Можно ли заменить кран маевского на шаровый кран: Как работает кран маевского. Альтернативные варианты замены. Видео: Установка крана Маевского

Установка крана маевского на батарею. Какие бывают ключи Маевского. Описание принципа работы и схема крана Маевского

Одной из распространенных причин нарушения работы отопительной системы является скопление воздуха. Образование пробки не позволяет воде свободно циркулировать. В результате радиатор со скопившимся воздухом не выполняет своей функции, снижается эффективность работы всей системы. Более восьмидесяти лет назад был изобретен кран Маевского, позволяющий легко и удобно «развоздушить» отопительную коммуникацию. Несмотря на свою простоту, это устройство является эффективным и надежным, потому используется в системах и сейчас. Рассмотрим подробнее его устройство и принципы работы.

Устройство крана Маевского и принцип его работы

Краном Маевского это сантехническое устройство называют только в народной среде. В государственных стандартах оно относится к категории запорных кранов, называется игольчатым радиаторным воздушным клапаном.

Сейчас промышленность предлагает несколько конструкций крана Маевского. Это позволяет выбрать наиболее удобный вариант с учетом места его установки. Классическая конструкция представляет собой устройство из двух деталей:

• винта конической формы;
• корпуса.

Элементы плотно прилегают друг к другу благодаря калибровке, поэтому в закрытом состоянии кран надежно удерживает теплоноситель. Отверстие для стравливания воздуха располагается в боковой части корпуса.

Изготавливаются краны Маевского чаще всего из латуни . Этот сплав обладает высокой степенью устойчивости к коррозии, что гарантирует долгий срок службы. В зависимости от разновидности конструкции, кран Маевского может открываться специальным ключом ICMA, отверткой или рукой.

В вертикальной отопительной системе, состоящей из нижнего трубопровода подачи воды и верхней нити отвода теплоносителя, такими элементами оснащаются все приборы, находящиеся на верхнем этаже. Краны Маевского подбираются по диаметру и вкручиваются в верхние футорки радиаторов. В горизонтальной отопительной системе эти устройства устанавливаются на каждой батарее. Для полотенцесушителя бокового подключения в ванной используется тройник . Он монтируется в вертикальном положении, отверстие крана должно быть направлено от стены. Установка кранов Маевского на радиаторы, конвекторы необходима, если в отопительной системе имеются участки, расположенные ниже, чем верхняя ось подключения прибора. В таком положении естественное удаление воздуха невозможно.

Обязательное развоздушивание проводится сразу после монтажа системы отопления, так как в начале работы в радиаторах пробки скапливаются в любом случае. Требуется проводить такую работу при включении системы после лета. Впоследствии локальные проблемы могут возникать из-за подсасывания в систему воздуха, что происходит во время ее работы, наличия в теплоносителе воздушных пузырьков. Причиной скапливания воздуха является и выделение водорода в процессе коррозии металлических частей коммуникации. Алюминиевые радиаторы без специфического покрытия внутренней поверхности постоянно выделяют этот элемент в теплоноситель, вступая с ним в химическую реакцию.

Перед проведением работы нужно:

Ручной кран Маевского обычно не используется в крупных магистралях, где скапливание воздушных пробок происходит постоянно. Для таких систем используются другие газоотводящие конструкции.

Ручной кран Маевского прост в эксплуатации , сложностей с ним не возникает даже у тех, кто никогда не занимался обслуживанием отопительных систем. Но в местах, где завоздушивание системы происходит регулярно, целесообразно установить автоматический воздухоотводчик. Такая проблема может случиться, если монтаж труб отопления был проведен с нарушениями.Кран с автоматической функцией удаления воздуха исключает необходимость вручную регулярно выполнять эту работу. Удобным такой вариант является для установки в труднодоступных местах.

Конструкции автоматических воздухоотводчиков могут быть различными, но принцип действия у них одинаковый. В корпусе имеется полое отделение с поплавком из пластмассы. Он при помощи флажка надавливает на шток с пружиной , доступ к атмосфере открывается, воздух выходит. Когда полость заполняется теплоносителем, поплавок надавливает на шток, закрывая отверстие, предотвращая выход воды.

