One of the main issues when choosing pipeline fittings is the type of connection to the system. Usually the existing pipeline system itself 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 connecting 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, and you will better understand the types of connections. We'll start with the most popular ones.
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 on the other side, thus pressing the flanges together. For greater reliability and tightness of the connection, protrusions, grooves, etc. are made on the plates, and between metal plates install gaskets. Most often the plates have a rounded shape, 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 strictly necessary, for example, if space limitations require it. Used on industrial pipelines with a diameter of DN 50 mm.
The word “flange” comes from the German flansch, which means the same thing 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 different varieties. Gray cast iron is the most inexpensive 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 cast iron, which is brittle but holds its shape well.
Video: installing a flanged LD 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 many times.
Flaws
- Large overall dimensions of the flange connection. Large mass.
- High metal consumption and labor-intensive production, and therefore the price.
- The bolts holding the flanges together must be tightened periodically to ensure proper tightness. This is especially important in systems where the pipe is subject to vibration (solved by installation in front of the flange connection) or temperature changes.
Threaded, coupling 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). Very often found in household pipeline fittings, for example for. Its essence is simple: the pipe has a thread and the fittings have a thread, the latter is screwed onto the former.
You can cut a thread on a pipe using special tools if it does not exist and the equipment has not been installed before. Threaded pipeline fittings at one end are made in the form of a hexagon for gripping wrench and screwing fittings onto the pipe threads.
Video: how to cut a thread on a metal pipe and install a threaded ball valve
There are various options execution of threaded connections: internal or external thread. The fittings may have an internal thread on one side and an external thread on the other, or the same type on both sides. There are also different thread standards, for example ISO 228/1 or DIN 2999. You need to take this into account when choosing.
The word “muff” comes from the Dutch word mouw, meaning “sleeve”.
To ensure the tightness of threaded types of connections, additional sealants are used in them - 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 subtype of threaded connection, which is used on taps of tiny sizes - up to DN 5. When connecting, the threaded fittings are tightened to the threads on the pipe with a union nut. Used for pipes for narrow purposes, such as laboratory pipes. Also used for implanting various measuring devices into pipelines.
Advantages of threaded connections for pipeline fittings
- Low price.
- Not required additional details for installation, such as flange 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 fittings onto the threads with a seal.
Welded connection
If the ends of the pipeline fittings look simply like pipes without any additions, then they are connected to the system by welding. This is the most reliable and hermetically sealed connection, and if done correctly, you can obtain absolute structural compliance of the materials. By welding a valve or tap to a pipe, you will not have to tighten the bolts, as with a flange connection, and the cost and weight of such fittings will be significantly 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. For a welded joint, the saying “set it and forget it” is typical. The main thing is to properly connect the pipe to the fittings so that the welding point is not weaker than the pipe wall.
The ends of the pipes must be prepared before welding, and each metal is prepared differently. We offer you a video with the most in a simple way welding
Advantages of a welded connection
- Absolute tightness correct execution welding procedures.
- Low cost of fittings.
- Light weight.
- Small size, the connection does not take up much space.
Flaws
- Qualified personnel are needed, which increases the final cost of installing such fittings.
- A labor-intensive dismantling process, such valves or taps must be installed once and for all.
Clamp quick release connection (Tri-Clamp)
Modern quick-release coupling for pipeline fittings, mainly used in Food Industry, pharmacology and other industries where sterility and cleanliness are important. After all, this type of connection allows you to regularly remove, clean, and 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 against the seal and against each other, resulting in a tight connection. We suggest you study what such a clamp is in the video.
Connections of fittings to the pipeline (Fig. 13.2) can be detachable (flange, coupling, pin) and permanent (welded and brazed). The most common is flange connection. The advantages of flange connection of fittings are the possibility of repeated installation and dismantling on the pipeline, good sealing joints and ease of tightening, greater strength and applicability for a very wide range of pressures and passages. The disadvantages of a flange connection are the possibility of loosening and loss of tightness over time (especially under vibration conditions), increased labor intensity of assembly and disassembly, large overall dimensions and weight. These flange disadvantages especially affect large-diameter pipelines designed for medium and high pressures.
When assembling such a connection, dozens of large diameter studs are tightened with a special tool. A team of machinists is often required to tighten these flange connections. With an increase in the nominal pressure and the flow area of the flanges, the mass of both the fittings itself and the entire pipeline (including counter flanges) increases and the metal consumption increases. Due to the indicated disadvantages of flange connections, as well as an increase in the diameters of pipelines and their operating pressures, fittings with welded connections are becoming increasingly common. In particular, main gas and oil pipelines are equipped with such fittings.
