Authoritative answers on automated particle counting, robotic Houillon viscometry, ISO 11171 calibration, NIST SRM 2806d traceability, and CINSTAN calibration, verification & process-control fluids.
The dilution test method for optical particle counting in lubricating and hydraulic fluids.
ASTM D7647 is the “Standard Test Method for Automatic Particle Counting of Lubricating and Hydraulic Fluids Using Dilution Techniques to Eliminate the Contribution of Water and Interfering Soft Particles by Light Extinction.” It was first published in 2010 to formalize the auto-dilution methodology for optical particle counters. Every CINRG auto-diluting particle counter — the CS-APC-3, CS-APC-2, and CS-APC-22M — meets the current revision of D7647.
An optical particle counter passes a metered volume of fluid past a laser beam. Particles in the fluid block (or scatter) light, producing a voltage pulse at a photodiode. The amplitude of each pulse is proportional to particle size, and the rate of pulses gives the count. CINRG instruments use a KLOTZ LDS 45/50 laser sensor with a 4µm to 70µm measuring range and a 4,096-channel KLOTZ USB counter. See CS-APC-3 or CS-APC-22M for full specs.
Used lubricating oils contain interferences that look like particles to an optical sensor — water droplets, varnish precursors, anti-foam additives such as polydimethylsiloxane (PDMS), friction modifiers, and other “soft” species. Diluting the sample with the correct masking solvent before testing dissolves or disperses these soft species so they no longer scatter light, leaving only the true abrasive contaminants to be counted. The result is repeatable counts that reflect actual contamination, not chemistry.
The CS-APC-3 large-format counter processes a complete 104-position tray in roughly 6 hours and delivers 130 to 140 samples per 8-hour shift. The benchtop CS-APC-22M processes a 22-sample tray in about 1¼ hours at 3.5 minutes per sample, also reaching 130–140 samples per 8-hour shift on multi-tray runs. Throughput is directly tied to the processing parameters; the figures above use default parameters.
Dilution ratio is set per sample in the batch file, anywhere from 1:0 (neat) to 1:9 (one part oil, nine parts solvent). A 1:1 dilution is the workhorse setting and handles the great majority of in-service samples. A 1:4 dilution is more than adequate for an oil with a viscosity of 1,000 cSt at 40°C. Samples below 46 cSt can be processed neat. The system corrects all reported counts back to undiluted-equivalent automatically.
Yes — this is one of the original drivers behind ASTM D7647. CINRG instruments routinely process samples up to ISO 23/23/21 and beyond, dark or opaque samples that defeat undiluted optical counters, and samples with up to 2% water (and higher in some configurations). Auto-dilution effectively converts a single counted volume into a virtual 100 mL sample, removing the need to pre-filter heavily loaded fluids onto a Millipore patch.
The CINRG software emits all three. ISO 4406:1999 is reported as a three-tier cleanliness code based on cumulative counts at >4µm(c), >6µm(c) and >14µm(c). SAE AS4059 is reported as both a Differential code (6–14, 14–21, 21–38, 38–70, >70µm) and a Cumulative code (>4, >6, >14, >21, >38, >70µm). The legacy NAS 1638 contamination class can be derived from the AS4059 differential output. Output format is set in the sample batch file.
The current D02.96 revision splits the method into Procedure A and Procedure B. Procedure A is the new automated path, restricted to a 90/10 toluene/IPA diluent and identified as the referee procedure; Procedure B retains the original manual workflow, with the diluents that were not part of the original interlaboratory study removed. CINRG instruments already operate as Procedure A by design and are part of the work group preparing the next ILS.
Why apparent ISO codes are sometimes wrong — and what the right solvent does about it.
A ghost particle (also called a soft particle) is a non-abrasive species in the lubricant that scatters laser light in the same way a hard contaminant does — but is not actually a wear-causing particle. The category includes water, insoluble oxidation by-products such as varnish precursors, certain dispersants, friction modifiers, and silicone-based anti-foam packages. Optical particle counters cannot tell ghost particles apart from real abrasives, which is why ASTM D7647 dilution exists.
CINRG’s recommended diluent is 75% toluene / 25% isopropanol (IPA). The IPA component dissolves up to 2% water at a 1:1 dilution; the toluene re-solubilizes varnish precursors and large-molecule additives. CINRG laboratory studies of toluene/IPA, butyl glycol (EGBE), Dowanol DPnP, kerosene, Varsol, and 67/33 kerosene/DPnP showed that 75/25 toluene/IPA gives the most consistent ISO codes across base oil, additive, and water-contamination scenarios. The 90/10 toluene/IPA blend is the diluent named in the upcoming D7647 Procedure A revision.
