light Accumulator Simulation Program - hydac.com · p0Tmax = 89.92 bar, which means the pre-charge pressure of the hydraulic accumulator reaches 89.92 bar at an ambient temperature

ASPlight Accumulator Simulation Program 5 HYDAC Technology GmbH Postfach 1251 D-66273 Sulzbach/Saar. Germany Industriegebiet D-66280 Sulzbach/Saar, Germany Tel.: +49 (0) 6897/509-01 Fax: +49 (0) 6897/509-464 (Accumulator Technology) E-mail: [email protected]

1/13 Version: 02-2015

OPERATING INSTRUCTIONS

ASPlight Accumulator Simulation Program Table of contents

1. Program description ............................................................................................. 2 2. System requirements – local application ........................................................... 2 3. Installing and uninstalling ASPlight .................................................................... 2 3.1. Installing ASPlight (USB memory stick) .................................................................. 2 3.2. Installing ASPlight (download) ................................................................................ 2 3.3. Uninstalling ASP ..................................................................................................... 3 4. Starting and exiting ASP ...................................................................................... 3 4.1. Starting ASPlight ..................................................................................................... 3 4.2. Exiting ASPlight (program sections) ........................................................................ 3 5. ASPlight ................................................................................................................. 4 5.1. User interface .......................................................................................................... 4 5.2. Calculation process ............................................................................................... 12 5.3. Example task ........................................................................................................ 13

ASP Accumulator Simulation Program 5

2/13 Version: 02-2015

1. Program description ASPlight enables you to calculate the: pressures, volume, temperature as well as pressure and flow ratios of an accumulator, simply by entering a few accumulator parameters.

The calculation is similar to that done on a pocket calculator.

Basic knowledge of the operating characteristics of hydraulic accumulators is required.

2. System requirements – local application Microsoft® Windows® XP, Windows® Vista, Windows® 7

Microsoft® .NET Framework 3.5 or higher (for more information, see http://www.microsoft.com/downloads)

Minimum resolution: 1152 x 864

3. Installing and uninstalling ASPlight Ensure that you are logged on to your computer as an administrator or have administrator rights.

3.1. Installing ASPlight (USB memory stick)

Close all open applications.

Connect the USB memory stick containing the ASP software to your computer.

If the installation does not start automatically, go to the Explorer directory for the USB port on your computer.

Double-click the installation file (file format = .msi).

Follow the instructions on the screen.

3.2. Installing ASPlight (download)

Download the latest ASP software from www.hydac.com and save it (ZIP file).

Extract the zipped files.

Double-click the installation file (file format = .msi).



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3.3. Uninstalling ASP

In the Windows task bar, click Start Control Panel.

Click one of the following buttons: - Windows Vista or Windows 7: Under Programs, click on Uninstall a program. - Windows XP: Click the Software icon.

Choose "ASP" from the list of programs and click Uninstall.


4. Starting and exiting ASP

4.1. Starting ASPlight

In the Windows taskbar, click Start Programs HYDAC Software ASP 5

4.2. Exiting ASPlight (program sections)

To close the ASP software, click the "X" in the upper right-hand corner of the of ASP user interface.


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5. ASPlight

5.1. User interface

As you can see from the picture below, the user interface for ASPlight is divided into different fields and includes: selection fields, function and input fields, as well as result and information fields. This section describes these fields in more detail.

= Operating gas: Choice between N2 (nitrogen), He (helium) and air

= Units: For temperature, pressure and volume

= Exchange speed: Choice between adiabatic (fast) and isothermal (slow) process

= Exchange direction: Choice between charge and discharge

= Calculation and input parameters: For accumulator parameters such as pressure, volume, temperature

= Number pad: Can be used for entering values

= Result button: Used here for calculating V0, for example

= Information field: Information about pressure/volume ratio

= Results field: In this case, "V0" at Tmin and Tmax


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5.1.1. Operating gas

The "Operating gas" selection field also offers the selection fields Helium (He) and (Air), in addition to the default gas type (N2) Nitrogen. You can set the desired gas type here.

Hydraulic accumulators must only be charged with nitrogen. Never use oxygen or air - Risk of explosion! If there are variations, please enquire.

5.1.2. Units

The physical units for temperature, pressure and volume can be selected as follows:

Temperature: Degrees Celsius (°C), Fahrenheit (°F), Kelvin (K)

Pressure: bar, psi, MPa (Mega Pascal)

Volume: Litres (L), gallons (Gal (US))

Click the appropriate button to activate the desired unit. The value that is input or output will then be in this unit.

The following overview shows the relationship between the physical unit and the calculation parameter.

Physical units Calculation parameters

Temperature [°C, °F, K]

Tmax Tmin T0

Pressure [bar, psi, MPa]

p2 p1 p0 p0Tmin

p0Tmax

Volume [L, Gal (US)]

∆V V0


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5.1.3. Exchange direction

Hydropneumatic accumulators are generally used for energy storage.

The accumulator must provide a certain amount of energy/fluid at a certain time. This means that it is discharged.

Conversely, select charge if the accumulator is to be charged in its application.

Both exchange directions, both charge and discharge, can take place quickly or slowly; see Exchange Speed.

discharge

charge


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Exchange speed in p-V graph

5.1.4. Exchange speed

In thermodynamics, there are different changes in state for gases. ASPlight is limited to the minimum and maximum values for the calculation:

Adiabatic (= isentropic) change of state = no heat exchange with the environment

With this option, the program is based on very rapid accumulator charging or discharging processes. In this case, heat exchange with the environment is not possible. This option results in large accumulator volumes or in small ∆V values.

