S-flow Houillon viscometer

Kinematic viscometry system for petroleum products
“The S-flow system was designed for maximum throughput and ease of use while minimizing sample quantity and solvent consumption. It is the ideal viscometer for quick and accurate results”.
Easy tube exchange
Small sample volume
High throughput
Highly accurate
Low solvent consumption
Maximum throughput and ease of use with very low sample and solvent consumption


The S-flow range of instruments consist of compact, bench-top automated viscometry systems for the analysis of Newtonian fluids. It complies fully with in ASTM D7279 and as such, has a direct correlation with ASTM D445. It is the ideal system for used oil analysis labs that need to test a wide range of lubricant viscosities. Quick analysis time, small sample size and low solvent consumption, combined with extreme ease of use and reliability make it the instrument of choice for many of our world-wide users.

The S-flow system is a self-contained viscometer system that consists of an accurately controlled thermostatic bath and a control touchscreen. Different models are available with either 1 or 2 baths, each of which contains 4 Houillon style tubes. Highly accurate optical sensors detect the flow of the sample through the viscometer tubes to obtain flow time results with 0.001 sec. precision. All measuring viscometer tubes function fully independently of each other allowing for very high throughput. 

Additional parameters such as tube constants and cleaning cycle are also controlled by the operator. Only requiring 0.3 ml of sample, the system performs the measurement very quickly, allowing a throughput of up to 80 tests per hour per bath. Options include dual solvent cleaning and integrated duplo testing which allows the operator to perform 2 flow time determinations with only 1 sample injection.


Omnitek S-flow is available in 3 different models 

S-flow 870

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S-flow 1250

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S-flow 3500

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Numer of baths


1 2

Viscometers per system

4 4 8

Time measurement

Automatic Automatic Automatic

Integrated cleaning pump

Yes Yes Yes

Chemically resistant

Yes Yes Yes

Solvent injection

Manual Automatic Automatic 

Software (optional)

Yes Yes Yes

Integrated Viscosity Index

No  No  Yes

Dual solvent option

No Yes Yes

Duplo measurement option

Yes Yes Yes

Samples per hour 

25-40 * 40-80 * 80-160 *

Temperature range (°C)

20-120 ** 20-120 ** 20-120 **

Integrated backflush

Yes Yes Yes

Warmup prior to measuring

Yes Yes Yes





Optional robotic operation

No Yes Yes

* Samples per / hour; depends on viscosity, tube, temperature and solvents chosen
** For temperatures around ambient, an external chiller is required

S-flow series specifications 
S-flow 870 / 1250 / 3500 

Standard methods

Complies to ASTM D7279, D2270 and Correlates to ASTM D445

Measuring range

0.3 – 3,000 mm2/s (cSt) @ 40°C 

Temperature range

20 – 120°C

Temperature stability

Better than ± 0.02°C

Timer resolution

0.001 s 

Sample volume

0.3 – 1.0 ml

Solvent consumption

2 – 3 ml per cycle

Sample throughput

Up to 80 samples per hour per bath (S-flow 1250 and 3500 models) **

Viscometer type


Sensor type


PC Control

Multiple instruments controlled with 1 PC


44 x 48 x 62 cm. Single bath models
70 x 48 x 62 cm. Double bath models

Weight 32 kg. Single bath models
62 kg. Double bath models

Data export

USB storage device

Power requirement

2.5 kW; 115/240V - 50/60Hz. Single bath models
5 kW; 115/240V - 50/60Hz. Double bath models

*  For temperatures around ambient, an external chiller is required
** In optimum conditions

Optional accessories & upgrades

Following items are optional accessories and upgrades to the instrument.

Dual solvent cleaning

A suitable solvent used for cleaning should have the following two main characteristics:

  • It should be able to dissolve the sample that was tested, i.e. clean the tube completely
  • It should evaporate quickly enough at the bath temperature so that the tube is fully dry after cleaning

If the solvent used does have the ability to dissolve the sample, but does not evaporate quickly enough, a second solvent can be used to rinse out the first solvent, as well as dry the tube. Usually, low boiling solvents are used for this purpose, such as Acetone or MEK. 

