
Accumulator Sizing  
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Posted by: adeel.khan ^{®} 01/04/2006, 13:31:09 Author Profile Mail author Edit 
I am trying to size an accumulator to be used in Emergency Operation and on that basis I will size the Auxiliary pump. The system is being designed for a Crane Winch. The only data I have is the System pressure of 210 bar. How can I proceed with the calculations for the accumulator charging times and capacity. 
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Re: Accumulator Sizing  
Re: Accumulator Sizing  adeel.khan  Post Reply  Top of thread  Forum 
Posted by: Kelly_Bramble ^{®} Administrator 01/04/2006, 15:11:47 Author Profile Mail author Edit 
See the following webpage; /hydraulic/accumulator_equations.htm

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Re: Accumulator Sizing  
Re: Accumulator Sizing  adeel.khan  Post Reply  Top of thread  Forum 
Posted by: jvan ^{®} 01/04/2006, 14:26:12 Author Profile Mail author Edit 
Sir,
I am assuming that you want to power a hydraulic winch motor To size an accumulator circuit you need a minimum of data; 1.)the system pressure, in your case 210 bar 2.)The minimum pressure to do the work, if you are lowering the winch and gravity is helping you, the minimum pressure is probably the pilot pressure required to open any load holding valves that are in the system, counterbalance valves or overcenter valves. If you are raising the load, then the minimum pressure will be the load pressure, this would have to be calculated or determined by using pressure gauges on both sides of the motor to determine the load pressure (differential across the motor). 3.)You also need to determine the volumne required, this can be determined by number of revolutions on the winch motor to lower the load times the displacement of the motor. With this information you can use any of the sizing programs available on the web to size the accumulator, one of the easiest to use is Inphorm on the Parker Corp. website.
Modified by jvan at Wed, Jan 04, 2006, 14:29:11 
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Re: Accumulator Sizing  
Re: Re: Accumulator Sizing  jvan  Post Reply  Top of thread  Forum 
Posted by: adeel.khan ^{®} 01/05/2006, 06:45:12 Author Profile Mail author Edit 
Thanks John. This was great help. I got the formula for designing an accumulator as Auxiliary Power Source from the Parker Website. For me the P2 = 3045.792 psi, P3 = 435.1132 psi and P1 = 391.6019 psi (90% of P3). I don't have any idea for the charging/discharging times for selection of f & n. I assume since the system is for Emergency Load Release, the discharging times would be very less. With some assumptions, I have managed to calculate V1 (Volume of fluid collected or discharged by accumulator) = 146. 457 cubic.inches. What does this indicate? How can I select an Auxiliary pump (serving as a piggy back for another pump) on that basis? Are accumulators selected on basis of Gas Volume or the Liquid Volume inside them? What does the nominal capacity indicate? 
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Re: Accumulator Sizing  
Re: Re: Accumulator Sizing  adeel.khan  Post Reply  Top of thread  Forum 
Posted by: jvan ^{®} 01/05/2006, 12:02:28 Author Profile Mail author Edit 
Thanks John. This was great help. I got the formula for designing an accumulator as Auxiliary Power Source from the Parker Website. For me the P2 = 3045.792 PSI, P3 = 435.1132 PSI and P1 = 391.6019 PSI (90% of P3). ........This means that the minimum pressure required to do the work is 435 PSI.
.......An accumulator will discharge as fast as you allow it, it is a function of the plumbing size and the valving. It is , in fact, an "expanding gas bubble" that is expelling the fluid. With some assumptions, I have managed to calculate V1 (Volume of fluid collected or discharged by accumulator) = 146. 457 cubic.inches. What does this indicate? How can I select an Auxiliary pump (serving as a piggy back for another pump) on that basis? .......This is saying that you need a total of 146 in^3 to do the work, i.e. if you were powering a 1 1/8 bore cylinder (approx. 1 in^2 area) with a 10 in stroke, for a total of 10 in^3 volume, you could stroke it approx. 14 times with your 146 in^3 of accumulator discharge. Since an accumulator follows the gas laws P1*V1=P2*V2; the early strokes would be at 3000 PSI, and the pressure would decay with each stroke to the minimum pressure of 435 PSI. Are accumulators selected on basis of Gas Volume or the Liquid Volume inside them?
The capacity of the system is required to be sufficient for: •Activating / reset for at least 3 times in quick succession
•Continuous activation duration at least 3 minutes. When the system is activated, the limit switch for the low hook shall be automatically overridden.
050b472e 
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