Many industries require water purified beyond the standard municipal water supply. Two industrial purified water standards are U.S. Pharmacopoeia Purified Water (USP PW) and Water-for-Injection (WFI) —the highest purity industrial water. PW and WFI are widely used in the food & beverage, cosmetics, pharmaceutical, biotech, and electronics industries. Industrial operators can configure their PW and WFI distillation as modular skid systems, enabling high-purity water to be generated easily and cost-effectively for a variety of applications. This blog is the final post in an occasional Magnetrol® blog series on modular skid systems and will discuss level and flow solutions for WFI distillation skids.
WFI Distillation Skid
Incorporating a multiple-effect still, this skid generates highly pure Water-for-Injection. The still can be configured to produce pure steam as an option. Level instrumentation should be of a hygienic design.
WFI production consists of a series of interconnected pressure vessels. These are called distillation columns (or effects). On each column a heat exchanger acts as an evaporator, its upper chamber used to separate pyrogens. The purified water is stored in a dedicated WFI tank.
Level and Flow Applications
- WFI Pump Protection
Whether caused by a closed valve or by pump cavitation, pumps operating in a reduced or no-flow condition can overheat, rupture the pump’s seal and cause a dangerous deviation in process pressure and temperature. A flow switch along a pump’s discharge piping will actuate an alarm and shut down the pump when liquid flow drops below the minimum flow rate.
Flow Alarm: Thermatel® Model TD1/TD2 Thermal Dispersion Switch for low-flow cutoff (Hygienic THERMATEL designs are available)
- Distillation Column Level
Depending upon its configuration, a WFI skid may contain one distillation column (Single-Effect Still); or, four or more columns (Multiple-Effect Still). Level switches in the separation columns provide control for the feedwater supply and feature alarm capabilities to ensure that all columns are operating at correct liquid levels.
Continuous Level: Eclipse® Model 706 Guided Wave Radar Transmitter or E3 Modulevel® Displacer Transmitter
Point Level: Model B35 External Cage Float Switch; or Echotel® Model 960/961 Hygienic Ultrasonic Switch
- WFI Storage Tank
Stainless steel WFI tanks typically utilize hygienic clamp-style connections, an aseptic manway, and a spray ball for interior sanitization. The vessel and all components are fabricated to ASME Section VIII, Division 1 requirements. Tank sizes may range from 250- to 10,000-gallons (945- to 37,800-liters). A hygienic level controller monitors the tank level and can activate an alarm in the event of underfill and overfill conditions.
Continuous Level: ECLIPSE Model 706 Guided Wave Radar Transmitter; Pulsar® Model R96 Radar Transmitter or Model R82 Radar Transmitter
Point Level: ECHOTEL Model 960/961 Hygienic Ultrasonic Switch