To connect hoses to each other, as well as to other aggregate units, a wide variety of different connecting elements are used. It is impossible to make a universal connector that would fit any piece of equipment, as each country has its own production standards
and consequently its own connection requirements. Modern connector manufacturers therefore offer several fitting variations. Depending on the type of connection, and the intended application, two main types of the hose clamping and crimping are used to ensure the integrity of the connection: manual and/or mechanical.
By Jurij Artiukhov, General Manager, PipeTime, LLC
Generally, the required fitting for an application is selected based on three primary criteria: the parameters of the counterpart – whether it is a hose or an equipment connection -, the assembly speed required, and if the system involves stationary operation for a long period of time. Whether the fitting is clamped or crimped manually is dependent on the pressure requirements of the hose.
Manual Crimp and Clamp Fittings
While there are several types of fittings that are manually installed, two of the most commonly used fitting that employ this method are camlocks and STORZ connections.
For applications which require a hose to operate at relatively low pressures – up to 40 bars, Camlocks are often the most popular option, see Image 2. These types of connections are divided into male and female categories, varying in diameter from 1″ to 6″, and have a working pressure between 10-16 bar.
Camlocks can be made to connect using either internal or external threads, or they are used with a counterpart in the form of a flange, or branch. They are often also connected to each other with the help of special clamps located on the sides of the connection. The material of the camlocks is selected in accordance with the product being pumped, and can range from aluminum to stainless steel and brass. Inside the mating part of the camlock there is a sealing rubber seal, which can also be selected depending on the aggressiveness of the pumped liquid – EPDM, TEFLON, and etc.
These fittings are often considered one of the most famous types of connections in the world. They are used in almost every country and sought out by operators as they allow for hose collection in the shortest possible time.
Image 1: Hydraulic hose crimping.
Another type of connection that has gained its fame in Europe and Asia is the STORZ type connection. This connection is most often found and used for firefighting needs; it can be found on fire hoses, fire hydrants, etc. see Image 3.
One of its advantages over, for example, a camlock connection is the absence of a division into male and female ends. The elimination of these ends prevents the loss of efficiency if the hose is laid out in the wrong direction and two female ends are accidentally intended to connect. The amount of time used to correct the hose can be problematic in an emergency, such as a fire.
STORZ connections have 2-3 claws on each end (mate), which are snapped together. The snapping is achieved by twisting the connecting elements; for diameters 4″ and above, a special connecting key is required, since installation without it will be difficult.
The connections themselves can range in diameters from 1″ to 6” and have a sealing rubber cuff to seal the joints. Typically, the seal is made of EPDM rubber, since STORZs are rarely used for pumping aggressive liquids. The connection body itself is generally made with aluminum, as these connections are primarily used in applications that pump water. Aluminum is a lightweight material, which makes it easier for the fire brigade to deploy the fire hose line.
In special cases, STORZ are made of bronze or brass. These materials are intrinsically safe, that is, they do not spark when they hit each other or other surfaces, which is a primary requirement for specialty applications, such as the shipbuilding industry.
Image 2: Camlock type couplings. Image 3: STORZ couplings.
Manual Installation Process
The connection installation principle for both these fittings is as follows:
• Before pushing the connection inside the hose, it is necessary to string the clamps on the hose.
• Clamps must be selected based on the operating pressure of the hose, see Image 4.
• The clamps themselves can be ordinary or reinforced. Conventional clamps are designed for a pressure of 3 bar or less. As a rule, two pieces are installed for each connection.
• Reinforced clamps come in two bolt and four bolt and are designed for pressures up to 20 bar. They can be installed one for each connection, but it is better to put two on each end of the hose.
• Clamps can be made of galvanized or stainless steel, it all depends on the nature of the pumped medium and external factors (presence of oil products, sea water, immersion in water or other solutions).
• Clamps are selected in accordance with the outer diameter of the hose, that is, if the outer diameter of the hose, is 25mm, for example, then
it is better to choose a clamp in increments of 5mm; a clamp with dimensions of 20-35mm. 20mm is the diameter of the clamp with maximum crimping, 35mm is a free state.
• When clamping the two clamps to the end of the hose, it is advisable to try to make the clamp bolts look in different directions. This is necessary for the convenience of crimping of the hoses.
• It is important not to overtighten the clamps, as they can damage the outer layer of the hose with their edges, even though the edges of the clamps are rounded.
