Category Archives: Blog

28 Dec

How Ball Valves Work?


Valves play an important role in manufacturing various kinds of items we use or come across on a day-to-day basis.

From bicycles or automobiles, jet airplanes, or the oil you use for cooking—all are results of valves in some form or another. However, there are a range of valves. Each differs in not just its shape and dimensions, but also its function and application.

In this post, we look at how ball valves work, its different types, and some reasons why it should be used.

What Are Ball Valves?

These are valves that make use of a ball to navigate the movement of substances from one seating surface to another. The function of the ball is similar to a track ball found in old computer mice.

However, the ball in the valve consists of a port, which changes alignment in response to the position of the valve. For instance, when the ball valve is set to open, the port changes the direction according to the flow of the substance. When the valve is closed, however, the port adopts a perpendicular direction and acts as a seal to block the flow of substances.

Ball valves vary in the degree to which the port can change directions. In most cases, the ball valve will adopt a 90 degree rotation. However, in other cases, a 360 degree rotation is more beneficial.

What Are The Different Types Of Ball Valves?

There are also different types of ball valves. Some of these include:

  • Floating Ball Valve
  • V Port Ball Valve
  • Trunnion Mounted Ball Valve
  • Multiport Ball Valve
  • Full Port Ball Valve

The ports are made from a number of materials and metals including titanium, CPVC, chrome, brass, bronze, and stainless steel.

Why Are Ball Valves Useful?

Since valves have considerable application for the distribution of liquids and gases, ball valves offer significant convenience of requiring low maintenance and lack of leakages.

They are also useful for utilization across a wide range of industries, markets, and applications. Some of the most common areas where ball valves are used include manufacturing, oil and gas, and chemical storage industries. Before purchasing ball valves for industrial or residential use, it is recommended to evaluate the conditions so that ball valves do not suffer from corrosion.

