In the pharmaceutical water systems, the conductivity of water produced by a multi-effect distilled water still is a core indicator for assessing the quality of Water for Injection (WFI). Addressing the technical concerns raised by our fellow pharmaceutical professionals, we provide a systematic review of the key factors influencing product water conductivity from both equipment engineering and operational maintenance perspectives, while also sharing some practical solutions grounded in our expertise in precision custom component manufacturing.
1. Quality of Feed Water (Purified Water)
The conductivity of the incoming purified water is the decisive foundation. Elevated levels of ions, dissolved CO₂, or organic compounds in the feed water will directly raise the distillate conductivity. Therefore, strengthening the operational management of the RO/EDI units in the purified water system is the first line of defense for ensuring final water quality.
2. Live Steam Pressure and Flow Rate
The stability of live steam pressure and flow significantly affects the distillation process. Sharp fluctuations in steam pressure can disrupt the temperature profile within the column, leading to increased mist entrainment. Insufficient steam flow may prevent complete removal of non‑condensable gases. Both conditions can cause abnormal conductivity readings. We recommend installing pressure regulating valves and flow meters to ensure that the steam supply remains within the designed operating envelope.
3. WFI Output Capacity Setting
The set production rate should not be overlooked. When the actual load deviates considerably from the rated evaporation capacity, the centrifugal separation efficiency of the entrainment separators declines, raising the risk of fine droplets escaping with the secondary vapor. Based on our operational experience, maintaining the output between 70% and 100% of the nameplate capacity generally yields more stable water quality.
4. Equipment Performance and Service Age
The cumulative effects of prolonged operation are substantial. Over time, silicate or calcium‑magnesium scales tend to form on the internal heat‑exchange tube surfaces. These deposits not only impair heat transfer efficiency but, more critically, their shedding and re‑dissolution equilibrium continuously release trace ions into the product water, causing a gradual conductivity increase. Additionally, if the final‑effect condenser experiences tube‑plate corrosion or expanded‑joint loosening, cooling medium (such as industrial cooling water or purified water) may leak into the condensate side, resulting in a sudden conductivity spike. To address such wear‑part replacement and retrofitting needs, Hansheng Automation can perform high‑precision custom machining of critical components – including heat‑exchange tubes, distributors, sealing rings, and more – based on customer‑provided original drawings or on‑site measurement data. We offer material options ranging from 316L and 2205 duplex stainless steel to titanium alloys, tailored to match the corrosion‑resistance requirements of various water quality conditions.
5. Online Conductivity Measurement Conditions
The sampling conditions for online conductivity sensors are often overlooked. When the WFI temperature exceeds 90 °C, dissolved oxygen outgassing and micro‑bubble interference can cause the online electrode to display falsely elevated readings. We suggest installing a suitable cooling coil upstream of the measurement point to reduce the sample temperature to 25–40 °C before measurement. Simultaneously, regular calibration with standard buffer solutions should be performed to eliminate inherent drifts in the measurement system.
6. Long‑Term Economic and Maintenance Considerations
From a long‑term operational cost perspective, if the still has been in continuous service for more than five years and shows an irreversible upward trend in conductivity, a comprehensive evaluation is necessary – whether to perform internal chemical cleaning, locally replace corroded components, or upgrade to new high‑efficiency separation internals. In this regard, we have extensive experience in reverse engineering and build‑to‑print custom fabrication. Whether it is supplying non‑standard spare parts for obsolete imported models or implementing localized modifications to boost output and reduce consumption for domestic units, we can offer a one‑stop service from single‑piece trials to small‑batch precision manufacturing, based on your specific process requirements. Our goal is to help pharmaceutical companies restore equipment effluent quality at a manageable cost.
In summary, the conductivity of water produced by a multi‑effect distilled water still is a comprehensive indicator governed by a four‑dimensional interplay: feed water quality, operating parameters, equipment condition, and measurement methodology. In daily management, we recommend establishing a trend‑analysis log and incorporating all control parameters into a deviation‑investigation framework. Once an issue is confirmed to originate from internal component failure or material aging, Hansheng Automation stands ready to respond promptly to your custom‑machining needs, ensuring pharmaceutical‑grade surface finishes and tight dimensional tolerances to provide a solid guarantee for your process water safety.
