One of the main issues when choosing pipeline fittings is the type of its connection to the system. Usually, the already existing piping system dictates to us which type of connection to choose. But if you are faced with the task of designing such a system, then it is important to know all the possible types of connection of pipeline fittings to the system in order to choose the ideal option for your conditions. From our article you will learn about all types, their pros and cons, you will better navigate the types of connections. We'll start with the most popular.
flange connection
This is a connection using two metal plates adjacent to each other. The plates have holes through which bolts or studs pass and are tightened with nuts from the other side, thus pressing the flanges against each other. For greater reliability and tightness of the connection, protrusions, grooves, etc. are made on the plates, and gaskets are installed between the metal plates. Most often, the plates are rounded, but this is not necessary. Occasionally you can find square flanges, rectangular or with three corners, but their production is more expensive. Such forms of flanges are used only when absolutely necessary, for example, if space restrictions require it. It is used on industrial pipelines with a diameter of 50 mm or more.
The word "flange" came from the German flansch, meaning the same as in Russian - a flat metal plate with holes.
Flange connection is one of the most popular connections in pipeline fittings. For the manufacture of flanges, cast iron is most often used - gray or malleable, as well as steel of various grades. Gray cast iron is the most cost-effective solution, but ductile iron tends to withstand a greater range of pressures and temperatures. An even more expensive and durable solution is cast steel flanges. But at the same time, steel is more susceptible to plastic deformation than brittle, but perfectly shaped cast iron.
Video: Installing an LD Flanged Ball Valve on a Pipe Using
Advantages of flange connection of pipeline fittings
- Strong, reliable connection.
- Withstands high pressure.
- High tightness. But it depends on the seals used.
- Can be mounted and dismantled multiple times.
Flaws
- Large overall dimensions of the flange connection. Big mass.
- High consumption of metal and labor intensity of production, and hence the price.
- The bolts pressing the flanges together must be periodically tightened to ensure proper tightness. This is especially important in systems where the pipe is subject to vibrations (decided by installation before the flange connection) or temperature changes.
Threaded, socket connection
Also one of the most popular types of connections, but for pipeline systems of small diameter (usually up to DN 50) and low pressures (up to 1.6 MPa). It is very often found in household pipe fittings, for example for. Its essence is simple: the pipe has a thread and the armature has a thread, the latter is screwed onto the first.
The pipe can be threaded using special tools if it is not available and the equipment has not been installed before. Threaded pipeline fittings at one end are made in the form of a hexagon for gripping with an adjustable wrench and screwing the fittings onto the pipe thread.
Video: how to thread a metal pipe and install a threaded ball valve
There are various versions of threaded connections: internal or external thread. The fittings can have an internal thread on one side and an external thread on the other, or the same type on both sides. And there are also various thread standards, such as ISO 228/1 or DIN 2999. You need to take this into account when choosing.
The word "coupling" comes from the Dutch word mouw, meaning "sleeve".
To ensure the tightness of threaded types of connections, they use additional seals - special FUM tapes, flax thread, as well as especially thick lubricants on top of them. All this is applied to the external thread.
Union connection
This is a subspecies of a threaded connection, which is used on valves of tiny sizes - up to DN 5. When connected, a fitting with a thread is pulled to the thread on the pipe with a union nut. It is used for narrow-purpose pipes, such as laboratory pipes. It is also used for implanting various measuring devices into pipelines.
Advantages of threaded connections of pipe fittings
- Low price.
- Does not require additional parts for installation, such as flanged type.
- Easy to install, even easier to replace.
Flaws
- Not suitable for high pressures.
- The larger the diameter, the more effort must be applied to screw the reinforcement onto the thread with the seal.
Weld connection
If the ends of the pipe fittings look just like pipes without any additions, then they are joined to the system by welding. This is the most reliable and hermetic connection, properly performed which, you can get the absolute structural conformity of materials. Having welded a valve or valve to a pipe, you do not have to tighten the bolts, as with a flange connection, moreover, the cost and weight of such fittings will be much less.
