Hoses themselves are not a ready-to-use product. In order to connect a hose to a technique or other aggregate unit, the device must be equipped with a suitable connection. Modern equipment manufacturers offer a fairly large variety of connections, though there is no one universal hose connection that fits every kind of equipment. So, how do you know the kind of equipment necessary for a hose installation?
By Jurij Artiukhov, General Manager, PipeTime, LLC
Understanding the Basics
Just like other manufacturing equipment, there is no one way to ensure a suitable connection for every hose-type. In fact, the choice of connection for a hose must be in accordance with the parameters and dimensions of the counterpart in order to be fully functional. These connections can be selected depending on the speed that is necessary, the duration of time that the hose will be used, whether it is possible to establish the connection manually, and several other factors.
High Pressure Hoses
The most commonly used hose technology is high pressure hoses. The choice of connection in these types of application implies an important parameter: resistance to high pressure. Installation, in this case, does not take place manually, but rather mechanically using a special crimping machine.
Standard industrial hose clamps are able to withstand pressures up to 16-32 bar, though in the case of hydraulic hoses, the pressure is an order of magnitude higher. There are several additional challenges in selecting a line of fittings for a high pressure hoses, including: the usage of different metric systems in certain countries, the wide variety of equipment and technology, and other features.
Typically, high pressure hose fittings from different areas of the world differ in seal and thread type, see Chart 1.
The type of fitting required for a high pressure hose is usually stationary. More specifically, a connection on a high pressure hose will not require additional movement following installation. As the installation of such a connection requires a certain amount of knowhow and skill, trained and qualified personnel are typically required.
If a solid and permanent solution is needed, the hose assembly can be flanged. Given the huge variability of flange standards, there should be few challenges encountered when selecting a flange; all sizes, the number of holes, and other standards are clearly elaborated by product manufacturers. The manufacture of such a connection takes place, in most cases, using a welding machine and a milling machine. The part of the fitting which is installed inside the hose is welded to the flange itself, and special wave-like notches are made onto the device. Afterward, when the connection is installed on the hose and crimped with clamps, these notches make it possible to exclude the outlet of the fitting from the hose when pressure is applied.
Crimping with clamps for a high pressure hose assembly can be done either manually or using a crimping machine. Such solutions are used where the risk of depressurization is unacceptable (for example, when pumping oil products), or it is necessary for the hose to work under pressure for a long time.
This type of hose assembly is most often used for rubber and composite hoses when pumping oil and petrochemicals, as the pressure that the flange connection withstands directly depends on the operating pressure of the hose itself.
Many industrial enterprises work with combustible materials such as nitrogen and other chemical liquids. Therefore, in addition to tightness, insurance is also needed in case of any spontaneous hose disconnection from the aggregate unit. For example, if a human error was made in forgetting to pull the fuel hose out of the gas station before beginning movement, the machine will pull the hose behind it and rip it out of the dispenser. For such cases, special dry disconnect couplings and burst couplings have been developed, which completely eliminate the risk of depressurization of the hose assembly.
On the contrary, when a maximum axial load occurs, the bolts are torn off and the inner section is closed, thereby preventing leakage of the fluid pumped inside. The material of the breakaway coupling is either aluminum or corrosion-resistant stainless steel. The coupling can withstand pressures up to 40 bar, though the connection can be either flanged or threaded (the type of thread is selected in accordance with NPT or BSP standards). The range of operating temperatures is from -163°C to + 200°C, with the operating pressure up to 25 bar, so the connection can be made of any kind of steel, depending on the requirements of the pumped product.
For cryogenics, special dry disconnect couplings have been developed that can withstand temperatures down to -20°C. In other words, a similar type of hose assembly is passive security against situations where a hose could be subjected to accidental high loads.
With the development of modern technologies, rubber hoses have begun to be replaced by hoses made of polymer materials. For example, hoses that are flat-rolled and made of thermoplastic polyurethane. These hoses are used in cases where it is necessary to quickly deploy the pipeline and start pumping in the shortest possible time. Of course, hose assemblies with flanges are not suitable for working on a permanent basis, since it is necessary to installation quickly. This is why special fast-removing couplings were invented.