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23 Dec

Temperature Considerations for Pressure Relief Valve Application

The process of selecting or evaluating correct set pressure for pressure relief valve application is relatively straightforward – the set pressure of the pressure relief valve is compared to the pressure vessel maximum allowable working pressure (MAWP). The correct set pressure can be determined by using ASME Code rules and the general principle that at least one valve must be set at or below the MAWP.
The Code does not thoroughly explain temperature considerations, and application concerns related to temperature are just as important as proper selection of the correct set pressure. The purpose of this article is to examine some of these concerns when applying pressure relief valves in pressure vessel service.
One concern is selecting correct material for pressure relief valve construction. For pressure vessels, service temperature is considered part of the vessel design conditions, and the maximum temperature is used to select allowable stress limits for the chosen vessel material. Design temperature is recorded on the pressure vessel’s data report and nameplate (Section VIII, UG-119). Additionally, minimum design metal temperature (MDMT) is also considered in material selection and marked on the nameplate.
Pressure relief valve stamping rules do not require temperature marking on the nameplate; therefore, the valve manufacturer’s literature must be consulted to determine appropriate temperature limits for valve design. The valve must be applied using this data since it represents the mechanical limits of the design. When low temperatures may be encountered, materials appropriate for this application must be selected. Particular attention is called out for application of carbon and low alloy steels when used below -20° F. Impact testing of valve body materials may be required, and alternative materials with better impact resistance characteristics are often selected for low-temperature applications.
Once proper material for a valve is identified, temperature effects on valve operation and capacity must also be considered.
Valves are required to be tested with test fluid similar to the application fluid [UG-136(d)(4)]. Steam valves are tested with saturated steam by the manufacturer; if they are used in saturated steam service, performance inservice should be very similar to how the valve was set.
Valves for gas applications are set using ambient temperature air. Liquid service valves are set using water. The Code makes provisions for use of a cold set pressure which compensates for the difference between test medium temperature during the manufacturer’s original test and the valve’s actual temperature encountered inservice. Temperature of the system fluid, and possibly ambient operating temperature, should both be considered in application of the cold set pressure.
Cold set pressure is typically within several percentage points of the specified valve set pressure. For example, a Dresser 1900 series valve specified for 400° F service will have a multiplier of 1.013 applied to the required set pressure to achieve the desired set pressure inservice. (Reference: Dresser maintenance manual 1900-MM, dated 2009.) For most designs in elevated temperature applications, set pressure on the test stand will be higher than the set pressure inservice. This is because of thermal expansion of the valve’s bonnet (where the spring is located), and relaxation of the spring when it is heated above ambient temperature.
Both final set pressure (set pressure desired inservice), and cold set pressure are listed on the valve nameplate. Cold set pressure is listed as CDTP (Cold Differential Test Pressure). CDTP also includes a differential value to compensate for the effect of back pressure on a conventional type design (no bellows), with the back pressure compensation first considered.
Example using the aforementioned Dresser 1900 series valve:
A valve is required to open at 500 psig inservice where the service temperature is 400° F, and back pressure = 25 psig.
Differential set pressure = 500 psig – 25 psig = 475 psig
Temperature multiplier: 1.013
Cold differential test pressure = 475 psig x 1.013 = 481 psig
This valve would have a stamped set pressure of 500 psig and a CDTP of 481 psig. Back pressure of 25 psig would also be marked. Once the valve is inservice with specified back pressure applied at service temperature of 400° F, it should open at the desired set pressure of 500 psig.
When inservice inspections are performed, stamped set pressure value is compared to the vessel’s MAWP to determine whether set pressure was correctly specified. However, when this valve is tested on a test stand to verify inservice condition, measured set pressure should be compared to the CDTP to evaluate performance.
Interestingly, cold set pressure is usually not specified for valves inservice where temperatures are below ambient. The maintenance manual referenced above did not include a multiplier value for cold temperatures. Another manufacturer of valves for cryogenic services reported it did not use a cold set factor for valves in low temperatures. The reason: the pressure relief valve is normally installed in a location where the valve body is at ambient conditions, and the valves are not normally insulated. Therefore, the valve will operate at a temperature not much different than ambient.
Valves used in superheated steam service will also require a temperature correction, even though tested with saturated steam. Superheated steam is steam with energy added so the temperature is above saturation temperature for the given pressure. Under those conditions, a temperature correction is also applied to test set pressure, based upon the difference between saturated steam temperature and the superheat steam temperature. Manufacturer’s literature should always be consulted to determine the proper use of correction factors.
Valve capacity is also affected by temperature. Valve capacity markings are reported in standard units of pounds per hour of steam, standard cubic feet per minute of air at 60° F, or gallons per minute of water at 70° F. Service fluid temperature may often be different from standard conditions for capacity marked on the nameplate. A conversion from capacity on the valve nameplate to service fluid must be performed to determine whether valve capacity is correctly sized at service temperature conditions.
This calculation can be done using the guidance of ASME Code Section VIII, Appendix 11. Paragraph UG-125(a)(2) of ASME Code Section VIII indicates it is the pressure vessel user’s responsibility to select required pressure relief devices for a pressure vessel prior to initial service. Calculations used to select the pressure relief device should reflect sufficient capacity. When necessary, these calculations must be made available to the inspection organization.
Pressure relief valves are provided for the purpose of plant and personnel safety, and consideration of temperature effects on valve set pressure and capacity are some important aspects to be reviewed during selection and inservice inspection of pressure relief valves for pressure vessel applications.
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19 Dec

Needle Valves- How Are They Different From Flow Control


Needle valves are fittings which are designed with a slender and tapered point at the end of its valve stem. This is the valve’s stem which is actually lowered right through the seat, to block or restrict the flow.

Needle valves are used to ensure that the fluid passes through the valve, and actually turns 90 degrees before it passes through an orifice which serves as the seat. This seat comes with a rod having a cone shaped tip. The valves are actually used to regulate the actual flow of liquids as well as gases, at rates which are set at a low flow.

The fine threading design of the needle valve stem, along with its large seat area, ensures that precise resistance will follow. These valves are used to control and check the flow of liquid and gases into the delicate gauges of the system, which are at a high risk of suffering damage if subjected to extreme pressure.

These valves are also utilized in industrial equipment, where the flow needs to be brought to a final halt. They are also utilized where a precise adjustment of the flow is considered essential, or wherever a small and controlled flow is needed. These valves can easily be used as both on and off valves, along with the use in a system for throttling service.

Difference Between A Flow Control And Needle Valve

Both of these fittings are used to control and reduce the flow of air in the leg of a pneumatic circuit. This results in slowing down the actuator speed. While the basic function of both the fittings is flow restriction, the main difference is that the needle valve controls the flow of liquid or gas in both directions, while the flow control valve only ensures control in one direction only.

