Aux 1 Unit 9 Q3

In the context of a hydraulic steering gear, motoring refers to the unintended rotation of an idle hydraulic pump caused by the flow of hydraulic fluid from the active pump within the system.

How it happens:

• Multiple Pumps: Hydraulic steering gears often have multiple pumps for redundancy and increased power. When only one pump is actively supplying fluid to the system, the other pump(s) remain idle.
• Fluid Flow: The pressurized fluid from the active pump flows through the system, including the hydraulic lines connected to the idle pump.
• Reverse Rotation: If not prevented, this fluid flow can cause the idle pump to rotate in the reverse direction, acting like a motor rather than a pump.

Why Motoring is Undesirable:

• Wear and Tear: Motoring puts unnecessary stress on the idle pump’s bearings, seals, and other internal components, leading to increased wear and tear and potentially reducing its lifespan.
• Efficiency Loss: The active pump has to work harder to overcome the resistance of the rotating idle pump, resulting in reduced overall system efficiency and increased energy consumption.
• Noise and Vibration: Motoring can generate noise and vibration within the system.

Prevention of Motoring:

Several methods are employed to prevent motoring in hydraulic steering gear systems:

• Automatic Isolating Valves: These valves automatically close when a pump is idle, preventing fluid flow through it and thus preventing motoring.
• Check Valves (Non-Return Valves): Check valves allow flow in only one direction, preventing backflow into the idle pump.   1. What is a Check Valve and How Does it Work? | The Lee Co – The Lee Company www.theleeco.com
• Bypass Lines with Restrictors: A small bypass line with a restrictor can be installed between the pump’s discharge and suction sides, creating a slight back pressure that prevents motoring.
• Mechanical Locking Devices (Older Systems): Some older systems might use mechanical devices like pawls and ratchets to physically prevent the idle pump from rotating backward.

Importance of Preventing Motoring:

• Increased Reliability: Preventing motoring helps maintain the health and longevity of the idle pump, ensuring it’s ready to operate when needed in case the primary pump fails.
• Improved Efficiency: Reduces energy losses and improves the overall efficiency of the steering gear system.
• Reduced Noise and Vibration: Minimizes unwanted noise and vibrations in the system.

In summary:

Motoring is an undesirable phenomenon in hydraulic steering gears where an idle pump rotates in reverse due to fluid flow from the active pump. This can lead to increased wear, reduced efficiency, and noise. Various methods, like automatic isolating valves, check valves, and bypass lines, are used to prevent motoring and ensure the smooth and reliable operation of the steering gear system.

In a hydraulic steering gear system with multiple pumps, it’s important to prevent the idle pump (the pump that’s not actively supplying fluid) from “motoring,” which means rotating in the reverse direction due to the flow from the active pump. This motoring can cause unnecessary wear and tear on the idle pump, reduce system efficiency, and potentially lead to damage. Here are some methods commonly employed to prevent this:

1. Automatic Isolating Valves:

• Function: These valves are installed in the discharge line of each pump. When a pump is idle, its associated isolating valve automatically closes, preventing fluid from flowing back through it and causing it to motor.
• Operation:
  • Pressure-Actuated:** The valves are typically pressure-actuated. When a pump starts and builds pressure, it overcomes a spring or pilot pressure in the isolating valve, opening it and allowing fluid flow. When the pump stops, the pressure drops, and the valve closes.
  • Solenoid-Operated: In some systems, the valves might be solenoid-operated, controlled by the control system based on pump status.

2. Check Valves (Non-Return Valves):

• Function: Check valves allow flow in one direction only, preventing backflow. They can be installed in the discharge line of each pump as an additional measure to prevent motoring.   1. What is a Check Valve and How Does it Work? | The Lee Co – The Lee Company www.theleeco.com
• Operation: When the pump is running, the pressure forces the check valve open, allowing fluid to flow. When the pump stops, the check valve closes, blocking any reverse flow.   1. What Does a Check Valve Do: The Critical Component in Fluid Control www.dombor.com

3. Bypass Line with Restrictor:

• Function: A small bypass line with a restrictor orifice can be installed between the discharge and suction sides of each pump.
• Operation:
  • When a pump is idle, a small amount of fluid is allowed to flow through the bypass line, creating a slight back pressure that prevents the pump from motoring.
  • The restrictor limits the flow, minimizing energy losses and ensuring the active pump can still deliver sufficient flow to the system.

4. Mechanical Locking Devices (Older Systems):

• Function: In some older systems, mechanical locking devices like pawls and ratchets might be used to physically prevent the idle pump from rotating in the reverse direction.
• Operation: When the pump is stopped, the pawls engage with the ratchet, preventing reverse rotation.

Importance of Preventing Motoring:

• Reduced Wear and Tear: Motoring causes unnecessary wear on the idle pump’s bearings, seals, and other internal components, potentially shortening its lifespan and requiring more frequent maintenance.
• Improved Efficiency: Motoring can lead to energy losses and reduced overall system efficiency, as the active pump has to overcome the resistance of the rotating idle pump.
• Noise Reduction: Motoring can also generate noise and vibration in the system.

Conclusion:

Preventing idle pump motoring is essential for ensuring the efficient, reliable, and long-lasting operation of hydraulic steering gear systems. By employing methods like automatic isolating valves, check valves, or bypass lines with restrictors, the system can effectively prevent backflow and protect the idle pump from unnecessary wear and damage.Sources and related content