How much do you know about common valve standards? Heating engineering commonly used valves

How much do you know about common valve standards? Heating engineering commonly used valves

BS 6364 low temperature valve
SHELL SPE 77/200 -50℃ below valve
SHELL SPE 77/209 0 ~ -50℃ valve
Heating engineering commonly used valves
There are many kinds of valves and a wide range of use. In the pipeline sometimes it is the main equipment, play a control role; Sometimes it is a secondary device and plays an auxiliary role. If used improperly, there will be “running, risking, dripping, leakage” phenomenon, light affect production, heavy cause accidents. So understanding and proper use of valves is a very important issue.
1 Valve classification
There are many types of valves used in heating systems. Such as gate valves, globe valves, ball valves, butterfly valves, check valves, safety valves, regulating valves, balancing valves, self-balancing valves and so on. Let’s go through them one by one.
1.1 gate valves
Also called gate valve, gate valve, is a kind of valve used.

Working PRINCIPLE: GATE sealing face and valve seat sealing face height smooth, smooth, consistent, processed into a very fit, tight sealing pair. Through the up and down pressure of the valve stem, the gate forms the conduction and shutdown of the medium. It acts as a shut-off in the pipeline.

Advantages: Low fluid resistance; The sealing surface is not eroded when fully opened; Can be used in the case of two-way flow medium, no directionality; Strong and durable; Not only suitable for making small valves, but also can make large valves.
Disadvantages: high height; Long opening and closing time; Heavy; It is difficult to repair; If it is a large caliber gate valve, manual operation is more laborious.
Gate valve according to the different clear rod type and dark rod type; According to the structure of the gate plate, the parallel type and wedge type are different; There are single gate, double gate points. In heating engineering, it is commonly used to open rod wedge type single gate valve (Z41H-16C) and dark rod wedge type single gate valve (Z45T-10), the former is installed in the primary side of the heat station, the latter is installed in the secondary side of the heat station. It generally plays two roles: as a switch for the main equipment; As auxiliary equipment installed before and after the main equipment for maintenance.
When the gate valve is installed, do not make the handwheel below the horizontal line (inverted), otherwise the medium will be retained in the valve cover for a long time, easy to corrode the stem. In heating engineering, the gate valve used to be the main force in the valve. Now with the adoption of butterfly valves, gate valves have been replaced by butterfly valves.
1.2 stop valve
It is also a type of valve that is used. The general caliber is below 100mm. It WORKS LIKE A GATE VALVE EXCEPT THAT THE SHUTOFF (DISC) MOVES ALONG THE CENTER LINE OF the SEAT. It plays a role in the pipeline shut off, can roughly adjust the flow.
Advantages: Easy to manufacture, easy to maintain, strong and durable.
Disadvantages: Only one-way media flow is allowed, directional when installed. Large flow resistance, poor sealing.

According to the structure of different points straight type, right Angle type, straight flow, balanced type. Flange straight (J41H) and internal thread straight (J11H) are generally used in engineering. Globe valve is directional, can not be pressed backwards. It should not be inverted.
In our production, life, the past commonly used straight-through, small caliber globe valve, now has been gradually replaced by ball valve.
1.3 ball valve
Compared with gate valve and globe valve, ball valve is a new type of valve that has been gradually adopted. Its working principle is: the spool is a ball with a cavity, and the spool rotates 90° through the valve stem to make the valve unblocked or blocked. It acts as a shut-off in the pipeline.
Advantages: In addition to the advantages of gate valve and globe valve, there are small volume, good sealing (zero leakage), easy to operate the advantages. At present, it is used in petrochemical, electric power, nuclear energy, aviation, aerospace and other sectors.
Disadvantages: Difficult to maintain.
Ball valves have two forms: floating ball type and fixed ball type. In heating engineering, some key positions, such as important branches, heat station connection population, DN250 below, often adopt imported ball valves. It is different from the structure of the domestic ball valve: the domestic ball valve body is generally two pieces, three pieces, flange connection; The valve body of the import ball valve is integrated, welded connection, the fault point is less. Its origin is Nordic such as Finland, Denmark and other heating technology more developed countries. For example, NAVAL,VEXVE from Finland, DAFOSS from Denmark, etc. Because of its good sealing, operation reliability, has long been favored by users. Ball valves are non-directional and can be installed at any Angle. Welding ball valve horizontal installation, the valve must be opened, avoid welding when the electric spark injury and ball surface; When INSTALLED IN VERTICAL PIPING, THE VALVE MUST BE OPENED IF THE UPPER CONNECTOR IS WELDED AND CLOSED IF THE LOWER CONNECTOR IS WELDED TO AVOID HIGH HEAT BURN INSIDE THE VALVE.
1.4 butterfly valve
In the heating system, is currently used, the most kinds of a valve.
Working principle: The disc is a disc, through the stem rotation, the disc in the seat range for 90℃ rotation, to realize the valve switch. It acts as a shut-off in the pipeline.
Can also adjust the flow rate.
Advantages: Simple structure, light volume, easy operation, good sealing.
Disadvantages: when fully open, the valve plate (seal ring) is eroded by the medium.
In the heating engineering, the butterfly valve has three eccentric metal seal butterfly valve, rubber soft seal butterfly valve.
1.4.1 Triple eccentric metal seal butterfly valve
The so-called “three eccentricity” refers to the valve shaft, valve plate in the valve relative position of the offset. Ordinary butterfly valve is an eccentric, that is, the valve shaft center line and sealing surface center line (valve plate center line) deviation; For high performance, add an eccentricity, that is, the center line of the valve shaft deviates from the center line of the valve (the center line of the pipe); The purpose of the double eccentricity is to remove the seal pair from each other after the valve plate is opened to 20°, thereby reducing friction (CAM effect). Three eccentric butterfly valve in the above double eccentric on the basis of adding a unique eccentric – oblique cone, that is, the offset of the valve plate (sealing surface and pipe vertical plane tilt an Angle). This makes the valve in the 90° travel range, complete separation between the sealing pair, not only strengthen the CAM effect, but also completely eliminate friction; Close the valve at the same time, when the seal pair gradually closed, the “wedge effect”, with a small torque to achieve the most tight off.

