Housings and FermProbe® pH electrodes are offered in a variety of lengths. This enables fermentation operators to select the optimum insertion length for the application at hand. The housing ordering information box lists the suitable electrode models and lengths for each particular housing style.
There is another way to match electrodes to housings. Each housing length is given a letter classification, i.e. “A”, “B”, “C”. Each electrode length is given a similar letter classification. Any Class “A” pH electrode will fit any Class “A” housing listed in this catalog. Similarly, any Class “B” electrode will fit any Class “B” housing. By matching the classifications, the electrode and housing will match.
The class information is found in the ordering information box for any electrode or housing in this catalog. If the class letters are the same for any electrode and housing then the two can be used together. See the illustrated example below:
- Choose a housing for the vessel and application.
- Note the class of the housing (i.e. A, B) in the ordering information box.
- Choose a style and model of electrode (see opposite page).
- Find the class of electrode that matches the class of the chosen housing.
How do I choose a housing style for my pH Electrode?
The electrode housing is designed to hold and protect the PH electrode while inserting it into the bioprocess vessel. There are various types of side entry ports and different groups of housings to fit each port type. The size and make of the port must first be identified in order to narrow the selection process.
The two most common types of entry ports found on pilot and production scale vessels are as follows:
Found on nearly all vessels other than those manufactured by B. Braun Biotech. The port bore is 25 mm i.d. and the housing o-ring seals to the inside of the port.
The housing is then secured to the port by a threaded retainer ring. The port is installed at a 15° angle for better electrode performance. See the cutaway drawing to the right for typical installation dimensions.
Found exclusively on vessels manufactured by B. Braun Biotech. This style of port is longer than the standard port and needs a special housing to fit correctly. (Note: The port opening on newer tanks is 30 mm i.d. and the port narrows down to 25 mm i.d. at the critical point where the housing o-ring seals to the inside wall of the port.) Again, the port is installed at a 15° angle for better electrode performance. See the cutaway drawing to the right for typical installation dimensions.
Additional sanitary installations
In addition to the standard types of entry ports featured above, there are other options for sanitary ports. These electrode housings are designed to hold and protect the pH electrode while insertion into sanitary pipe tees and NovAseptic’s sanitary side ports. Both entry ports require a unique housing with a narrow front end. Specifically housing models 357 and 367.
Sometimes found on vessels in biotech facilities, this style of port is flush to the vessel wall to minimize crevices. The unique design of the port offers increased drainage around the port and more effective Clean-In-Place (CIP).
The NA-connect® port from NovAseptic is compatible with a special sanitary housing, which is secured to the port by a clamp. The port is installed at a 15° angle to allow for proper electrode performance. See the cutaway drawing to the right for typical installation dimensions.
In-line measurements in a sanitary pipe tee require sanitary flange housings. Since the sanitary gasket is the primary seal, no o-ring is required on the outer portion of the housing.
Commonly used in both the food and pharmaceutical industries, the Model 357 and 367 housings are suitable for sanitary pipe systems with CIP requirements. These housings are most often found in downstream processes such as purification.
The housings are secured into a sanitary pipe tee with a standard flange clamp sealed with a flange gasket. The pH electrode is then inserted into the housing for on-line measurements. When using a standard sanitary tee, the sensor is positioned such that the tip of the sensor is in the middle of the process flow.