What is the purpose of this article?
To provide guidelines on how the Rheonics SRV inline viscometer or SRD density and viscosity meter can retrofit the BTG, Metso, and Valmet inline blade consistency meter.

What products are involved?
SRV - Inline Viscosity Meter and SRD - Inline Density and Viscosity meter

Introduction

At times, users want to replace an existing viscometer or density meter from their processes due to malfunction, lack of spare parts, or simply to try out Rheonics sensors technology.

In these cases, users typically want to install Rheonics SRV or SRD probes in the same port or location as the previous sensor. Rheonics Type-SR sensors are well-suited for retrofit installations thanks to their modular design. They are available in various configurations, including flush, short, and long insertion lengths, with multiple process connection types.

For details, see Process Connections Rheonics Viscometer and Density Meter

By varying the insertion length and process connection of the probes, the Rheonics Type-SR sensors can be ordered to retrofit almost all existing installations. Figure 1 illustrates the SRV-X1-34N short probe with threaded connection, the SRV-X3 short probe, and the SRV-X5 long insertion, both with a Tri-Clamp connection, as examples.

Rheonics process connections favor open standards that facilitate customers to order an alternative sensor in case they plan to replace Rheonics sensors in the future.

Figure 1 - Rheonics SRV sensor: versatility in installation options.

Note: Rheonics sensors are suitable for retrofits, but care should be taken to comply with the minimum installation requirements for the sensing element to ensure reproducible and repeatable readings. These can be reviewed in the installation guideline articles for SRV and SRD.

Disclaimer: Pictures, photos, and images used are for illustration purposes and do not constitute any warranty or assertions on the suitability of use and should not be construed as an explicit or implicit recommendation or endorsement. All illustrations are given proper credit from our source of access and by their use here we do not specify or establish any copyright which belongs and stays unaffected with the existing copyright holder of that material.

Rheonics Type-SR Inline Viscosity and Density Sensors Overview

Rheonics Type-SR sensors (SRV and SRD) measure viscosity, density, and temperature in line for process control and monitoring. SRV measures viscosity, while SRD measures density and viscosity. Both sensors measure temperature with an inbuilt RTD.

These sensors are factory calibrated and do not need recalibration over their operational lifetime. However, clients may require calibration or verification for instruments used in their industry as part of their Quality Control. Optional re-adjustments or offset corrections can be performed if needed to match specific references. For more details, see Calibration of inline process viscometer SRV in field and factory.

Rheonics sensors technology is based on a balanced torsional resonator (BTR). This patented technology has a significant advantage over competitors since it allows the sensors to be compact, lightweight, and unaffected by external vibrations.

Figure 2 - SRV and SRD X5 Long NPT 1.25 versions

Blade Consistency Transmitter (BTG, Metso & Valmet)

Blade consistency transmitters are widely used in the pulp and paper industry to measure the fiber concentration, which is known as consistency within pulp suspensions. These devices are typically installed directly in the process line.

They operate using the shear force principle, where the resistance of the fiber network flowing past a static blade is translated into a mechanical movement, which is then converted into an electrical signal proportional to consistency.

This measurement is essential for maintaining a uniform product quality and optimizing chemical and energy usage across the production process.

Figure 3 - Valmet: Blade Consistency Transmitter [1]

Legacy systems from companies like BTG, Metso, and early Valmet models have widely deployed blade consistency transmitters across the pulp and paper industry. As these systems age, retrofitting them with other alternatives becomes a practical solution. This article compares installation and integration requirements, demonstrating the feasibility of Rheonics sensors to retrofit existingequipment.

Blade Consistency Transmitter retrofitting

This section outlines benefits and key considerations when replacing legacy sensors with Rheonics probes, focusing on mechanical compatibility, integration with existing control systems, and the key points to select a retrofit replacement.

What are the benefits of changing a consistency meter to an SRV or SRD?

Repeatable and Reproducible Measurements

SRV and SRD sensors use a patented Balanced Torsional Resonator (BTR) to ensure repeatability and reproducible measurements, and strong resistance to noises caused by flow disturbances and vibration. For more details, see Measurement device (sensor) repeatability and reproducibility.

Multi-Parameter Measurements

SRV integrates viscosity and temperature, while SRD adds density. Both sensors multi-parameter measurement allows for deeper insight into process conditions, reduces the need for multiple instruments, and enables calculation of kinematic viscosity and other derived properties.

Compact Design and Easy Installation

SRV and SRD sensors are built for industrial use, constructed in 316L stainless steel and rated for extreme conditions (up to 500 bar and 300 °C). Their versatile construction makes them easy to integrate into different applications.

Low Maintenance and Long-Term Stability

Once installed, SRV and SRD sensors require no recalibration and minimal maintenance. They are factory-calibrated for life and include software tools for field verification, significantly reducing operational downtime and costs.

Built-in Intelligence & Configurability

SRV and SRD electronics, SME (Rheonics transmitter), can be configured in many parameters through the included software RCP (Rheonics Control Panel). Users can configure useful calculated parameters, such as temperature-compensated viscosity, density, mathematical models, correlations, and concentration values of interest. For more details, see Using calculated data from SME.