The needle valve is bi directional, while the flow control is one directional only. In both the fittings, there is a finely threaded stem, which allows the gradual adjustment of the quantity of controlled flow, which passes through the valve. This controlled flow enters the input port and travels through the orifice, which is actually sized by the tapered stem, and out through the output port.

The flow control fitting actually features a simple by pass feature, which is then allowed to ensure a rapid and free flow, out from the output port of the fitting, by means of the input port.

Two types of flow control fittings are used for the purpose of selection and placement, within a carefully designed electric circuit and which in turn greatly affects the overall functions of an actuator.

A meter out valve is a very common type of flow control fitting, which is used to control the actual exhaust flow being emitted by an actuator. While a meter in flow is a fitting which is used to restrict the overall flow of actuator. It is also termed as reverse flow control.

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06 Dec

What Is A Plug Valve And When Is It Used?


We’ve previously discussed how to select specific valves for improving production time and MTBF and thought it would be a good time to review one of the most simple and economical valves available: the plug valve.

Plug Valve Basics

 A plug valve is shaped like a cylinder or cone and can be rotated inside the valve body to control flow of fluids. Plug valves have one or more hollow passageways often placed horizontally to allow ease of flow through the valve when open. The most common type of plug valve is the 2 port model with an open and closed position. The two ports are usually located on opposite sides of the valve with one passageway leading from inbound to outbound and the stem and handle located on the top. A plug valve also uses a quarter turn valve, which is useful where quick and frequent operation is essential. The valve ends can be flanged, hub type, or butt weld.

Plug Valve Types and Their Uses

 Although there are many types of plug valves, there are four general categories, each with their own benefits.

1. Lubricated Plug Valve

 As the name suggests, a lubricated valve uses a lubricant usually made up of a base oil and viscosity improver (like amorphous or fumed silica) that is injected under pressure between the plug face and body seat to reduce friction and seal ports. Valve manufacturers generally recommend lubricant suitable for the process fluid, and the valves often must be resealed after only a few cycles, and in some cases, after every cycle. Considered a high maintenance plug valve, they are often used in applications that have infrequent operations. Lubricated plug valves perform well in processes that utilize fluids which carry mildly abrasive particles such as dirty upstream applications, gas pipeline systems that need bypass valves, and as blow-down valves on valve stations and kicker valves.

2. Non-Lubricated Plug Valve

This plug valve utilizes a tapered or cone-shape that acts as a wedge and presses a polymeric sleeve against the body cavity. The use of the sleeve reduces friction between the plug mechanism and body.  Non-lubricated plug valves are often used instead of lubricated ones in applications where maintenance needs to be kept to a minimum, such special services in sulphur, hydrogen fluoride, or where liquids could be trapped or solidify and potentially jam the valve. However, non-lubricated plug valves are limited by temperature and chemical compatibility of the non-metallic materials they are made of.

The three main types of non-lubricated plug valves are:

Lift-type plug valve

Elastomer sleeved plug valve

Fully lined plug valve

3. Eccentric Plug Valve

The design of this plug valve uses a half plug that is advantageous for applications needing a higher seating force with minimal friction from open to closed position. The torque seated valves also feature improved shut off capabilities. Eccentric plug valves are used for a wide range of flow control and isolation applications including clean and dirty water, sewage, sludge and slurries, air, and other services.

4. Expanding Plug Valve

 This complex plug valve uses multiple components that allow the valve to mechanically expand and give it a true double block and bleed function in one valve. The plug valve uses a mechanism that rotates between the open and closed position and protects both seals from the flow path. During rotation there is no contact between body and seals, and slips expand onto the body seat when the valve is closed to avoid causing any wear or abrasion to the seals. They are often used to prevent product contamination in applications that do not require a double isolation.

In conclusion, plug valves have a number of useful applications, and new technology and designs are sure to give them an even wider variety of applications within many processes. And if you need more information on different types of valves, check out this piece on check valves or the rest of the site.


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02 Dec


Various types of pipe fittings are available in plumbing systems for different purposes and functions. A pipe fitting is used in plumbing system to join multiple pipes of same size or different sizes, to regulate the flow or to measure the flow. They are made up of different materials like copper, iron, brass, PVC etc.


Types of Pipe Fittings in Plumbing System

Different pipe fittings and their functions are explained below.

