Lesson 1

Your first scheme

An open pipe blowing air from a compressor — the simplest consumer there is, and one of the most expensive. Place two items, join them, type in a handful of numbers and see what that pipe costs a year.

Every number you need is given in the lesson, and so is every number the program should give back. If your results match the tables, the scheme is right; if they do not, the difference tells you which input to look at.

1. Set the units

   Open the Units tab on the right panel. The figures in this lesson are in the units below — set the lists to them before you type anything, so that a 4 means 4 mm and not 4 ft. At the top of the tab, Input units must be on As output: then what you type is read in the same units the results are shown in. Original would take every number in the unit written on the item's own card.

   List	Choose
   Air consumption	L/min
   Pressure	bar
   Mass flow	kg/s
   Weight	kg
   Length	mm
   Force	N
   Temperature	°C
   Air cost	Nm³
   Currency	€

   Choosing any list by hand turns System into Custom; that is expected. The lists not named here (Velocity, Capacity) do not matter for this lesson.

   Air flow is shown in two scales from the same list: an actual flow L/min and a normal flow NL/min — the same air brought to normal pressure and temperature. You will see both in the results.

2. Place the open pipe

   Open the Items tab. The tree is built from the Elements folder next to the program: every subfolder is a branch, every symbol a leaf. Type blow in the Filter box above the tree — the branches with nothing matching are hidden, the rest open on their own.

   Click blowing_tube under # Generic elements #. It stays selected — the sheet is now in placing mode. Click on the right half of the sheet and the item is dropped there.

   A generic element has no catalog data of its own: you describe it with your own numbers. That is exactly what we want for a first lesson — nothing in the result comes from a card you cannot see.

3. Place the compressor

   Type compressor in the filter, click compressor under # Generic elements #, then click the sheet well to the left of the pipe. Leave a hand's width between them — the connection needs somewhere to run.

   While a tree entry is selected every click on the sheet drops another copy. To go back to normal editing, click the selected entry again.

   Check

   Both symbols sit on the sheet and neither is selected. If one landed in the wrong place, drag it; if you dropped a third copy by accident, Ctrl+Z.

4. Join them

   Point at the compressor. The cursor turns into a target and the connection points of the object light up: red is an outlet, green an inlet, yellow a false connector. Press the left button on the red outlet of the compressor, drag to the green inlet of the pipe and release.

   The dots are coloured by kind, not by state, and they show on the object under the pointer and on the selected one. Once joined, a point is drawn as a small dot on the line.

   The line is routed on its own: an orthogonal path with the fewest bends, around anything in the way. You can also release the button over the body of the item instead of over a dot — the program takes the first free point of the matching kind.

   A connection is a drawing, not a pipe: it carries air with no loss. When the length and the bore of a line matter, you put a pipe item into it — lessons 6 and 7 do that.

5. Describe the pipe

   Click the pipe and open the Item tab. Three rows are green — those are yours to fill in. Click the value cell, type, press Enter:

   Row	Value	Unit
   Diameter	4	mm	bore of the pipe end
   Length	100	mm	not used in the result, but the row must be filled
   Pin	6	bar	gauge pressure at the pipe

   The table is colour-coded, and the colour tells you who owns each row:

   Colour	Row	What to do with it
   Black	Catalog data	Comes with the item. To change it, place a different item.
   Green	Your input	Click the value cell and type, or pick from the list.
   Blue	Calculated result	Rewritten at every calculation. Empty until you run one.
   Dark red	Out of range, or did not converge	Look at this row first when a result surprises you.

   Pressures on cards and in the Item table are gauge — above atmosphere, as a pressure gauge shows them.

6. Set the conditions the plant works under

   Open the Input parameters tab and enter:

   Field	Value
   Normal temperature (C)	20
   Ambient temperature (C)	20	same as normal — makes the hand check below easy
   Pressure of air (Bar)	6	the pressure the air cost below was quoted at
   Compressed air cost (€/nm3)	0.024
   Hours per day	8
   Days per year	240	8 × 240 = 1920 hours a year
   Normal pressure (Bar)	1
   Electricity cost (€/kWh)	0.13
   Carbon intensity (gCO2/kWh)	400

   Leave the other fields as they are: the open pipe does not use them.

   Look at the labels. Every pressure field must show its unit in brackets — Pressure of air (Bar), Normal pressure (Bar). Empty brackets mean the number is taken as pascals, and every flow in normal units comes out a hundred thousand times too large.