Cooling spiral & cooling circulator

For measurements close to ambient (± 8°C), an additional cooling circulator is required to create sufficient offset for the temperature control unit. Each bath needs to be fitted with a cooling spiral, to which an external cooling circulator can be easily connected. Complete with tubing and fittings. Cooling spiral and cooling circulator will be supplied separately on request. 



EasyFlow viscometers tubes

For high viscosity, EasyFlow can be great use. EasyFlow viscometers can be provided starting from tube constant 1.0.


Single                   Duplo


Duplo measurement tubes

The optional duplo measurement upgrade adds another array of optical fibers to the instrument, bringing the total number of detection points to three per tube instead of two.  Together with adapted S-flow tubes, which are fitted with two measuring trajectories, this enables the S-flow 870, S-flow 1250 and the S-flow 3500 to perform duplo measurements with a single sample injection, increasing productivity, saving even more on solvent consumption and runtime.


Omnitek S-flow systems operate on clean and dry 5 bar @ 5 l/min of compressed air. A suitable compressor can be supply from Omnitek if no compressed air is available.

Positive - displacement pipette

Air-displacement pipette is supplied with S-flow series as a standard. It is recommended to use positive displacement pipette especially at higher viscosities (300 mm2/s and above) to avoid operator errors and for more accurate and repeatable injections. 


All Omnitek S-flow systems utilizes advanced and easy to use multi-lingual software, it can be operated directly from the touchscreen, and both calibration and viscosity measurements can be performed without PC or software. However, to have more control, dedicated software is available, which can be used to control multiple systems.


A PC system can be sourced locally or through Omnitek. Omnitek supplies the latest model entry level laptop or, if required, desktop. When sourcing locally, make sure the operating system is Windows 7 or later and that the PC/Laptop has 1 free USB port per instrument.


Any kind of printer can be used if instrument is connected to a PC via software. A printer can be sourced locally or through Omnitek. Omnitek supplies the latest model entry level laser printer.

Robotic Operation

Omnitek offers “Robotic Operation” for models S-flow 1250 and 3500 for customers that run large numbers of samples (>500 samples per day) and want to automate their sampling process. As each laboratory will have its own requirements, automation is a highly customized product which requires elaborate preparation. Please contact us for specific solutions to your sampling needs.

ASTM Thermometers

All S-flow units can be equipped with ASTM thermometers. The recommended thermometers that can be supplied are the modern digital contact thermometers (DCT), used at multiple temperatures.

  • Applicable for fuels, base oils, formulated oils, and petroleum products as well as water-based fluids.
  • Compliant with requirements for ASTM D7279, ASTM 2270 and correlation to ASTM D445.
  • High throughput: up to 80 samples per hour per bath under ideal operation conditions.
  • Very easy to use and maintain.
  • Small sample volume: 0.3-1.0 ml.
  • Low solvent consumption: 2-3 ml per sample.
  • Extremely accurate temperature control and flow-time measurement independent of fluid type.
  • Automatic flow time measurement with ultraprecise meniscus detection.
  • Fully automatic cleaning and drying (model dependent).
  • Fast & easy tube replacement (tubes are not connected to optical sensors).
  • No need to drain bath during tube replacement.
  • Single or dual solvent injection (model dependent).
  • Integrated VI calculations (on 3500 model only).
  • Stand-alone unit. No PC required. Software operation is available as an option. 
  • Chemically resistant to allow for all common solvents.
  • Optional duplo measurement capability.
  • Integrated back flushing.

This product is compliant with the following test methods:

  •  ASTM D7279 
  •  ASTM D2270

This product is correlating with the following test method:

  •  ASTM D445
Petroleum Based Samples
Other Sample Types


Lubricating Oils

Printer ink

Terminals (Fuel Distribution)


Lubricant Manufacturers Base Stocks  

Additive Manufacturers

Industrial Oils


Condition Monitoring Labs

Transmission Oils


Third Party Testing Labs

Hydraulic Fluids


Research & Development Labs

Used Oils


Quality Control Labs

Waste Oils


Military Labs

Crude Oils


Power Plants

Fuel Oils









Bio Fuels



Marine Fuels


Chemical Plants



Iron & Steel








For other fluids / solutions please send your inquire