  • Elbow
  • Reducer
  • Tee type
  • Cross type
  • Coupling
  • Unions
  • Adaptors
  • Olet
  • Plug
  • Cap
  • Valve


Elbow Pipe Fittings

Elbows are used to change the direction of flow between two pipes. Elbows are generally available with an angle of 22.5o, 45o and 90o. If pipes are of same diameter then normal elbows are used otherwise Reducer elbows are used. Elbows are made of different materials. These are generally coming with female threads and we can fix them by butt or socket welding also.



Reducer Pipe Fittings

Reducer is a pipe fitting component which reduces the flow size from larger to smaller by reducing size of pipe. Usually there are two types of reducers are available. One is concentric reducer which is like cone shaped with gradual decreasing around the pipe but in this case accumulation of air may possible and it results in cavitation. Other one is eccentric reducer which is having one edge parallel to connecting pipe due to which air accumulation is not possible.



Tee type Pipe Fitting

Tee type fitting is a component of plumbing system which is in T-shape. It is having one inlet and two outlets, outlets are arranged at 90o to the main line connection (inlet). It can also be used to combine the flow from two inlets to one outlet. They are also available in different materials and different sizes. If the 3 sides of T-fitting are similar in size then it is called as Equal tee otherwise it is called as Unequal tee.



Cross type

Cross type fittings contains 4 opening in 4 directions. These are connected when there are 4 pipes are meeting at a point. These fittings generate more amount of stress on pipe as the temperature changes, because they are located at the center of four connection points. Cross fittings are generally used for fire sprinkler systems.



A coupling is used to connect the pipes of same diameter. Coupling are also useful if the pipe is broken or leakage occurs. Generally there are two types of couplings are available. Compression coupling and slip coupling. Compression coupling is regular coupling which is connected between two pipes and it prevents leakage by the arrangement of gaskets or rubber seals on both sides, otherwise glue is provided. Slip coupling is easier to install and it contains two pipes which are arranged as one into other, inner pipe can slide up to some length. So, we can fix long length damaged pipe by slip coupling.




Union is a type of fitting, which functions as similar to coupling. But coupling cannot be removed after fixing but in this case we can remove the union whenever we needed. Unions consists nut, male and female ended threads. So, this is also useful for maintaining purpose of pipe.




If the pipes are not having special ends or plain ends then adaptors make them threaded either male or female whichever is needed. Adopters are generally used for copper and PVC pipes. Male adapters contain male threads and female adapters contains female threads. One end of adapter is plain which is glued or welded or soldered to the plain pipe end.




Olets are used when there is standard sizes of fittings are not suitable for our requirement. Sometimes the inlet pipe size is larger compared to outlet pipes in t-sections then also Olets are used. There are many types of olets are available. Some important types of olets are:

  • Butt-Weld Olet
  • Socket weld Olet
  • Threaded olet
  • Elbow olet
  • Nipple olet
  • Lateral olet
  • Sweep olet
  • Flanged olet

Olet Pipe Fittings



Plug is a component of plumbing component which is generally used to close pipe opening during inspections and repairs. Plug are generally contains male threads.

Plug for Pipes



Cap is a type of pipe fitting which function is same as plug but the only difference is plug contain male threads and cap contain female threads which is screws on the male thread of pipe. These are available in different materials like rubber, copper, steel, plastic etc.

Pipe Cap


Valves in Pipe Fittings

Valves are components of plumbing system which are used to stop or regulate flow of fluid in its path. Different types of valves are available depending up on their applications.

Valves in Pipe Fittings

Some important types of valves and its applications are listed below.

  • Gate valve, plug valve and Ball valve – used for isolation only
  • Globe valve – used for throttling
  • Check valve – used for preventing reverse flow (non-return)
  • Butterfly valve – used for isolation as well as throttling
  • Diaphragm valve – used for isolation as well as throttling


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29 Nov

Installation Guidelines for a Check Valve

installation-guidelines-for-a-check-valve   Check valves are simple devices that allow fluid media (gas, liquid or solids such as sand or slurry) to flow only one way. Typical check valve installations are found in industrial plants, automobiles, plumbing and ventilation systems. Usually, check valve are relatively inexpensive, compared to more accurate control valves. For a given application, the valve body must be able to contain the media and pressure, and the gate action must have a durable service life. Installing check valves is a matter of determining the correct flow direction for the media and ensuring proper fittings for the inlet and outlet port.

Installing the correct check valve for a particular process means knowing the media the valve will control. Caustic or abrasive media (lime slurries, acids, cement mixes, etc.) require a check valve resistant to severe corrosion; stainless steel or ceramic check valves work well for such applications. A check valve installed to control hot water flow in a plumbing installation can be made from PVC plastic, brass or steel. As long as the valve can handle the heat and pressure of a standard water line, it will work well.