This type of connection can often be found on pipeline systems transporting liquids and gases hazardous to health, where the slightest leaks cannot be allowed and absolute tightness is required. Welded joints are characterized by the saying “set it and forget it”. The main thing is to qualitatively connect the pipe with the fittings so that the welding place is not weaker than the pipe wall.
The ends of the pipes must be prepared before welding, and each metal is prepared in its own way. We offer you a video with the simplest welding method.
Advantages of a welded joint
- Absolute tightness when the welding procedure is carried out correctly.
- Low cost rebar.
- Light weight.
- Small size, the connection does not take up much space in space.
Flaws
- Qualified personnel are needed, which increases the final cost of installing such fittings.
- A laborious dismantling process, such gate valves or taps need to be installed once and for all.
Clamp quick-release connection (Tri-Clamp)
A modern quick-release fitting for pipeline fittings, mainly used in the food industry, pharmacology and other industries where sterility and cleanliness are important. After all, this type of connection allows you to regularly remove and clean, disinfect the equipment installed with this mount.
The clamp connection consists of two fittings, a seal and a clamp. The clamp presses the two fittings to the seal and to each other, resulting in a tight connection. What is such a clip, we invite you to study the video.
In apartment buildings, residents mainly use the services of the central heating network for space heating. The quality of these services is influenced by many factors: the age of the house, wear and tear of equipment, the condition of the heating main, etc. In the heating system, a special scheme is also essential, according to which the connection to the heating network is carried out.
Connection types
Connection schemes can be of two types: dependent and independent. Connecting by dependent method is the simplest and most common option. An independent heating system has gained its popularity recently, and is widely used in the construction of new residential areas. What solution is more effective for providing warmth, comfort and coziness to any room?
dependent
Such a connection scheme, as a rule, provides for the presence of in-house heating points, often equipped with elevators. In the mixing unit of the heat station, superheated water from the main external network is mixed with the return one, while acquiring a sufficient temperature (about 100 ° C). Thus, the internal heating system of the house is completely dependent on external heat supply.
Advantages
The main feature of such a scheme is that it provides for the flow of water into the heating and water supply systems directly from the heating main, while the price pays off rather quickly.
Flaws
Along with the advantages, such an attachment also has some disadvantages:
- inefficiency;
- temperature control is much more difficult during weather changes;
- overexpenditure of energy resources.
Connection methods
The connection can be made in several ways:
Independent
The heat supply system of an independent type allows you to save consumed resources by 10-40%.
Operating principle
The connection of the heating system of consumers occurs with the help of an additional heat exchanger. Thus, heating is carried out by two hydraulic isolated circuits. The circuit of the external heating main heats the water of the closed internal heating network. In this case, mixing of water, as in the dependent variant, does not occur.
However, such a connection requires considerable costs for both maintenance and repair work.
water circulation
The movement of the coolant is carried out in the heating mechanism thanks to the circulation pumps, due to which there is a regular supply of water through the heating devices. An independent connection scheme may have an expansion vessel containing a supply of water in case of leaks.
Components of an independent system.
Scope of application
It is widely used to connect to the heating system of multi-storey buildings or buildings that require an increased level of reliability of the heating mechanism.
For objects that have premises available, where access by unauthorized service personnel is undesirable. Provided that the pressure in the reverse heating systems or heating networks is above the permissible level - more than 0.6 MPa.
Advantages
Negative points
- high price;
- complexity of maintenance and repair.
Comparison of two types
The quality of heat supply according to a dependent scheme is significantly affected by the operation of the central heat source. This is a simple, cheap, low maintenance and repair cost method. However, the advantages of a modern independent connection scheme, despite the financial costs and complexity of operation, are obvious.
The word "flange" came into Russian from the German language along with the flange itself, and was not assigned on the basis of some analogies. In German, the noun Flansch means exactly the same thing as the Russian word “flange” derived from it, ─ a flat metal plate at the end of a pipe with holes for threaded fasteners (bolts or studs with nuts). It is more usual when this plate is round, but the shape of the flanges is not limited to one disk. For example, square and triangular flanges are used. But round ones are easier to make, so the use of rectangular or triangular flanges can be justified for really good reasons.
