Metering tank

▍ Working principle

The working principle of the metering tank is based on a combination of hydrostatic level measurement and volumetric metering to achieve material storage and quantitative output.

1. Feeding and Storage: Material is injected into the tank through the top feed inlet. Operators can observe the liquid level in real time through a transparent sight glass or a display instrument配套 with a level gauge.

2. Level Monitoring and Metering:

● Basic Metering: The tank sidewall is usually marked with a scale. By directly reading the liquid level position on the scale, the volume of material in the tank can be roughly estimated.

● Precise Metering: To achieve high-precision control, the tank can be equipped with a level sensor (such as a magnetic float level gauge, hydrostatic level transmitter, etc.). The sensor converts the real-time liquid level signal into an electrical signal, which is transmitted to the display instrument in the control room or the DCS/PLC system, thereby accurately calculating the volume or weight of the material in the tank.

3. Quantitative Output: According to the preset required quantity, the material is discharged through the discharge valve at the bottom of the tank. When the liquid level drops to the target mark or the control system sends a signal, the valve closes, completing one quantitative feeding or dispensing operation.

4. Optional stirring function: For materials requiring mixing or to prevent sedimentation, the top stirring device can be activated to keep the material in the tank uniform and ensure accurate metering.

▍ Structural features

The design of PP metering tanks fully considers practicality, safety, and durability.

1. Tank Body:

● Material: Made of high-quality PP (polypropylene) sheets, typically 8mm to 15mm thick, ensuring sufficient mechanical strength and pressure resistance.

● Manufacturing Process: Hand-welded or automatically welded using a large extrusion welding gun, resulting in uniform, high-strength welds and preventing leaks.

● Shape: Usually a vertical flat-bottom, flat-top or vertical elliptical head structure, providing structural stability and ease of placement and operation.

2. Interfaces and Accessories:

● Inlet: Located at the top of the tank, usually equipped with a flange cover or quick-opening blind flange for easy feeding and cleaning.

● Outlet: Located at the lowest point of the tank, ensuring complete material discharge; can be connected to pipes and valves (such as PP ball valves and diaphragm valves).

● Level Gauge Interface: Standard interfaces are provided on the side wall for installing magnetic level gauges, level tubes, etc.

● Sight Glass: A transparent sight glass is installed on the side wall of the tank for direct observation of the material and liquid level inside.

● Manhole: For large metering tanks, a manhole is provided at the top for easy access by maintenance personnel for inspection and thorough cleaning.

● Breather/Exhaust Port: Prevents excessive positive or negative pressure inside the tank, maintaining a normal pressure.

● Overflow Port/Drain Port: Used for safe venting and cleaning of contaminants.

● Support Legs: PP or carbon steel-clad PP support legs are welded to the bottom for stable support.

3. Optional Configurations:

● Agitation System: Optional top-entry mechanical agitator, including corrosion-resistant PP or SS316 material impellers; motor power is configured according to the material viscosity.

● Temperature Control: Can be installed with a coil or jacketed structure, allowing steam or cooling water to be introduced for heating or cooling of the material inside the tank.

● Instrumentation system: It can integrate level transmitters, temperature sensors, pressure sensors, etc., to achieve fully automatic control and remote monitoring.

▍ Core advantages

1. Excellent Corrosion Resistance: PP material resists corrosion from most inorganic acids, alkalis, salt solutions, and organic solvents, resulting in a service life far exceeding that of ordinary carbon steel tanks, eliminating the need for expensive anti-corrosion coatings.

2. Clean and Non-toxic, Meeting Hygiene Standards: PP is a food-grade plastic, non-toxic and odorless, does not scale, does not breed bacteria, and is easy to clean. It fully complies with GMP and FDA hygiene requirements in the food, pharmaceutical, and drinking water industries.

3. Lightweight and Easy to Install: With a density only 1/8 that of metal, it significantly reduces the difficulty and cost of transportation and installation.

4. Good Insulation: Non-conductive, eliminating concerns about electrochemical corrosion (such as rust), ensuring safe use.

5. High Cost-Effectiveness: The initial investment cost is lower than that of tanks made of stainless steel or fiberglass of the same specifications, offering extremely high cost-effectiveness.

6. Easy Maintenance: Clean appearance, not easily attracting dirt. Only simple daily cleaning is required, with virtually no maintenance needed.

▍ Scope of application

PP metering tanks are widely used in the following fields due to their unique advantages:

● Chemical Industry: Used for the storage, metering, and transfer of corrosive chemical reagents such as acids, alkalis, and salts. For example, in the treatment of electroplating solutions, sulfuric acid, hydrochloric acid, and hydrogen peroxide.

● Environmental Water Treatment: Used as dosing tanks, flocculant preparation tanks, and neutralizing agent storage tanks for the quantitative addition of PAC, PAM, acids, and alkalis.

● Food and Beverage Industry: Used for the storage and quantitative distribution of materials such as syrups, fruit juices, edible oils, food additives, and brewing mash.

● Pharmaceutical and Bioengineering: Used as storage tanks for purified water and water for injection, as well as mixing tanks and temporary storage tanks for various intermediates and active pharmaceutical ingredients.

● Electronics Industry: Used for storing ultrapure water, developing solutions, etching solutions, and other precision chemicals.

● Laboratories: Used as raw material storage tanks and metering containers for small to medium-sized experiments.

Precautions: Although PP material has a wide range of corrosion resistance, it is not suitable for strong oxidizing acids (such as concentrated sulfuric acid and concentrated nitric acid), chloroform, aromatic hydrocarbons such as benzene, and halogenated hydrocarbons. When selecting PP material, the chemical properties of the medium must be clearly defined to determine its suitability.

▍ Summarize

PP metering tanks are economical, practical, and corrosion-resistant standardized devices made of high-performance engineering plastics. They perfectly meet the comprehensive requirements of modern industry for equipment corrosion resistance, hygiene, and cost control, making them a reliable choice for liquid metering and storage in various process industries.