In a CINRG study using a Medium Test Dust spike with 1% water, the undiluted ISO code read 22/22/22. The same sample diluted 1:1 with 75/25 toluene/IPA reported 21/19/16 — effectively returning the cleanliness code to the dust-only baseline. Without dilution, even modest water levels (0.35% to 2%) inflate counts by several ISO codes and produce false “dirty” verdicts.
Yes, and this is often underappreciated. Anti-foam additives (polydimethylsiloxane / PDMS) and friction modifiers (e.g., glycerol monooleate) are particularly active. In a study of an ATF, the base oil read ISO 19/15/10; adding the friction modifier and anti-foam package alone shifted the apparent cleanliness to ISO 22/20/15 — with no change in actual contamination. Aggressive sub-micron filtration to chase those false counts can strip the additive package from the oil.
Kerosene and Varsol (Stoddard solvent) do not effectively mask water or dissolve varnish precursors and friction modifiers. In the same matched-sample studies, kerosene-diluted samples typically reported the same inflated ISO codes as the undiluted sample, while toluene/IPA brought counts down by 5–8 ISO codes. The newer ASTM D7647 revision restricts allowed diluents specifically because non-masking solvents produced unusable interlaboratory data.
MPC quantifies insoluble varnish on a filter patch, expressed as ΔE. CINRG comparison work shows that a high MPC value (e.g., 60) almost always co-occurs with inflated optical particle counts on the undiluted sample — classic ghost-particle behaviour. Once a 1:1 toluene/IPA dilution is applied, the ISO code drops to a value consistent with what a Millipore-patch microscope count would have produced, while MPC remains a useful independent indicator of varnish potential.
Automating kinematic viscosity for high-throughput commercial labs.
ASTM D7279-14 is the “Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids by Automated Houillon Viscometer.” It defines the use of automated Houillon-type capillary viscometers for rapid viscosity analysis at 40°C and 100°C. The CINRG CS-HVA-2 and CS-HVA-4 robotic systems meet the requirements of D7279-14.
The CS-HVA loads a sample every 40 seconds (90–100 samples per hour). A 4-bath CS-HVA-4 system completes 4 trays of 200 samples in roughly 8 hours of bath time, giving up to 1,200 viscosity measurements per shift. The 2-bath CS-HVA-2 is half that capacity. Both run unattended overnight and include an idle timeout that shuts down the vacuum pumps when the queue is empty.
Three controls work together. First, the syringe penetrates only as far into the oil as needed and tracks the falling level during uptake, minimising the wetted area of the needle. Second, after dispensing the sample into the capillary, the needle returns to a wash station where six 45° jets clean the inside and outside with solvent, and a drying pad removes residual solvent. Third, automated solvent filling holds the cleaning reservoirs at constant level so the rinse pressure is reproducible cycle to cycle.
Each sample in the batch file carries an expected viscosity at 40°C and at 100°C. The CS-HVA software uses fuzzy logic to assign the sample to the correct tube factor, queues it for the next available tube of that factor, and skips the sample temporarily if no suitable tube is free, returning to it later. This avoids the operator-error mode of manually selecting an inappropriate tube and producing an out-of-bounds time.
CINRG ISO/IEC 17025 validation runs against Conostan certified standards have produced internal-standard sample populations of n=196 and better, with measured KV40 and KV100 values consistently inside the ±2% certified bounds. Internal standard distributions tightened markedly after CS-HVA installation in the customer’s lab compared with the prior manual workflow, and that improvement is reproduced across customer sites.
The CS-HVA can take multiple certified standards per bath and per tube during calibration rather than a single point. A multi-point fit produces a more accurate factor across a wider viscosity range, which has a particularly large impact on KV100 results because viscosity values at 100°C span a narrower numerical band — small calibration errors translate into proportionally large reported errors. Multi-point calibration is a default workflow in the CINRG software.
Each capillary tube can be configured with up to 2 process-control standards (PCS), and the four-bath system supports up to 16 PCS in total. If a PCS measurement falls outside the configured upper or lower threshold, the tube is automatically locked out of service, samples already run on that tube are quarantined to a fail directory for review, and the tube cannot return to service until a fresh PCS passes.
ISO 11171, NIST SRM 2806, and the µm(b) / µm(c) transition explained.
ISO 11171 — “Hydraulic fluid power: calibration of automatic particle counters for liquids” — is the international procedure for sizing-calibrating optical particle counters using a NIST-traceable Medium Test Dust (MTD) primary standard. It defines factory calibration (Annexes A through E for noise, coincidence, flow rate, resolution and accuracy verification) and the laboratory sizing-calibration procedure. The current revision is ISO 11171:2022.
NIST SRM 2806 is a series of MTD-based primary calibration fluids issued by the National Institute of Standards and Technology since 1997. The original SRM 2806 (1997–2004) was followed by SRM 2806a (2013), SRM 2806b (2014–2020), and SRM 2806d (current, certified 2020). SRM 2806e and SRM 2806f are next in the queue; CINRG was one of the participating laboratories in the interlaboratory study (ILS) certifying these batches.
