Sometimes it is hard to choose between using a knife gate valve or a butterfly valve for certain applications. Both have their merits and both should be picked according to the media and how it will be used. Both are available in manual operation (hand wheel, gear box or lever) as well as withpneumatic or electric actuators Ask these questions before making the choice: l Is the media abrasive? l Will there be large suspended solids? l Is there likely to be solid material present in the line when closing? If the answer to any of the above question is yes, a knife gate valve is what you’re supposed to have. Typical applications for knife gate valves include; - Sewerage & Effluent - Vacuum Trucks - Fluid Transfer Trucks - Slurry - Grain Silos Xiamen Dervos is an API Certified check valve manufacturing and trading company that specializes in the production of various kinds of valve. In addition toKnife gate valve, we also produce other industrial pipeline valves, such as ball valves, globe valves, plug valves and butterfly valve. To learn more about our industry-leading products, contact us today.

WAFER check valve is a general one-way valve for fluid.Lightweight, small-sized, WAFER check valve iseasy to install between the flange. The interior of the valve consists of two semi-circular taut springs and plates that fixed to the valve body with a pin. Moving fluid make the spring deform and get through the valve. The valve closes when the spring lose fluid pressure. The spring deforms quickly, which keeps the pipeline from the damage of water hammer. Keep these in mind when install WAFER check valve 1. First, the priority among priorities, make sure the opening direction is in line with the the flow direction when you put your WAFER check valve in place. 2. Put them in vertical pipelines and, for horizontal pipelines, install check valves vertically. 3. Use a expanding tube between the WAFER check valve and the butterfly valve. Don’t connect them to other valves directly. 4. Keep pipe joints and blockagesaway from the operating radius of the valve plate. 5. Do not install a reducer in front of or perhaps behind the WAFER check valve. 6. When the WAFER check valve have to be installed near a elbow pipe, leave a large enough space. 7. If WAFER check valve is placed at the outlet of pump , allow space at least six times the diameter of the valve to ensure that the butterfly plate can be pushed by fluid. Xiamen Dervos is an API Certified check valve manufacturing and trading company that specializes in the production of various kinds of valve. In addition to WAFER check valve, we also produce other industrial pipeline valves, such as gate valves, ball valves, globe valves, plug valves and butterfly valve. To learn more about our industry-leading products, contact us today.

The butterfly plate of the wafer lug butterfly valve is installed at the cross section of the pipeline. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0°and 90°, and the valve is fully open when it rotates to 90°. Structure of lug type butterfly valve The lug type butterfly valve is connected between two pipeline flanges with double-headed bolts. Its structure is simple, small in size and light in weight, and consists of only a few parts. And it can be opened and closed quickly by just rotating 90°, which is easy to operate, while the valve has good fluid control characteristics. When the butterfly valve is in fully open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated through the valve is small, so it has good flow control characteristics. The double-offset butterfly valve has two types of seal, elastic seal and metal seal. For resilient seal valves, the seal can be set on the valve body or attached to the butterfly plate perimeter. Application of lug type butterfly valve Butterfly valve is not only widely used in general industries such as petroleum, gas, chemical, water treatment, etc., but also used in cooling water system of thermal power station. Used for gas pipeline in sulfuric acid industry: furnace front blower inlet and outlet, relay fan inlet and outlet, electric mist elimination tandem and coupling valve, S02 main blower inlet and outlet, converter regulation, preheater inlet and outlet, etc. to regulate and cut off gas volume use. It is used for sulfur burning, conversion, dry suction section in sulfur acid system, and is the preferred brand of valve for sulfur acid device, and is considered by the majority of users as a butterfly valve with good sealing performance, light operation, vice corrosion, high temperature resistance, easy operation, flexibility, safe and reliable use, and has been widely promoted and used. Lug type butterfly valve is also widely used in: chemical, petrochemical, smelting, pharmaceutical, food and other industries in SO2, steam, air, gas, ammonia, CO2 gas, oil, water, brine, lye, seawater, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid and other media in the pipeline as a regulating and intercepting device use. Structural features of lug type butterfly valve ①The unique design of three-way eccentric makes the sealing surface frictionless between the transmission, which prolongs the service life of the valve. ②Resilient seal generated by torque. ③The ingenious wedge design makes the valve have the automatic sealing function of tightening the more it is closed, with compensating and zero leakage between the sealing surfaces. ④Small volume, light weight, light operation and easy installation. ⑤Pneumatic and electric devices can be configured according to user requirements to meet the needs of r...

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.