What is the purpose of this article?
Review the installation criterias, recommendation and examples for Slurry applications using Rheonics inline viscometers and density meters to enable control and monitoring of the process.
What products are involved?
SRV - Inline Viscosity Meter and SRD - Inline Density and Viscosity meter


1. Installation principles for SRV and SRD

2. Installation Considerations for Slurries

3. Cleaning Requirements for Slurries

4. Installation Examples for Slurry Applications and Considerations

5. Sensor Calibration for Slurries

1. Installation principles for SRV and SRD

For extensive detail in installation recommendations for Rheonics sensors visit the next pages: for SRV and SRD.

Key installation principles are specified in the next figure. 

  • The user should be familiar with the sensing zones of the SRV and SRD sensors and ensure these are immersed in flowing fluid. 
  • Static and moving states of fluid will show differences in viscosity. This is due to the non-Newtonian behavior of the fluid.
  • Density values for the SRD can vary throughout the process with time as the slurry ages or is mixed.

Rheonics sensors installation criterias

Figure 1: Rheonics SRV and SRD installation requirements.

2. Installation Considerations for Slurries

As described in this article Managing slurry weight and rheology using inline process density meter and viscometer, slurries can have a fluid- or solid-like behavior and important rheology parameters such as viscosity and density can be monitored and controlled using the SRV and SRD sensors from Rheonics.

Matching VISCOSITY with offline tools: Most traditional methods to measure the viscosity of slurry are done offline. The SRV and SRD sensors are not intended to match offline readings, these sensors are built for inline operation. 

The user can still compare the SR readings and the traditional readings, plot graphs, and create a correlation table as on-site references for operators. 

Slurries can also have polymeric additives that would have significant time-dependent changes in viscosity. This means that there can be differences between viscosity readings due to the elapsed time for the same slurry.

Matching DENSITY with offline tools: Most of the time, the density measured by the SRD sensor matches the traditional offline readings since density is not dependent on the measuring technology and states of the slurry (static or moving states). 

Variations can still occur as a result of a non-homogeneous fluid. For example in a tank, density can vary at different layers within the fluid if the slurry is not correctly mixed or is in static conditions (solids concentrate at the bottom). While some offline measurements take samples from the slurry at the surface, the SRD is always immersed in the fluid and helps monitor the changes in density throughout the process.

3. Cleaning Requirements for Slurries

Rheonics sensor probes withstand the rigors of continuous operation in the most aggressive slurries, just as well as cleaning procedures for removing dried-on residues, without ever requiring recalibration.

Cleaning frequency for the SRV or SRD sensor probe varies for each application and installation. It is recommended that the user visually checks the probe, especially in early tests, and looks for deposits or layers in the sensor surface or sensing area (Figure 1) that can affect the readings. This way the user can determine the cleaning period for the sensor.

Review this article for cleaning recommendations: How to clean your Rheonics probe?

The SRV can send an alarm for cleaning through the sensor status. The SRD can’t detect deposits but these can be inferred from the readings. Usually, if the sensor is obstructed, readings can have frequent spikes and an increasing slope or tendency in viscosity and/or density.

3.1 Cleaning methods for slurry applications

  • First and most common solution to clean the probe for slurry applications is inmersing the Rheonics probe in a clean water bucket. This is done either by manually removing the sensor or by inserting it automatically (robotic arm or structure).
  • Do not allow slurries to dry on the sensor probe. This can lead to solidified build ups on it. If this happens, mechanical removal should not be performed, since it risks damaging the sensing element of the probe. Instead, try with chemical removal, as long as fluids are compatible with Stainless Steel 316.
  • Washdown or hosing the probe is also a solution frequently seen to be enough to clean the probe.
  • Never use ultrasonic cleaning machines to clean Rheonics sensors.

4. Installation Examples for Slurry Applications and Considerations

4.1 Installation in Tanks

Open Tank - Installation from the top

  • Install the sensor at a depth that ensures the sensing element is always immersed in slurry.
  • Tank mount adapter TMA-34N is used to avoid the sensing element getting damaged from other objects in tank or while it is handled outside, eg. If dropped or knocked against the tank wall or bottom.
  • A quick-release mounting system can be used to facilitate easy removal of the probe from the drum when visual inspection or cleaning are necessary.

Rheonics viscometer and density meter for slurry applicationsFigure 2: Rheonics Type-SR sensor installed in open tank.

Various Installations in Tank

Rheonics sensors can also be mounted in wall or bottom of tank. Rheonics flexible design ensures repeatable and reproducible readings across all variants as long as the installation principles are followed (review for SRV and SRD).

  • Install the sensor to avoid collision with rotating blades or other objects in tank. The sensing element even though robust may be damaged irreversibly if it is hit by blades and nozzles.
  • Sensor connection with easy disassembly will be useful for periodic inspection and in-line or manual cleaning.

Rheonics viscometer and density meter flexibility for installation in tank

Figure 3: Rheonics Type-SR sensor various installation options in tank.

Long insertion probes are useful to avoid deposits on walls.

Rhoenics long insertion viscometer and density meter for installation in wall

Figure 4: Rheonics Type-SR long insertion probes (-X5) installation.

4.2 Installation in Pipes

Common installations for slurries in pipes are in recirculation lines. 