The advantages of connecting fittings to a pipeline by welding are great, first of all, complete and reliable tightness of the connection, which is especially important for pipelines transporting explosive, toxic and radioactive substances. In addition, the welded joint does not require any maintenance or tightening, which is very important for main pipelines where a minimum of maintenance is desired. A welded connection provides greater savings in metal and reduces the weight of fittings and pipelines. It is especially effective to use fittings with welded ends on pipelines where the pipeline itself is assembled entirely by welding.
The disadvantage of welded joints is the increased complexity of dismantling and replacing the fittings, since to do this it has to be cut out of the pipeline.
For small fittings, especially cast iron, the coupling connection is most often used. In this case, the ends of the reinforcement have the form of couplings with internal threads. Since flanges for small fittings have a relatively large mass (often of the same order as the mass of fittings without flanges), the use of flanges in such conditions leads to an unjustified increase in metal consumption. In addition, tightening bolts for small-diameter flange connections is more labor-intensive than tightening a coupling connection and requires the use of special torque wrenches.
Rice. 13.2. Main types of connecting fittings to a pipeline:
a - flanged (cast flanges with a connecting lip and a flat gasket); b - flanged (butt-welded steel flanges with a protrusion-valley type seal with a flat gasket); V- flanged (cast flanges with a tongue-and-groove seal with a flat gasket); g - flanged (flat welded steel flanges with a flat gasket); d - flanged (cast steel flanges with lens gasket); e- flanged (cast steel flanges with oval gasket); and - coupling; h – pin-type.
The coupling connection is usually used in cast fittings, because casting is the easiest way to obtain the external configuration of the coupling (hexagon on a turnkey basis). In this regard, the main area of application of coupling connections is low and medium pressure fittings. For small high-pressure fittings, which are usually made from forgings or rolled products, a pin connection with external thread under the union nut.
Flange connections of pipelines and fittings, designed for a nominal pressure of 1-200 kgf/cm 2, are standardized. At the same time, the types of flanges (GOST 1233-67), their connecting dimensions (GOST 1234-67), designs, design dimensions and technical requirements are standardized. In special, technically justified cases (with shock or increased load, short service life, specific properties of the environment - toxicity, explosiveness, chemical aggressiveness, etc.), the standard allows the manufacture of flanges according to industry standards or drawings that deviate from GOST, but with the obligatory implementation of connecting sizes according to GOST 1234-67.
Flanges are usually made round. The only exceptions are cast iron flanges, tightened with four bolts, designed for a pressure p not higher than 40 kgf/cm2. They can be made square.
Standard valve flanges are divided into several types according to the design of the gasket connection. The simplest of them is with a smooth front surface (with or without a connecting protrusion), unprotected type, without a recess for the gasket. These flanges are the simplest for mounting and dismantling fittings and for replacing gaskets, however, the tightness of the connection they create is the least reliable.
Flanges designed for high pressures (from 40 to 200 kgf/cm2) are used with serrated steel gaskets, for low pressures - with soft or soft-core gaskets. To protect soft gaskets from being knocked out by pressure working environment The fittings use flanges with a cavity for the gasket. In this case, the counter flanges are made with a protrusion, so that on the outside of the gasket the flanges form a lock protecting it. Such flanges are used with soft gaskets or metal ones with a soft core. The third type of valve flanges, designed for the same gaskets as the previous one, are flanges with a groove for the gasket. The counter flanges have a spike. Thus, the gasket is protected by the flange lock both outside and inside, which increases the reliability of the connection. However, installation, dismantling of fittings and replacement of gaskets are somewhat more difficult here compared to flanges of the first type.
For high pressures, starting from p y = 64 kgf/cm 2, seals of two more standard types are used in flanges - for a lens gasket and for an oval gasket. These seals are more economical and reliable at high pressures than conventional flat gaskets. In such flange connections, the gaskets touch the sealing surfaces of the flanges, theoretically along a line, but practically along a very narrow ring. This allows, given equal overall dimensions flanges and tightening forces create high specific pressures on the seal. Thus it becomes possible use massive steel gaskets of high strength and durability in place of conventional soft ones.
Has an internal threaded connection. Thanks to this threaded connection, the coupling valve has less construction length and mass.