Для удобства проведения ремонта в случае неисправности или замены изношенного крана, устройство оснащается отсекающим клапаном. Он вкручивается в отопительную систему, затем накручивается воздухоотводчик. Кран нажимает на флажок в клапане, исключая утечку теплоносителя. Автоматические воздухоотводчики в магазинах представлены в большом ассортименте. Они могут быть специальными, радиаторными, прямыми, угловыми. Поэтому подобрать такой элемент можно для любой отопительной системы.

Установка крана Маевского и уход за ним

Установка крана Маевского не требует опыта или высокой квалификации. Нужно только правильно подобрать устройство по размеру. Эти сантехнические приспособления могут иметь резьбу 1 дюйм, ¾ дюйма, ½ дюйма. Кран располагается в верхней части радиатора, на стороне, противоположной входу теплоносителя. Перед проведением установок кранов воду из отопительной системы нужно слить. Затем в пробке радиатора выкручивается заглушка и на ее место монтируется кран. Эти устройства оснащаются уплотнительными кольцами из резины, но обмотку, при установке желательно использовать. Для подстраховочной герметизации на резьбу наматывается ФУМ-лента или льняное волокно.

В современных радиаторах в пробках предусмотрены отверстия для установки крана , что упрощает работу. Если в батарее установлена заглушка другого типа, без отверстия для воздухоотводчика, ее можно заменить. Кран нужно монтировать таким образом, чтобы отверстие находилось на стороне, противоположной от стены, было направлено немножко вниз. Это позволит при стравливании воздуха подставить емкость и аккуратно собрать воду. Выбор ручного или автоматического воздухоотводчика зависит от личных предпочтений и особенностей системы отопления.

В старых чугунных радиаторах, возможно, придется провести некоторые предварительные работы для установки крана Маевского. При этом нужно знать следующее :

• для установки в чугунном старом радиаторе крана Маевского нужно высверлить отверстие в верхней заглушке , нарезать резьбу, затем вкрутить воздухоотводчик;
• устанавливать автоматические краны Маевского на таких радиаторах в центральной отопительной системе не рекомендуется. В таких коммуникациях теплоноситель бывает сильно загрязненным, поэтому воздухоотводчик придется часто очищать . Кроме того в домах порой отключается отопление и воздушные пробки создаются часто;
• в центральных системах отопления порой наблюдаются гидравлические удары , силой до 15 атмосфер. Поэтому требуются специальные автоматические воздухоотводчики OMEC или МС-140, которые способны выдерживать температуру до 150 градусов.

Кран Маевского отличается высокой надежностью , в течение многих лет исправно выполняет свою функцию. Но, если в теплоносителе имеются загрязнения, отверстие устройства может забиваться. В таком случае его требуется прочистить. Оно может находиться непосредственно в латунном корпусе или в специальной подкладке из пластмассы. В любом случае скопившиеся загрязнения легко удаляются обычной булавкой или иглой.

Низкая эффективность работы отопительной системы в большинстве случаев объясняется просто: батареи завоздушены. Небольшое количество воздуха попадает в систему, накапливается в отдельных ее элементах и препятствует нормальной циркуляции теплоносителя. Решить радиаторов н

