Shut-off valves play a regulatory and anti-emergency role in the operation of the pipeline system. Its main elements — a valve and a valve have a difference in design, principle of operation, with the same operational requirements for them. Knowing these differences will allow you to install an element that will ensure the greatest efficiency of the network.
What is meant by valve
The valve is a shut-off element of the pipeline, which can not only block the flow of the working substance, but also regulate it. Its design allows you to set an adjustable flow: from maximum to its complete cessation with a number of average values.
Design features in
- Frame. Most often cast, but there are models with collapsible parts. It has two holes through which liquid, gas passes. A locking mechanism is installed inside. For mounting in a pipeline system, it has two threads or holes for flange mounting. The valve will be through if these fastening pipes are located on opposite sides. The category of angular includes a valve with mutually perpendicular axes.
- Locking device. Constipation — a valve system with a spindle, which are threaded to the guides. The valve in the form of a shutter is needle-shaped and poppet-shaped.
- Flywheel. This is a valve handle brought out to the outside, creating a load on the thread. Turning the handle lowers and raises the valve.
Seals for high-quality overlap are used in some types. When the valve is opened, the plate comes off the seat.
How to install
The fitting is installed so that the flow of the working medium is bent at a right angle twice in two parallel planes. In this case, liquid or gas flows under the plate, which creates pressure on it in the “closed” mode of operation from the side of the seat. This pressure somewhat helps to separate the plate from the seat when the valve is opened.
Note! If the direction of flow is reversed, then when it opens, its pressure will create an additional load on the valve and may rip off the stem.
Types of valve shut-off device
According to the type of constipation, valves are classified into
- Valve (valve crane). It has two partitions dividing the body into two parts. The partition can be made in the form of a cone. The valve, as part of the stem, abuts against an elastic gasket in contact with the seat. Turning the threaded connection raises and lowers the valve. This type of valve is designed for high pressure flow, easy to operate, its shut-off device can be easily replaced in the event of a breakdown. The disadvantage is the rapid wear of the rubber gasket.
- Ball or valve. The locking device is made in the form of a ball with a through slot. The size of the slot is determined by the required flow of the working medium. To completely block the flow, the ball is moved so that its slot is oriented perpendicular to the flow. Such a valve loses its regulating function.
What is meant by a valve
A gate valve is a shut-off element of the pipeline, in which the gate moves perpendicular to the axis of the flow of the working medium. It has the ability to only completely block the flow without the regulation function. The blocking element of the valves moves up — “open”, down — “closed”.
Design features of gate valves
- Frame. Made by casting.
- Locking mechanism. It has the shape of a wedge that hides at the top of the saddle in the closed position.
- Flywheel. It has a threaded handle connected to a wedge.
When the flywheel is turned, the wedge goes down, enters the lower part of the seat surface with rubber seals and blocks the through hole. Due to the constant friction of the wedge against the seal, the latter quickly becomes unusable.
Important! The gate valve can be installed regardless of the direction of flow in the pipe, due to the perpendicular orientation of the locking mechanism and the complete absence of mixture movement resistance.
Material for the manufacture of valves
There are valves and gate valves for installation in pipelines in internal (sheltered) and external areas. Common are constipation made of brass, bronze, steel, including stainless steel, cast iron. Recently, plastic valves have become widespread. When choosing a shut-off valve, the following factors are guided:
- The most reliable, durable, functional devices are made from brass and bronze. They are suitable for any type of working mixture. Valves made of these materials have proven themselves well in heating systems: due to the absence of scale, there is no heat loss. The main disadvantage is the high cost, which does not allow their use for large diameter pipes;
- External sections of pipelines, large-diameter pipes are equipped with shut-off valves made of cast iron and steel. These materials are strong enough to withstand the high load pressure in the line, but at the same time they are much cheaper than analogues made of bronze, brass;
- The most common and optimal option in terms of «price-quality» for internal water, gas, heating systems is stainless steel. Due to their performance characteristics, stainless steel valves are suitable for installation in all internal pipeline networks, even at high pressure. But it is not recommended to block pipes with hot mixtures with such constipation. Scale builds up inside the device over time, which causes a decrease in fluid flow;
- Budget option — plastic valves. It is not recommended for use in industrial highways, in external sections of individual gas and water supply systems. Suitable for interior spaces. It is installed only on plastic pipes.
General signs of valves
Valves and gate valves are designed to stop the flow of the working mixture in pipelines for various purposes. They can be threaded or flange mounted. For pipelines with a pressure of 1.6 MPa, a threaded connection is considered functional and durable. Industrial engineering systems with a working pressure of more than 10 MPa from cast-iron (steel) elements are blocked by shut-off valves installed on flanges. Plastic valves are welded by special welding.
The price is formed from the cost of the material, design features, additional parts used.
In general, there are four main differences:
- The valve has additional functionality in the form of regulation of the flow of liquid, gas. The valve serves only to shut off the pipe;
- Gate valves are more often used for large-diameter, high-pressure pipes, where, due to one-way pressure, the valve is very tightly adjacent to the seat. Valves in such conditions close the pipeline faster and easier, but opening is difficult. With a strong hydraulic shock, the locking mechanism may become unusable;
- Valves fail faster as internal seat O-rings wear out;
- Blocking the supply of liquid, gas in the valve occurs in a parallel plane, and in the valve — in a perpendicular one;
- Valves are more expensive.
All types of valves serve have their own characteristics. Knowing how the valve differs from the valve in the design, the option is selected that will ensure the smooth operation of the system.