Hydraulic Hose Volume Calculator
Estimate hydraulic oil held in one or many hose lines, then add accumulator allowance, fitting reserve, temperature expansion, and oil weight for service planning.
Load a realistic hydraulic line, then adjust hose ID, length, line count, oil density, accumulator allowance, and temperature rise.
Hydraulic Hose Volume Results
| Common hose ID | Dash size | Volume per 10 ft | Typical service note |
|---|---|---|---|
| 1/4 in / 6.4 mm | -4 | 0.025 gal / 0.09 L | Pilot, gauge, compact actuator, brake and control lines |
| 3/8 in / 9.5 mm | -6 | 0.057 gal / 0.22 L | Pressure feed, small auxiliary circuit, short jumpers |
| 1/2 in / 12.7 mm | -8 | 0.102 gal / 0.39 L | Medium pressure, cylinder A/B pair, normal return line |
| 5/8 in / 15.9 mm | -10 | 0.159 gal / 0.60 L | Higher flow tool circuit or low restriction return |
| 3/4 in / 19.1 mm | -12 | 0.229 gal / 0.87 L | Return, suction, case drain header, pump inlet estimate |
| 1 in / 25.4 mm | -16 | 0.408 gal / 1.54 L | Main return, suction line, high flow power unit plumbing |
| Fluid preset | Density lb/gal | Density kg/L | Expansion note |
|---|---|---|---|
| ISO VG 22 mineral hydraulic oil | 7.18 | 0.86 | Light oil; use default thermal expansion for planning |
| ISO VG 32 mineral hydraulic oil | 7.22 | 0.87 | Common mobile oil with moderate viscosity change |
| ISO VG 46 mineral hydraulic oil | 7.25 | 0.87 | Default general hydraulic oil in this calculator |
| ISO VG 68 mineral hydraulic oil | 7.31 | 0.88 | Heavier oil; confirm density at operating temperature |
| Universal tractor hydraulic fluid | 7.18 | 0.86 | Use when machine oil is a combined hydraulic and transmission fluid |
| Water glycol hydraulic fluid | 8.75 | 1.05 | Heavier fluid; use the data sheet expansion coefficient |
| Allowance item | Typical entry | Volume effect | Calculator use |
|---|---|---|---|
| Straight hose only | 0% allowance | Matches bore volume only | Use for exact replacement hose capacity checks |
| Couplers and adapters | 5% to 10% | Adds small unmodeled oil pockets | Good default for normal field hose assemblies |
| Long machine routing | 15% to 20% | Adds purge and route uncertainty | Use when measured length is approximate or routing is complex |
| Accumulator exchange | Fixed volume | Adds explicit reserve oil | Enter expected usable oil volume or service fill margin |
| Hot oil expansion | Temp rise | Raises occupied volume | Use fill and operating temperatures for reservoir headspace checks |
A hydraulic system contain many volumes of fluid that are located within the hoses of the hydraulic system. The hoses may appear simple and small in size, yet they can hold many gallon of oil. The total volume of the oil in the hose depends upon the length of the hoses, the inside diameter of those hoses, and the number of hoses that is running in parallel with one another.
The total volume of the oil in the system is needed for determining the size of the reservoir, the amount of fluid that is needed to refill the system with the correct amount of fluid, and to determine if the accumulator of the system has enough reserve fluid to handle a spike in the system’s pressure. If the total volume of the oil in the system is not accurately calculate prior to operation, the fluid level within the reservoir may drop to a level further than that which was initially calculated when the machine begins to heat during operation. The inside diameter of the hoses is the single most important factor to consider in calculating the total volume of the oil within those hoses.
How to Find the Oil Volume in Hydraulic Hoses
Hoses with a quarter-inch inside diameter will contain very little oil compared to a suction line with a three-quarter-inch inside diameter. In many cases, individuals may incorrectly use the size of the dash on a fitting to determine the inside diameter of the hoses. The inside diameter of the hoses is often smaller than the size of the dash due to the diameter of the liner and reinforcement layers of the hoses.