90000 Mitral valve problems — NHS 90001 90002 90003 The mitral valve is a small flap in the heart that stops blood flowing the wrong way. Problems with it can affect how blood flows around the body. 90004 90005 90002 The main problems that affect the mitral valve are: 90005 90008 90009 mitral valve prolapse — the valve becomes too floppy 90010 90009 mitral regurgitation — the valve leaks and blood flows the wrong way 90010 90009 mitral stenosis — the valve does not open as wide as it should 90010 90015 90002 These conditions can be serious, but they’re often treatable.90005 90002 In some cases, mitral valve surgery may be needed. 90005 90020 Mitral valve prolapse 90021 90002 Mitral valve prolapse is where the mitral valve is too floppy and does not close tightly. 90005 90024 Symptoms 90025 90002 Many people with a mitral valve prolapse do not have symptoms and it may only be spotted during a heart scan (echocardiogram) carried out for another reason. 90005 90002 Mitral valve prolapse can sometimes cause: 90005 90024 Treatment 90025 90002 You probably will not need treatment if you do not have any symptoms.90005 90002 Your doctor may suggest: 90005 90008 90009 making lifestyle changes, such as giving up cigarettes, caffeine and alcohol — these things can cause your heart to become overworked 90010 90009 having regular check-ups to monitor your condition 90010 90015 90002 If you have symptoms or your mitral valve is very floppy, your doctor may recommend: 90005 90008 90009 medication to relieve your symptoms, such as beta blockers for an irregular heartbeat 90010 90009 mitral valve surgery to repair or replace the mitral valve 90010 90015 90024 Causes 90025 90002 Mitral valve prolapse is usually caused by problems with the tissues that join the mitral valve to the heart muscles.90005 90002 Some people with the condition are born with it, and it’s more common in people with connective tissue disorders, such as Marfan syndrome. 90005 90002 Rarely, it can be caused by damage to the heart muscles themselves — for example, as the result of a heart attack. 90005 90020 Mitral regurgitation 90021 90002 Mitral regurgitation is where some blood flows the wrong way in the heart because the mitral valve does not close properly.90005 90024 Symptoms 90025 90002 Mitral valve regurgitation does not always have symptoms. 90005 90002 Sometimes it can cause: 90005 90002 If not treated, it can lead to: 90005 90024 Treatment 90025 90002 You might not need treatment if you do not have any symptoms. Your doctor may just suggest having regular check-ups to monitor your condition. 90005 90002 If you have symptoms or the problem with your valve is severe, your doctor may recommend: 90005 90008 90009 medicines to relieve your symptoms — such as diuretics to reduce breathlessness and medicines for atrial fibrillation 90010 90009 open heart surgery — to repair or replace the mitral valve 90010 90009 keyhole surgery — a small clip is attached to the mitral valve to help it close; the clip is guided into the heart through a thin tube inserted into a vein in the groin 90010 90015 90024 Causes 90025 90002 Mitral regurgitation happens if the mitral valve can not close properly.90005 90002 This is usually caused by either: 90005 90008 90009 the mitral valve becoming too floppy (mitral valve prolapse) 90010 90009 the ring of muscle around the valve becoming too wide 90010 90015 90002 These problems often develop with age — for example, because of «wear and tear» over time or damage caused by untreated high blood pressure. 90005 90002 Mitral regurgitation can sometimes be caused by a problem such as: 90005 90020 Mitral stenosis 90021 90002 Mitral valve stenosis is where the mitral valve does not open as wide as it should, restricting the flow of blood through the heart.90005 90024 Symptoms 90025 90002 Mitral valve stenosis may not have any symptoms. 90005 90002 Sometimes it can cause: 90005 90002 If not treated, it can lead to: 90005 90024 Treatment 90025 90002 You might not need treatment if you do not have any symptoms. Your doctor may just suggest having regular check-ups to monitor your condition. 90005 90002 If you have symptoms or the problem with your valve is severe, your doctor may recommend: 90005 90008 90009 medicine to relieve your symptoms — such as medicines called diuretics to reduce breathlessness and medicines for atrial fibrillation 90010 90009 mitral valve surgery — to replace the valve or stretch it with a small balloon (balloon valvuloplasty) 90010 90015 90024 Causes 90025 90002 One of the main causes of mitral valve stenosis is rheumatic heart disease.90005 90002 This is where an infection causes the heart to become inflamed. Over time, it can cause the flaps of the mitral valve to become hard and thick. 90005 90002 Other causes include hard deposits that form around the valve with age or a problem with the heart from birth (congenital heart disease). 