µm(c) sizes are based on certified counts traceable to SRM 2806a / 2806d. µm(b) sizes were a temporary reporting convention introduced when SRM 2806b certifications produced count data significantly higher than 2806a. ISO 11171:2016 allowed laboratories to derive (b) values directly or convert to (c) values using a fixed conversion factor (dc = 0.898 db). The 2022 revision discontinued µm(b) reporting entirely — all reporting is now in µm(c).
SRM 2806b certified counts were 49% higher than 2806a at >4µm, 45% higher at >6µm, and 86% higher at >14µm. About 6% of the change was explained by a higher test-dust concentration in the new batch; the remaining 40% to 75% was attributed to a certification “error” in 2806a, not to anything physical changing in customer fluids. CINRG’s OilDoc 2017 paper documents the issue with paired counts on identical samples. See the blog on the SRM 2806b transition.
An ILS is a multi-laboratory round-robin that establishes the certified count values for a primary calibration fluid. SRM 2806d was the first NIST calibration fluid certified by ILS (rather than by a single SEM/imaging lab); SRM 2806e and 2806f are being certified in the same way. CINRG participated in the ILS for the next batches in 2025 alongside Atmus, CFPC, D-2 Inc., Donaldson, NIST, Pamas and Stanhope-Seta — 14 sensors across 4 countries.
IVL is the maximum allowable difference (expressed as a percentage) in particle counts between repeat runs on the same sample, calculated as Dq = (X_max − X_min) / X_avg. ISO 11171 and ASTM D7647 each specify default IVL values, and CINRG software ships with those values pre-loaded. End users can tighten the IVL but not relax it. Each sample run reports IVL:PASS or IVL:FAIL alongside the count data.
CINRG recommends a verification check at the start of every sample batch using a CINSTAN Verification Fluid (CS-CINSTAN-VF), and a process-control standard (CS-CINSTAN-PCS) at both the start and end of the run, with an upper/lower control limit set per the ASTM D7647 repeatability statement. Annual sizing calibration with a CINSTAN Calibration Kit (CS-CINSTAN-CFK) closes the loop. The sensor-noise check should pass first; signal-to-noise of 1.5 or higher is preferred, and 1.2 is the minimum acceptable.
The KLOTZ LDS sensor produces a small baseline noise voltage even when running ultra-clean fluid. The 4µm channel calibration mV setting must be comfortably above that noise floor; otherwise the sensor will count its own noise as small particles, inflating low-end counts. CINRG’s sensor-noise procedure measures the noise threshold using Super Clean Fluid through a temporary tubing path and computes Signal-to-Noise = (4µm mV setting) / (average noise mV). If the ratio falls below 1.2, the sensor needs service before any calibration is attempted.
NIST-traceable secondary standards for ISO 11171 calibration of optical particle counters.
A primary calibration fluid is sold by NIST itself (the SRM 2806 series). It is produced under contract for NIST, certified by external parties, and is expensive (about US$4,742 for 3 × 400 mL of SRM 2806d). A secondary calibration fluid is prepared by certified manufacturers like CINRG with traceability to the NIST primary, and runs typically a quarter of the cost. Both are valid for ISO 11171 calibration; secondaries are how most commercial labs calibrate. CINSTAN is CINRG’s secondary line.
The CFK is a single-calibration kit for any CINRG auto-diluting particle counter. It includes one 400 mL bottle of CINSTAN-2806d calibration fluid, one 400 mL bottle of CINSTAN Super Clean Fluid (SCF), and three 200 mL bottles of CINSTAN PSL40, PSL60 and PSL80 — polystyrene-latex monosphere blends in SCF for the 38µm and 70µm calibration channels. The 2806d component is traceable to NIST SRM 2806d; the PSL spheres are unaffected by MTD calibration changes.
A Verification Fluid (CS-CINSTAN-VF) is a NIST-traceable reference material used to confirm that the calibration of the instrument is still valid — typically a one-shot check at the start of a measurement campaign. A Process Control Standard (CS-CINSTAN-PCS) is a low-cost reference blended in ISO 40 API Group II white oil that is run repeatedly throughout production batches and trended against upper/lower control limits to confirm day-to-day instrument performance. The two are complementary: one validates calibration accuracy, the other validates statistical control.
CINSTAN fluids are certified for 4, 6, 14 and 21µm(c) channels, prepared in accordance with ISO 11171:2022 and traceable to NIST SRM 2806d. Each shipment includes a Certificate of Analysis. The PSL40/60/80 components in the Calibration Kit cover the larger 38µm and 70µm channels using polystyrene-latex monospheres, which are unaffected by MTD certification changes.