Thus, the user will have a more accurate total volume if they uses the true measured bore of the hoses in the calculations. Additionally, the temperature of the hydraulic fluid can impact the total volume of the fluid. When the oil within the system is filled at a temperature of sixty degrees, those fluids will expand to occupy more space within the hoses when the fluid temperature reaches temperatures of around one hundred forty or one hundred fifty degrees.
Though the expansion of oil within a single line of a hydraulic system is small, the expansion of the oil in a large number of lines will be significant. Thus, the system’s reservoirs are sized to provide headspace for the oil to expand in size, as are the accumulator of the system. If the temperature increase within the system is ignored, the fluid may expel from the breather of the reservoir as the oil expands within the system.
The density of the oil introduces another factor into the calculations. The density of the fluid will impact the total weight of the fluid in each of the hoses. The heavier the fluid, the more weight will be placed upon the reels of the fluid, the amount of force that is used to support the booms of the machines, and the amount of force that is used to drain the fluid from the system.
Additionally, if there is too much resistance in the suction lines for the hydraulic pumps to effectively move the fluid from the reservoir, the pumps may become starved of fluid. A calculator allows for the selection of a common grade of hydraulic oil or for the entry of a custom value for the density of the fluid. The accumulator is a component of the system that exists outside of the hoses, yet it is a component that must still be accounted for when calculating the total volume of oil within the system.
The accumulator is used to store the fluid that will be released later within the system, and the pressurized fluid must come from somewhere within the system. Thus, a fixed volume of fluid for the accumulator must be accounted for in the calculations to ensure that there is enough fluid to supply the system if the accumulator is used to supply the system. Additionally, the volumes for the fittings of the system and the purge allowance should also be accounted for within the calculations.
The type of service provided by the hoses can have a major impact upon the calculations of the total volume of oil within the system. For instance, suction lines require more conservative sizing in comparison to the other lines in the system. Additionally, velocities within the fluid within return lines can produce heat that the reservoir removes from the system, and high velocities of fluid can contribute to the formation of aeration within the system.
Likewise, the velocity within the pressure lines, which exist in between the suction and return lines, impacts both the amount of heat created within the system as well as the chance of formation of pressure spikes. Thus, each type of line require different calculations for the total volume of oil to be present within those lines. Most actual machines incorporate many hoses in place of the single hose that may be represented in some of these calculations.
For instance, excavators can incorporate many hoses that are located along the boom of the excavator. Thus, the total volume calculations will have to consider each of those hoses to accurately calculate the amount of fluid that may be required by those machines. The calculator can account for multiple lines or sets of lines in parallel if the number of lines is entered in the calculator.
Thus, the total volume of each of the hoses in the machine can be calculated to provide insight into how much fluid is used by the hoses in total. Most individuals that attempt to calculate the total volume of oil in the hoses will commit a few common mistakes. For instance, individuals often use the size of the hoses instead of the inside diameter of the hoses.
Additionally, individuals often do not account for the fluid on both sides of the cylinder. Other errors may involve ignoring the effect of temperature upon the fluid, or ignoring the volume of the accumulator. By knowing the total volume of oil that is used in the system, individuals can make a few different decisions regarding operation of the system.
For instance, the total volume can help to indicate how high to set the fluid level within the reservoir. Additionally, knowing the total volume will also prevent the reservoir from being overfilled with oil, which could lead to spillage of that oil when the machine heats during operation. Additionally, the total volume can provide insight into how much of the fluid can be ordered for the machine to replace the fluid that is used.
Though these factors are small in impact, they are still factors that should of been considered for those that use the machines. Referencing a table that includes common sizes for hoses and fluids can help individuals to verify the entered values. Additionally, the tables can help to ensure that the density of the fluid that is entered is consistant with the grade of oil that is used in the machines.
Additionally, the tables can help for those that work with both imperial and metric units and need to refer to the other system to make certain that they have properly entered the sizes of each component of the system. By accounting for each of these variables and factors, the system will be able to have its hose volumes accounted for and controlled. By accounting for the inside diameter of each of the hoses, the length of those hoses, the number of hoses, the temperature of the fluid, the volume of the accumulator, and the volume of the fluid in the system, the hydraulic system will behave in a manner that is expected and controlled.
Thus, the accuracy of each of these variables will ensure that the individual making the calculations will experience fewer surprises when the machine is running at its normal operating temperature with its normal load.