90005 90020 Mitral valve surgery 90021 90002 Mitral valve surgery may be recommended if you have symptoms caused by a problem with your mitral valve or if the problem is quite severe.90005 90002 The most common mitral valve procedures are: 90005 90008 90009 mitral valve repair 90010 90009 mitral valve replacement 90010 90009 balloon valvuloplasty — where the mitral valve is stretched with a small balloon 90010 90015 90024 Mitral valve repair 90025 90002 Mitral valve repair is an operation to make the flaps of the mitral valve stay closer together. This will help stop blood flowing the wrong way through the valve. 90005 90002 It’s mainly used to treat mitral valve prolapse or regurgitation, if the problem is severe and causing symptoms.90005 90002 The operation is carried out under general anaesthetic, where you’re asleep. 90005 90002 Your surgeon will usually get to your heart through a single cut along the middle of your chest, but smaller cuts between your ribs are sometimes used. 90005 90002 The flaps of the mitral valve are then partially sewn together. 90005 90002 Most people experience a significant improvement in their symptoms after surgery, but speak to your surgeon about the possible complications. 90005 90024 Mitral valve replacement 90025 90002 Mitral valve replacement is an operation to replace your mitral valve with a man-made valve (a mechanical valve) or a valve made from animal tissue (a bioprosthetic valve).90005 90002 This is usually only done if you have mitral stenosis or mitral prolapse or regurgitation and are unable to have a valve repair. 90005 90002 The operation is carried out under general anaesthetic, where you’re asleep. Your surgeon will usually replace the valve through a single cut along the middle of your chest. 90005 90002 Most people experience a significant improvement in their symptoms after surgery, but speak to your surgeon about the possible complications. The risk of serious problems is generally higher than with mitral valve repair.90005 90002 You’ll also need to take medication to prevent blood clots for a long time after this operation. If you have a man-made valve, you’ll need to take this medication for life. 90005 90024 Balloon valvuloplasty 90025 90002 Balloon valvuloplasty, also called percutaneous mitral commissurotomy, is a procedure that can be used to widen the mitral valve if you have mitral stenosis. 90005 90002 It’s usually done using local anaesthetic, where you remain awake but your skin is numbed. 90005 90002 A small cut is made in your groin or neck and a thin tube is passed along a blood vessel to your heart.90005 90002 The end of the catheter has a small balloon attached to it. This is inflated inside the narrowed valve to stretch it wider. The balloon is then deflated and removed along with the catheter. 90005 90002 This procedure is generally less effective than replacing the mitral valve, but recovery tends to be quicker and it may be a better option if your valve is not too narrow or you’re at an increased risk of surgery complications (for example, if you ‘re pregnant or frail). 90005 90002 Page last reviewed: 25 September 2017 90185 Next review due: 25 September 2020 90005 .90000 Learn about 6 Types of Ball Valve 90001 90002 A Ball valve is a quarter-turn rotary motion valve that uses a ball-shaped disk to stop or start the flow. It resembles a plug valve in many ways. When a port in the ball is in line, it allows flow whereas when you rotate the valve 90 degrees, solid part of the ball stop the flow. 90003 90002 Most ball valves are of the quick-acting type, which requires a 90 ° turn of the valve handle to operate the valve. But in case large size valve which required considerable force to open or close the valve, the gear-operated actuator is used.With this arrangement, a small handwheel is enough to operate a fairly large valve. 90003 90002 In this article, I have covered following types of Ball Valves that used in piping. 90003 90008 90009 Floating 90010 90009 Trunnion Mounted 90010 90009 3 Way 90010 90009 Top entry 90010 90009 Side entry or split body 90010 90009 Three-piece body 90010 90021 90002 Check this video for the better understanding on this topics. 90003 90024 Floating Ball Valve 90025 90002 In a floating ball valve, the ball is held in the position by the compression of the two elastomeric seats against the ball.The ball is free to float inside the valve body. See the highlighted portion in the image and remember as you will see the difference when I will explain to you about the trunnion mounted valve. 90003 90028 90002 The stem is connected to a slot at the top of the ball which allows the ball to rotate a quarter turn (90 degrees). The shaft allows for a certain amount of lateral movement of the ball that is generated from the upstream pressure acting on the ball. This small lateral movement, in fact, produces a load on the ball that presses it against the downstream seat which improves leak tightness of valve.This type of valve design is capable of bi-directional shut-off. The floating valve is very difficult to operate when upstream pressure is high. You can see the image of a floating type valve. 