A check valve for water applications requires as much considerations as you would collect in any other valve selection. Same as various other media, water has its own unique features curve that should be accommodated to the valve for specific use in those media. Of course, this is an simple matter, but some less obvious reasons may be included when it come to choosing the perfect check valve for water. Problems with water delivery Water Hammer: Although this hydraulic problem can be discerned in other fluids, water hammering hits when the medium is forced to stop or change direction suddenly. As water or other media is trapped in the pipe with only two directions to pass,th is situation comes with vibrations of the pipe andirritating noise. Both hurt the system. Transporting water is a ordinary thing in countless applications, but it remains a hard case nowadays because it’s almost impossible to maintain the flow indefinitely steady.The most common cause of water-hammer is when a pump stops working without any warning. Water flows back ward to the pump, because the check valve is not able to react fast enough. Water hammer is sometimes referred to water slam. Reverse Flow: If left unchecked, reverse flow of water or any medium can render the pump spin backwards, causing unexpected damage. Likewise,if water flows in the wrong direction, for any length of time, it will hurt the entire system seriously. Unlike a back flow preventer, which consist of, work in andem with multiple check valves, a single check valve is not a panacea. Valve chatter: Valve chatter occursif valves open and close constantly and frequently. Valve chatter can cause damage to the valve and piping and can inflict total failure to the system. Checking for water problems Though check valves areremarkable reliable and endless new model and design are brought to the field every year, all problems theytry to answer to are just these three listed above. Due toits simple structure, it can be immune from external factorslike power failure, but is still affected by flow direction, and by check valve design features and defects. There are two basic designs of check valves. One uses a disc (basically a flap) and one uses a free floating ball. They both have a single direction, which means that their job is to prevent water from flowing backwards through the pipe. Both types have advantages and disadvantages, but perform the same job with fairly equal success.Ultimately, however, the success of a check valve rest with an not-too-fast-or-too-slow action. Finally, like most valves, its sealing performance determines the success of a check valve . All of these things should be taken into account when selecting a check valve.

Check valve is a valve that its opening and closing part relies on the medium flow and force to move, precluding the back flow of the medium.As one of automatic valves, check valve mainly used for one-way flow of media on the pipeline, allowing the media to flow in one direction only.The fluid under pressure makes the valve flap open and flow from the inlet side to the outlet side. When the pressure on the inlet side is lower than the outlet side, the valve flap automatically closes under the action of fluid pressure an Check valve according to its structural characteristics can be divided into WAFER check valve, lift check valve, swing check valve, counter weight check valve, etc. WAFER check valve 1. Compared with swing check valve, the flow resistance is large,Wafer check valve is not suitable for the outlet of high pressure (Class900 and above) pumps and compressor; not suitable for pulsating media conditions;not suitable for oxygen conditions. 2. Because it’s Structure of WAFER,Wafer check valve is not suitable for large diameter (DN600 or more), high pressure (Class900 and above) occasions. 3. Wafer check valve should as far as possibleinstalledhorizontally. In case of vertical pipeline, make sure the media flowfrom top to below. Lift check valve 1. Subject by the working principle,lift check valve can only be installed in the horizontal pipeline. 2. Compared with the swing check valve,its flow resistance is large,lift check valve is not suitable for large diameter (DN50 and above) occasions, in general,it’s suitable for DN40 and smaller application. Swing check valve 1.  Swing check valve should as far as possible installed horizontally. In case of vertical pipeline, make sure the media flow from top to below. 2.  limited by the structure,swing check valve should not be used for DN40 and below on the pipeline. 3. For large diameter pipelines (e.g. DN400 and above), Tilting swing check valves are recommended. Counter weight check valve 1. Choose according to needs 2. Counter weight check valveis used inwhere serious water hammer may occur.

