What products are involved?
SRD - inline density and viscosity meter.
What is the purpose of this article?
To show how to align the fluid end of the sensor sensing element to streamline fluid flow across it. Demonstrate the use of a flow direction guide on the sensor to orient the sensor fluid end.

1. Overview

SRD is Rheonics inline density and viscosity probe. It can be installed in any position as long as the fluid to be measured is in full contact with the sensing element of the probe.

Rheonics, however, recommends to take some considerations to ensure the best measuring conditions for the sensor. The SRD sensor probes have a marking (e.g. a black dot or notch) next to, and aligned with, the M12 connector. From this marking, a sensor orientation plane can be drawn as in Figure 1. 

Figure 1: SR-Sensor top view.

In particular for the SRD, the orientation plane has the marking and the SRD fluid end coplanar or aligned to each other. The sensor fluid end refers to the sensing tip. It is recommended to orient the SRD so its fluid end is parallel to the flow, avoiding recirculation zones around it. The marking, like the black dot in some probe versions, helps the user to know how to orient without seeing the fluid end itself. 

Figure 2: SRD long axis and axis fluid end.

Note: Some older versions of the SRD may not have the tip or fin orientation aligned with a marking. In those cases, user should align the probe's end visually.

2. Related installations

This orientation consideration is relevant for a tee or weldolet installation on pipe, and not on an elbow or tank and chamber installation.

a. SRD in pipeline - Recommendation applies

In this example, a SRD NPT 3/4”-14 is installed on a 2” pipe with the WOL-34NS accessory (see Rheonics accessories table). Sensing element is fully submerged in fluid, distance between SRD tip and inner wall is 12mm minimum and the sensor paddle is aligned with the fluid flow. Same would be recommended for a tee installation.

Figure 3: SRD installation on pipe with WOL-34NS.

b. SRD installed at an angle - Recommendation applies 

This is a less frequent but still valid installation option of the SRD with some considerations. Special attention should be given to possible dead space around the sensor. It is usually better to install the sensor perpendicular to the pipe, on an elbow or with the use of a flow-cell.

This is, however, useful to point out that, this article recomendation is not about the sensor being always perpendicular to the flow. It is fine if the SRD is tilted, since the long axis fluid end could still be parallel to the flow as in next figure. Considerate that, on a position near the 90°, installation would be on an elbow pipe, in which case the sensor orientation is not relevant any more.

Figure 4: SRD tilt degrees 

c. SRD in elbow - Recommendation doesn’t apply

On an elbow installation, the SRD long axis is parallel to the fluid, which makes the axis fluid end orientation not relevant any more.

Figure 6: SRD FPC installed on an elbow.
3. Demonstrative Video


[1]: rheonics SRD » Density Meter inline online specific gravity concentration 

[2]: Accessories » rheonics :: viscometer and density meter