Hose assemblies with fast removing couplings are a connection in which the hoses are attached to each other using a special sealing cuff, which is fixed between two counterparts with a lock. The diameters of such connections vary from 25mm to 300mm, though depending on the material of manufacture, as a rule, this is often either galvanized or stainless steel. It is also worth noting that such hose assemblies can withstand pressure from 10 to 100 bar, as the pressure directly depends on the diameter of the hose — the larger the diameter, the less pressure the hose can withstand. This type of connection can be manually installed in the field and does not require special skills from the operating personnel. The connection itself is fixed to the hose using a special crimp three-piece coupling, which only requires a wrench. In addition, the hose assemblies can include various tees and elbows.
Tees, Joints, Claws, and Connections
A common problem when laying a flexible pipeline, are both the man-made and natural obstacles; these can lead to the formation of kinks in the hose. It is necessary for process operation that the hose be installed without any bends.
If a line needs to be divided into several streams, hose tees are used to do so. A special groove is cut out on the tee and the branch, which is suitable for the installation of the lock connection to ensure complete sealing of the hose. On rubber, composite, and other hoses, Camlock, Storz, Geka joints are also used.
Types of Joints
Camlocks, an American-type joint, are divided into male and female couplings that are manufactured from aluminum, brass, or stainless steel in order to suit the pumped product and its chemical properties. In the case of brass, intrinsic safety is required. They are joined together by clicking special cam joints. This type of connection can withstand working pressures up to 16 bar, and can include diameters that vary from 1″ to 6″. Connections can be presented in the form of a counterpart with an internal or external thread and a flanged end. This is perhaps one of the most common connections in the world (since they are very easy to install on a hose) as this design is enough to insert the fitting inside and squeeze it from above with a clamp using a wrench. No special qualifications are required from the service personnel preforming these types of assembly.
One of the negatives of the aforementioned connection is its division into female and male counterparts. This situation can be problematic if the operator buys two hoses to connect to each other and both ends are male; the hose will have to be supplied with the matching half. In the case of a line length of several tens of meters, it can create certain inconveniences during installation.
Hose assemblies of the Storz type are a universal joint, which is not divided into male and female counterparts, but is rather a coupler with several canines (two or three claws depending on the diameter). Connection diameters can range from 1″ to 6″; from 4″ onward a special wrench is required and manual installation is difficult.
It is worth noting that different manufacturers have a different distance between the canines, or the so-called KA. Therefore, this is the main parameter that should be monitored during assembly of Storz. For example, for a 2 1/2″ connection, the distance between the claws can be 81mm or 89mm. It is very difficult to see this difference, and therefore, this feature should be taken into account prior to assembly. The fangs are also quite fragile and can be damaged if dropped from a height, so the material of manufacture should be considered; this is also true of Camlock aluminum stainless steel, or brass joints. These hose assemblies are mainly used on military and civilian ships.
Connections like Geka, Tankwagen, Guillemin are analogues of the Storz system, and have a similar range of diameters and materials used in the manufacture. The primary difference between the two is that the Tankwagen connection has 12 claws instead of two or three. All connections of this type are used as a temporary solution and are not used on a permanent basis.
In order to ensure adequate hose sealing, special rubber hoses are used which can be made of both EPDM rubber and Teflon, especially if special resistance to high temperatures and aggressive pumped medium is required.
Auxiliary and extremely useful equipment for hose assemblies can be special suspension devices, such as hosebuns. They are used in cases where it is necessary to exclude the hose from the hall in the case of its hanging above the ground. Hosebun is made of special urethane and can support hose assemblies with diameters from 32mm up to 300mm.
Each country has its own specific standards of connections used for hose assembly, many of which are regulated at the state level. It is common that the connection within a hose is used only within one country and is not known to the rest of the world. For example, in Russia, a Bogdanov type connection is used for fire hoses and is not seen in other countries. Thus, whether it is a manufacturing enterprise, or a ship, or even a private user, it will always be possible to find the right hose assembly. Everything will depend only on the cost and the process. It is also important to take the requirements of the application into consideration when selecting which type of assembly is most suitable for the hose at hand.
ABOUT THE AUTHOR
Jurij Artiukhov works as the General Manager at PipeTime, LLC. He previously worked as a Sales Manager for MTT Company and Project Manager for SOL SP Company. He holds a graduate degree from the University of Foreign Affairs, Economy and Law.