• If overtightened, the bolt may crack and the clamp will not work. It is, therefore, always good to have spare clamps in case it fails, or is rejected, during installation.
• The connection shank is stocked inside the hose. If the connection does not fit well into the hose, oil or soap can be used as a lubricant.
• Nearing the very end of the installation process, a hammer is required to completely drive the hose shank into the hose. Tapping with a hammer, or sledgehammer, is carried out strictly on an intermediate surface. This is typically a board or a piece of rubber, and is used in order to prevent bending or breakage of the connecting elements (for example, the fangs of the STORZ connection).
• During the operation of hoses, it is imperative to check the tightening torque of the bolts each time the hose is put into operation; it is desirable to carry out hydraulic tests in the field of hose assembly, see Image 5.
Image 4: Clamps. Image 5: Installed Camlock fitting.
As an exception, it should be noted that camlocks can be mechanically installed on hoses. For example, camlocks are installed by welding to the hose body on cryogenic hoses.
Another common exception where Camlocks are mechanically installed in with polyurethane flat-folding hoses. This type of hose can also be fitted with connections such as STORZ, GEKA, etc., however they are generally reinforced clamps. Given the fact that flat hoses can handle pressures up to 63 bars, special fast removing couplings (FRC) have also been developed, see Image 5.
FRC couplings are available in aluminum, stainless steel, copper, and brass. The process of the clamping and crimping is as follows:
- An FRC shank is pushed into the hose. To facilitate the installation process, lubricants or a special jack can be used to expand the hose inlet.
- After stuffing the shank into the hose, it can be slightly knocked out with a hammer or a sledgehammer strictly through a cushioning material – a board or a piece of rubber.
- Crimping is then done using three sectional crimps, which have a semicircular shape and the inside of which is wavy.
- It is desirable to control the tightening torque of the bolts with a torque wrench. The use of other tools can result in overtightening and breaking the bolt.
- After installation of the connections, it is imperative to carry out hydraulic tests in order to identify possible leaks in the connections caused by incorrect installation.
In fact, the installation is simple, but it requires a certain skill from the person who performs it. Each of the clamped sections must have a certain gap from the previous section; it is a very controlled process.
Mechanical Installation Process
Hose clamping and crimping with mechanized installation is used for high pressure hoses, where the pressure can reach up to 400 bars. There is a substantial number of connections used for high pressure hoses as many pieces of equipment that are manufactured in one country are exported to other countries and therefore have different metric systems.
Fittings for high pressure hoses are divided according to the type of seal and the type of thread.
Seal types include:
• BSP, JIC, JIS – cone seal;
• DKO-L, DKO-S, SFS, SFL, STECK -ring or cone seal;
• DK – spherical compaction;
• NPTF, BSPT, NKT – taper thread seal;
• ORFS – gasket seal;
• Banjo – bolt seal.
Thread types include:
• European type (DIN);
• English (BSP);
• American (SAE).
Mechanical hose clamping and crimping takes place with the help of specialized devices called hydraulic crimping presses, which require mandatory qualification and training of personnel, see Image 1.
• High pressure hoses, in most cases, require mechanized stripping of the inner and outer rubber layer before crimping the connector.
• With the help of special lubricating fluids, the connection is installed inside the hose.
• If considering industrial-scale crimping of the hoses, then it is necessary to use pneumatic units, which speed up and facilitate the installation process by an order of magnitude.
• After installing the bushing inside the hose, its outer part is crimped with a crimping bushing or crimping hose, which allows the shank to be fixed inside the hose, see Image 7.
• Hose clamping and crimping personnel must consider the fact that if the crimping press compresses the crimping hose too much, the high-pressure hose reinforcement cage will collapse. If the cage collapses, the hose will be rejected; the damaged section will have to be cut out with a cutting tool (mechanical cutter and etc).
• After the hose clamping and crimping process, it is mandatory to carry out hydraulic tests. It is advised that the test be conducted at ultra-high pressures with a pumped aggressive medium. These tests are required before each hose is put into operation.
Depending on the type of connections chosen, the process of hose clamping and crimping may vary. Each of the methods, both manual and mechanical, have their pros and cons. All of the varying factors must be taken into account and controlled to avoid injury or down times. For this, personnel must be trained or read the installation instructions.
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.