Hamilton sensor holders come with a variety of process connections to match those commonly found in sanitary and bioprocess applications.

G 1-1/4"

This process connection is also sometimes referred to as an Ingold fitting. It uses a female threaded union nut on the holder to mate with a fixed socket welded to the bioreactor vessel. The seal between the sensor holder and the socket is created with the o-ring on the holder body. The o-ring position for the holder should match the length of the socket. This creates a flush seal with the inner wall of the vessel and avoids any dead space where contamination might occur.

Example of a FlexiFit Bio Sensor Holder with G 1¼" process connection (left) with Safety Socket (right). The Safety Socket would be welded to the process vessel or piping.


TriClamp process connections rely on a tapered flange on the sensor holder. This flange mates with a similar tapered flange welded to a nozzle off the process vessel. A sanitary gasket is placed between the two flanges to form a seal. Finally, a mechanical clamp is tightened around both flanges to affix the holder in place. TriClamp connections come in different diameters typically ¾, 1½, and 2 inch. The flange size of the sensor holder much match the flange size on the vessel. Furthermore, the insertion length of the sensor must be considered to ensure that the tip of the sensor is flush or slightly extended into the vessel. Proper insertion length avoids excess dead space within the nozzle.

A Flexifit holder with 1½ TriClamp connection flange shown above.


The Varivent process connection is a flush flange connection. It is similar to the TriClamp connection in that it relies on a clamp to hold the flange of the sensor holder together with a matching flange on the process connection. Varivent connections use an o-ring seal around the internal diameter of the connection. Varivent connections are most commonly found in breweries, dairies and other food applications. They are sometimes known as Tuchenhagen connectors from the name of the company that invented them.

Varivent DN50 connectors such as shown above with the Flexifit holder provide a nearly flush process connection with the mating flange on the vessel or pipeline.

Swagelok Fittings

Swagelok fittings are used with metallic tubing to provide a leak-tight seal. These connectors use a combination of ferrules that deform the tubing as the external nut is tightened down. The tubing size must match the fitting size to create a proper seal. Swagelok fittings are found on Hamilton flowcells.

The Hamilton SL10 Flowcell shown above uses Swagelok fittings for the inlet port (left) and the outlet port (top). Liquid flow is directed past the sensor tip in a 90 degree path.

ANSI and DN Flanges

These process connections use flanges found in industrial piping. The flange on the sensor holder mates with the process flange using external bolts that fit through holes in each flange. ANSI flanges are used in North America and are designated with the piping diameter (typical 1¼ or 1½ inch) and a pressure rating (typically 150 lb). DN flanges are found in all countries using metric measurements. DN32, DN40 and DN50 designations refer to the piping diameter in millimeters. These process connections are not considered sanitary. They rely on a gasket between the face of each flange to seal against process pressure.

ANSI and DN Flanges are found on the Hamilton Retractex sensor holders.

Less Common Process Connections

NPT – NPT refers to National Pipe Thread. This is a tapered pipe thread commonly found in North America. NPT connections are more common in North America. The Retractex C sensors holders have male NPT threaded options for process connections.

NEUMO BioControl – NEUMO is a German company that has designed many different sanitary connections. Their BioControl connection uses a bolt down flanged process connection with an o-ring seal around the internal lip of the flange to form a flush process connection. NEUMO BioControl connections are an option on Retractex C sensor holders.

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