Isothermal change of state = complete heat exchange with the environment

With this option, the program is based on very slow accumulator charging or discharging processes. In this case, there is complete heat exchange with the environment. This results in smaller accumulator volumes, or large ∆V values, comparatively speaking.


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5.1.5. Calculation and input parameters

The selected area consists of the calculation parameters (p2, p1, p0, ∆V, V0) as well as the input parameters (T0, Tmin and Tmax).

The calculation parameters are the input and output values required for calculating a hydraulic accumulator. They can be thought of as a mathematical equation that is manipulated according to the desired size.

A value cannot be calculated until all other calculation parameters have been entered.

The value p0 is suggested automatically based on T0, Tmax as well as p1. If an input value for p0 must be specified, i.e. forced by the user, it must be changed manually after the temperature and also after the p1 have been entered.

The following table shows the input and display options for the parameters:

Input parameter Input option

Abbreviation Description Input value Output value (calculation possible)

p2 Maximum operating pressure x x

p1 Minimum operating pressure x x

p0 Pre-charge pressure x

∆V Usable volume x x

V0 Effective gas volume x x

T0 Gas pre-charge temperature x

Tmin Minimum operating pressure x

Tmax Maximum operating pressure x

p0Tmin Pre-charge pressure at Tmin x

p0Tmax Pre-charge pressure at Tmax x

p2 : p0 Pressure ratio x

V0 : V2 Volume ratio x

If an input value for p0 must be specified, i.e. forced by the user, it must be changed manually after the temperature and also after the p1 have been entered.

Calculation parameters

Input parameters


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For a diagram, see PV graph of an accumulator cycle.

This contains all the parameters of the accumulator calculation.

Exchange direction in the PV graph

5.1.6. Number pad

The number pad is arranged like the number pad of a calculator. As an alternative to entering the calculation parameters via the keyboard, they can also be selected using the mouse/touchpad.


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5.1.7. Result button

The label on the result button will change depending on the calculation parameter activated (e.g., p2 =, p1 =, ∆V =, V0 =). It is the same as the "equals" button on a pocket calculator.

5.1.8. Information and results fields

After you press the result button, the following information and results fields are displayed on the left and right side.

Results field

In order to select the calculation parameter to be displayed for Tmin and Tmax in the results field (in this case V0Tmin and V0Tmax), click in the calculation parameter area

Result button, in this case showing "V0", because calculation parameter "V0" has been activated for calculation, all other parameters have been entered

Results field with "V0" at Tmin and Tmax

Activated calculation parameter, in this case "V0"

Information field: Volume ratio Attention, this is only displayed when the critical condition is reached.

Results field: The label changes according to the calculation parameter selected.

Information field:Pressure ratio

Information field:Pre-charge pressure at Tmin and Tmax


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Information fields

In addition to the actual results field, ASPlight provides important information that suggests an accumulator model (bladder, piston or diaphragm accumulator).

p2 : p0 = Max. pressure ratio, in this case p2 : p0 = 2.5 : 1

V0 : V2 = Volume ratio is only displayed when the critical condition is reached. The critical state is when V0 : V2 > 4 : 1 or V0 : V2 > 10 : 1. In the example above, the piston accumulator would be recommended, depending on the application, diaphragm accumulators could also be used. This must be agreed with HYDAC.

p0Tmin = Hydraulic accumulators must be pressurised with a pre-charge pressure and prior to commissioning (p0 at T0). These values indicate the pre-charge p0Tmax pressure at minimum or maximum ambient temperature, in this case:

p0Tmin = 79.68 bar, which means the pre-charge pressure of the hydraulic accumulator reaches 79.68 bar at an ambient temperature of 10 °C

p0Tmax = 89.92 bar, which means the pre-charge pressure of the hydraulic accumulator reaches 89.92 bar at an ambient temperature of 40 °C. The pre-charge pressure changes as the operating temperature changes.


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5.2. Calculation process

Calculation in ASPlight is similar to using a pocket calculator.

This section describes the calculation process:

1. Select the gas type

2. Define units (default setting is adopted)

3. Define exchange speed

4. Define exchange direction

5. Enter known calculation parameters

(p0 is suggested automatcally by the program based on T and p1)

6. Activate desired calculation parameter (here: V0)

7. Press result button (label can vary according to calculation parameter selected)

8. Read and evaluate result and information fields


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5.3. Example task

5.3.1. Situation

A consumer requires 2.5 litres of hydraulic fluid within a very short time. The minimum pressure must not fall below 180 bar. The pump charges the accumulator to a maximum of 350 bar. The accumulator is pre-charged at 20°C.

5.3.2. Task

Accumulator nominal volume = V0

5.3.3. Solution method

V0 at Tmin = 19.07 l

V0 at Tmax = 12.9 l

Additional information:

p2 : p0 = 2.8 : 1

p0Tmin = 124.85 bar

p0Tmax = 161.48 bar

5.3.4. Evaluation

Because the pressure ratio is 2.8 : 1, bladder, piston and diaphragm accumulators can be used. However, because the V0 result is between 12.9 and 19.07 litres, a bladder or piston accumulator is recommended. Diaphragm accumulators are only available with a maximum nominal volume of 4 litres.

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light Accumulator Simulation Program - hydac.com · p0Tmax = 89.92 bar, which means the pre-charge pressure of the hydraulic accumulator reaches 89.92 bar at an ambient temperature