In municipal water supply, building pump house and circulating water system, silencing check valve is the core pipe fitting for preventing medium backflow and protecting pump unit. HC41X and HC42X are two kinds of soft seal silencing check valves purchased frequently in the domestic water supply and drainage field. Many foreign trade customers and engineering purchasers often mix up the two types of products. The wrong model will cause excessive noise, water hammer impact, frequent valve damage and other problems.

HC41X is a lift-off silencing check valve, which drives the valve clack vertically up and down along the guide rib in the valve body by the medium thrust to realize on-off. Open the valve clack when the medium flows forward, and the valve clack will fall back and seal by gravity after the pump stops and loses pressure. It features simple structure, less parts, low difficulty in casting and machining of valve body, sufficient supply in the market and more advantageous price. However, due to the limitation of lifting structure, HC41X is preferentially installed vertically from top to bottom, and the valve clack may be clamped or not tightly sealed in horizontal installation; At the same time, the valve disc travel is longer, the closing speed is slower, the flow resistance coefficient is higher than HC42X, and the pressure loss is more obvious under the large flow condition.

HC42X silent check valve adopts sleeve-type built-in guiding structure, the valve disc moves axially in short stroke in the sleeve, and the opening and closing response speed is fast. At the moment of closing, the valve clack is stably buffered, and the collision noise is greatly reduced. The buffering structure can effectively reduce the water hammer pressure when the pump is stopped. The mute and water hammer protection performance are its greatest advantages. Strong installation compatibility, normal use of horizontal pipes and vertical pipes, suitable for complex pipeline layout of pump house. The disadvantage is that the internal sleeve assembly is precise and has more processing procedures. Under the same aperture and pressure rating, the procurement cost is higher than HC41X and the requirements for medium cleanliness are higher. The medium containing sediment and impurities is easy to block the guide pair.

The two check valves also have the same characteristics: both adopt rubber soft seal, with good sealing performance and zero leakage under low pressure; The main material is QT450 nodular cast iron, the seal is EPDM rubber, and it is suitable for normal temperature clean water; Flange is mainly used for connection, supporting PN10 and PN16 nominal pressure, with diameter covering DN40-DN600.

From the selection of working conditions: common vertical water supply branch pipe, water inlet rear end of water tank, newly built pipe network with limited budget, clean and stable medium, no strict noise reduction requirements, HC41X is preferred; High-rise secondary water supply pump house, frequency conversion pump outlet, hospital hotel and other places with strict noise control, long-distance water transmission pipeline, water hammer protection pipeline and pressure gauge shall be controlled, and HC42X silent check valve is recommended.

At the same time, the use boundary of the two shall be clear: HC41X and HC42X are only suitable for clean water, and sewage, medium containing particles and impurities and high temperature oil medium are not suitable; Either type, it is recommended to equip the front of the valve with a Y-shaped filter to prevent impurities from blocking the valve disc and extend the service life of the valve. In addition to the model and caliber pressure, it is also required to confirm the flange standard, valve body material, sealing material, whether the inspection report, EAC and other certification documents are required, so as to avoid delivery deviation in the later period.

To sum up, HC41X is superior in simple structure, high cost performance and suitable for vertical pipelines; HC42X is sound-proof and hammer-proof, with flexible installation and strong adaptability to pump room scenes.