Due to the sensing zones of the SRV and SRD sensors, a perpendicular installation inline would require a pipe with an ID of approximately 60mm (i.e. 2.5” pipes or ANSI 2” pipes). Installation in 2.5” or bigger lines should be straightforward.

For installations in 2” (ID<55mm) or 1.5” pipes Rheonics accessories come in handy to ensure the installation criterias (Figure 1). Some of these accessories are: FET-15T, FTP-15T, WFT, Varinline Connection, etc.

Accessories for installation in 1” (DN25) pipes are the IFV-25N (for SRV and SRD) or HPT-12G (only for SRV).

For installation of the SRD in pipelines, follow this article for correct orientation of the sensor tip.

Deciding between installation in tank or line? Visit this article this article for advantages and disadvantages of each case.

Table 1: Accessories for Installation in Pipe

Installation in Pipe
Parallel Installation
Part/Accessory Code

Used for installation at 90° elbows. Short sensors can be installed against the fluid in an axial installation with enough immersion. Suitable for long insertion probes (SRV-X5 and SRD-X5).

Version with 2” size (-20T) also available.


Rheonics HPT-12G

Only available for SRV.

Flow cell with G 1/2” threaded ports.

Avoid deposits or solids in fluid.

Perpendicular Installation
Part/Accessory Code
Rheonics  FTP-15T-XXX

Spool tee piece for perpendicular installation with a shortened port for enough immersion of sensor probe. Available from 2” size up.FTP-15T-XXX
Varinline Housings
By using Varinline Housings, Rheonics sensors can be installed in 1”, 1.5”, 2” and bigger lines with perpendicular installation.
SRV-X4-VN Varinline Housing DN50 
Rheonics IFC-V25-PLG
Plug piece required for installation in 1” and 1.5” Varinline Housings.
SRD-X4-VF IFC-V25 Housing DN25

For slurries however, experience has shown that small pipes or narrow places are not ideal to install the sensors and measure viscosity and/or density since most slurries are prone to buildups around the sensing element which affects the readings. The SRD is especially affected by near obstructions due to its bigger sensing zone.

Common good installations in pipes for slurries are shown in Figure 5. We can review each case:

Rheonics viscometer and density meter flexibility for installation in pipeFigure 5: Rheonics Type-SR sensor installation examples in line.

1. Perpendicular installation. For the SRV and SRD short sensors, perpendicular installations in 2.5" pipes or bigger, as in Figure 5, has shown good results for slurries. Periodic cleaning is required to remove buildups, if they are created, which tend to affect readings by increasing values.

Example uses threaded connection 3/4" NPT with WOL-34NL weldolet from Rheonics. 

2. Tri-Clamp connection. Common installation for batter slurry, but useful in all cases for easy disassembly for inspection and cleaning. Example in Figure 5 uses the WFT-15T Tri-Clamp ferrule weld-on from Rheonics.

3. Elbow installation. This requires the long insertion (-X5) SRV and/or SRD probes to immerse the sensing element in the straight section of the pipe with the fluid against the probe (recommended flow orientation). An elbow installation is ideal for most applications with Rheonics sensors in high-viscosity fluids. Also, a long immersion enables the use of the SRD in higher temperature applications (higher than ambient temperature). Example in Figure 5 uses an NPT 1.25” connection. See a closer view in Figure 6, review the drawing here.

Rheonicsc long insertion viscometer and density meter in elbow installation

Figure 6: SRD-X5-A180-B1N25 parallel installation in elbow


4. For small pipes. For pipes of size 2” and 1.5”, elbow installation is possible with Rheonics FET-15T or other flow cells for the viscometer SRV and density meter and viscometer SRD. Perpendicular installation in these sizes may not allow for enough space for the sensing elements (Figure 1), Varinline Housings can be used for those cases. 

Varinline DN25 and IFC-V25-PLG can be used for 1” or DN25 pipes for the SRV and SRD installation.

In small pipes, care should be taken to:

  • Maintain minimum clearance required around sensing elements (Figure 1).
  • Avoid deposits with proper cleaning and inspection.
  • Avoid slurries with solids.

5. Sensor Calibration for Slurries

Rheonics sensors do not need recalibration due to absence of long term drift.. However, as part of Quality control Procedures clients need to verify calibrations after certain time of operation.

Calibration checks can be perfomed with following methods:

  • Air check: Remove the probe from the line, clean it and leave it in air. Sensor should output zero for viscosity and density (for SRD). If that is the case, the calibration still holds true.  This is the simplest way to check if calibration of the sensor have been affected. However, this is more an easy and quick check rather than an actual calibration verification required by customer’s Quality Control
  • Calibration fluid: Remove the sensor from the line and test it with a calibrated fluid. Rheonics recommends NIST traceable Cannon fluids, which are used for factory calibrations. Review more information here: Calibration verification procedure for inline viscometer and density meter. Readings from the Rheonics sensors can then be compared with the infosheet of the calibration reference fluid that should specify the Viscosity (Kinematic and/or Dynamic), Density and Temperature.
  • Rheonics Calibrator: Rheonics calibrator allows easy calibration check of Rheonics sensors. It requires the use of calibration fluids. It comes with a software for configuration and easy export of results.


[1]: Foundry 4.0 – Shell Room Experience with SlurryTrack Inline Viscosity Monitoring and Control System  

[2]: Rheonics Accessories List