The UK and continental European construction equipment market is valued at £5.5 billion and is expected to reach £7.9 billion by 2027, registering a Compound Annual Growth Rate of over 6% during the next five years. As the construction industry grows, so does the hydraulic fitting market.
The most common hydraulic fitting threads styles in much of the world, and particularly in Europe, are BSP and DIN. Each is available with O-ring connections for specific applications. While the JIC fitting is also very popular in Europe, its 37° flare seating surface with straight threads provides optimum metal-to-metal sealing without the need for an O-ring or tapered threads.
While BSPP fittings require a bonded seal ring or O-ring to seal, BSPT and JIC fittings do not due to their tapered threads providing a positive metal-to-metal seal. However, the ORB and Face Seal fittings use O-rings to establish excellent leak-free connections. How and where are these fittings used by heavy equipment OEMs in the UK and Europe?
The five largest UK and European OEMs of construction, agricultural and road equipment are:
- CNH Industrial NV (headquartered in the UK/incorporated in Amsterdam, Netherlands)
- JCB (UK)
- Liebherr Group (Germany-Switzerland)
- Volvo Construction Equipment (Sweden)
- Wirtgen Group (Germany)
It’s no surprise the UK’s JCB primarily uses British Standard Pipe (BSP) fittings in their equipment. Though JCB equipment is popular in the UK, they enjoy sales in 150 countries around the globe. They are widely used in other parts of Europe, plus the U.S., China, India and Brazil, where they have wholly owned manufacturing plants.
German/Swiss OEM Liebherr and Volvo Construction Equipment, based in Sweden, they both predominantly use the European metric DIN (Deutsches Institut für Normung) fitting thread style.
BSP Fittings
BSP, also known as Whitworth style threads, have metal to metal angled surfaces or incorporate metal to metal with an O-ring and sealing surfaces of 60°.
The two BSP thread forms are BSPP (British Standard Pipe Parallel) and BSPT (British Standard Pipe Tapered):
1. BSPP have parallel straight threads and can withstand high temperatures and extreme pressures with a bonded ring seal that is wedged between the base of the male fitting and the female BSPP hole. They are excellent for forming a pressure tight seal and do not require a thread sealant.
2. BSPT do not have a ring seal to secure the connection. Therefore, they require a thread sealant to ensure a leak tight seal.
DIN fittings are the most frequently used metric hydraulic fitting in Europe. DIN (Deutsches Institut für Normung) is a German standardization and are regularly used in construction equipment, industrial hydraulic and pneumatic applications, and the oil & gas industry.
DIN 2353 Pressure Series come in 3 different pressure styles:
- LL = Extra Light for low-pressure
- L = Light in medium pressure
- S = Heavy for high-pressure
1. DIN 2353 24° Cone Light Series (DKL/DKOL): DKL has a 24° cone and DKOL incorporates a captured O-ring seal, each with straight metric threads. The tube OD mates with a 24° recessed counter bore to mate with the male fitting.
2. Metric Standpipe hose fittings have a smooth hose tail on one end and male metric thread on the opposite end. They follow either the DIN 3852 or ISO 6149 standard. These adjustable standpipe fittings enable connection of a 24° conical bore with a metric tube.
3. Banjo Fittings come in metric and BSPP for medium to high-pressure applications (up to 800 bar/11,600 psi and have two components; a spherical union for fluid transfer and a perforated hollow bolt for fluid to pass and are used with rigid or flexible hose.
Many of the thread sizes in each of these series are the same, yet the Heavy Series tube OD is smaller and has a thicker tube wall, rendering it with a smaller ID to handle higher pressures. It's important to note that the light and heavy series are NOT interchangeable due to the different sizes of the tube and sealing cone.
JIC Threads: A U.S. Standard with a European Popularity
Let's first understand the distinction in applications for O-ring Boss and JIC fittings. SAE O-Ring Boss fittings provide superior leak control and vibration resistance in medium to high pressure applications.
The JIC AE J514/MIL-F-18866 standards fitting design comes from the Joint Industry Council
specification and is one of the most common American fitting styles in Europe. JIC fittings (generally known as the JIC 37° flare surface angle with UNF/United National Fine straight threads) give a secure metal to metal seal without requiring an O-ring. JIC fittings provide an excellent sealing capability under high working pressures. They are widely used by Case, a U.S. OEM manufacturer of agricultural machinery owned by CNH Industrial NV, headquartered in the UK.
Depending on the material, such as stainless, JIC fittings are particularly efficient at high pressures of up to 690 bar and temperatures ranging from -254°C to 649°C in many fluid power and fuel delivery applications in construction and agricultural equipment.
BSPP and Metric O-ring Fittings
BSPP fittings use an ISO 1179 O-ring, adjacent to the flat face of the male fitting, instead of a bonded ring seal. In fact, BSPP, O-ring face seal and ISO 6149 metric O-Rings tube fittings use a soft polymer seal to ensure leak-free connections. For applications experiencing high pressure, frequent vibration and/or shock O-ring fittings are typically the preferred connection. However, they are not recommended for use in the presence of high temperatures.
When connecting to a port instead of a matching fitting, the BSPP female port uses an O-ring with a retainer holding it in place. Alternatively, the O-ring can be placed inside a groove in the smooth surface that surrounds the port.
Conclusion
Regardless of the style, fittings with a metal-to-metal sealing surface are typically best for corrosion resistance, high pressures and temperatures- particularly those made of stainless steel. Comparatively, those with O-rings are best for applications experiencing high vibration or shock and can also withstand high pressures.
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