The material, types and design features of the flanges are determined by the nominal diameter, pressure of the working medium and a number of other factors.
For the manufacture of flanges of pipeline fittings, gray and malleable cast iron, different grades of steel are used.
Ductile iron flanges are designed for higher pressures and a wider temperature range than gray iron flanges. Cast steel flanges are even more resistant to these factors. Steel welded flanges, just as easily enduring high temperatures, are inferior to cast flanges in the maximum allowable pressure.
The design features of the flanges may be the presence of protrusions, chamfers, spikes, annular selections, etc.
The prevalence of flanged pipe fittings is due to their many inherent advantages. The most obvious of them is the possibility of multiple assembly and disassembly. The temptation to add the adjective “light” to the noun “installation” is somewhat reduced if we remember how many bolts will need to be unscrewed and tightened when disassembling and joining large diameter flanges (flange connections are usually used for pipes with a diameter of 50 mm or more). Although in this case, the complexity of installation work will not go beyond the reasonable.
Flanged connections are durable and reliable, which allows them to be used to complete pipeline systems operating under high pressure. Under a number of conditions, flanged connections provide very good tightness. To do this, the butted flanges must have similar connecting dimensions that do not go beyond the permissible error. Another of the conditions is the mandatory periodic tightening of the joints, which allows maintaining the "grip" of bolted joints at the proper level. This is especially important when they are constantly exposed to mechanical vibrations or there are significant fluctuations in temperature and humidity of the environment. And the larger the diameter of the pipeline, the more relevant it is, because as it increases, the force on the flanges increases. The tightness of flange connections largely depends on the sealing ability of the gaskets installed between the flanges.
Deformations cannot be discounted. Moreover, flanges made of different materials are subject to them to a different extent, so the material from which it is made is the most important parameter of the flange. Thus, ductile steel flanges deform more easily than those made of more brittle, but much better shape-holding cast iron.
The disadvantages of flanged fittings are a continuation of its advantages. High strength results in significant overall dimensions and weight, which, in turn, mean increased metal consumption (in the manufacture of large-sized flanges, you have to use a thick metal sheet or large-diameter round profiles) and labor-intensive production.
Weld fittings
Reinforcement welding is resorted to when the reliability and tightness of other types of joints is considered unsatisfactory. Welding is especially in demand in the construction of pipeline systems in which the working medium is toxic, poisonous or radioactive liquids and gases. In this case, a welding joint that, when properly designed, provides 100% tightness, can be the best, and often the only acceptable solution. It is only important that such a section of the system does not need frequent dismantling of the equipment, the implementation of which every time will lead to the complete destruction of the welded joints.
Thanks to welding, which unites the fragments of the pipeline system into a single whole, it is possible to ensure harmony, or, in technical language, structural compliance between all its elements ─ pipes and pipeline fittings. The main thing is that due to differences in the mechanical properties of the welded joint and other components of the pipeline system, it does not become its weak link.
The connecting ends of the reinforcement are prepared for welding by leveling and grinding the surface of the fragments to be welded, removing the required chamfers.
Welded joints can be made in the socket and butt. In the first case, the weld is located on the outside of the pipe. This option is usually used for steel fittings of relatively small diameter, mounted in pipelines operating at high pressure and temperature of the working medium.
In the second case, the connection can be supplemented with a backing ring, which excludes distortion of the connected parts. It is these connections, distinguished by reliability and absolute tightness, that are used in the installation of pipeline systems of hazardous production facilities, for example, power units of nuclear power plants.
Important advantages of welded joints, especially in comparison with flanged ones, are minimal weight, compactness and space saving.
Coupling fittings
One of the most common in technology is the coupling connection of reinforcement.
It is used for various types of fittings of small and medium diameter, operating at low and medium pressures, the body of which is made of cast iron or non-ferrous metal alloys. If the pressure is high, then it is preferable to use a pin fitting.
