What products are involved?
Rheonics RPA System to use with inline process viscometer and density meter in variants Type-SR X8: Teletube Ultra-Long Insertion Probe, SRV-X5, and SRD-X5.

What is the purpose of this article?
To give an overview of the Rheonics Retractable Probe Assembly, Rheonics-RPA, description, and where to use it.

1. Overview

In industrial applications often there is often a need to remove instrumentation from pipes or tanks, without emptying the equipment or stopping the production. In these cases, Rheonics inline process viscometer SRV and density meter, and viscometer SRD sensors can be installed with the Rheonics Retractable Probe Assembly - RPA.

The Rheonics RPA allows the retraction and insertion of Type-SR Sensor probes from the line without disrupting the process. This minimizes downtime for probe inspection or line cleaning since the user doesn’t need to stop the process, drain the lines, or create work stoppage orders to remove instrumentation during pigging operations.

The Rheonics Retractable Probe Assembly can use the long insertion probe (X5 option) or the teletube (X8) variant (explained in detail in the ordering section below). The RPA uses a ball valve to isolate process fluid from the outside environment. The probe is inserted or retracted through the open ball valve. After the probe is retracted, the ball valve is closed to isolate the probe from the fluid inside the line. For sealing purposes, the Rheonics RPA uses a compression fitting nut to fix or allow the movement of the probe. A vertical guide rod allows the linear motion of the probe without undesired movements during insertion or retraction.

Figure 1. Retractable Probe Overview

2. Where to use the Rheonics Retractable Probe Assembly?

In certain industrial applications, removing sensors without draining the line might be necessary for maintenance, cleaning, or replacement without interrupting the production processes. 

In addition, when a line should be piggable, it is required for the probe to be removed from the line when the pigging operation is ongoing. Instead of removing the complete probe, a more time-efficient mechanism is to use retraction to remove the probe from inside the line thus removing any obstruction from the path of the pigging device. Once the pigging operation is finished, the probe can be reinserted.

Another use case is when the probe needs to be checked or cleaned during operation, the retractable assembly is able to remove it from the process line for in-situ or external verification and cleaning.

This ability allows for minimizing downtime, reducing product loss, and maintaining operational efficiency. Some of these industries are:

• Crude oil transfer pipelines
• Chemical Processing.
• Oil and Gas Industry.
• Water Treatment Plants.
• Food and Beverage Production.
• Pharmaceutical Manufacturing.
• Industries using Pigging system.

Advantages of retractable density meter and viscometer:

• Removal of the sensor without affecting the ongoing process
• Ensuring the process line is piggable.
• In-situ cleaning of the probe without contaminating the process fluid (option through upgrades).
• In-situ calibration verification using known fluid check in the RPQ assembly (option through upgrades).

3. Parts Index

Figure 2. Retractable Probe Parts

4. What is included in a standard delivery?

Item	Name	Quantity	Reference Image
1	1 ½” NPT Ball Valve + 1 1/2” NPT Retract Adapter	1
2	Retract Guiding Rod	1
3	Retract Probe Assembly	1
4	Retract Support Sleeve	1
5	50 mm Wrench	1

5. How to prepare a pipe or tank for the RPA installation?

The Rheonics Retractable Probe (RPA) can be seamlessly integrated into the process by using a male 1 1/2” NPT thread, allowing for the valve to be securely threaded. This could be, for example, using a standpipe or an existing port with an adapter to transition to the required thread.

The installation must have a minimum inner diameter of ⌀35 mm to ensure proper immersion and retraction of the sensor probe.

Figure 3. Retractable Probe Installation Interface

To prepare the pipe or tank for the RPA installation, follow these instructions:

1. Identify and define the installation point; only a male 1 1/2” NPT Thread is required. This could be using a standpipe or using an existing port with an adapter to transition to the required thread.
   
2. Now, follow the detailed assembly instructions below to install the RPA.

6. Assembly and Installation Instructions

The assembly of this product is simple because most of the parts are delivered assembled. Follow the next steps to start using the retractable probe.

1. Installation and Commissioning

Steps	Drawing
How to install and commission the RPA?
1. Add PTFE tape to the 1 1/2” male thread of the installation point and, using the 55mm wrench, connect the BV1N50-RPA with 1N50-RPA to the process. Follow the NPT thread assembly general instructions.
2. With the Hex Key #6 and the M8 screw, tighten the guiding rod to the stationary sheet. Make sure the locking pin is at a comfortable operating position, ideally upwards.
3. Put some lubricant on the O-ring at the front of the 1N50-RPA. With the BV1N50-RPA closed, connect the RSS-RPA on the front of the adapter.
4. There are two options: If the teletube probe isn’t assembled, please follow these steps to do it. Ultra-Long TT Sensor viscometer and density meter assembly. If the teletube is assembled or is an SRx-X5 long insertion probe, continue to step 5.
5. Install the APC on the probe body to be used in the next steps. Note: The Rheonics APC generally comes already assembled with the Movable Guide Slab, if this is not the case, follow the instructions on the APC article to assemble it, the Movable Guide Slab works as a process connection.
6. Slide the front of the probe on the RSS-RPA and connect the MS-RPA of the probe assembly to the RD-RPA.
7. Push the probe into the 1N50-RPA until the MS-RPA touches the SP-RPA. Take the RSS-RPA out once the probe is sufficiently inserted into the 1N50-RPA.
8. Now the probe is engaged on the O-ring, the BV1N50-RPA can be safely opened without process fluid being spilled. Open the BV1N50-RPA, take the SP-RPA out, and insert the probe to its final position. Put back the SP-RPA.
9. Using the WRC-50, tighten the CN-RPA to fix the probe to the 1N50-RPA. Now the sensor probe is ready to get measurements.

2. Probe Removal

Steps
How to remove the sensor probe from the mainpipe?
Please make sure that the pipe and process are at an ambient pressure to remove the probe from the line.
1. Using the WRC-50, loosen the CN-RPA that fixes the probe to the 1N50-RPA.
2. Slide the probe out until the MS-RPA touches the SP-RPA. The BV1N50-RPA can now be closed.
3. Take the SP-RPA out and, with the help of the RSS-RPA, slide the probe out completely. Put back the SP-RPA. Once the previous steps are done, you can remove/change the probe or clean the line safely.

3. Probe Reinsertion

Steps	Drawing
How to reinsert the RPA in the process?
1. Open the BV1N50-RPA, take the SP-RPA out, and with the help of the RSS-RPA, reinsert the probe to its final position. Put back the SP-RPA.
2. Using the WRC-50, tighten the CN-RPA to fix the probe to the 1N50-RPA. Now the sensor probe is ready again to take measurements.

7. Installation examples

A common installation for the Rheonics RPA is in a line that has a pigging cleaning system. For this case, the sensor probe needs to be removed from the pipe to avoid an impact between the pigging head and the sensor probe. This is easily achieved by using the Rheonics RPA for both the process density and viscosity meter SRD as well as the process viscometer SRV.

8. How to order the Rheonics Retractable Probe?

A: Retractable Probe Assembly

B: Sensor Type (SRV or SRD)

C: Wetted Material

D: Certifications (Optional)

E: Density Range (Only for SRD version)

F: Density Calibration (Only for SRD version)

G: Viscosity Range 

H: Viscosity Calibration

I: Electronics Variant

J: Communication Protocols

K: Temperature Rating

L: Pressure Rating

M: Variant Design (See options below)

• XW: Select between X5 and X8 Variant
• AYYY: Insertion length required (Consider the Standpipe length and the immersion required)

N: Cable variant and Length