90003 90002 Check the video below to learn how this floating type valve works. 90003 90024 Trunnion Mounted Ball Valve 90025 90002 Trunnion mounted valve is a solution to the problem of excessive torque required by a floating type valve in high-pressure service. A short shaft like an extension which is known as a trunnion set in the body.You can see this in the image. In this design steam and ball work as a single unit. The ball is supported by two floating or spring-loaded seats that remain in constant contact with the ball. 90003 90037 90002 Image — TROUVAY & CAUVIN 90003 90002 Trunnion ball design required a lower operating torque. Hence, reduces the size of the actuator and overall costs of the valve. This cost difference becomes an important factor when the pressure class and valve size increases. Check the video below for an animation of this type of valve.90003 90002 Check this video to know how Trunnion Mounted Ball Valve works. 90003 90044 90024 3 Way Ball Valve 90025 90047 90002 Depending on your requirements, you can arrange the port of valve in the three-way. 90003 90050 90009 One inlet and two distribute 90010 90009 One inlet and one outlet with diverting a flow 90010 90009 Stright pass the fluid without No inlet 90010 90057 90002 Three patterns are available. Venturi port type, full port type, and reduced port type.The full-port ball valve has an inside diameter equal to the inside diameter of the pipe. This design allows pigging. In the venturi and reduced-port types, the port is generally one pipe size smaller than the line size. 90003 90002 The ball type disc can be a free float or fixed in the valve body. A free-floating valve is known as a floating type whereas a fixed type valve is known as a trunnion mounted valve. 90003 90002 Image — TROUVAY & CAUVIN 90003 90024 Types of Ball Valves based on Body Construction 90025 90002 Ball valves are manufactured in different body arrangements.Based on this valve can be classified in the following ways; 90003 90008 90009 Top entry 90010 90009 Side entry or split body 90010 90009 Three-piece body 90010 90021 90002 For Extremely high pressure and temperature services, the full welded body is also used. 90003 90078 Top-Entry Ball Valve 90079 90080 90002 Image — TROUVAY & CAUVIN 90003 90002 As you can see in the image above, removing bonnet cover of top entry valves, allows access to valve internals for assembly, disassembly, repair, or maintenance without removing the valve from the pipeline.90003 90078 Split-Body Ball Valve 90079 90002 In this design, a valve body is divided into two or three body parts. A ball, seat rings, stem, and other internals set inside the larger body part and held together with smaller parts by bolting. 90003 90002 For a split body, two pieces valve, refer floating ball valve image. Refer below image for split body three pieces type valve. 90003 90091 90002 Image — TROUVAY & CAUVIN 90003 90024 Ball Valve Parts 90025 90096 90002 Major components of the valve are the body, spherical ball, steam, and seats.It can be metal seated or soft seated. This valve may be unidirectional, bidirectional, or multidirectional, depending on the number of valve ports and the number of valve seats. Same as multiport plug valve. In the image below, you can see the 3-way ball valve. 90003 90024 Applications of the Valve 90025 90008 90009 It can be used in different types of fluid services as an on-off stop valve that provides bubble-tight shutoff. 90010 90009 It can be used in air, gaseous, and vapor services as well as hydrocarbon services.90010 90009 Metal seated valves can be used in high-pressure & temperature applications. 90010 90009 it is widely used with instrument tubing to connect instruments. 90010 90021 90078 Advantages 90079 90008 90009 It is quick to open and close type that provides bubble-tight reliable sealing in high-pressure temperature applications. 90010 90009 It is smaller and lighter than a gate valve of the same size and rating. 90010 90009 Several designs of ball valves offer the flexibility of selection so that you can choose the valve that suits your requirements.90010 90009 Easy to operate and Cost-effective maintenance. 90010 90021 90078 Disadvantages 90079 90008 90009 It can not be used in service that required throttling. 90010 90009 In slurry or other similar applications, the suspended particles can settle and become trapped in body cavities causing wear, leakage, or valve failure. 90010 90009 Due to rapid opening and closing, surge pressures may arise which could damage downstream equipment. 90010 90021 90002 90134 Click here to learn about Other Types of Valve 90135 90003 .90000 What is a Check Valve? Learn about Check Valves Types and Parts 90001 90002 What is a Check Valve? 