Feature	Blade Consistency	Transmitters Type-SR Sensor
Technology principle	Shear force detection via blade deflection	Balanced torsional resonator (BTR)
Temperature compensation and multiparametric measurement	Requires a separate temperature input for compensation if needed	Measures up to 3 variables simultaneously (viscosity, density, temperature)
Wear due to mechanical movement	Present (blade deflects with flow force)	None (Non-moving parts)
External vibration immunity	High	Completly inmune
Installation and Commissioning	Requires on-site calibration set after installation	Factory-calibrated, no need for recalibration over its lifetime operation
Hygienic design	No	Yes (can be CIP/SIP compatible)
Installation orientation	Often limited (specific alignment or accessories required)	Flexible (only minimal considerations required)
Process connection	Usually requires a factory-supplied weld-on coupling	Favors open-standard connections, can be ordered to retrofit non-standard ports
Calibration requirements	Frequent	None (factory calibrated)

Mechanical Installation Considerations

Rheonics Type-SR sensor probes: General installation considerations

Before comparing the mechanical aspect of the sensors, it is important to mention some key points to consider for both Rheonics sensors, SRV and SRD. These have the same resonator across all their variants, with installation requirements related to the sensing area of the probes (shadowed red areas, Figure 4.1), which are:

These areas should be free of deposits or obstructions
These areas should be completely filled with the fluid of interest.
Maintain thermal stability when the fluid and the external environment have a temperature gradient greater than 15°C. (Only for SRD, more information here: Maintaining the SRD's temperature balance for high-density accuracy)
Align the sensing tip with the fluid flow direction as shown in Figure 4.2. (Only for SRD, more information here: SRD fluid end orientation)

These conditions can be reviewed in more detail in the next article, SRV and SRD Suitable Installations.

Figure 4.1 - Type-SR sensors: Installation considerations

Figure 4.2 - SRD recommended tip orientation

Mounting and Port Compatibility between the Type-SR sensor probes and Blade Consistency Transmitters

Blade consistency transmitters are typically installed perpendicularly across the pipe, as shown in the BTG SBT-2400 mounting instructions, Figure 5. The nominal diameter of pipes may vary for application, but can go from 4” to 24” (DN100 to 600) depending on the application.

SRV and SRD sensors can also be installed in the same configuration, where the probe is at a 90° angle to the fluid flow, as shown in Figure 6. This mounting method is effective but must be used with caution with fiber-bearing or high-viscosity fluids, as deposits may accumulate around the probe, and non-movement zones should be avoided, as shown in Figure 7. These risks are preventable with correct installation, insertion depth, and occasional cleaning.

Figure 5 - BTG: SBT-2400 - Mounting Instructions [2]

Figure 6 - Typer-SR sensor probes perpendicular installation

Figure 7 - SRV sensor: Perpendicular installation with custom insertion length

Blade consistency sensors use a custom clamp-on type mount that usually requires a factory-supplied weld-on coupling, as shown in Figure 8.

SRV and SRD sensors support a wide variety of industrial standard process connection designs. For example, if the connection port uses a Tri-Clamp (or Tri-Clover), Rheonics offers this option, as seen in Figure 9, and a wide range of options to ensure compatibility.

Figure 8 - Valmet SP Blade consistency transmitter: Process couplings [1]

Figure 9 - SRV sensor: Tri-Clamp connection components

It is important to mention that Rheonics sensors don’t need the use of a factory-designed port or accessory for operation, since Rheonics favors open standards, but the sensor can be ordered to retrofit a non-standard BTG, Metso, or Valmet port in case these do not follow a standard type.

For more details, visit Type-SR Sensors Industrial Process Connections or contact our support team.

Integration of Electronics and Communications

Electronics housing solutions

Rheonics SME (Rheonics transmitter) comes in multiple versions for installation into a wide range of applications and industrial systems, as shown in Figure 10. Each version is designed to be used in different environments and has different key properties, as illustrated in the table below.

Figure 10 - Rheonics SME (Sensor Module Electronics) alternatives

Model	Key Features
SME-TRD	IP 66 Housing with display
SME-TR	IP 66 Housing with solid cover (blind version)
SME-DRM	IP 20 DIN rail mount
SME-BOX	IP 40 Housing with Integrated PC

Communication interfaces solutions

As presented in Figure 11, Rheonics offers multiple electronics configurations and communication interfaces to match a variety of integration needs into existing analog, digital, or fieldbus systems. Such as 4-20 mA, Ethernet, Modbus, HART, Profinet, etc. Many communication protocols come standard with the sensor, while others are available upon request at the time of ordering.

Explore more about Rheonics electronics and communication options here.

Figure 11 - SME Overview

How to order a Rheonics Type-SR sensor for retrofitting

This section provides the key considerations for ordering a Retrofit replacement. These are the points to follow:

a. Define the connection type needed, specify the norm/standard, and size. Along with the insertion length required. A reference drawing is also useful.

b. Use online RFQ pages for SRV inline viscometer and SRD viscosity and density meter.

c. Select the connection code correctly. Rheonics offers various sensor connection configurations. For these retrofit applications, the following are typically recommended:

Figure 12 - Type-SR sensor probes variants examples

Sensor code	Variant design type
X2	Short Probe with Custom connection. For more information, please refer to: SRV-X2: Inline Process Viscometer with Custom Flange SRD-X2: Inline Process Density meter with Custom Flange
X3	short Probe with Tri-Clamp connection. For more information, please refer to: SRV-X3: Inline Process Viscometer with Tri-Clamp SRD-X3: Inline Process Density meter with Tri-Clamp
X4	Flush design Probe with Custom connection. For more information, please refer to: SRV-X4: Flush sensor for Hygienic and Sanitary applications SRD-X4: Flush sensor for Hygienic and Sanitary applications
X5	Long Insertion Probe with custom process connection. Requires specification of Insertion length “A” and custom connection “B”. For more information, please refer to: SRV-X5: Inline Process Viscometer with long insertion and custom connection SRD-X5: Inline Process Density meter with long insertion and custom connection