Saybolt Viscometer for Petroleum Products

What is the Saybolt Viscometer for Petroleum Products?

A Saybolt viscometer measures the time for 60 mL of petroleum product to flow through a calibrated orifice at a set temperature, reported as Saybolt Universal or Furol seconds. It is used under ASTM D88 for lubricants and fuel oils where legacy specifications still use Saybolt units.

Overview

The Saybolt viscometer is an efflux-type instrument. A brass sample tube with a calibrated orifice at the bottom sits inside a temperature-controlled oil bath. Two orifice sizes exist: the Universal orifice for lighter oils, reported as Saybolt Universal Seconds (SUS), and the larger Furol orifice for heavy fuel oils and road oils, reported as Saybolt Furol Seconds (SFS). The sample is heated to the test temperature, typically 37.8 or 50 °C for Universal and 50 °C for Furol, then the cork stopper is removed and the time to fill a 60 mL receiving flask is measured with a stopwatch. The result in seconds can be converted to kinematic viscosity using ASTM D2161. Because ASTM now favors capillary kinematic methods, the Saybolt instrument is mainly retained for continuity with older contracts and product specifications, for which conversion tables are available.

How does it work?

Kinematic viscosity testers time the gravity-driven flow of a fixed liquid volume through a calibrated glass capillary viscometer held in a constant-temperature bath. Viscosity equals the measured flow time multiplied by the tube constant, expressed in mm²/s, and bath temperature must be held within about 0.02 °C because viscosity changes rapidly with temperature. Rotational instruments drive a spindle or rotor in the sample and measure the torque required, giving dynamic viscosity in mPa·s. Cold-cranking simulators rotate a rotor inside a stator at low temperature and relate motor speed to apparent viscosity for engine oils. Efflux cup methods such as Saybolt measure time for a set volume to drain through an orifice. Key components are the bath, thermostat, viscometer tubes, timing device and, in automatic models, optical or ultrasonic meniscus sensors.

What are the key features?

• Universal and Furol orifice options
• Brass sample tube with calibrated orifice
• Thermostatic oil bath with stirrer
• 60 mL receiving flask with marked volume
• Results convertible to kinematic viscosity
• Simple mechanical construction

What are the technical specifications?

A typical saybolt viscometer for petroleum products configuration offers test method of ASTM D88, ASTM D2161, IP 70, orifice types of Universal and Furol, temperature range of Ambient to 100 °C, temperature stability of ±0.03 °C, sample volume of 60 mL receiving volume and viscosity range of 32–1000 SUS (Universal), 25–300 SFS (Furol). Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Saybolt Viscometer for Petroleum Products is used in legacy lubricant specifications, fuel oil viscosity checks, road oil and asphalt binder testing and contract verification in regions using Saybolt units. Across the wider Viscosity Testers class, laboratories also deploy it for lubricant viscosity grade verification, fuel oil and diesel specification testing and engine oil low-temperature grading.

Which standards and certifications apply?

Relevant standards and methods include ASTM D445, ISO 3104, ASTM D88, ASTM D2983, ASTM D5293, SAE J300, IP 71, GB/T 265 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Level the bath and keep it away from drafts and vibration, because temperature stability and tube verticality drive precision. Use certified viscosity reference standards to calibrate tubes and check the bath thermometer against a traceable reference at least annually. Filter or degas samples to remove particles and bubbles, and allow adequate thermal equilibration, usually 15 to 30 minutes. Clean viscometer tubes with suitable solvents and dry with filtered air so residue does not change the tube constant. Inspect glass for cracks or chips. Replace bath fluid at intervals recommended by the supplier. For rotational and cold-cranking instruments, verify torque and speed calibration with standard oils and keep cooling systems free of moisture build-up.

How do I select the right Saybolt Viscometer for Petroleum Products?

Select a Saybolt viscometer only when a contract or specification requires Saybolt seconds. For new work, D445 capillary methods are preferred because they give direct kinematic values. In an RFQ specify Universal or Furol orifice, test temperatures, bath liquid, and whether calibration with viscosity standards is included.

How does it compare with other Viscosity Testers variants?

Choose by the method named in your product specification. ASTM D445 capillary viscometry is the reference for kinematic viscosity of fuels and lubricants, and automatic multi-tube instruments raise throughput and remove timing subjectivity. Saybolt viscometers remain in use where legacy specifications are expressed in Saybolt seconds. Rotational instruments suit non-Newtonian or very viscous products and low-temperature lubricant tests, while cold-cranking simulators are specific to engine oil low-temperature grading under SAE J300. Consider the temperature range, from 40 and 100 °C for routine oils to -40 °C for low-temperature work, and confirm the bath can maintain stability. Check the tube range, sample volume, cleaning and drying arrangements, and calibration fluid availability. For large workloads, automatic cleaning stations and multi-position baths reduce labor considerably.