90003 90004 The valve that used to prevent backflow in a piping system is known as a check valve. It is also known as a non-return valve or NRV. The pressure of the fluid passing through a pipeline opens the valve, while any reversal of flow will close the valve. 90005 90004 It allows full unobstructed flow and automatically shuts as pressure decreases. The exact operation will vary depending on the mechanism of the valve.90005 90002 Parts of Non-Return Valve 90003 90004 It is consists of body, cover, disk, hinge pin, and seat ring. In the image below you can see the parts of the valve. 90005 90012 90004 Image- TROUVAY & CAUVIN 90005 90002 Types of Valves 90003 90004 The type of disk will decide the type of valve. Most common types of Check valves are 90005 90019 90020 Swing Type. 90021 90020 Lift Type 90021 90020 Dual Plate Type 90021 90020 Stop Check Valve 90021 90028 90004 Let’s learn about each of them.90005 90002 Swing Check Valve 90003 90033 90004 Image — DOE Handbook 90005 90004 The disc in a swing type valve is unguided as it fully opens or closes. This Valve operates when there is flow in the line and get fully closed when there is no flow. Turbulence and pressure drop in the valve is very low. Disk and seat designs can be of metal to metal or metal to composite. 90005 90004 The angle between the seat and the vertical plane is known as the seating angle and varies from 0 to 45 degrees.Usually, the seat angles are in the range of 5 to 7 degrees. Larger seat angles reduce the disc travel, resulting in quick closing, thus minimizing the possibility of water hammer. A vertical seat has a 0-degree angle. 90005 90040 90004 The swing type valve allows full, unobstructed flow and automatically closes as pressure decreases. Usually installed in combination with gate valves because they provide relatively free flow combinations. 90005 90004 A basic swing type valve consists of a valve body, a bonnet, and a disk that is connected to a hinge.90005 90002 Tilting Disc Check Valve 90003 90047 90004 Image — DOE Handbook 90005 90004 The tilting disc type valve is designed to overcome some of the weaknesses of conventional swing type valves. The design of the tilting disk enables the valve to open fully and remain steady at lower flow rates and close quickly when the forwarding flow stop. 90005 90004 The dome-shaped disc floats in the flow and fluid flow on both the bottom and top of the disk surfaces. As the disk is spring-loaded, when forward flow pressure reduces, the spring force helps the valve to close fast.In the image above, you can see the flow from the valve. 90005 90004 Tilting Disc type Valve is available in wafer type and lug type design. 90005 90002 Ball Type and Plug Type Lift NRV 90003 90004 The seat design of a lift Check valve is similar to a Globe valve. A piston or a ball is usually used as a disk. 90005 90004 Lift Check valves are particularly suitable for high-pressure service where the velocity of flow is high. The disk is perfectly set on the seat with full contact.They are suitable for installation in horizontal or vertical pipelines with upward flow. 90005 90004 When the flow enters below the seat, a disk is raised from the seat by the pressure of the upward flow. When the flow stops or reverses, the backflow and gravity forced the disk downward to set on the seat. Commonly used in piping systems that used globe valves as a flow control valve. 90005 90064 90004 Here you can see the plug or piston type and ball type check valve. These valves provide superior leak-tight characteristics to those of swing check valves.90005 90004 Some design in plug type uses spring to retain the disk in a closed position. This will ensure that the valve allows fluid flow only when there is enough pressure in the flow direction. 90005 90004 A ball-type valve is very simple as it simply works on the principle of gravity. When there is enough pressure in the flow, it lifts the ball upward but when pressure reduced ball roll down and closed the opening. 90005 90002 Dual Plate / Dual Disc Check Valve 90003 90073 90004 A dual plate check valve is known as a butterfly check valve, Folding Disc Check Valves, double-disc, or splits disc check valve.As the name suggests, two halves of the disk move towards centreline with the forward flow and with reverse flow two halves open and rest on the seat to close the flow (Flapping action). 90005 90004 Use of Dual Plate Check Valve is popular in low-pressure liquid and gaseous services. Its lightweight and compact construction make it a preferable choice when space and convenience are important. 90005 90004 It is 80 to 90% lighter than the conventional full body check valve. Frequently used in systems that used butterfly valves.The cost of installation & maintenance is very low compared to other types. 