Commonly known as manual butterfly valve, butterfly valve with lever and butterfly valve with gearbox are both valves that require manual operation, but there are still differences between the two in use.   1. The lever of manual butterfly valve directly drives valve plate, switching quickly, but laborious; Gearbox butterfly valve drives valve plate by gearbox, switching slowly but effortless. Therefore, when the pressure inside the pipeline is large, it will be especially laborious to use the handle butterfly valve, and Dervos recommends you to choose the gearbox butterfly valve.   2. In engineering projects, the gearbox butterfly valves are preferred. Because in addition to saving labor, its sealing performance is also better than that of the handle butterfly valve, especially under the working conditions that require frequent switch, the gearbox butterfly valve will have a longer service life.   3. Handle butterfly valve is generally used more in small diameter (within DN200) because small diameter butterfly valve has less torque and can be opened and closed directly by hand, while gearbox butterfly valve uses gear box to drive the stem, which is more labor-saving.   When the torque of the valve stem is greater than 300N-M, use the gear box drive, otherwise, the handle drive.

Butterfly valves are suitable for regulating and intercepting the flow of medium in the pipelines of various corrosive and non-corrosive fluid media in the engineering systems of furnace, gas, natural gas, liquefied petroleum gas, city gas, hot and cold air, chemical smelting and power generation and environmental protection.   Butterfly valve is suitable for flow regulation. Since the pressure loss of butterfly valve in the pipeline is relatively large, about three times that of the gate valve, therefore, when selecting the butterfly valve, full consideration should be given to the pipeline system affected by the pressure loss, and the sturdiness of the butterfly plate to withstand the pressure of the pipeline medium when it is closed should also be considered. In addition, it is also necessary to consider the limits of the working temperature of the resilient valve seat material under high temperature.   When its under special working conditions such as throttling adjustment, or requiring strict sealing, or severe wear, or low temperature (cryogenic), it is necessary to use specially designed metal sealed triple or double eccentric butterfly valves with regulating devices.   Concentric butterfly valves are suitable for pipelines that require complete sealing, zero leakage in gas test, high life expectancy and working temperature from -10 to 150℃ for fresh water, sewage, seawater, salt water, steam, natural gas, food, medicine, oil and various acid and alkali and others   Soft seal eccentric butterfly valves are suitable for bi-directional opening and closing and adjustment of pipeline for ventilation and dust removal. Soft seal eccentric butterfly valves are widely used in metallurgy, light industry, electric power, petrochemical system of gas pipeline and waterway, etc.   Metal-to-metal line sealed double eccentric butterfly valves are suitable for urban heating, steam supply, water supply and gas, oil, acid and alkali pipelines, as a regulating and intercepting device.

Triple eccentric hard seal butterfly valve has played a very important role in the petrochemical industry. The triple eccentric hard seal butterfly valve can accurately break off the working condition when the system fails, greatly preventing worse consequences. Secondly, the triple eccentric hard seal butterfly valve is also very easy to operate, and it can also enjoys a strong stability.   The triple eccentric hard seal butterfly valve is designed with the principle of three-dimensional eccentricity, which idealizes the spatial movement trajectory of the sealing surface. And the sealing surfaces are free from friction and interference with each other. Coupled with the proper choice of sealing materials, its sealing performance, corrosion resistance, high temperature resistance and wear resistance of the butterfly valve are firmly guaranteed.   Its main features are as follows.   1、Small opening torque, flexible and convenient, labor-saving and energy-saving. 2、Triple eccentric plate makes the butterfly disc tighter and tighter the more it is closed. Its sealing performance is reliable. 3、Remarkable resistance for high pressure, corrosion and wear; longer service life, etc.

When we mention Cryogenic Valves, usually it refers to service temperature from -46 °C to -196 °C, and extended stem or extended bonnet. Here are the advantages of extended stem or bonnet:  1.The extended stem/bonnet can protect the stuffing box from low temperature and make sure low leakage here. 2.This design can also facilitate rapid replacement of main valve parts, where you don’t need to disassemble the valve body, all you need to do is just removing the cover to replace the parts. What could be the disadvantages of extended stem or bonnet?  First, it requires larger room for installation. Second, the stem or the bonnet will easily get bent or deformed due to moment by the actuator or the inappropriate calculation of its length.  Dervos is a leading industrial valve maker and trader in China, specializing in the production of cryogenic valves. In addition to those in rare conditions, we also produce other industrial pipeline valves, such as trunnion-mounted ball valves, shut-off pig valves and so on. To learn more about our industry-leading products, contact us today.