A fix water line valve is a diaphragm valve that controls the liquid level using a float-operated pilot valve. It is primarily used in water supply systems for automatic regulation of water tanks, towers, and pools. The valve consists of a main valve, a pilot valve, and a float. When the liquid level reaches the set height, the float-operated pilot valve closes, and the main valve shuts off the water pump. When the liquid level drops, the float-operated pilot valve opens, and the main valve opens the water pump. Level control valves effectively prevent water hammer, protect pipeline systems, and feature accurate level control, immunity to water pressure interference, and flexible installation. The applicable medium is clean water, and the working pressure is typically 0.6 MPa to 2.5 MPa. Materials commonly used include gray cast iron, ductile iron, and stainless steel.
Working Principle
The level control valve employs a diaphragm structure, controlling valve opening and closing through the pressure difference between the upper and lower chambers:
When the water level rises to the set height: the float pilot valve closes, the pressure in the upper chamber increases, the diaphragm moves downward, closing the main valve and stopping water supply.
When the water level drops below the set height: the float pilot valve opens, the pressure in the upper chamber decreases, and the pressure in the lower chamber pushes the diaphragm upward, opening the main valve and restoring water supply.
Structural Features
Main Valve: Composed of valve body, valve cover, valve disc, etc., with an internal diaphragm dividing the valve body into upper and lower chambers.
Float Pilot Valve: Detects water level changes via a float and controls the pressure in the upper chamber through a pilot valve.
Float: Rises and falls with the water level, transmitting signals to the pilot valve via a linkage mechanism.
Diaphragm: Made of specially reinforced nylon or rubber, separating the upper and lower chambers, its deformation adjusts the pressure difference to achieve valve opening and closing.
Sealing Device: Rubber or metal sealing rings ensure no leakage when the valve is closed.
Technical Parameters
Nominal Diameter: DN40mm to DN600mm, covering common pipe specifications.
Nominal Pressure: 0.6MPa to 4.0MPa, adapting to different system pressure requirements.
Applicable Temperature: ≤80℃ (some models can reach 120℃), suitable for ambient and warm water systems.
Control Accuracy: Liquid level error ≤±5cm, some high-end models can reach ±2%, meeting high-precision control requirements.
Anti-Air Clogging Design: Automatic air vent valve is installed at the highest point of the pipeline network to prevent air clogging from affecting valve performance.
Applications
Building Water Supply and Drainage: Maintaining constant water levels in domestic water tanks and fire-fighting water tanks to ensure stable operation of the water supply system.
Agricultural Irrigation: Controlling water levels in irrigation ponds or storage tanks to ensure stable operation of the irrigation system and improve water resource utilization efficiency.
Industrial Water Treatment: Regulating water levels in cooling towers, neutralization tanks, sedimentation tanks, etc., to ensure stable process flow.
Firefighting System: Ensures the water level in fire pools or elevated water tanks meets firefighting requirements, automatically shuts off domestic water supply during a fire, and guarantees fire-fighting water supply.
Landscape Water Features: Maintains the water level of artificial lakes, fountains, and other landscape water features to preserve their aesthetic appeal.
Advantages and Limitations
Advantages:
Automatic Adjustment: Requires no manual intervention; senses water level in real time and adjusts automatically, increasing system automation.
Energy Efficiency: Requires no external power (such as electricity or gas); relies solely on buoyancy, reducing operating costs.
Simple Structure: Low failure rate, easy maintenance, and low overall cost.
High Reliability: Mechanical linkage, unaffected by power outages or gas supply failures, highly adaptable.
High Adaptability: Suitable for various media such as clean water, sewage, and industrial wastewater, meeting the needs of different operating conditions.
Limitations:
Limited Adjustment Accuracy: Compared to high-precision electric and pneumatic control valves, the adjustment accuracy is relatively low.
Water Quality Affects Valve Performance: Diaphragms and other elastic components are in constant contact with water. Poor water quality can lead to corrosion and scaling, resulting in decreased valve performance and shortened lifespan.
Slow Response Speed: Because diaphragm deformation and valve core movement require time, the valve's response speed is relatively slow. In situations with rapid water level changes, timely adjustments may not be possible.
Selection Considerations
Nominal Diameter: Select a valve with an appropriate nominal diameter based on the water tank or pool's inlet flow rate and pipe specifications to ensure the valve meets the system's flow requirements.
Operating Pressure: Consider the system's maximum operating pressure and select a valve capable of withstanding that pressure. The valve's nominal pressure should exceed the system's maximum operating pressure to ensure safe operation.
Water Level Control Range: Select a valve with a suitable water level control range based on the water tank or pool's design water level requirements. The valve's water level control value can be set by adjusting the regulating rod, but it's crucial to ensure the adjustment range meets actual needs.
Media Characteristics: Understand the temperature, pH, impurity content, and other characteristics of the medium to select valve body, diaphragm, and valve core materials suitable for the medium's requirements. For example, for water systems containing corrosive media, corrosion-resistant stainless steel valve bodies and rubber diaphragms should be selected.
Quality Certification: Select products with relevant quality certifications, such as product qualification certificates issued by the State Administration for Quality Supervision, Inspection and Quarantine. Quality certification ensures that the product's quality and performance meet national standards and specifications.
Installation and Maintenance
Installation Requirements:
Follow the principle of unidirectional media flow during installation, ensuring that the arrow on the main valve body aligns with the flow direction of the pipeline system.
Layout the hydraulic control valves rationally, ensuring sufficient space for management, operation, installation, and maintenance.
When installing valves horizontally, the valve cover and stem should face upwards; when installing vertically, the valve cover and stem should face outwards.
Before installation, a strength and tightness test should be performed. The test pressure should be 1.5 times the nominal pressure, lasting for at least 3 minutes, and there should be no leakage from the shell, packing, and valve disc sealing surfaces.
Maintenance and Care:
Monthly inspection of the float, connecting rod, valve core, and seals for damage or jamming.
Clean debris from the float and water tank to prevent clogging; regularly clean debris trapped by the Y-type filter.
Regularly lubricate moving parts such as the connecting rod and valve stem.
Apply an anti-rust coating to the valve body to extend its service life.
Slowly fill or drain water, observing whether the water level stabilizes near the set value; adjust the float and connecting rod length or valve core opening to optimize response speed; after closing the valve, check for leaks.
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