Aug. 19, 2024
Hydraulic hose fittings are crucial for connecting hoses, tubes, and pipes to components such as pumps, valves, and cylinders within a hydraulic system. Selecting the wrong fitting can severely impact the efficiency of the entire system and potentially create significant safety hazards. If you're feeling overwhelmed by the variety of shapes, materials, threading, and sealing options available, refer to our guide to help you choose the most suitable fitting for your needs.
When assembling a hydraulic hose, the selection of the correct fitting often becomes a key decision. Crimping is the most common method used for this assembly. Before starting, it's essential to consider five key factors, summarized by the acronym S.T.A.M.P.: Size, Temperature, Application, Materials/Media, and Pressure. Once these specifications are clear, a hose assembly technician can proceed with the process.
The typical crimping procedure involves the technician marking the hose for insertion depth, applying lubricant to the fitting stem, and inserting the stem into the end of the hose. The hose and fitting are then placed into the crimper die. The technician activates the crimper to apply pressure and secure the fitting onto the hose. If you have any questions or need assistance in choosing the best fitting, a hose assembly technician can provide valuable guidance and support.
Hose fittings come in various materials, each affecting their performance and suitability for different applications. The choice of material determines the fitting's properties, including its strength, durability, and resistance to environmental factors. Common materials for hydraulic hose fittings include plastic, steel, stainless steel, and brass.
Plastic fittings are resistant to corrosion but are generally weaker and less durable than metal fittings. Despite their affordability and corrosion resistance, they are less commonly used in hydraulic applications due to their lower pressure ratings.
Steel fittings, made from a mix of iron and other metals, offer greater durability and heat resistance. For example, carbon steel fittings, composed of iron and carbon, can handle temperatures ranging from -65°F to 500°F. They are more suitable for high-pressure applications compared to plastic fittings.
Stainless steel fittings are ideal for extreme temperature ranges from -425°F to 1200°F and are highly resistant to corrosion. They are typically rated up to 10,000 psi, with some specialized designs reaching up to 20,000 psi. However, their high cost often leads users to consider other options if budget constraints are a concern.
Brass fittings are less durable than stainless steel but still offer reliable, leak-free performance. They meet various industry standards such as SAE, ISO, DIN, DOT, and JIS. Brass fittings can operate within a temperature range of -65°F to 400°F and handle pressures up to 3000 psi, though lower pressure ranges are generally recommended for optimal performance.
Hydraulic hose fittings generally fall into two main categories:
These are the most commonly used fittings and require a crimping machine for attachment. The crimping process ensures a secure and permanent connection between the hose and fitting.
Ideal for situations where a crimping machine is unavailable, field attachable fittings can be assembled in the field without specialized equipment, provided that the hose is compatible with these types of fittings.
Hydraulic fittings can also be classified based on their shape into the following types:
- Plugs
- Unions
- Elbows
- Crosses
When using NPT (National Pipe Taper) pipe thread fittings, be cautious. While tightening these fittings may seem like an easy fix for leaks, it can increase the risk of cracking, especially with repeated adjustments. To reduce this risk, use O-rings with elastomeric seals such as DIN 2353 or SAE J1453, and consider switching to untapered JIC fittings. Ensure elastomeric seals operate within their recommended temperature range, as exceeding this can damage the seals and cause leaks.
As equipment modernizes, higher operating pressures often result. Many customers now prefer O-ring seals for their resistance to cracking and their ability to prevent over-torqueing and leakage. Stainless steel fittings offer the highest pressure ratings and are well-suited for high-pressure applications.
Vibration can affect hydraulic plumbing by shifting torque and causing fatigue. Regularly inspect areas prone to high vibration for signs of leaks and damage to ensure system integrity.
The temperature range for tube fittings is determined by the material, plating, and any seals used. For leak-free performance, use O-ring seals if the operating temperature permits. Refer to the temperature range tables for common fitting and seal materials. For extreme temperature conditions, special hydraulic hoses and fittings are available—contact us for more information.
Ensure that the hose's inner tube, cover, fittings, and O-rings are chemically compatible with each other. Pay particular attention to hoses used for gaseous applications to avoid risks such as explosions or exposure to toxic fumes. Verify with the manufacturer that all components are chemically compatible. Additionally, ensure that the seals are compatible with the hydraulic fluid in your system. Refer to Parker’s Guide for Chemical Resistance Information for more details.
Timely replacement of fittings is crucial, especially if lead times are long. Most NPT and JIC fittings are widely available and come in various configurations. To avoid delays, choose fittings that are readily accessible or keep a stock of specific fittings with longer lead times.
Both SAE and ISO standards advise against mixing hose end fittings and hoses from different manufacturers. This recommendation primarily centers on safety. Combining fittings from one manufacturer with hoses from another can lead to failures or ruptures at the crimp due to incompatibility. Variations in how fittings are secured to hoses and differences in allowable crimp tolerances can contribute to these issues.
Regular inspection of your hoses and fittings is crucial to ensure secure connections and to check for leaks, ideally every few months. Even newly selected fittings can cause problems if not chosen correctly. While choosing hydraulic fittings can seem daunting, following our straightforward guide should simplify the process.
For more information on selecting hydraulic fittings, contact us to speak with a fluid connector specialist.
