Large pipelines intended for operation in difficult operating conditions must be protected from pressure drops and prevent the formation of reverse flows in them, etc.
If this is not done, the system may fail, which is not so easy to solve. The simplest and most effective tool for such tasks is rightfully considered to be a wafer or ball tool.
They all have differences in design, but have one goal - to protect the pipeline from negative influence reverse flows and everything connected with them.
Contents of the article
Features and purpose
As we noted above, the reverse, as well as their varieties, essentially perform similar, almost identical tasks.
They protect water supply or heating equipment from:
- reverse flows;
- water hammer.
Let's figure out what this reverse flow is. Reverse flow in pipes is an interesting phenomenon characterized by a change in the direction of flow in pipes.
Imagine, for example, a heating system in a private house. In heating, the heated medium must move through the pipes constantly, so that the water does not stagnate; small circulation pumps are installed.
The pump, by its operation, provokes movement by increasing pressure in the pipes. If you turn it off, a kind of vortex may form inside the pipeline for a short period. Confusion with pressures will cause water to flow in the opposite direction.
For heating systems such things are not particularly scary. But we are not limited to them. For sewerage, large water supply pipes, industrial systems transportation, etc. backflow is very undesirable. Therefore, such things are strictly regulated there, and all dangerous places are protected.
Second dangerous factor– water hammer. Water hammer is the name given to sudden changes in pressure in pipes, when a kind of shock wave is formed, passing along its entire length. When it encounters resistance, it has a destructive effect on problem areas. One water hammer is not a problem. Even a dozen will not have a serious negative effect.
The danger here is that water hammer is a periodic phenomenon, over time they will provoke destruction or severe wear of sections of the pipeline, which is desirable to avoid.
The steel check valve prevents such problems. It becomes a kind of bulkhead, airlock doors dividing the system into isolated sectors. Problems that appear in one sector remain in that sector.
Operating principle
The steel check valve operates thanks to its unique and very convenient design. This design is simple, but at the same time extremely effective.
Let's consider a standard steel sample, without going into the details of its individual varieties for now.
The basic steel receiving fitting consists of a body and a locking element. The body is made of steel or cast iron, with a certain diameter and properties.
There is a locking mechanism inside the housing. The mechanism, no matter whether it is ball, double-leaf or lifting, works due to the pressure of a special spring. The spring stiffness can be adjusted.
The spring works in one direction, that is, it allows the locking element to open when the flow in the pipes moves correctly.
If the water begins to move, it begins to put pressure on the shutter or shut-off element of the check valve. The spring will withstand the pressure until it exceeds the permissible limit, then the valve will begin to open.
A decrease in pressure signals that the water flow is weakening. The lower the pressure, the more the spring works. As soon as it falls below a certain point, the spring will close.
All the water that managed to pass through the bulkhead will remain in its place and flow further. The flow cannot be reversed, since the shut-off element in the valves opens only in one direction - in the direction of the given flow movement.
Types and properties
Let us draw your attention to the fact that the design of such equipment may differ depending on what tasks it faces and what specific type we are considering. - is not the same as a wafer butterfly valve, and both are different from what a grid foot valve is.
So, by type of construction The steel sample is divided into:
- Turning.
- Lifting.
- Double-leaf.
- Reception, with mesh.
In order to avoid such inconveniences, manufacturers came up with a rotating steel sample with a soft closing mechanism. It's a pleasure to work with him. The only negative is the cost.
The lifting sample uses a spool as a shut-off element. Lift valves are installed exclusively vertically. The spool, under the pressure of the flow, rises along its vertical axis and falls to its original place.
involves the use of a ball valve. It is characterized by large dimensions, therefore it cannot be used as a wafer unit. Otherwise it is a standard locking part.
A bileaflet valve is usually made up of two operating leaflets. They are both connected to an internal spring that regulates the resistance force of the sashes. The doors are miniature and take up almost no space, so products with them are very compact.
A foot valve with a filtration mesh is a type of fittings designed exclusively for pumps that extract something from the bowels of the earth. The mesh prevents large debris from getting inside the pipe, and the locking mechanism prevents the pumped out liquid from returning back. A striking example of such equipment is the 16ch42r model.
Model 16ch42r – check valve for large pumps. 16h42r fittings are produced mainly from steel or cast iron. The 16ch42r valve is good for its versatility. It shows itself effectively in the production of both water and oil and gas.
Connection types
This type differs in the method or location of connection.
Select valve:
- flanged;
- Wafer;
- welded coupling;
- coupling threaded.
The flanged model has flanges welded onto the ends of the body. It is specifically designed to solve problems in industrial areas or large-scale civil water supply systems.
The wafer valve is characterized by the absence of fastening elements as such. It looks like a short (up to 10 cm wide) piece of pipe with valves. It does not need to be welded or screwed, just place between flanges, or rather, seal them, and then tighten the flanges with long studs.
Contrary to popular belief, the wafer pattern holds up, provided it is installed correctly and well secured, no worse than its counterparts with a more traditional approach.
Coupling models are designed for installation on medium and small pipelines with DN25-D32. Quite rarely, coupling samples with DN50 or more are found. The welded coupling element is accordingly welded to the pipes, and the threaded element is oriented for installation by screwing union nuts onto a pre-prepared thread.
Wafer check valve and its subtypes (video)
Pressure and nominal diameter
In terms of characteristics, when choosing, pay attention to the nominal diameter and pressure.
Working pressure is marked with the abbreviation RU. For example, adding the entry RU16 in the name means that we have a fitting that can withstand a nominal pressure of 16 bar. It is assumed that at this pressure level it operates without any wastage or excessive wear.
