防倒流装置

Product Overview

The Stainless Steel Backflow Preventer is a safety device used to prevent contaminated water from flowing back into potable water supply pipelines. It is a reduced pressure zone (RPZ) type backflow preventer. Featuring an all‑stainless‑steel body (CF8/304 or CF8M/316), it offers excellent corrosion resistance and a hygienic surface finish, making it particularly suitable for corrosive media, high‑purity water, food, and pharmaceutical applications.

The device consists of two independent check valves and an intermediate relief chamber. Under any backpressure or backsiphonage condition, it automatically discharges reverse water to the atmosphere, completely eliminating backflow contamination. It provides the highest level of backflow protection (AA级 according to EN 1717 or ASSE 1013) and is the preferred safety device for high‑risk applications such as drinking water, chemical processing, pharmaceuticals, and food production.

Product Structure

The Stainless Steel Backflow Preventer mainly consists of the following parts:

1. Body: Precision cast stainless steel (CF8/304 or CF8M/316) with flanged or threaded ends. The body is divided into an inlet chamber, an intermediate relief chamber, and an outlet chamber.

2. First Check Valve (inlet side): Spring‑loaded lift check valve with a rubber soft seal (NBR/EPDM/FKM), allowing forward flow.

3. Second Check Valve (outlet side): Same construction as the first, providing dual sealing redundancy.

4. Intermediate Relief Chamber: Located between the two check valves, incorporating a relief valve (safety valve / drain port).

5. Relief Valve: Spring‑loaded differential pressure control valve that automatically opens when the intermediate chamber pressure exceeds the inlet pressure by a set value (typically 0.14 bar), discharging reverse water to atmosphere.

6. Test Cocks: Test ports located at the inlet, outlet, and intermediate chamber (typically 3–4 ports) for field verification of each check valve and the relief valve.

7. Drain Connection: The outlet of the relief valve, usually threaded, for connecting a drain pipe.

Compact construction, all‑stainless‑steel material with no corrosion risk, and the surface can be electropolished to meet sanitary requirements.

 Function

1. Prevents Backpressure Backflow: When outlet pressure exceeds inlet pressure (backpressure condition), both check valves close, the intermediate chamber pressure rises, the relief valve opens, and any potential leakage is discharged to atmosphere, preventing contamination from entering the upstream.

2. Prevents Backsiphonage: When upstream supply pressure drops sharply (e.g., pipe burst) creating negative pressure, the relief valve in the intermediate chamber draws in air or discharges water, preventing downstream sewage from being siphoned back upstream.

3. Dual Sealing Redundancy: Two independent check valves provide redundant sealing. Even if one check valve slightly leaks, the relief valve in the intermediate chamber will activate, ensuring absolute upstream water safety.

4. Visual/Audible Discharge Indication: Relief valve discharge is usually visible or audible, indicating abnormal conditions.

5. Corrosion Resistance & Hygienic Design: The all‑stainless‑steel body resists corrosion from acids, alkalis, seawater, and chemicals. The smooth internal bore with no dead spots makes it suitable for high‑hygiene applications such as food and pharmaceuticals.

6. In‑Line Test Capability: The sealing integrity of each check valve and the relief valve set pressure can be tested using the test cocks without removing the valve from the pipeline.

Working Conditions

1. Applicable Media: Drinking water, purified water, corrosive chemicals, acid/alkali solutions, seawater, food pastes, pharmaceutical water, etc.

2. Temperature Range: 0°C to +80°C (standard EPDM seals); –20°C to +120°C (FKM seals).

3. Pressure Rating: PN10, PN16, PN25 (Class 125, Class 150, Class 300).

4. Nominal Diameter: DN15 – DN300 (1/2″ – 12″), with DN15 – DN200 most common.

5. Installation Position: Horizontal pipeline (drain port facing downward); not to be installed upside down.

6. Typical Applications:

   1. Chemical plant corrosive media makeup water lines

   2. Pharmaceutical purified water distribution systems

   3. Food & beverage production line CIP cleaning circuits

   4. Seawater desalination plant drinking water outlets

   5. Laboratory high‑purity water systems

   6. Boiler chemical dosing lines

   7. Wastewater treatment plant chemical dosing unit makeup water

Summary

The Stainless Steel Backflow Preventer (reduced pressure zone type), with its advantages of all‑stainless‑steel corrosion‑resistant body, dual check valves + relief chamber redundant design, highest level of backflow protection, and in‑line test capability, is the ideal safety device for backflow prevention in corrosive media and high‑hygiene applications. Compared with brass or cast iron backflow preventers, the stainless steel version resists corrosion from acids, alkalis, seawater, and many chemicals, and its smooth, dead‑spot‑free surface meets the sanitary standards of the food and pharmaceutical industries.

Whether in chemical makeup water lines, pharmaceutical purified water systems, or food CIP circuits, the Stainless Steel Backflow Preventer provides absolutely reliable cross‑connection control, safeguarding upstream water quality. For pipeline systems that require the highest backflow prevention level and involve corrosive or high‑purity media, the Stainless Steel Backflow Preventer is an indispensable core safety component.