What products are involved?
SRV and SRD sensors with Tri-Clamp connections
What is the purpose of this article?
To give guidelines on the selection and compatibility of Tri-Clamp connections across known standards, sizes and Rheonics SR-sensor designs (flush, short and long insertion).

1. Introduction

A Tri-Clamp (TC) fitting allows for an easy process installation in pipes and tanks. It is widely used in the food industry for hygienic purposes, and at any place where frequent cleaning and disassembly are required. Pressure and temperature ratings vary for a Tri-Clamp connection based on the type of clamp used. 

A Tri-Clamp connection is composed of 3 main parts: the ferrules, a gasket and a clamp. These parts can be supplied in the market under different standards and sizes. Each standard can use a code or dimension to identify the parts. 

In the case of the Rheonics sensors, a TC connection is welded in the probe (Figure 1) and should be clamped with a ferrule welded inline. Find out how to select the correct gasket here

Figure 1: SRV X3 Tri-Clamp mounting parts

Rheonics sensors can be ordered with different Tri-Clamp connections. Rheonics also offers EHEDG certified sensors, find the certifications here. The customer can specify the required standard and size for the connection on the probe in any design (flush, short and long insertion) but should be familiar with the next points for a good sensor configuration and installation:

  • Sizes (in different standards) compatible with each Rheonics sensor design (flush, short and long insertion).
  • Sizes compatible with EHEDG certification for Rheonics sensors.
  • Compatibility between Clamp sizes in different standards.

2. Compatibility table

To understand the points mentioned above, Rheonics provides the next table. When reviewing the table consider the following: 

  • First column stands for the ferrule bigger OD (TC diameter). Rows with the same TC dimension can be clamped together. 
  • Three norms are evaluated, these are ISO 1127, DIN 32676 (DIN 11850) and ASME-BPE. 
  • The ID and OD dimensions are based on the ISO 1127 norm, but are very proximate for the other two standards studied.
  • Rheonics sensor designs are Flush, Short and Long. 

Figure 2: Ferrule dimensions

TC (mm)ISO 1127DIN 32676ASME-BPEID (mm)OD (mm)Flush  (SR-X4)Slimline (SR-SLP)Short (SR-X3)Long (SR-X5)
Long Hygienic (SR-HS-X5)**
DN 8DN 83/8"10.313.5-----
34DN 10DN 101/2"14.017.2x*----
34DN 15DN 15-18.121.3x----
34DN 20DN 20-23.726.9xx---
50.5DN 6DN 6-7.010.2-----
50.5DN 6DN 81/2"10.313.5-----
50.5DN 10--14.017.2x*----
50.5DN 15-3/4"18.121.3x----
50.5DN 20-1"23.726.9xx---
50.5DN 25DN 251 1/2"29.733.7xxx-
50.5DN 32DN 32-38.442.4xxxx-
DN 40-3841xxxx-
64DN 20--23.726.9xx---
64DN 32--38.442.4xxxx-
64DN 40--44.348.3xxxxx
64-DN 502"47.550.8xxxxx
77.5DN 50--56.360.3xxxxx
77.5--2 1/2"60.263.5xxxxx
91DN 65DN 653"72.176.1x

x* Seal gasket will be over the weld line, care should be taken to use sufficiently conformal gaskets to seal. ONLY AVAILABLE FOR ISO 1127

**For EHEDG compliant installation, the rule D-d>L must be maintained. See EHEDG installation guidelines.

What about bigger Tri-Clamp sizes?

Welding bigger Tri-Clamp sizes on the sensor body is possible but may only make sense for the Long insertion probes. For flush and short sensors a big TC would force to use a long standpipe or long matching ferrule neck, placing the sensing element in a dead zone. Consider installation principles for the SRV and SRD. 


[1]. TC Ferrules acc. ISO 1127

[2]. TC Ferrules acc. ASME BPE

[3]. TC Schweissstutzen nach DIN 11850