CINSTAN-2806d, CINSTAN-PCS and CINSTAN-VF have a 24-month shelf life from production date with a minimum 12 months remaining when received by the customer. CINSTAN-PSL40, PSL60 and PSL80 have a 90-day shelf life from production with a minimum 60 days remaining when received. CINSTAN Super Clean Fluid (SCF) has no expiry. See CINSTAN product details.
Add a configurable suffix (default “PCS”) to the sample number in the batch file. The CINRG software detects the prefix or suffix and applies the upper/lower control limits in the 4µm, 6µm and 14µm channels rather than the regular sample logic. PCS results are written to a separate output file and a system parameter controls whether a PCS failure stops the run or simply quarantines the failing batch.
Bringing automated particle counting onto a benchtop in your own lab.
The CS-APC-22M is purpose-built for in-house labs. It is a benchtop unit (16½″ W × 20½″ H × 24″ D, 68 lb) with a 22-sample tray, fully ASTM D7647-10 compliant, and uses the same KLOTZ LDS 45/50 sensor as the production-floor CS-APC-3. For a fleet operator, a maintenance-engineering team, or a lubricant blender that wants accurate ISO codes without sending samples out, the 22M is the appropriate scale.
16½ inches wide by 20½ inches high by 24 inches deep (42×53×61 cm). Weight 68 lb (31 kg). Voltage 100–120/230–240 VAC selectable, 50/60 Hz, 3.5 A at 120 V. It fits on a standard laboratory bench and runs from a single outlet.
About 35 mL of dilution solvent per sample at a 1:1 ratio with default parameters. Solvent usage scales with the dilution ratio chosen in the batch file. A typical 22-sample tray run consumes well under one litre of toluene/IPA, including system flushes and the verification position.
Pour homogenized oil into 2 oz (32 mL) sample cups, drop the cups into a 24-position tray (positions 1 and 2 hold cleaning beaker and verification solvent), import a CSV batch file from the LIMS or build one in the CINRG software, click Run. Sample volumes do not have to be metered — the level sensor measures cup volume to ±2% before dilution. Higher accuracy is available by pipetting and recording volumes in the batch file.
Yes. The batch file remains editable after processing has begun. You can add new samples, remove queued samples, or set a priority flag to push a sample to the front of the queue, all while the instrument is running. Samples already processed and the in-progress sample are locked from editing.
Routine operation is “pour, load, click Run.” The deeper system parameters (cleaning thresholds, IVL bounds, dilution ratios, processing-parameter sets 1–4) are exposed only in Admin Mode and are typically configured once during installation. CINRG provides a detailed standard operating procedure for on-site calibration and a sensor-noise verification procedure that a single trained operator can follow.
Automating the front end of elemental analysis.
ASTM D5185 is the standard for multi-element determination of used and unused lubricating oils by ICP-AES. The original method specifies weight/volume sample preparation; most commercial oil-analysis labs use a volume/volume modification, designated D5185m, for speed and ease of automation. A new ASTM method has been proposed to formalize volume/volume preparation. The CS-SDS-2 is built around the modified D5185m workflow.
Custom dilution ratios from 1:3 up to 1:100 (sample:solvent), set per sample in the batch file. The system uses a Gilson 4220 Verity dual-syringe pump (one 25 mL, one 1 mL) with a t-piece valve, and a Baumer UNKC 09 ultrasonic level sensor (±0.1 mm from 3 to 150 mm) to measure each sample. The system is suitable for any pre-dilution method that uses organic solvents and petroleum-based fluids.
30 seconds per sample; 120 samples per hour. The sample table accommodates up to eight laboratory racks — typically up to seven input racks plus a single output rack of diluted samples and a standards rack. At 30 seconds per sample, the system can prepare close to 960 samples in a standard 8-hour shift.
Three controls: a piston-driven sampling needle that limits initial plunge depth and minimizes wetted area; an integrated wash station that cleans both internal and external needle surfaces with solvent and mechanical agitation between samples; and a drip-removal feature that prevents fluid bridging between source and target wells. Verified carry-over is below 0.1%, equivalent to less than 2 ppm following a 2,000 ppm standard.
Yes. Up to eight input/output rack types can be defined in software, each with its own (x, y, z) positions for every sample well. Wash-station coordinates, dilution ratios, and the insertion of internal control standards every N samples are all parameter-driven. CINRG configures the system around the customer’s laboratory and ICP rack geometry at build time, and the system can be reconfigured on-site if needed.
No. While ASTM D5185m is the design driver, the CS-SDS-2 is suitable for any pre-dilution workflow that uses organic solvents with petroleum-based fluids — for example, sample preparation for ICP-MS, certain ASTM D2622 sulphur methods, and other elemental techniques that benefit from accurate volume/volume dilution.
Tell us about your throughput, your test methods, and your facility. A CINRG engineer will help you scope the right configuration — and put you in touch with your nearest dealer.