In the connecting pipes of coupling fittings, the thread is on the inside. As a rule, this is a pipe thread ─ inch thread with fine pitch. It is formed in various ways ─ knurling, cutting, stamping. It is important that with a fine thread pitch, the height of the teeth does not depend on the diameter of the pipeline.
Outside, the connecting ends are designed in the form of a hexagon, so that it is convenient to use the key.
The word "coupling" came into Russian from German, and possibly from Dutch, where mouw means sleeve. The coupling, like the valve, is an example of how tailoring and the production of pipeline fittings each use in their special terminology words that are the same in sound, but carry a different semantic load. In technology, a sleeve is not called a sleeve, but a short metal tube that provides connections for the cylindrical parts of machines.
The fine thread of the coupling joint plus the use of special viscous lubricants, linen strands or fluoroplastic sealing material (FUM tape) guarantee its high tightness. The sleeve connection does not require the use of additional fasteners (for example, bolts or studs, as in a flange connection). But it must be taken into account that screwing the coupling onto a thread with a seal requires considerable effort, the greater the greater the diameter of the pipeline.
Choke fittings
The German origin of the term "fitting" from the verb stutzen (cut, cut) even betrays its sound. So because of the presence of a rifled barrel, the muskets used to arm armies were called until the 19th century. In modern technology, this noun is used to define a short piece of pipe (in other words, bushings) with threads at both ends, which serves to connect pipes and pipeline fittings to units, installations and tanks. In a union connection, the connecting end of the fitting with an external thread is pulled to the pipeline by means of a union nut. It is used for fittings of small and extra small (with a nominal diameter up to 5.0 mm) diameters. As a rule, these are laboratory or other special fittings. For example, gearboxes mounted on compressed gas cylinders. With the help of a nipple connection, various control and measuring devices (CIP) are “implanted” into pipeline networks, evaporators, thermostats, and many types of equipment that are part of chemical production process lines are mounted.
Tie-down fittings
The term "trunnion connection" came into wide use at the end of the 19th century. Its main attributes for pipeline fittings are connecting pipes with external thread and the presence of a shoulder. The end of the pipeline with a collar is pressed against the end of the valve branch pipe with a union nut.
The pin connection is used for small size high pressure fittings, in particular instrumentation. It is effective when screwing fittings into the body of vessels, apparatuses, installations or machines. Its tightness is ensured by the presence of gaskets and special lubricants.
An example of a pin connection is the connection of a fire hose to a fire hydrant.
All threaded connections are characterized by such advantages as the minimum number of connecting elements, low metal consumption and, accordingly, low weight, manufacturability. Effective installation of threaded connections requires the matching of internal and external threads, the use of soft or viscous materials for sealing. But it should be borne in mind that threading reduces the thickness of the pipe wall, so this type of connection is not well suited for thin-walled pipes.
In addition to those listed, there are other ways to attach reinforcement. So, in pipeline systems, durite compounds can be used. These are connections by means of cylindrical couplings, consisting of several layers of rubberized fabric (in simple terms, fragments of hoses), which are pushed onto the protrusions made on the nozzles and fixed with metal clamps.
Another way to attach fittings is soldering, which is used for copper pipes with a small diameter. The end of the pipeline treated with solder is inserted into the groove made in the branch pipe.
The functionality, performance and reliability of the pipeline system is determined not only by the parameters of the fittings included in it, but also by how wellperformed rebar connection , the selection and implementation of which should always be given increased attention.
It has an internal threaded connection. Thanks to this threaded connection, the coupling valve has a smaller overall length and weight.
Scheme of a ball coupling valve
The advantage of the crane is that no additional fasteners are needed for a reliable connection. It is also indispensable in those sections of the pipeline where there is not enough space to work with a wrench.
Flanged ball valve
Attaches to flanges. Accession is provided by two flanges, a sealing ring, connecting bolts and nuts.
Flanged ball valve scheme
The valves are easy to install and maintain, they can be mounted and dismantled many times, while the flanged valves are large and heavy. They are used, as a rule, on pipelines where frequent installation and dismantling of cranes is required.
Ball valve
This is a tap with an external thread to which a nipple with a union nut is attached. The design ensures the small size and weight of the product, while such a crane is easy to maintain and install.
