Corrosion protection by low flow control

December 20, 2022 Jos Abbing
Corrosion protection by low flow control

Experiencing harsh industry applications for many years now, I have seen several unpleasant results of corrosion.
To prevent corrosion a corrosion inhibitor can be added to the process. The right amount of inhibitor can be injected using a flow meter with a valve or pump. Using a low flow control system like this, can help you dose more accurate amounts of corrosion inhibitors. Accuracy is crucial here; it greatly influences the efficiency and minimizes environmental impact of an inhibitor system.

Corrosion inhibitor systems

A corrosion inhibitor system will add (inhibit) small concentrations of (bio) chemicals into the process. The effectiveness of an inhibitor system depends on the injection amount of the inhibitor concentration. The amount of the added chemicals is influenced by the environmental- and process conditions.

The required weight fraction of the inhibitor substances may vary between 0.001 and 0.1 weight %. Inhibiting system may inject in parts per million (PPM) to achieve low concentrations to be effective. Both continuous- and shot dosing systems are used, based on the situation.

Ex Zone 1 scale inhibitor with Coriolis mass flow controller
Ex Zone 1 scale inhibitor with Coriolis mass flow controller

Traditional inhibitor systems

Traditional methods of injecting inhibitor substances into the process, often involve manually tuned piston pumps with check valves. Verification of flow, by changing the stroke length, is carried out manually with a stopwatch and graduated gauges. This traditional approach makes it impossible to actively compensate to any changing process conditions, such as temperature changes caused by day or night. The result may be a bad flow setting, increasing chemical use, environmental impact and also cause over-dosing (!) of chemicals under normal operation conditions.

Flow meters for an accurate flow control

Accurate flow control of the inhibitor substance enables cost effective applications with less environmental impact. High accuracy and high turndown ratio can be achieved by pure mass measurement with a Coriolis flow meter (e.g. mini CORI-FLOW series). This mass flow meter can directly control valves and pumps by an on-board PID control (proportional-integral-derivative) and can be further optimized with PLC and HMI control extending both performance and flexibility.

Flow meters in chemical pilot plant

Corrosion protection by low flow control

For an accuracte injection of inhibitor substances, we offer a low flow Coriolis dosing system. This dosing system with digital communication, enables real-time monitoring, control and logging of injection rates of the inhibitor substances.

This allows online checking of flow rates and instantaneous re-setting of the required flow rate. Asset management and preventive maintenance is supported with several active diagnostics such as on-board status alarms enabling; steering monitoring, density alarm changes, single or multi point totalisation for costs calculations, empty tank alarm, and pump protection shut down.

We have been supporting field applications and R&D research projects with extensive know how on low flow systems. The ongoing research for even more environmental friendly solutions, such as biodegradable based inhibitors, is gladly supported by us.

Corrosion inhibitors are also used in other kind of industries, e.g. the public water systems.

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