How to check the pressure loss and system fever of hydraulic system

The checking calculation of pressure loss and system heating of hydraulic system involves a series of calculation steps and formulas.

The following is a detailed explanation of these two aspects:

Checking calculation of pressure loss:

The pressure loss of the hydraulic system mainly includes the pressure loss ΔpL along the way of the oil flowing through the pipeline, the local pressure loss Δpc and the pressure loss ΔpV flowing through the valve components. The total pressure loss Δp can be calculated by the following formula:

Δp = ΔpL Δpc ΔpV

The pressure loss along the path ΔpL: when the flow in the pipe is laminar, the following empirical formula can be used to calculate:
ΔpL = 4.3V · q · L× 10 ^ 6/d^ 4 (Pa)

Where q is the flow rate through the pipeline (m3/s);L is the pipeline length (m);d is the pipeline inner diameter (mm);υ is the kinematic viscosity of the oil (m2).

Local pressure loss Δpc: can be estimated by the following formula:
Δpc = (0.05~0.15)ΔpL

The pressure loss ΔpV of valve components can be approximately calculated using the following formula:
Δpv = Δpn (qv/qvn) ^ 2 (PA)

Where, qVn is the rated flow of the valve (m3/s);qV is the actual flow through the valve (m3/s);Δpn is the rated pressure loss of the valve (Pa).

After checking the pressure loss, it is necessary to determine whether the requirements are met according to the adjustment pressure of the system. The adjustment pressure p0 of the system should be greater than or equal to the sum of the working pressure p1 of the actuator and the total pressure loss Δp, namely:

p0 ≥ p1 Δp

System fever checking:

The heating of the hydraulic system is mainly caused by the power loss. The calorific value per unit time Φ can be calculated by the following formula:

Φ=P2-P1 (kW)

Among them, P2 is the input power of the system (that is, the input power of the hydraulic pump), and P1 is the output power of the system (that is, the output power of the actuator).

If there are a plurality of processes in one work cycle, the average calorific value per unit time of the system can be obtained from the calorific value of each process. The specific formula relates to the working cycle period T, the working time ti of each process and the input power Pi of the corresponding process.

In addition, the heat dissipation of the hydraulic system needs to be considered. When the hydraulic system works for a period of time, it reaches a thermal equilibrium state, and the calorific value of the system is equal to the heat dissipation. The heat dissipation coefficient and heat dissipation area are the key factors affecting the heat dissipation effect, which need to be calculated and selected according to specific conditions.

Please note that the above are only basic checking steps and formulas. In practical applications, other factors may need to be considered, such as oil temperature, oil quality, and equipment aging. Therefore, when checking the pressure loss and system heat of the hydraulic system, it is recommended to refer to the relevant engineering manuals, standards or consult professional engineers for more accurate guidance.