Scheme of a spherical choke valve
Easy to assemble and maintain, they can be mounted and dismantled many times. Unlike flanged valves, it takes up less space and can be installed in hard-to-reach places.
Welded ball valve
Has welding ends. Such cranes are light in weight, are hermetically attached to the pipe, but are difficult to maintain: their dismantling and replacement are quite laborious.
Scheme of a ball valve
Designed for high pressure of the working medium, therefore, they have high tightness of the overlap and the strength of the connection.
Electric drives are produced with the highest torques from 0.5 to 850 kgf-m in normal and explosion-proof versions with different explosion protection categories. These and other parameters of electric drives are reflected in the symbol of the drive, which consists of nine characters (numbers and letters). The first two characters (numbers 87) designate an electric drive with an electric motor and a gearbox. The next sign is the letter M, A, B, C, D or D, indicating the type of connection of the actuator to the valve. Type M connection is shown in fig. II.2, types A and B - in fig. II.3, types C and D in - fig. II.4, type D - in fig. P.5. The dimensions of the connecting elements are given in table. 11.106.
11.106. Dimensions of connecting elements of unified electric actuators of valves
All actuators are attached to the valve with four studs. The diameters of the studs and the dimensions of the support areas for different types of connections are different. With an increase in the torque developed by the drive, they increase. Types C, D and D connections are provided with two keys in order to unload the studs from shearing forces created by the torque transmitted from the actuator to the valve.
The next figure conditionally indicates the torque of the electric drive. In total, seven gradations are provided for the total range of torques from 0.5 to 850 kgf-m (Table 11.107). Within the prescribed interval, the adjustment to the required torque is made by adjusting the torque limiting clutch.
11.107. Symbols of parameters of electric drives
The next figure conventionally denotes the rotational speed (in rpm) of the drive shaft of the electric drive, which transmits rotation to the valve stem nut or spindle. Eight frequencies of rotation of the drive shaft of the electric drive are provided - from 10 to 50 rpm (Table 11.107).
Then, conditionally, the total number of revolutions of the drive shaft is indicated, which it can make, depending on the version of the box of limit and torque switches. In total, six gradations are provided (Table 11.107).
This limits the first group of characters. The second group consists of two letters and a number. The first letter of the second group of designations indicates the version of the drive according to climatic conditions: Y - for a temperate climate; M - frost-resistant; T - tropical; P - for elevated temperature. The second letter indicates the type of connection of the control cable to the electric drive box; Ш - plug connector; C - gland entry. The last digit indicates the explosion protection version of the actuator. The number 1 indicates the normal version H; the remaining numbers from 2 to 5 indicate the explosion protection categories: 2 - VZG category; 3 - category B4A; 4 - category V4D; 5 - category РВ. Thus, the electric drive under the designation 87V571 US1 has the following data: 87 - electric drive; B - type of connection; 5 - torques from 25 to 100 kgf-m; 7 - frequency of rotation of the drive shaft 48 rpm; 1 - total number of revolutions of the drive shaft (1 - 6); U - for a temperate climate; C - gland entry of the control cable; 1 - explosion protection standard N.
Below are brief technical characteristics and overall data of electric drives of a unified series.
Electric actuators of normal execution with type M connection with a two-way torque limiting clutch (Fig. A.6). Symbols 87M111 USh1 and 87M113 USh1. Designed to control pipeline valves in structures with a maximum torque of up to 2.5 kgf-m. Torque control limits from 0.5 to 2.5 kgf-m. The total number of revolutions of the drive shaft 1 - 6 (87M111 USh1) and 2 - 24 (87M113 USh1). Drive shaft speed 10 rpm. The drive is equipped with an AB-042-4 electric motor with a power of 0.03 kW and a rotation speed of 1500 rpm. The gear ratio from the handwheel lever to the drive shaft = 1. A force of up to 36 kgf can be applied to the flywheel rim. Electric drives have a built-in box! travel and torque switches. The mass of the electric drive is 11 kg. The overall dimensions of electric drives 87M111 USh1 and 87M113 USh1 are shown in fig. P.6.
