German HAAG valves HAAG models HAAG prices

HAAG valves are globe valves that use a diaphragm as the closing element to seal the flow passage, shut off fluid, and separate the valve body cavity from the valve bonnet cavity. Diaphragms are commonly made of elastic, corrosion-resistant, non-permeable materials such as rubber and plastic. Valve bodies are mostly made of plastic, fiberglass, ceramic, or metal with rubber lining. They feature a simple structure, good sealing and anti-corrosion performance, and low fluid resistance. They are used for media with low pressure, low temperature, strong corrosiveness, and suspended solids. Structural forms include weir type, globe type, and gate type. Drive methods include manual, pneumatic, and electric.

HAAG valve functions

A diaphragm valve contains a flexible or composite diaphragm inside the valve body and bonnet, with a closing member connected to the diaphragm via a compression mechanism. The valve seat can be weir-shaped or the wall of a straight-through flow passage. The advantage of a diaphragm valve is that the operating mechanism is isolated from the media path, ensuring the purity of the working medium and preventing media impact on the operating components. Additionally, no separate sealing is required at the stem unless used as a safety feature for controlling hazardous media. In diaphragm valves, only the diaphragm and valve body contact the working medium; since both can be made from various materials, the valve can ideally control many working media, especially those with chemical corrosiveness or suspended particles. The operating temperature of a diaphragm valve is usually limited by the materials of the diaphragm and valve body lining, with an approximate range of -50 to 175°C. The diaphragm valve has a simple structure, consisting mainly of three components: the valve body, diaphragm, and valve head assembly. It is easy to disassemble and maintain quickly, and diaphragm replacement can be completed on-site in a short time.

HAAG valve working principle

Diaphragm valves use a corrosion-resistant lined valve body and a corrosion-resistant diaphragm instead of valve core components, utilizing diaphragm movement for regulation. The valve body material is cast iron, cast steel, or cast stainless steel, lined with various corrosion-resistant or wear-resistant materials; diaphragm materials include rubber and PTFE. The lined diaphragm has strong corrosion resistance, suitable for regulating strongly corrosive media such as strong acids and alkalis. Diaphragm valves have a simple structure, low fluid resistance, and greater flow capacity than other valve types of the same specification; they are leak-free and suitable for regulating high-viscosity media and media with suspended particles. The diaphragm isolates the medium from the upper chamber of the valve stem, so there is no packing and no external leakage. However, due to limitations of the diaphragm and lining materials, pressure and temperature resistance are relatively poor, generally applicable only up to 16MPa nominal pressure and below 150°C. The flow characteristic of a diaphragm valve is close to quick-opening; it is approximately linear before 60% travel, and the flow change is not significant after 60%. Pneumatic diaphragm valves can be equipped with feedback signals, limiters, and positioners to meet the needs of automatic control, program control, or flow regulation. The feedback signal of pneumatic diaphragm valves uses non-contact sensing technology. This product uses a diaphragm-type actuating cylinder instead of a piston cylinder, eliminating the drawback of piston ring damage causing leakage and failure to open or close the valve. In case of air source failure, the handwheel can still be operated to open or close the valve.

HAAG valve applications

A diaphragm valve is a special type of shut-off valve whose closing element is a diaphragm made of soft material, separating the valve body cavity from the valve bonnet cavity. Due to limitations in valve body lining and diaphragm manufacturing processes, it is difficult to produce large linings and large diaphragms; therefore, diaphragm valves are not suitable for large pipe diameters and are generally applied in pipelines ≤DN200. Due to limitations of diaphragm materials, diaphragm valves are suitable for low-pressure and low-temperature occasions. Generally, they should not exceed 180°C. Since diaphragm valves have good anti-corrosion performance, they are mostly used in devices and pipelines for corrosive media. The applicable temperature and media for diaphragm valves are limited by the valve body lining material and diaphragm material.

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