Are Your Hydraulic Hoses STAMPED?
Hoses are a critical component in any hydraulic system, and choosing the right hose for the job is vital as there are a number of aspects to take into consideration. Matching your hydraulic hoses to the specific characteristics of your application will ensure optimal performance and extend the lifetime of your hydraulic equipment.
When it comes to selecting the proper hose for your application, there is an industry-standard acronym you can follow to help guide you: STAMPED. Using this acronym, you can successfully determine the right hose for the specific needs of your hydraulic systems.
Factors in Selecting Hydraulic Hoses
The correct hose size brings into context the inside diameter, the flow requirements, and the length of the entire assembly. Since you need to minimize pressure loss and ameliorate the chances of hose damage due to excessive heat, take into account flow velocity with a mind toward reducing turbulence. As happens within even the best engineered hydraulic systems, bear in mind the impact of high shock loads. Hoses are sized to specific flow velocities either by calculation or by chart. When using a specific hose manufacturer’s nomographic charts, the results are based on hydraulic oil having a viscosity of 315 SSU (Saybolt Seconds Universal) at 100° F (38° C). However, changes in temperature, viscosity, ID roughness and number of bends or fittings can add to pressure loss, so using a 2X to 3X factor is recommended.
Hydraulic hose design includes the working temperature of the liquid flowing through them, typically between 90°-140°F (32° – 60° C) and the ambient temperature of the work environment. Exposing your hoses to temperatures outside of the range for which they’re rated leads to premature deterioration, reduced flexibility, and makes the hoses unreliable. Using the proper viscosity of hydraulic oil protects the hoses from high temperatures. And, design considerations come into play as the hose may be routed near high-temperature components.
High-pressure hydraulic lines need to be placed parallel to the machine’s contours when possible. This requires the hose to meet the required bend radius, which may be different for each hose. Additional factors that may reduce hose life to take into consideration, according to FPJ (Fluid Power Journal) include:
- Operating above maximum or below minimum temperature range,
- Exposing the hose to surge pressures above the maximum working pressure,
- External abrasion, and twisting, pulling, kinking, or crushing.
Across the board, all hose manufacturers recommend never Intermixing hose, connectors, or assembly equipment that they don’t specifically approve. This can void warranties and/or lead to premature failure.
Check your equipment’s compatibility chart to ensure the material composition of the hose assembly is suitable for the fluids used. Take into consideration the impact of gaseous applications where permeation may occur. Loss of fluid may result through the hose pores from effusion or permeation. Here’s some examples; air and compressed gases, liquid, and gaseous fuels, refrigerants, fuel oil, helium and/or natural gas. To combat this, give consideration to using pin-perforated covers which helps avoid fluid build up under the cover. This needs to be considered in every assembly and we recommend the use of chemical resistance tables that list the relative resistance of hose and fitting materials to the more common chemicals. And be mindful of the effect on O-rings as they become a weak link if they are not chemically compatible. Again, hose manufacturers will recommend O-ring material and appropriate lubricants. Fluid concentration, contamination, and temperature all play a role in hose and fluid compatibility. Modern petroleum-based hoses and new biodegradable fluids may not be as compatible as older fluids have been.
A hydraulic hose’s working pressure must be determined and take into account pressure spikes. The possible pressure of a spike must not exceed max pressure of the hose being recommended. An improperly maintained hose can be damaged and burst during a pressure spike, causing catastrophic results. Conversely, pressure drop, the difference between the pressure entering the hose assembly and the pressure at the exit end, has to be taken into consideration. These can be affected by flow rate, friction, velocity, fluid type, assembly length as well as fluid type and temperature
Using a hose with a compatible coupling-to-hose mechanical interface, appropriate matching of threads, helps prevent leaks. Field-attachable couplings provide you with more flexibility for field repairs, while permanent couplings are more commonly used on all equipment. We recommend to our clients that hoses be matched to fittings (end connectors) by the same manufacturer.
Having the correct parts on-hand is key. Without them, maintaining consistent operation of your hydraulic system is put into question. If the hose needs to be certified and/or tested, it needs to be delivered very quickly so that the requisite preparation can be made. This is especially true if the ends need to be specially assembled or installed. DHI offers hose (and tube) assembly fabrication while you wait or they can be ordered ahead of time for pickup or shipping.
Hydraulic Inlet and Return Line Hoses
Not to be overlooked are the hydraulic fluid inlet and return lines. They are often thought of as the least important part of a hydraulic system, but they are as important to the hydraulic “ecosystem” as are the other components. Because return lines carry the hydraulic fluid, typically to a filter on its journey to the reservoir, and the inlet line delivers the oil to your pump (under a vacuum) As such, all hoses need to be paid attention to equally. Applying the STAMPED decision-making process to your inlet and return lines adds an additional layer of protection when it comes to the health and safety of your hydraulic equipment.
Expert Guidance on Hydraulic Hose Selection
Having the right hydraulic hoses for your application can mean all the difference between successful operation and possible damage to your facility or hydraulic systems and equipment, as well as compromising the safety of your working environment. Devine Hydraulics has an experienced, STAMPED-trained, knowledgeable team that can help you find the right hydraulic hoses for your applications, as well as help you maintain them to improve equipment longevity.
Are your hoses stopping you from achieving optimal hydraulic system performance? Contact DHI today.