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Kunasinsaw24
Topic Author
Posts: 7
Joined: Sun Aug 12, 2018 3:07 am

Fully charge and pre-charged accumulator?

Wed Oct 03, 2018 10:24 am

Hello, I just wanted to ask on what is a fully charge and pre-charged accumulator? What does it do?
 
Lpbri
Posts: 273
Joined: Tue Sep 27, 2016 7:18 pm

Re: Fully charge and pre-charged accumulator?

Wed Oct 03, 2018 1:22 pm

It means the nitrogen pressure on the gas side of the accumulator is correct. There are 2 types of accumulators really. System accumulators absorb pressure surges in the system during normal operation. Component accumulators, such as for brakes, T/Rs etc provide a backup of a few times in the event of a system pressure loss.
 
Apprentice
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Joined: Sat Jan 19, 2013 12:51 pm

Re: Fully charge and pre-charged accumulator?

Wed Oct 03, 2018 2:03 pm

Hi: Do not Know about official way to say. For mechanics:
-Precharged: is when accumulator has necessary press of Nitrogen,PNo, with no Hydraulic Pressure
Charged, when, with Precarged on, Acummulator have and Hold Hydraulic Pressure.

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Apprentice
Posts: 778
Joined: Sat Jan 19, 2013 12:51 pm

Re: Fully charge and pre-charged accumulator?

Wed Oct 03, 2018 2:03 pm

Hi: Do not Know about official way to say. For mechanics:
-Precharged: is when accumulator has necessary press of Nitrogen,PNo, with no Hydraulic Pressure
Charged, when, with Precarged on, Acummulator have and Hold Hydraulic Pressure.

Rgds
“An4; IL18; IL6; Tu5; D10; MD11; MD83; B32; B34: B37; B744; B748; B752; B763; B772; B773; B77W; A320; A332; A333; A342; A343.
"A NO" is a positive answer., "DON'T KNOW" is not. My Tutor (a wise man)
“CUBANA” 90 years Flying”
 
StereoTechque
Posts: 194
Joined: Sat Nov 28, 2015 7:24 am

Re: Fully charge and pre-charged accumulator?

Wed Oct 03, 2018 3:16 pm

Hi, Im a Mechanic myself and precharge means the charge that the Air/Gas Pressure that you have to charge the accumulator to be available in an unused state (Green Band). It normally varies iaw the ambient Temperature.
Looking California.. Feeling Minnesota.... R. I.P. Chris Cornell...
 
stratclub
Posts: 1382
Joined: Fri Jan 05, 2018 10:38 pm

Re: Fully charge and pre-charged accumulator?

Thu Oct 04, 2018 1:46 am

A hydraulic accumulator stores hydraulic pressure and smooths out hydraulic pressure pulses in the hydraulic system.
https://www.hydraulicspneumatics.com/20 ... cumulators

Image

With the system pressure at zero, the air (gas) side of the accumulator is charged with nitrogen to a specific pressure that is compensated for temperature. If system pressure is lost, the air charge of the accumulator gives back some stored pressure to the system, I think the term "pre-charge" is somewhat of a misnomer to what an accumulator does. The accumulator is charged with air under specific conditions to a specific pressure so that the hydraulic system can work as designed.

Do you "pre-charge" your tires or just plain old air them up to their proper operating pressure?
 
747Whale
Posts: 725
Joined: Fri Dec 07, 2018 7:41 pm

Re: Fully charge and pre-charged accumulator?

Tue Dec 11, 2018 7:00 pm

The picture above explains it well. Think of an accumulator as doing two things; it stores energy/pressure, and it also stores fluid; it's a buffer that absorbs pressure bumps in the hydraulic system. You could think of it, as shown in the picture above, as a tube with a balloon inside. When the system isn't pressurized and the hydraulic fluid is let out of the tube, the "precharge" is the pressure in the balloon. It's fully charged when the correct amount of "precharge" nitrogen is applied. Some systems use a sliding piston, others a flexible membrane, or bladder (the balloon).

Fluid can be pumped into the cylinder, and the pressure of the nitrogen behind the piston or in the balloon resists the incoming hydraulic fluid. Imagine if fluid could be pumped into that cylinder then capped off; the fluid remaining in the system would be under pressure; the pressure would come from the nitrogen charge behind the piston or in the balloon. Think of it in a similar way to how a spray can of shaving cream or hair spray works; fluid, with compressed gas in the can; the compressed gas forces the fluid back out when an opening occurs.

Same for the accumulator. A series of check valves, or one way valves, are arranged in the hydraulic system; fluid enters the accumulator from one direction, but can only go the other direction when leaving because of the way the valves are arranged.

Accumulators can provide emergency braking, absorb system bumps by giving some flexibility to the system, and make operation smoother. Accumulators are used with some propeller systems for feathering/unfeathering of a propeller.

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