottle … Since settling and aggregation can drastically affect the measured particle count, the samples are PUBLISHER Mike Ramsey - mramsey@noria.com GROUP PUBLISHER Brett O'Kelley - bokelley@noria.com EDITOR-IN-CHIEF Jason Sowards - jsowards@noria.com SENIOR EDITOR Jim Fitch - jfitch@noria.com TECHNICAL wRITERS Jeremy Wright - jwright@noria.com Wes Cash - wcash@noria.com Alejandro Meza - ameza@noria.com Bennett Fitch - bfitch@noria.com Loren Green - lgreen@noria.com CREATIvE DIRECTOR Ryan Kiker - rkiker@noria.com GRAPHIC ARTISTS Julia Backus - jbackus@noria.com Terry Kellam - tkellam@noria.com Josh Couch - jcouch@noria.com Patrick Clark - pclark@noria.com ADvERTISING SALES Tim Davidson - tdavidson@noria.com 800-597-5460, ext. 224 MEDIA PRODUCTION MANAGER Ally Katz - akatz@noria.com CORRESPONDENCE You may address articles, case studies, special requests and other correspondence to: Editor-in-chief MACHINERY LUBRICATION Noria Corporation 1328 E. 43rd Court • Tulsa, Oklahoma 74105 Phone: 918-749-1400 Fax: 918-746-0925 Email address: jsowards@noria.com MACHINERY LUBRICATION Volume 15 - Issue 2 March-April 2015 ( USPS 021-695) is published bimonthly by Noria Corporation, 1328 E. 43rd Court, Tulsa, OK 74105-4124. 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Noria shall not be liable for any inju- ries, loss of profits, business, goodwill, data, interruption of business, nor for incidental or consequential merchantability or fitness of purpose, or damages related to the use of information or recommendations provided. Machinery Lubrication March- April 2015 | 3 Time for Particles to Settle 4 Inches in SAE 15W40 Oil Particle Size (microns) Silica Steel Aluminum Copper Chromium 1 20.8 days 4 days 13.8 days 2.8 days 4.2 days 5 16 hours 3.3 hours 15 hours 2.8 hours 4.1 hours 10 5 hours 1 hour 3.3 hours 40 minutes 1 hour 50 12 minutes 2.1 minutes 9 minutes 0.8 minutes 2.5 minutes 100 3 minutes <1 minute 2 minutes <1 minute <40 seconds FIgURE 3 Time Required for a 20-micron Particle to Settle 1/2 Inch 10 cSt Oil 32 cSt Oil 100 cSt Oil Steel Particle 1.5 minutes 5.8 minutes 18 minutes Silica Particle 10 minutes 32 minutes 100 minutes Babbitt Particle 1.2 minutes 4 minutes 12.4 minutes FIgURE 4