Installing a check valve is similar in procedure to installing any other valve with one important distinction: direction. The valve must be installed in the media’s flow direction–nothing can move against a closed check valve gate. Check valve manufacturers include on the valve body an arrow indicating proper flow direction.

Incoming and outgoing lines can be connected using clamps, swage fittings (fittings using a collar around the line, with the fitting and the valve stem hydraulically compressed together) or threaded fittings.

Check valves work automatically to eliminate back flow in a process line. There’s no need for manual operation–the valve can be installed in relatively inaccessible locations. Although other valve installations may require clearance for actuators, access to a manual valve shut off or other features, check valves require little maintenance.

If installed as a diversion valve to relieve excess pressure or heat, the check valve gate can be adjusted to respond to specific pressure settings. For example, a check valve can prevent a steam boiler from building up too much pressure or a car’s radiator from rupturing when the coolant fails: the check valve will divert the high pressure media away from the process and avoid catastrophic failure. When pressure and heat amounts remain within operating limits, the check valve will stay closed.


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16 Nov

Things You Must Know Before Purchasing Precision Pipe Fitting Tubes


Precision pipe fittings, tubes, and adapters come in the vast range of products such as Hex Nipples, hex reducing nipple, adapter gasket, hex coupling, and much more. These are important partsof the industrial components, especially in the gas, power, fertilizer, and other industries.

It’s important for you to know the standard required before making the selection. These products should be made of very high quality raw materials to ensure the international quality.

Design features

These are the following design specifications to consider:

  • Fittings are properly packaged with exposed threads protected to ensure they are not damaged during delivery.
  • Working pressures calculated in accordance with Power Piping Code, Process Piping Code & Pressure Vessel Code.
  • Full form threads are machined to ensure leak-free & reliable systems.
  • Large choice of connections and configurations should be available.

How to select the right parameters

You need to ask right questions:

    • Can it bear the pressure?
    • Can it withstand the high temperature?
    • Are the joints and seals reliable?
    • Are the manufacturers reliable?

Choosing the right pipe fittings and adapters should be done with a lot of caution. Industrial applications are sensitive and compromise with the quality may result to untoward accident. Only those products should be selected that follow the Pressure Equipment Directive ofinternational standards

These are international standards for the design and fabrication of pressure equipment for piping, safety valves and other components and assemblies subject to pressure loading. Good companies such as Seal Excel follow such international standards.

Apart from that quality companies follows other international standards which ensure the safety of the equipment working in the potentially explosive material.

Certification ensures that the equipment or protective system is fit for its intended purpose and that adequate information is supplied with it to ensure that it can be used safely. There are four ATEX classifications to ensure that a specific piece of equipment or protective system is appropriate and can be safely used in a particular application.

Seal Excel instrumentation precision pipe and Tube fittings are completely heat code traceable. The company has a high standard of manufacturing process which completely follows the chemical and physical makeup. Our Instrumentation Pipe Fittings are manufactured under the international standard specifications and we strive hard to thoroughly clean the contamination during the process.

Summing up

Pipe Fitting Tubes are an important part of the industrial application and you need to be very careful while making the choice. Apart from the quality of the product, you also need to consider the brand and pricing before making the final decision.


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10 Nov

Tips for Choosing the Correct Pneumatic Fittings




Typically, you will find a range of varying pneumatic fittings easily in the market. However, the problem is that choosing an appropriate one is not simple. To take the right decision, you must be aware of the tubing to be utilized, the functional pressure of air, type of thread required for the receiving fitting, and lastly, the extent of vibration tolerable by the fitting.


Commonly Used Fittings

Outlined below are some of the common kinds of pneumatic fittings to help you choose the right one:


Quick Connect Couplings

Quick Connect Couplings are indispensable when it comes to connections that direct the flow of gas, water or air. Alternatively known as quick disconnect or quick release couplings, they offer a swift connection for transferring fluids. Usually operated manually, they serve as a great substitute for threaded and flanged connections.


Check Valves

In the simplest sense, check valves permit the flow in a single direction; hence, preventing reverse flow. Being a self-automated valve, they consistently work even if the manufacturing facility falls short of air, electricity or manual assistance. Not just manufacturing plants, check valves are found everywhere – even homes. In case you have a sump pump, it must have a check valve fitted over the discharge line. Check valves are utilized in every industry that makes use of pumps.


