Rheonics Support

What products are involved?
Rheonics DVP High accuracy simultaneous density and viscosity meter

What is the purpose of this article?
To give an overview of the Rheonics DVP sensor and installation information.

TABLE OF CONTENTS

• Overview
• General Installation Guidelines
• DVP Installation Examples
• Process Connection Installation Instructions

Overview

DVP is Rheonics high accuracy sensor for online density, viscosity, and temperature measurement. Combining both a process density meter and viscometer in one instrument, the probe style sensor is easy to install in tanks and lines. Read more on DVP here.

Rheonics DVP makes simultaneous process density, viscosity, and temperature measurements. It is used by customers for the measurement of liquids, gases, and cryogenic fluids even in the harshest conditions with high accuracy, for example, the viscosity and density of LPG, Butane, Propane, CBM, CNG, LNG, SNG, and supercritical CO2. It is also used for measuring low and high-molecular-weight hydrocarbons including solvents. 

DVP is made of Titanium grade 5 and offers a compatible material where stainless steel 316 is not desirable.

General Installation Guidelines

This section provides guidelines for installing Rheonics DVP to achieve repeatable, and reproducible high-accuracy density and viscosity readings.

1. Submersion

DVP probe has a recommended area to have fluid and no stagnation which is shown in the red section in Figure 2. This area allows the density and viscosity measurements of the fluid that is in contact with it. 

As shown in Figure 3, DVP’s sensing area is small and surrounded by two semi-circular walls called probe fingers as part of the ∅28mm wetted section (Figures 1 and 2). The fluid goes through the two walls around the sensing area. Deposits or big particles in the fluid should be avoided since these can get sucked around the sensing area thus affecting the sensor accuracy.

DVP is also not recommended for fluid with magnetic particles like ferrous particles.

2. DVP Orientation

When fluid flow direction is defined and well known, DVP’s front end should be oriented to the flow such that the fluid goes through the probe fingers and surrounds the sensing element, as in Figure 4. This ensures good fluid contact and transfers around the sensing element.

For easy orientation adjustment, DVP sensor probe has an Alignment Notch or orientation indicator located on the back end of the probe body next to the M12 connector (Figure 5). This Notch should be pointing along the flow direction, that way the sensing element is correctly aligned with fluid flow and there is lower interference with flow.

3. Flow

Flow rate or state (flowing and static) of the fluid will impact density and viscosity differently.

Density readings will not be affected by flow rate or if the fluid is static. Rheonics DVP will measure the same density as long as the fluid composition is the same.

If fluid is Newtonian, viscosity readings will not be affected by flow rate or fluid’s state. DVP will measure the same values in static and moving states of a fluid. Newtonian fluids are relatively few in the industrial world and are limited to some applications (e.g. oils, honey, alcohol, aqueous solutions like brine and sugar syrup, acid, alkalis, etc.)

For most applications, Non-Newtonian fluids are encountered. Here, depending on the shear sensitivity of the fluid, viscosity readings will differ between static and moving conditions, and can also vary at different flow rates. 

When using Rheonics DVP, it is recommended to keep flow rate constant for shear-sensitive fluids. If flow rate changes, DVP will show these variations in the viscosity readings due to shear sensitivity of the fluid.

Flow rate is also relevant to ensure the full submersion of the DVP sensing element into the fluid. For a process with a low flow rate, pipes may not be full of fluid at all points, so DVP should then be placed in a section where the pipe is usually full of fluid (i.e. after a pump). Installing the sensor probe upwards can be a solution against low flow rates, but should not be considered for fluids with solids or characteristics that can create deposits around the sensing element.

In all cases, the DVP’s sensing element should be submerged into the fluid. Avoid installations with long standpipes (i.e. using a long weldolet or tee), since that may lead to incomplete immersion or inefficient fluid transfer around the sensing element resulting in measurements that do not reflect the current characteristics of the fluid.

DVP Installation Examples

Installation in 2” or larger Pipes

Rheonics DVP can be installed in 2-inch or bigger pipes using a commercial 1” - 11.5 NPT Weldolet. User should ensure that the clearance between the probe tip and the wall of the pipe is at least 5.5 mm to avoid the probe hitting the base of the pipe.

In small lines, consider that when the DVP probe is installed in a line, it can create pressure drops due to the probe’s body.

Installation in 1” Tee

For parallel installations, the Rheonics DVP Probe can be installed in a 1” NPT Tee, with the flow direction against the sensing element tip, it will ensure that the whole sensing element is in contact with the fluid. 

Customers should evaluate the pressure drops generated by this kind of installation and be careful not to hit the probe’s wetted portion against the pipe installed on the other side or use a Tee with longer arms.

Figure 8. DVP-X1-1N0 Installation in 1in Tee

Installation in Tank

DVP can be also installed in the side or the bottom of a tank using a 1” - 11.5 NPT Weldolet. if this is a mixing tank ensure that the sensor probe is aligned with the flow as mentioned before in the “DVP Orientation” section. See an example of this installation in Figure 9. 

Installation from the top of the tank is possible using a long insertion DVP, with a custom insertion length.

Figure 9. DVP-X1-1N0 Installation in Tank

Process Connection Installation Instructions

Connection steps

Wrap a sealing compound (e.g. Teflon tape) around the sensor NPT thread 1.5 to 3 times in a clockwise direction, to ensure a leak-free seal for some fluids.

i. Place the sensor in the female threaded accessory.

ii. Turn by hand the sensor NPT thread until hand tightened.

iii. Use a wrench (27.5mm size or 1.08”) to give the sensor from 1 up to 3 more full turns.

In total, according to ASME Standards, at least 3.5 and at maximum 6 full turns need to be ensured for a correct NPT installation. The sensor shouldn't be completely tightened.

Specific Process Connection installation instructions

• In line: Ensure the sensing element is exposed to fluid, and avoid stagnation and dead zones. Consider placing the sensor upwards or parallel to the fluid for small flow rates that can’t fully surround the sensing element.
• In tank: Place the sensor at the bottom, wall, or side of the tank as long as the sensing element can be fully submerged in the fluid and dead zones are avoided.
• Others - Thread flange: The DVP sensor can be mounted on a threaded flange as long as the thread has the same size (1"-11.5). The flange needs to have an inner diameter larger than 28mm on the process side.
  Once again, in these and any installation cases, stagnation zones around the sensing element should be avoided. For thread flanges, the height of the standpipe of the connection should be kept as small as possible. See an example in the next figure.

Figure 10. DVP Threaded Flange

References:

[1] Rheonics DVP Website