   Pressure of air is not the pressure the compressor makes — the calculation finds that itself. It is the pressure at which the compressed air cost was quoted: air delivered at a lower pressure costs less, at a higher pressure more.

7. Calculate and read the pipe

   Press Calculate. In design mode EasyCAS works from the consumers back to the compressor: it takes what each consumer needs and finds the flow and pressure the compressor has to deliver. Click the pipe — blue rows have appeared under your green ones:

   Row	Expected	Unit
   m	0.0208	kg/s	mass flow
   F	8.3257	N	blowing force
   Qn	1048.25	NL/min	normal flow — what the compressor must deliver
   Q	149.75	L/min	actual flow at 6 bar

   Check by hand

   Q and Qn are the same air at two pressures. At equal temperatures they differ by the ratio of absolute pressures: (6 + 1) / 1 = 7, and 149.75 × 7 = 1048.25. Last-digit differences are rounding; anything bigger means a unit or an input differs from the tables above.

   An open pipe chokes: the air leaves it at the speed of sound, so the flow depends only on the bore and the pressure. 4 mm at 6 bar is about one normal cubic metre a minute — roughly what a 7 kW compressor delivers, spent on a single pipe end.

   One more row sits under the results. ↔ Count of analog Pistols is a recommendation: the number of blow guns in your catalog that give at least the same force (26 with the standard catalog — yours may differ). The ↔ means the row opens a list; lesson 3 uses it. The status bar now reads Recommendations: 1 — that is this row. There are no errors and no warnings in this scheme: if the status bar shows one, an input differs from the tables above. Lesson 8 is about reading these counters.

8. Read what it costs

   Click the compressor. Its rows are the bill for everything downstream of it — here, the one pipe:

   Row	Expected	Unit
   Pout	6	bar	equals Pin of the pipe: the connection has no loss
   Qn	1048.25	NL/min	equals Qn of the pipe
   Q	149.75	L/min
   New unit cost	0.024	€/Nm³	Pout equals Pressure of air, so the price is unchanged
   Cs	2898.2	€	cost of the air a year
   Electricity consumption	22293.9	kWh	a year
   CO2	8917.55	kg	a year

   Check by hand

   1048.25 NL/min is 62.9 Nm³/h. Over 1920 hours that is 120 758 Nm³, and at 0.024 €/Nm³ it costs 2898.2 €. Divided by the electricity price, 2898.2 / 0.13 = 22 294 kWh; at 400 g/kWh that is 8.9 tonnes of CO₂.

   The top row of the compressor, ↔ Compressor selection, opens the window where a real machine is chosen for this demand. Leave it for now.

   Cost of air is not a decoration. Energy, money and CO₂ in every later report come from the Input parameters tab. Enter what the customer actually pays, or leave the figure out of the report.

9. Change one number

   Most open pipes run at full network pressure because nobody ever turned them down. Click the pipe, set Pin to 4 and press Calculate again:

   Row	Pin 6 bar	Pin 4 bar	Unit
   F, pipe	8.3257	5.53	N
   Qn, pipe	1048.25	748.75	NL/min
   Q, pipe	149.75	149.75	L/min
   New unit cost, compressor	0.024	0.0188	€/Nm³
   Cs, compressor	2898.2	≈ 1622	€

   Two things happened. The pipe passes less air — Qn falls in step with the absolute pressure, 5/7 of what it was, while Q at the pipe stays the same because the outlet is still choked. And each cubic metre got cheaper, because it is compressed to 4 bar instead of 6. Together they take 44 % off the bill, for a third less force.

   Set Pin back to 6 and calculate once more before you save: lessons 3 and 4 start from this file.

10. Save it

    File → Save as writes a .gf9 file holding the items, the connections, your input data and the results. Keep it — lessons 3 and 4 open it, and lesson 3 looks for a nozzle that gives the same force for a fraction of the air.

    If something went wrong on the way, the finished scheme of this lesson is examples/myFirstFile.gf9 — open it and compare it with yours row by row.

When it does not work

Try this next

• Set Diameter to 6. The flow goes up 2.25 times — with the area, that is, with the square of the bore: about 2358.6 NL/min and 6521 € a year.
• Switch the Air consumption list to m3/h. The compressor now shows 62.9 Nm³/h; the scheme has not changed.
• Undo your way back to the empty sheet with Ctrl+Z, then forward again with Ctrl+Y.

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