Guarding Water Quality: Meijie Full-Automatic Dosing System for Circulating Water Treatment

As high-efficiency central air-conditioning machine rooms become increasingly widespread, it is well understood that maintaining the design COP over the long term depends not only on the chillers and pumps themselves—chemical water quality control of the circulating water system is equally critical. Many projects focus early on only physical side-stream filtration for suspended solids removal while neglecting precise chemical dosing; manual periodic dosing leads to fluctuating dosing amounts and unstable chemical concentrations, still resulting in scaling, pipeline corrosion, biological slime growth, and other hidden risks. The Mejor fully automatic chemical dosing system, as the core skid-mounted equipment for circulating water chemical treatment, complements the shallow sand filter side-stream filtration equipment—one chemical, one physical—together safeguarding stable water quality in high-efficiency machine room circulating water systems.

The Mejor fully automatic dosing system is an integrated complete unit, mainly consisting of a PE chemical tank, metering pumps, piping and valve assemblies, a liquid level controller, and a PLC touch-screen control cabinet, all integrated on the same base frame; online pH, ORP, and conductivity water quality monitoring instruments can be optionally configured, available in versions with or without an agitator to accommodate liquid chemicals, adapting to different chemicals.

Operating logic: closed-loop feedback automatic dosing 1. Online water quality sensors collect real-time water quality data from the central air-conditioning circulating cooling water or chilled water, transmitting pH, conductivity, and ORP signals to the PLC control system;

2. The control system compares the data against pre-set water quality thresholds and automatically calculates the required chemical dosing amount;

3. It drives high-precision metering pumps to quantitatively inject corrosion and scale inhibitors and biocides/algicides into the circulating water pipeline; the chemicals circulate and diffuse with the system water flow, forming a dense protective film on the heat exchange copper tubes and pipe inner walls, inhibiting scale precipitation while suppressing bacteria and algae growth;

4. The liquid level sensor monitors the chemical tank level in real time; when the chemical solution is at a low level, an automatic audible and visual alarm is triggered and the metering pump is interlocked to stop, preventing dry-run damage to the pump; the equipment also supports local manual/automatic switching and can reserve communication interfaces for connection to the upper-level machine room central control system for remote monitoring.

5. A timed dosing mode can also be adopted, automatically starting and stopping the metering pump by time cycle, suitable for some simpler projects.

Note: The non-agitating model is suitable for direct dosing of finished liquid chemicals, requiring no on-site dissolution and preparation of dry powder chemicals; for dry powder dissolution conditions, the agitator motor version is recommended.

The energy-saving goal of a high-efficiency machine room is built on the long-term cleanliness of the condenser heat exchange surfaces. The role of the fully automatic dosing system is to control scaling, corrosion, and microbial risks at the chemical level, working with the shallow sand side-stream filter to remove solid suspended solids from the water, achieving coordinated physical-chemical treatment of the entire circulating water system.

Precise and controllable chemical dosing reduces chemical waste — bid farewell to the traditional extensive operation mode of one-time large manual dosing. The metering pump dosing frequency is dynamically adjusted according to real-time water quality changes, keeping chemical concentrations in the system within a reasonable range long-term—no chemical waste from overdosing, and no loss of protection from underdosing—reasonably reducing chemical consumable costs.

Suppressing scaling and corrosion preserves chiller heat exchange efficiency — continuous dosing of corrosion and scale inhibitors prevents calcium and magnesium ions in cooling water from precipitating and scaling; at the same time, a protective film forms on metal pipe walls, reducing electrochemical corrosion risks in carbon steel pipelines and copper condenser piping. It effectively controls the condenser approach temperature difference, allowing chillers to maintain factory-design heat exchange conditions over the long term, preventing year-by-year increases in chiller power consumption and ensuring the energy-saving benefits of the high-efficiency machine room are realized.

Suppressing bacteria, algae, and biological slime reduces blowdown and make-up water — combined with continuous dosing of biocides/algicides, it suppresses algae and bacteria growth inside cooling towers and reduces biological slime adhesion; together with conductivity-linked automatic blowdown control, it reasonably manages the system concentration cycles, reducing frequent blowdown and saving municipal make-up water resources.