Improve Sour Water Corrosion Control with Smart Digital pH Sensors and HART/AMS Compatible Transmitters

Refineries use steam as a stripping medium in many different distillation processes. The operators condense steam into a liquid and remove it as sour water. During the distillation process, the condensate captures hydrogen sulphide (H2S) and ammonia (NH3).
The largest source of sour water is in the Crude Distillation Unit (CDU). It comes from the steam stripping of crude in the atmospheric and vacuum tower. Large amounts of sour water is also produced in the hydrodesulphurization units (HDS), Fluidized catalytic crackers (FCC) and hydrocrackers.

Our Solution

Sour water monitoring is challenging for pH electrodes because the junction can be plugged by solids & sulfides. This can cause sensors to drift or fail. The SE 554 Memosens pH sensor is ideal for use in this application. The sensor’s open junction design is resistant to plugging media. In addition, the polymerized KCL electrolyte prevents poisoning of the Silamid® reference, which greatly extends sensor life.
A microprocessor in the head of the pH sensor allows for offline calibration and sensor health analysis. When using a Portavo portable analyzer, technicians can calibrate and troubleshoot in the shop or lab instead of inside the process unit. Controlling the pH buffer solutions allows for more precise calibrations. After calibration, the technician simply carries it out to the installation, disconnects the Memosens inductive cable, and does a “hot-swap” with no additional calibration or configuration.
The Stratos Pro is a two-wire loop powered Class 1 Div 1 FM/CSA rated transmitter. It provides a 4…20 mA output, superimposed with HART process and diagnostic data. Plant operations can view the diagnostic data when using AMS software. Therefore, operators can now predict maintenance requirements, reducing the potential for unscheduled process interruptions.
Double block and bleed installations are a requirement in refineries. The CSR 3600 B is a simple ball-valve retractable holder which allows the user to easily insert or remove the sensor through a ball valve.

What was this Customer’s Return on Investment?

• Reduced sensor replacements & maintenance costs: The Knick SE 554 pH sensor lasts longer under difficult process conditions and requires fewer calibrations, resulting in reduced maintenance costs.
• HART diagnostics for AMS: HART with AMS compatibility clearly indicates required maintenance. The customer now uses a predictive, rather than a preventative maintenance schedule. Consequently, fewer trips to the pH sensor increases available maintenance man-hours for other tasks.
• Improved corrosion control: Having a reliable pH measurement, the customer was able to reduce their capital equipment cost due to improved corrosion control.