The so-called “metal seal” refers to the valve seat, sealing ring using wear resistance, corrosion resistance, high temperature resistance of the quality alloy made; At the same time in order to avoid the sealing ring and the seat hard, the sealing pair is designed to be flexible contact, namely the formation of “elastic metal seal”, to ensure close tightly, open frictionless. With THE “three eccentric” structure, coupled with the “elastic metal seal”, such valves are easy to operate, durable and sealed well.
Three eccentric metal seal butterfly valve is generally used in the heating system of the main line and the main branch. Caliber DN300 or above.
Imported three eccentric metal seal butterfly valve has no direction, but generally recommended installation direction, should not be reversed; Domestic directional, general reverse than forward difference of a leakage level or one to two pressure levels, can not be reversed. If welding on the horizontal pipe, the valve should be closed to protect the seal ring; In THE CASE OF VERTICAL pipe welding, the valve should be closed and water should be added to the valve plate during welding to extinguish welding slag. When INSTALLED ON THE HORIZONTAL pipe, it is recommended that the position of the stem be inclined horizontally or vertically to ensure that the bottom bearing is clean.
1.4.2 Rubber soft seal butterfly valve
The butterfly plate is generally plated nodular cast iron, and the sealing ring is rubber. The sealing material used is different, the performance is different. Commonly used are: Dingqing rubber, applicable temperature of a 12℃ a +82℃; Ethylene propylene rubber, applicable temperature a 45℃ a +135℃; Heat-resistant ethylene propylene rubber, suitable for a temperature of 20℃ +150℃.
Heating engineering commonly used in the sandwich (D371X), flange (D341X). DN125 below available handle drive (D71, D41X). The wafer butterfly valve is small and light, quick opening and closing, easy to operate, easy to install, easy to maintain, good sealing and adjusting performance, high cost performance, so it should be vigorously adopted. Soft seal butterfly valve has no direction, can be installed arbitrarily.
When the butterfly valve is in storage, the valve plate should be opened 4° to 5°. In order to avoid long-term compression and deformation of the sealing ring, affecting the seal.
1.5 check valve
Also called check valve, single flow door. A commonly used auxiliary valve.
Working principle: Depending on the force of the fluid itself and the weight of the disc, the valve automatically opens and closes. As the name suggests, its job is to stop the medium from flowing back. Generally installed at the pump outlet to prevent water hammer damage to the pump.
Commonly used in heating engineering are horizontal lifting type (H41H), single valve swing type (H44H), double valve butterfly type (H77H).
The check valve is directional and cannot be installed backwards. Different forms of check valves, according to their structure, have a fixed installation, must not be installed wrong. The horizontal lifting type can only be installed in the horizontal pipeline, and ensure that the valve disc is in the vertical state; Single disc swing type can only be installed in the horizontal pipeline, and ensure that the disc shaft is in a horizontal state; Double valve butterfly can be installed arbitrarily.
1.6 the regulator
Also called throttle valve. It is a common valve for secondary heating system.

Working principle: shape, structure and stop valve similar. Only the sealing pair is different, the valve disc and seat similar to the thermos bottle stopper and bottle mouth, through the movement of the valve disc to change the flow area to regulate the flow. A ruler on the valve shaft indicates the corresponding flow rate.
Function: Adjust the medium flow distribution between pipes to achieve thermal balance.
Heating engineering used to be straight through (T41H), but it has some disadvantages: high flow resistance, not vertical installation. So with the progress of technology, balance valve (PH45F) instead of regulating valve.
1.7 balance valve
Improved type regulating valve. The flow channel adopts straight flow, the seat is changed to PTFE; It overcomes the disadvantage of large flow resistance and increases two advantages: more reasonable sealing and cutoff function.
It is used in the secondary network of thermal station in heating engineering, and has excellent flow regulation characteristics, especially suitable for variable flow system.
It is directional and can be mounted horizontally or vertically.
1.8 Self-balancing valve
Also called flow control valve. Its working principle is: in the valve there is a spring and rubber film composed of the mechanism, it is connected with the stem. If THE FLOW RATE INCREASES, AN UNBALANCED FORCE WILL BE CREATED ON IT, CAUSING THE DISC TO MOVE IN THE CLOSED DIRECTION TO REDUCE THE FLOW AREA, REDUCE THE FLOW RATE, AND RETURN THE FLOW RATE TO THE SET POINT. And vice versa. Thus, the flow rate after the valve is always kept unchanged to achieve the purpose of controlling the flow rate.
Installed in the heating system at the thermal population branch point. Automatic elimination of hydraulic imbalance, improve system efficiency, to achieve economic operation. Self – balancing valve directional, do not install reverse.

In addition, there are environmental corrosion and protection of the valve, corrosion and protection of the medium to the valve, temperature and pressure and sealing and leakage problems and so on. In short, although the valve is small, knowledge is great, waiting for us to continue to learn and summarize.