Hi-Duty Flareless Fittings

These fittings fall into the sub-category of compression fittings. However, they are particularly made applications that involve high pressure; usually more than 1000 PSI.


Push-Connect Fittings

Push-Connect Fittings use a similar mechanism as compression fittings. However, instead of using a metal-ferrule, these fittings utilize an O-ring (made using vulcanized rubber) that possesses the ability to get its actual shape let loose.

Consequently, this feature permits the fitting to get easily undone—just the way it was manufactured. Push-connect fittings have applications that involve lesser pressure. These fittings are extremely simple to connect, disconnect and then reconnect, ideal for applications that involve frequent alterations. Moreover, they can be utilized with brass, steel, copper, nylon, etc.

In addition to the above stated pneumatic fittings, there are a range of varying options, depending on the application. The more different the job requirements are, the more atypical the fittings will be.

Generally, compression fittings, push-connect fittings, specialty compression fittings can be easily bought and utilized for a broad array of applications. Find a comprehensive range of pneumatic fittings at SEALEXCEL.

Recognized as one of the finest pneumatic fittings manufacturers and suppliers, we additionally manufacture stainless steel push-in fittings, push-on fittings, monoflange valves, and more.


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03 Nov

What is a Plug Valve?


A plug valve is a simple type of valve that allows or blocks the flow of a liquid through a pipe. The plug itself is often shaped like an upside-down ice cream cone or a cylinder. A handle on top allows the user to turn the plug valve so it rotates and stops or starts the flow of liquid. A minimum of two holes, known as ports, must exist in the plug for liquid to flow. The ports are located on opposite sides of the plug, and when the plug is turned to the open position it creates a passage for the liquid to flow through.

This arrangement of two ports is known as a 2-port valve. The pipe in which the plug valve is installed has an area for liquid to flow in and another for liquid to flow out. When the 2-port plug valve is turned on, the ports line up with the holes in the pipe and the liquid flows straight through as if the plug valve was not there. Other, more complex plug valves known as 3-way valves allow liquid to flow to a combination of different ports. One port may connect to either of the opposite two ports, or all three may connect at once.

Two major categories of vales exist: stop valves and check valves. Stop valves follow a basic design structure to turn the flow of liquid on and off, or allow partial flow. Check valves, in contrast, allow liquid to travel only one way and often do not have a handle. Plug valves fall into the stop valve category.

Other stop valve types include gate valves and ball valves. Though similar to plug valves, the shape of the parts and how they work to stop the flow of liquid typically determines the specific group they belong to. Regardless of group, stop valves typically control liquid through the use of a handle.

Operation of a plug valve is simple, making it a common valve choice. The user twists the handle and the ports are moved away from the opening in the pipe. In certain valves, a full turn is not required. Quarter-turn valves, for example, only require the user to make a short, quarter turn to stop the flow of liquid. Often, plug valves can lessen the flow without turning off completely if the user turns the valve half-closed but leaves it open wide enough for some liquid to make it through the ports.

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27 Oct

How Does a Water Check Valve Work?


    Check Valves

  • Check valves are devices that are installed in pipelines in order to stop the backflow of material. In many cases, the material flowing through the pipe is water, and the check valve keeps the water from flowing backwards in the pipe. They do not require any outside activation, but are rather designed with mechanisms that block the water from reversing direction at a certain point.


  • Water check valves are used in several different devices, and they are advantageous for several reasons. For example, they stop flooding or overflowing in sump pumps and water heaters. They protect equipment in control valves, strainers and flowmeters. They also save power, because the backwards-flowing water would use up electricity even when the device was off.


  • There are several types of check valves that are installed in water-using devices, but they are all based on the same underlying principle. A ball check valve consists of a ball held in place by a spring. When the water flows forward, the spring contracts and the ball is pushed away from the opening of the valve. Therefore, the water can flow through the valve. When the water stops flowing, the spring pushes the ball back into the opening in the valve and stops the water from flowing backwards.Swing valves work in a similar way. Instead of a ball, swing valves contain a small door on hinges. When the water flows by the door, the door swings back on its hinges and allows the water through. When the water stops flowing, the door slams shut and stops any backflow from forming.Similarly, a split-disk check valve contains a metal plate that folds in half as the water flows past it. When the water stops flowing, the plate springs open and blocks the entrance of the valve.



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