The approximate diameter is indicated by the abbreviation DU. Accordingly, a valve with DN25 in the name will have a nominal diameter of approximately 25 mm, with DN32 - 32 mm, with DN100 - 100 mm, etc.
The remote control determines where we can use the fitting and for what purposes. The valve's remote control must necessarily correspond to the remote control of its adjacent parts. A check valve with DN80 can be connected to pipes and fittings only with DN80 and nothing else.
As a rule, small-sized models such as DU25 - DU50 are used for civil pipelines and are focused primarily on, and anything larger is industrial products.
As a rule, check valves can be divided into two categories, depending on the specific connection to the pipeline - flanged or wafer connection.
What is a flanged check valve
Eg, flanged check valve actively used in the water supply system, thereby preventing possible water hammer or reverse flow of water. This device does not belong to the group shut-off valves. According to own design features, this model can be of several types: spring, ball or lifting.
The presented device is used to pass various liquids exclusively in one specific direction, and a special flange connection is used as fastening.
In general, a flange is a corresponding connecting part of a pipeline system, which is a disk or a small frame with special holes for bolts.
Such a valve is mounted on horizontal pipes in order to automatically shut off the flow of water or other working fluids that are transported through the pipeline. These devices can be considered a regulatory mechanism.
What is a Wafer Check Valve
As for the second type of connection, wafer models are usually used for installation on appropriate technical pipelines for high-quality protection and quickly shutting off the water flow in automatic mode. Wafer check valves are used for all kinds of liquids, including gas or steam. Thanks to certain design features, such devices are characterized by maximum tightness and completely eliminate the possibility of even the slightest water hammer. 
Unlike flanged models, Wafer valves can be installed in absolutely any convenient position - horizontally or vertically. During installation, such a valve will be securely fixed between two flanges (hence the name). It is important to note the fact that the flow of incoming liquid must go in the direction of the valve disk itself, where a special arrow will point.
In heat and water supply systems, it is customary to use thermal locking wafer devices, which guarantee high quality protection for any pipeline.
Where can I buy both types of pipeline fittings?
You can order and purchase on our official website right now.
In a lift check valve, the shut-off element is a lift spool. Under the influence of water pressure, the spool rises, allowing flow to pass through. When the pressure drops, the spool moves down onto the seat, preventing the flow from flowing back. Such valves are installed only on horizontal sections pipelines. A prerequisite is the vertical location of the valve axis.
Valves are divided into four groups according to the method of fastening:
- Weld fastening: the check valve is attached to the pipeline by welding. Used when working in aggressive environments.
- Flange mounting: The check valve is connected to the pipeline through sealed flanges.
- Coupling connection: the valve is attached to the pipeline through a threaded coupling. It is used in systems not large diameter.
- Wafer mounting: the check valve does not have its own mounting unit. Clamped between pipeline flanges. Used in areas with limited dimensions.
Lift check valves that have a protective mesh at the inlet and are designed to be installed at the beginning of the suction pipeline are called foot valves.
Advantages of lift check valves:
- simplicity of design;
- reliable tightness;
- possibility of repair without dismantling the entire valve.
Disadvantages of lift check valves:
- high hydraulic resistance;
- the possibility of the valve jamming 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, the valve is a ball element. A spring is used as a pressing element, pressing the ball to the seat. Such valves are usually made for small diameter pipelines and are used as household plumbing equipment. The ball check valve is inferior to the spring disc valve in terms of dimensions.
Check valves, operating principle:
In this design, the locking element is a spool - a “flap”. The axis of rotation of the “flap” is located above the passage hole. Under the influence of pressure, the “flap” reclines and does not interfere with the passage of water. When the pressure drops below the permissible value, the spool falls and slams the passage channel. In large-diameter check valves, the spool strongly impacts the seat, which leads to rapid failure of the structure. At further exploitation this provokes a 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 shock 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 their ability to operate in systems large sizes and low sensitivity to environmental pollution.
A flange check valve is a type of protective pipeline fitting. It differs from other modifications in the type of connection (flange). Refers to types of direct-acting fittings with automatic control– passes the flow of the working medium in one direction. When the direction is changed to the opposite, the valve automatically closes the flow area. For this purpose, the force from the gravity of the bolt, from the spring, from the lever-load mechanism is used.
Using flanged valves
The placement of check valves prevents the occurrence of emergency situations in pipeline systems in case of emergency pressure drop. Flanged check valves are installed on pressure sections of pipelines (according to the number of pumps connected in parallel), on pipelines after the meter (flow meter), in complex systems heating, water supply, and other working media in areas that require movement in only one direction (feeding valves of closed systems; valves in front of cleaning filters).
Advantages
The flange design slightly increases the size of the connecting size. This feature is compensated by the ease of installation, maintainability of the valve, unpretentiousness in operation (no need for Maintenance). In addition, flanged check valves are reliable in operation and provide complete shutoff of the reverse flow of the working medium. It is possible to select a full bore valve design with a minimum of hydrodynamic losses.
Design Features
Flanged valves have a cast metal (usually cast iron) body. There are connecting flanges on both sides. Internal structure determined by the type of shutter mechanism used. The most common types of mechanisms are: lifting, ball, disk, rotary.
Installation of flanged valves
All types of flanged check valves are installed in the pipeline taking into account the direction of forward flow. In valves with a lifting plug mechanism, normal closed position the shutter is supported by a spring. When flow moves under the valve, the valve opens. Such a valve is mounted on vertical, inclined, and horizontal sections.
Ball valves use a locking element in the form of a metal ball. In the absence of flow or in the opposite direction, the ball under its weight blocks through hole. Installation of such a flanged valve is carried out with the ball chamber oriented upwards.