Diagram of a coupling ball valve
The advantage of the crane is that additional fasteners are not 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.
Flange ball valve
Attaches to flanges. Connection is ensured by two flanges, an O-ring, connecting bolts and nuts.
Diagram of a flanged ball valve
The valves are easy to install and maintain, they can be mounted and dismantled many times, while flanged valves have big sizes and weight. They are usually used on pipelines where frequent installation and dismantling of valves is required.
Ball valve
This is a valve with an external thread, to which a nipple with a union nut is attached. The design provides small sizes and the weight of the product, while such a crane is easy to maintain and install.
Diagram of a ball valve
They are easy to install and maintain, they can be mounted and dismantled many times. Unlike flanged valves, it takes less space and can be installed in hard-to-reach places.
Welded ball valve
Has welded ends. Such taps are lightweight, hermetically attached to the pipe, but are difficult to maintain: dismantling and replacing them is quite labor-intensive.
Diagram of a welded ball valve
Intended for high pressure working environment, therefore they have high tightness of the overlap and strength of the connection.
FEDERAL AGENCY FOR TECHNICAL REGULATION AND METROLOGY
NATIONAL
STANDARD
RUSSIAN
FEDERATION
Pipeline fittings ROTARY ACTION DRIVES Connecting dimensions
Industrial valves - Multi-turn valve actuator attachments
Industrial valves - Part-turn valve actuator attachments
Official publication
Standardinform
Preface
1 DESIGNED Closed joint stock company"Research and production company "Central Design Bureau of Valve Engineering" (JSC "NPF "TsKBA") based on ST TsKBA 062-2009 "Pipeline fittings. Rotary motion drives. Connecting dimensions"
2 8NESEN Technical Committee for Standardization TC 259 “Pipe fittings and bellows”
3 APPROVED AND 8PUT INTO EFFECT by Order of the Federal Agency for Technical Regulation and Metrology dated August 20, 2013 No. 529-Art.
4 This standard takes into account the main regulatory provisions of the following international standards:
ISO 5210 “Pipeline fittings. Connecting dimensions of multi-turn actuators" (ISO 5210 Industrial valves - Multi-turn valve actuator attachments", NEQ):
ISO 5211, “Pipeline fittings. Connecting dimensions of part-turn actuators" (ISO 5211 "Industrial valves - Part-turn valve actuator attachments", NEQ)
5 INTRODUCED FOR THE FIRST TIME
The rules for applying this standard are established by GOST R 1.0 - 2012 (section 8). Information about changes to this standard is published in the annual (as of January 1 of the current year) information index “National Standards”, and the official text of changes and amendments is published in the monthly information index “National Standards”. In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the next issue of the monthly information index “National Standards”. Relevant information, notices and texts are also posted information system for general use - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet (gost.ru).
© Standardinform. 2014
This standard cannot be fully or partially reproduced, replicated or distributed as an official publication without permission from the Federal Agency for Technical Regulation and Metrology
1 ... 1 ... 1 ..2 16
1 area of use............................................... ...........................................
3 Terms and definitions................................................... ....................................
4 Types of connections................................................... ...........................................
5 Designation of connection types.................................................... ...................
Appendix A (mandatory) Connecting dimensions of multi-turn valves
drives for connection types MCH. MK. AC. AK. B. C. D. D...........................
Bibliography
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
Pipeline fittings
ROTARY DRIVES
Connection dimensions
Pipeline valves. Drives of rotary action The connecting dimensions
Date of introduction -2014-02-01
1 area of use
This standard applies to rotary actuators and actuators (hereinafter referred to as actuators) (multi-turn and part-turn, electric, pneumatic, hydraulic, as well as gearboxes) and establishes the types of connections of actuators to pipeline fittings, the connecting dimensions of actuators and the dimensions of counter connections of the pipeline fittings controlled by them .
2 Normative references
This standard uses normative references to the following standards:
GOST R 52720-2007 Pipeline fittings. Terms and Definitions
GOST 22042-76 Studs for parts with smooth holes. Accuracy class B. Design and dimensions
3 Terms and definitions
In this standard the following terms are used with their corresponding
definitions:
3.3 multi-turn actuator: A device that imparts a torque to the valve sufficient for at least one revolution. May have the ability to withstand axial load (1].
3.4 part-turn actuator: A device that transmits torque by rotating its output element by one revolution or less, and does not have the ability to withstand an axial load.
3.5 gearbox: A mechanism designed to reduce the torque required to control pipeline fittings)
