check valves. Check valve (flanged, wafer type) Flanged water check valve

The check valve is a protective fitting that is installed on the pipeline. The main task of the part is to prevent the reverse flow of the substance in the event that the pump is turned off or fails, the pipeline breaks. Simply put, the valve is a fuse that activates automatically.

What is the feature of the check valve?

An element such as a check valve protects pipelines, equipment and the pumps themselves during an emergency. At the same time, the valve is used to combine the activities of several pumps into one line. The main task of the valve in this case is to protect the devices from excessive pressure.

The mechanism of the device is simple. If there is no flow of the working medium, the flap is in the closed position under the influence of its own weight. If the working medium moves through the pipeline, then under its weight the seat opens. But as soon as the substance changes direction, the flap returns to its original position.

All check valves fall into two categories:

• check valves are made of steel and cast iron. The main areas of application are water supply and heat supply systems, water distribution and pumping stations. There are rotary, lifting, spring, coupling and reverse;
• check valves - the shutter is made in the form of a disk.

Return products are most often mounted on horizontal sections of pipelines.

Five advantages of safety valves:

• simplicity of structure - makes it possible to easily and quickly maintain and repair parts;
• small stroke - to completely block the passage, only 0.25 Dy is required;
• compact dimensions and low weight;
• additional regulatory functions;
• the possibility of functioning of the pipeline at high operating pressures and with solid pressure drops.

In the lift check valve, the shut-off element is the lift spool. Under the action of water pressure, the spool rises, passing the flow. When the pressure drops, the spool drops onto the seat, preventing the flow from flowing back. Such valves are installed only on horizontal sections of pipelines. A prerequisite is the vertical position of the valve axis.

Valves are divided into four groups according to the method of attachment:

• Butt Weld Attachment: The check valve is welded to the pipeline. It is used when working in aggressive environments.
• Flange mounting: the check valve is connected to the pipeline through sealed flanges.
• Coupling: The valve is attached to the pipeline through a threaded coupling. It is applied in systems of small diameter.
• Wafer fastening: the check valve does not have its own fastening unit. Clamped between pipeline flanges. It is applied on sites with restriction on dimensions.

Lift check valves with a protective mesh at the inlet and intended to be installed at the beginning of the suction pipeline are called foot valves.

Advantages of check valves:

• simplicity of design;
• reliable tightness;
• possibility of repair without dismantling the entire valve.

Disadvantages of check valves:

• high hydraulic resistance;
• the possibility of jamming the shutter in the guide part of the cover when using the valve in systems with a contaminated working environment;

Ball check valves

In a ball check valve, a ball element serves as a shutter. As a clamping element, a spring is used that presses the ball to the seat. Such valves are usually made for small diameter pipelines and are used as domestic plumbing fixtures. The check ball valve loses to the spring disc valve in dimensions.

Check valves, principle of operation:

In this design, the locking element is a spool - "slam". The axis of rotation of the "flap" is above the through hole. Under the action of pressure, the "clap" leans back and does not prevent the passage of water. When the pressure drops below the permissible value, the spool falls and slams the through passage. In check valves of large diameter, the spool hits the seat hard, which leads to a quick failure of the structure. During further operation, this provokes the occurrence of water hammer when the check valve is activated. Therefore, rotary check valves are divided into two groups: Simple - valves with a diameter of up to 400 mm. They are used in systems where impact phenomena cannot seriously affect the operation of the hydraulic system and the valve itself. Impactless - valves with devices that ensure a smooth and soft landing of the spool on the seat. The advantage of rotary valves is the ability to operate in large systems and low sensitivity to environmental pollution.

Flanged check valve Granlok RD30 is designed to protect pipelines from the reverse flow of the working medium. It is intended for the pipelines transporting technical hot, cold water, steam, neutral environments.

Installation

The rotary check valve can be installed both in horizontal and vertical position. Installation to the pipeline is carried out using flanges. The direction of medium flow must match the direction indicated on the valve. The valve is installed on a horizontal pipeline so that the axis of the disc is higher than the axis of the pipeline and is located in a horizontal plane. On a vertical pipeline, valves are installed with the inlet pipe down so that the axis of the disk is in a horizontal plane

Specifications

Flange connection according to DIN 2501 (DIN 2633 at PN 1.6 MPa) / EN1092-2.

It is possible to use Russian-made counter flanges in accordance with GOST 12820-80, 12821-80 for PN 1.6 MPa.

Specification

Overall dimensions and parameters

The PASADOR company offers to buy check valves of various modifications at attractive prices. We supply products to all regions of Russia.

Pipe fittings of this type are used to prevent the reverse movement of the working medium (water hammer or back pressure). Our range includes threaded, flanged and wafer products designed for industrial and domestic applications and designed for a long service life.