90005 90002 Stop Check Valve 90003 90082 90004 Image- DOE Handbook 90005 90004 Stop Check Valve is a combination of a lift check valve and a globe valve. It can either be used as a check valve or as an isolation (stop) valve like a globe valve. These valves can be closed with the help of a stem that is not connected to the valve disc during normal operation and make it possible to use these valves as a regular NRV.90005 90004 However, when needed, the stem is used to holds the free-floating disc against the valve seat, just as a globe valve. These valves are available in tee, wye, and angle patterns. Swing type and piston lift type valves are commonly used as stop check valves. 90005 90002 Application of Check Valve (NRV) 90003 90004 Check valves (Non-return valve) are used in a piping system to prevent backflow. The discharge line of rotary equipment such as pump and compressor always fitted with a check valve to prevent backflow.90005 90002 Advantages & Disadvantages 90003 90004 Can you guess why I have not mentioned any advantages or disadvantages of the check valve? 90005 90004 The only function of a Non-return valve is to prevent backflow. There is no better alternative. Yes, you can choose the best NRV from the various available type that you have learned but you can not supplement the Non-return valve with another valve. 90005 90004 90100 Click here to learn about Other Types of Valve 90101 90005 .90000 What is a check valve? Read about the function 90001 90002 When choosing a check valve it is important to make a cost-benefit analysis of the specific system. Often focus is to reduce cost and at the same time obtain the lowest possible pressure loss, but when it comes to check valves a higher safety equals a higher pressure loss. So in order to make sure the check valve protects the system properly, each system has to be assessed individually, and factors such as the risk of water hammer, acceptable pressure loss, and the financial consequence of installing a check valve with a too high safety margin against water hammer have to be considered.Please go to How to choose the right check valve for more details. 90003 90002 There are various types of check valves available for water and wastewater applications. They work in different ways but serve the same purpose. AVK offers a wide range of swing check valves, ball check valves, tilted disc check valves, slanted seat check valves, nozzle check valves and silent check valves. Please go to SWING CHECK VALVES and BALL CHECK VALVES for more information. 90003 90006 What is water hammer? 90007 90002 In a pumped system, the water is forced from a lower level to a higher level by means of a pump.The fluid flows in one direction only when the pump is in operation. When the pump stops, the flow of fluid will reduce until it also stops. Because the overall pipeline will be rising, when the fluid stops, it will then return back down the pipe. To prevent this flow reversal entering into the pump, well or intake, a check valve is installed. 90003 90002 In many cases, the rate of fluid reversal is not a cause for concern and standard check valves will perform well. However, in pumped systems where fast flow reversal can occur, the selection of the correct check valve is crucial.90003 90002 If a pump stops and the forward flow reverses back down the line towards the pump before the check valve has fully closed, the flow will force the valve door to slam onto its seat. This scenario can almost instantaneously stop the reverse flow and it is this instantaneous stoppage which results in pipeline water hammer. This can produce loud hammer noises which is not the noise of the valve coming into its seated position but is the stretching of the pipe under these conditions. 90003 90002 The consequent pressure wave (surge) can cause considerable damage to the system including pipe cracks, bursts, cavitation and implosion due to vacuum pressures being formed.It is also important to note that these failures may not be due to one single, large surge pressure but by repeated surges which eventually cause fatigue failure of the system. 90003 90002 It is important to note that other factors are required to ensure a safe and trouble free system. The correct number, types and sizes of air valves, closing and opening times of isolation valves, flow control valves etc all require to be considered to protect the system from pressure surges. 90003 90002 To prevent the occurrence of check valve slam, the valve should close either very quickly to prevent the onset of reverse flow or very slowly once reverse flow has developed.For a check valve to close slowly, this requires additional ancillary equipment such as hydraulic dampers which act to cushion the valve door as it comes into its seated position. However, this slower closure does allow the fluid to pass through the check valve until it closes and consideration must be given to the upstream pump to ensure that it is suitable for reverse spin and flow. 90003 .