11. 108. Symbols of electric drives
11.109. Brief technical characteristics and mass of electric drives
11.110. Symbols of electric drives
Electric actuators of normal execution with type A connection with a two-way torque limiting clutch (Fig. II.7). The maximum torques created by the drives are 6 and 10 * kgf-m. Eight modifications of electrical appliances are provided (Table 11.108). Specifications and mass of electric drives are given in Table. 11.109. Rotational speed of the electric motor shaft 1500 rpm Gear ratio from the flywheel of the handwheel to the drive shaft i = 3. The electric drives have a built-in box of travel and torque switches. The overall dimensions of the electric drives are shown in fig. P.7.
Electric actuators of normal execution with type B connection with a two-way torque limiting clutch (Fig. II.8). The maximum torque on the drive shaft is 25 kgf-m (regulation interval from 10 to 25 kgf-m). There are twelve modifications of electric drives (Table 11.110). Technical characteristics of electric drives are given in table. 11.111. The frequency of rotation of the motor shaft is 1500 rpm. The overall dimensions of the electric drives are shown in fig. II.8. The mass of the electric drive is 35.5 kg.
11.111. Brief technical characteristics of electric drives
Electric actuators of standard execution with type B connection with a two-way torque limiting clutch (Fig. II.9). The highest torque on the shaft is 100 kgf m (regulation interval from 25 to 100 kpm). There are twelve modifications of electric drives (Table 11.112). Technical characteristics and mass of electric drives are given in Table. II. 113. The frequency of waxing the motor shaft is 1500 rpm. The overall dimensions of the electrical wires are shown in fig. II.9.
Electric actuators of standard design with G-type connection with a two-way torque limiting clutch (Fig. 11.10). The highest torque on the shaft is 250 kgf-m (regulation interval from 100 to 250 kgf). There are twelve modifications of electric drives (Table 11.114). Technical characteristics and mass of electric drives are given in Table. 11.115. The frequency of rotation of the motor shaft is 1500 rpm. The overall dimensions of the electric drives are shown in fig. UFO.
11.112. Symbols of electric drives
11.113. Brief technical characteristics and mass of electric drives
11.114. Symbols of electric drives
11.115. Brief technical characteristics and mass of electric drives
Electric actuators of standard design with type D connection with a two-way torque limiting clutch (Fig. 11.11). The highest torque on the drive shaft is 850 kgf-m (regulation interval from 250 to 850 kgf-m). Drive shaft speed 10 rpm. There are six modifications of electric drives (Table 11.116). The gear ratio from the flywheel to the drive shaft i = 56. Permissible force on the rim of the flywheel handwheel 90 kgf. The electric drives are equipped with an AOC2-42-4 electric motor with a power of 7.5 kW and a shaft speed of 1500 rpm. The mass of the electric drive is 332 kg. The overall dimensions of the electric drives are shown in fig. 11.11.
Rice. 11.12. Electrical control circuit for electric drives of a unified series:
D - asynchronous electric motor with a squirrel-cage rotor; KVO, KVZ - travel microswitches MP 1101 opening and closing; KV1, KV2 - additional travel microswitches MP 1101; VMO, VMZ - moment microswitches MP 1101 opening and closing; O, 3 - magnetic starters for opening and closing; LO, LZ, LM - signal lamps "Open", "Closed" and "Clutch"; KO, KZ, KS - control buttons "Open", "Closed" and "Stop"; 7 - potentiometer PPZ-20, 20 kOhm; Pr - fuse; A - automatic; 1 - 4 - contacts of microswitches
Explosion-proof electric drives are also provided:
11.116. Symbols of electric drives
The electrical control circuit of electric drives (the same for all) is shown in fig. P. 12. In the “Open” position, the LO signal lamp is on, in the “Closed” position, the LZ and LM lamps are on, in the “Emergency mode” position, the LM lamp is on. The operation of the microswitches is clear from the table. 11.117.
11.117. Operation of microswitches (Fig. 11.12)
