Question

***THis question relates to water resources engineering***

What are some importances of closed loops in water distributions systems for purposes of maintaining system pressures?

Answer 1

Closed loop hydraulic system are also commonly known as hydrostatic drives and is a system commonly found on mobile machines such as skid-steer loaders and dozers, and on insdustrial machines such as conveyors. In a hydrostatic drive fluids flows directly from a piston pump to a motor and returns directly to the pump without entering a reservior. The speed and direction of the fluid controls the motor and, since this is a simple closed loop, the system can operate in either direction just as easily. To control speed and direction, this type of systems features a displacement controller attached to the swash plate of the piston pump. Moving the control lever forward sets the pump swashplate angle to deliver fluid to the motor and the motor begins to turn. If the operator pushes the lever forward more, the swashplate angle increases, which results in greater fluid displacement. Which means more fluid is delivered to the motor, which turns even faster. To protect the system from exessive pressures, closed loop systems also commonly feature a cross port relief valve. If the pressure rises beyond the limit of the motor, the relief valve opens and short circuits the loop by passing the motor and sending the fluid flow straight back to the pump. Thus, the motor stalls, but is protected from a spike in pressure which would otherwise cause the system to over pressurize, resulting in a blown hose, snapped coupling or other catastopic failure mode.

Closed loop systems are compact, light-weight and offer precise motor control, which is why they are generally used in mobile power transmission applications. Closed loop systems have more control options and the direction of travel can be reversed without the use of valves . This type of system is simple and cost-effective and generally less expensive to maintain.