The DO sensor rebuild repair consists of the following 7 steps:
Inspect the Connector Plug and Wiring
Occasionally the connector pins become bent or broken during use. The connector will be replaced if necessary. The optional right-angle connector minimizes cable fatigue and makes it easier to remove the sensor. Its low profile will also provide additional clearance between vessels. Any DO sensor with a straight connector can be easily converted to this right angle style.
Replace Cathode Assembly
This is the heart of the sensor. The glass tip should never be bumped or hit. Imperfections in the polish or curve of the tip will affect sensor readings and calibration. For example, nicks in the glass allow pools of electrolyte to form. During the process, Oxygen will collect in these same spots and interfere with the reading. If a pool were near the platinum wire of the cathode, the sensor would not zero.
Replace all O-rings
All o-rings are replaced during the rebuild. The unique feature of the Broadley-James DO sensor is that all seals are mechanical seals. There are no adhesive sealants to leak or fail while the sensor is in process.
It is much easier to replace o-ring seals rather than sealant. With sealant, it is necessary to eliminate all residue before re-applying another seal. Always inspect o-rings for wear prior to use. Good o-ring seals are critical to sensor performance for the following reasons:
- To keep moisture out of the wiring pocket allowing the sensor to withstand washdowns and autoclaving.
- To prevent the process from contaminating the sensor and wiring.
- To seal the sensor securely into the port to prevent leakage.
Polish the Outer Body
The sensor is polished down to the base metal. Dirt, tarnish and steam scorch marks are removed from the surface. The body of the sensor is fabricated from 316L stainless steel to withstand repeated exposure to both CIP and SIP conditions. Anything less would allow pitting and corrosion of the metal over time. The extra polishing step ensures the sensor is as clean as possible before returning it to service after the rebuild.
Replace Membrane Cartridge
The silicone membrane is reinforced with stainless steel mesh and can be damaged easily. Just a bump can ruin its integrity. Eventually, it will become clogged, stretched or damaged and should be changed regularly. Inspection and calibration of the sensor will determine when to change the cartridge. Broadley-James has designed a membrane testing kit to confirm the membrane has not been compromised prior to use. The membrane cartridge is replaced during a rebuild.
Refill Electrolyte Solution
It is recommended that the electrolyte be changed after every run for the sensor to work at optimum reliability. The surface of the cathode assembly is ground to allow a thin layer of electrolyte to be trapped between the membrane and the glass. It is this solution which completes the circuit of the sensor. The electrolyte, along with the membrane, is replaced during the rebuild.
Provide Quality Assurance Certificate and 1-Year Warranty
As a final step, Broadley-James Ltd will test it to ensure it is working correctly. A QA certificate is provided which includes the date of rebuild and calibration results. The serial numbers of the sensor and cathode are kept on file. This documentation will serve as the new warranty against manufacturer’s defects in parts and workmanship.