Crane Hydraulic Return Flow Control to Prevent Pressure Spikes
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Solution Overview
Problem
Hydraulic systems in cranes experience pressure spikes and drops due to high return flow rates, often exceeding pump delivery rates, which can damage components, and over-dimensioning components to handle these spikes is costly and undesirable.
Innovation Solution
A method to control hydraulic systems by determining the total return flow rate and adjusting the flow rate into hydraulic cylinders using proportional control valves to maintain a predetermined return flow rate limit, reducing flow rates when necessary to prevent pressure spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components are over-dimensioned to handle high return flow rates, then system reliability is improved, but device complexity and cost increase
Solution Approach 1:
The control valve dynamically adjusts the flow rate to the cylinder based on real-time return flow rate feedback. When the return flow rate approaches the predetermined limit, the valve automatically reduces the flow rate, preventing pressure spikes without requiring oversized components. This dynamic adaptation allows components to be sized for normal operating conditions rather than peak stress conditions.
Solution Approach 2:
The control system continuously monitors the return flow rate and uses this feedback to modulate the control valve's opening position. The feedback loop compares the actual return flow rate against the predetermined limit and adjusts the flow rate accordingly, enabling the system to self-regulate and protect components from excessive stress without over-dimensioning.
2Object-affected harmful factors
If flow rate is reduced to prevent pressure spikes, then component stress is reduced, but productivity decreases
Solution Approach 1:
The control system operates in discrete control cycles, continuously monitoring the return flow rate and making periodic adjustments to the control valve. This allows the system to maintain high flow rates during normal operation for productivity, then quickly intervene when return flow rate approaches limits, creating a rhythm of full-power operation punctuated by protective reductions only when necessary.
Solution Approach 2:
The system changes the flow rate parameter dynamically based on operating conditions. During normal operation, the flow rate is maintained at high levels for productivity. When the return flow rate approaches the predetermined limit, the system changes the flow rate parameter to a reduced level to prevent pressure spikes, then can restore it when conditions normalize.
Data Source
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AI summary
A hydraulic system for operating a working equipment, said hydraulic system comprising a set of hydraulic cylinders (5, 6, 7), each having a first port (17, 18,19) and a second port (20, 21, 22) on opposite sides of respective piston (8, 9, 10), a tank (23) for housing hydraulic fluid, a pump (24) configured to pump hydraulic fluid from the tank (23) to each cylinder, and a set of hydraulic control valves (25, 26, 27), one for each cylinder, each control valve (25, 26, 27) being configured to control a flow of hydraulic fluid from said pump (24) to one of the first port (17, 18, 19) and the second port (20, 21, 22). The hydraulic system comprises means for determining the total return flow rate from said cylinders (5, 6, 7) to the tank (23), and a control unit (28) configured to control the flow rate of hydraulic fluid to said first or second port (17-22)) of the cylinders (5, 6, 7) on basis of the determined total return flow rate, such that a predetermined return flow rate limit is not exceeded.