By David Marlowe, Owner/CEO • DMAR Technical Training and DMAR Business Centers USA
In previous issues we have discussed fluid and flow characteristics, reservoir sizing and purpose, suction pipe size with fluid flow requirements, strainers, filter effects on the pump and the pump itself. Before we continue discussing individual system components, we will discuss how the hydraulic system is divided into three general divisions, beginning with the first division—the power plant.
To understand the transfer of energy, one must understand that energy cannot be created or destroyed. It simply changes face.
a) The definition of energy is “The ability to do work (W).”
b) Work is defined as: Force × Distance = Work
F × D = W
c) Power is defined as: Force × Distance / Time = Power
F × D = P
T
d) Horsepower (hp) is defined as: Force × Distance / Time = Work / Time
F × D = W
T T
Example: 1 hp equals the amount of energy required to move 33,000 ft-lb (also 746 W), or any calculation that equals the above.
The first division is where combustion energy (engine) or electrical energy (ac/dc motor) is converted to mechanical energy (torque) and mechanical energy is then turned into fluid power (velocity).
The electric motor takes electrical power and converts it to mechanical power. To understand how much mechanical power is converted, we must first understand the relationship between horsepower (hp), revolutions per minute (rpm) and torque. To calculate the amount of torque converted we would use the following formula:
horsepower × constant / rpm = torque
hp × 5,252 = torque
rpm
The constants are: ft-lb = 5,252 in.-lb = 63,024
The mechanical energy of the motor shaft is converted to the mechanical energy to the pump shaft then converted to (fluid velocity) power into the fluid. Fluid pressure is generated by resistance to flow.
In an ideal world, the horsepower out would equal the horsepower in (100% efficient). However, this is totally dependent on the efficiency between the motor, fluid and pump, design factors associated with the motor and pump, proper fluid viscosity, operating temperature, cleanliness, and fluid flow rate from reservoir through pump. All alignments within the components and to the motor and pump must be within recommended specifications.
How much work the equipment completes compared to the cost for the completion is the efficiency of your power plant, which is dependent on how well you maintain your equipment and system.
There are three choices when it comes to maintenance management of your hydraulic power plant.
The first is the most common maintenance management tool used in industry today: “run to Failure,” which often means ignoring it, tweaking it, kicking it, or whatever it takes to keep it running until it breaks, falls apart and shuts down the entire system. The worst problem with this maintenance system is when one component fails, it usually takes several other components with it. This system is also the most expensive to operate.
The second most common management system is the Preventative Maintenance System (PMS). PMS is a time-based maintenance check on the system and components. This system returns better results than “Run to Failure” does, but this is the “one-size-fits-all” option recommended by the equipment manufacturer.
The third system is the Proactive and Predictive Maintenance system. The U.S. Navy has used this one forever. Select the correct equipment to do the job, install the system and components (using precision maintenance procedures) properly. Then, as the system is operating, maintain system operating temperatures and pressures while making adjustments as needed to keep within system operating parameters. If it is noted that a specific component is failing, shut the system down and replace the component (using precision maintenance procedures) then put the system back in operation.
Attention to detail will go a long way in the operating efficiency, maintenance downtime and costs associated with operating your hydraulic power plant and system.
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Filed Under: Mobile Hydraulic Tips