The advantages of check valves are:

• automatic operation without additional energy consumption;
• reliability;
• performance of functions both in normal and emergency operating conditions;
• no significant impact on the throughput of the pipeline.
• valve opening at a minimum pressure of 0.5 bar (gravity).
  

You can buy check valves from us for domestic and process water supply systems, heating, steam systems, oil and chemical industries, sewerage at affordable prices. Products can be used in pipelines for transportation of non-corrosive liquids and gases.

The catalog contains check valves with threaded, flanged and wafer mounting in a body made of cast iron, carbon and stainless steel, brass, bronze. Most models are designed for horizontal and vertical installation.

The design consists of a body and a shutter, the mechanism of which is a spool. In the absence of flow, this type of valve is in the closed state. Under the influence of a moving working medium, the shutter automatically opens and closes when it stops. The spool only opens in one direction, so no reverse flow is possible.

Types of check valves

We offer ball and straight check valves with various mounting options.

Conventional feed-through models are designed for horizontal mounting only. Ball check valves can be installed in a horizontal and vertical position, as they use a ball element as a shutter. These types of fittings are available with threaded and flange mounting.

Wafer type check valves are installed in flanged pipe breaks. They can be mounted in vertical and horizontal position. A flat disk is used as a shutter. Designs with double-leaf gates are equipped with damping elements to successfully resist water hammer.

The main task that the flanged check valve, installed on pipelines for various purposes, solves is to ensure the movement of the transported medium in one direction. The design features of the check valve, for installation of which a flange is used, allow such a device to automatically stop the movement of the transported medium at the moment when such movement begins to be performed in the wrong direction. Check valves of flange type are installed mainly on pipelines through which liquid media are pumped.

Features and applications of check valves

Check valves of various types (including flanged ones) are used to protect the pipeline from:

• the occurrence of reverse flows of the working environment in it;
• hydraulic shocks.

The reverse flow in pipelines, as is clear from its name, is the movement of the working medium in the opposite direction. This can happen, in particular, when the pump that provides the supply of the working medium and its movement is switched off. If for heating systems such a phenomenon as reverse flow is not particularly critical, then it cannot be allowed to occur in sewer and water systems, as well as in pipelines through which oil products and other media are transported. That is why the use of check valves in such pipeline systems is a mandatory requirement.

Another undesirable phenomenon, from the consequences of which pipeline systems are able to protect a flanged, wafer-type check or any other valve, is water hammer. It is characterized by the fact that a sharp pressure drop of the transported medium occurs in the pipeline, which leads to the formation of a shock wave passing along the entire length of the pipeline system.

Water hammer can eventually lead to the destruction of individual sections of the pipeline and the failure of the elements that are used to ensure its normal operation. With the help of check valves installed by means of flanges or in any other way, the system is divided into separate isolated sectors, which makes it possible to effectively protect it from the effects of water hammer.

Operating principle

The principle by which check valves work is quite simple, however, such devices are very effective and are able to provide reliable protection for parts of pipeline systems. Any check valve, regardless of the type, is made up of a body (steel or cast iron) and a locking element located in it. The locking mechanism works due to the pressure of a special spring, the rigidity of which can be adjusted.

The spring, which is equipped with non-return valves, ensures the opening of their locking elements only in one direction - in the direction of the correct movement of the transported medium. By exerting pressure on the locking element held by such a spring, the liquid or gas pumped through the pipeline opens it and begins to move in the required direction. As soon as the pressure of the working medium in the opening direction of the valve begins to fall, the locking element closes, preventing the liquid or gas from moving in the opposite direction.

Types and properties

The design of the shut-off elements of check valves, for the installation of which flanges are used, may be different. The choice of a flanged valve with a certain type of locking element depends on the tasks for which such a device is intended.

So, depending on the design of the locking element, there are:

• rotary valve;
• lift type check valve;
• non-return valve with ball locking element;
• double-leaf check valve;
• receiving check valve equipped with a grid.

The rotary check valve is a locking device, the main part of which is a steel slamming disk fixed on a spring-loaded axle. At the moment when such a check valve is open, the disk in its inner part is parallel to the movement of the working medium, and when it is closed, it is perpendicular. Flanged swing check valve has a simple structure and, accordingly, low cost. If we talk about the disadvantages of check valves of this type, the most significant of them is that their rotary mechanism slams the shut-off disk too much at the moment of closing, which eventually leads to wear of the seat. Rotary check valves, equipped with a special mechanism that ensures smooth closing of the locking disc, are deprived of such a disadvantage. However, these improved flanged rotary valves are more expensive, which somewhat limits their application.

In flange-type lifting check valves, a special spool is used as a shut-off element, which, under the pressure of the working flow, rises along the vertical axis, and when the pressure decreases, it falls to its seat, blocking the movement of the medium transported through the pipeline. It should be borne in mind that due to the peculiarities of their design, such valves can only be installed in a vertical position.

Ball check valves, as their name implies, use a spool made in the form of a ball as a shut-off element. Their large size does not allow them to be used as wafer locking devices.

The double-leaf check valve, which is produced mainly in a wafer design, involves the use of two slamming flaps in its design at the same time. Each of them is connected to a spring, which regulates the force of their resistance to the pressure of the working flow. Due to the small size of its shut-off elements - flaps, the wafer type butterfly valve is very compact in size.

Check valves, the design of which is additionally equipped with a strainer, are used for installation on pipeline systems for pumping oil, gas or water from underground sources. Such devices, the most popular model of which is 16Ch42R, simultaneously solve two important problems: their locking mechanism prevents liquid or gas from returning back to the source, and the mesh protects the pipeline from large debris entering it.

Model 16Ch42R, which body is made of steel or cast iron, is highly versatile and can be installed on pipelines or pumps used for pumping both liquid and gaseous media.

Flanged vs Wafer Check Valves: Differences

Check valves that use flanges for installation in piping systems can be one of the following types:

• flanged;
• interflange.

On flange-type devices, the flange on the supply part and the return flange are welded to the valve body and form an integral whole with it. Flanged check valves are mainly used to equip large-diameter pipes, with the help of which the transport of working media is carried out on an industrial scale.

There are virtually no fasteners in wafer type check valves. This type of installation, as mentioned above, is very often used for the installation of double-leaf check valves. In this case, the valve itself (in particular, a double-leaf wafer valve) is installed between two flanges fixed at the ends of the connected pipes. After its placement in special seats, which are equipped with sealing elements, the flanges are pulled together using threaded studs. Despite the apparent unreliability of such a connection, if it is done correctly, the wafer check valve is fixed with the same reliability as any other type of device.

Check valves can be installed on pipeline systems using not only flanges, but also couplings or welded joints. However, if we talk about pipelines of large diameter, such valves are installed on them only using flanges.

Advantages and disadvantages of flange type check valves

Since flange-type check valves are most often used to equip pipelines through which the working medium is transported with high intensity, the internal elements of such devices (in particular, the locking mechanism) experience significant shock loads during operation. In addition, the flange-type check valve, due to its significant dimensions, is itself the cause of water hammer. In the process of closing the valve flaps in the pipeline in which it is installed, the pressure inevitably increases, which leads to the formation of a water hammer.

In those pipeline systems in which water hammer is not able to have a significant impact on the performance of both individual elements and the system as a whole, check valves of a simple type are used. The diameter of the latter, as a rule, does not exceed 400 mm. In other cases, non-impact type check valves are used. Smooth and soft closing of the locking element in flanged shockless type valves can be provided by special weights or hydraulic dampers. Meanwhile, when choosing non-impact type check valves for equipping a pipeline system, it should be borne in mind that they can only be installed in horizontal sections.

Some of the most significant benefits of flanged check valves include:

• compact dimensions, which allows you to install such devices on almost any part of the pipeline system;
• the ability to work effectively even in those systems in which the working environment is characterized by severe pollution;
• the possibility of installation on pipelines with a large diameter.

Features of choice

The main parameters that you should pay attention to when choosing a check valve (including a flanged one) are:

• operating pressure at which such a device can operate;
• conditional diameter.

You can find out what operating pressure the check valve corresponds to by marking the device, in which this parameter is denoted by the letters RU. The numbers in the marking after such letters indicate the working pressure for which the device is intended. For example, the designation RU16 indicates that a flanged valve can operate at a pressure of 16 bar without being subject to excessive wear.

The nominal diameter, on which it depends on which pipeline a flange-type valve can be installed, is indicated by the letters DU. Accordingly, the numbers following these letters in the marking indicate the nominal diameter of the check valve in millimeters. When choosing a check valve for this parameter, keep in mind that such a product can only be mounted on pipeline elements that have the same dimensions. In other words, model DU80, for example, can only be installed on pipes or other elements of the pipeline system, the bore diameter of which corresponds to a value of 80 mm.

When installing flanged check valves, the following rules must be strictly observed.

• Installation must be carried out by specialists who have previously been trained and received permission to perform work of a similar plan.
• The part of the pipeline system where installation is performed is completely disconnected from the supply of the working medium.
• Before starting installation, you should make sure that the product being installed, according to its characteristics, fully corresponds to the climatic conditions in which it will be operated.
• If a wafer check valve is installed, then its flange part is first mounted, and only then it is fixed in it.
• Before supplying the process flow to the pipeline, check again that the non-return valve is securely installed and that all required connections have been made.

And in conclusion, a short video with a visual demonstration of the principle of operation of a rotary check valve.