How Many Cycles?

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Lenp
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How Many Cycles?

Post by Lenp » Fri Feb 24, 2017 10:43 pm

I have a wire terminal crimper, machine, model AM-10 (available all over the net), that uses compressed air. Rather than using a compressor for this machine, I am considering nitrogen gas since it's use will be is infrequent, cleaner and quieter.

We already have a 40 Cu Ft Nitrogen tank, that is empty but when filled, is a nominal 2200 psi. The regulator controlled delivery pressure is 120 Psi. The machine's pneumatic cylinder volume is estimated to be 20 Cu In, but because it is a dual acting cylinder It will use twice that volume per cycle, so 40 Cu In (.03CuFt) per cycle is the worst case value since the cylinder's external measurements were used, and the true bore and stroke dimensions are unknown.

So now the question. How many cycles can I reasonably expect until the cylinder pressure drops too low to operate the machine?

I have both a compressor, and the bottled gas hardware on hand, so startup cost is near nil. I am just trying to get a handle on the potential gas costs.

This question was posted on an engineering forum and I got many different answers. Unfortunately they ranged from 28,000 to 120 cycles and to 'go buy a compressor'!

Some said that the CFM rating of the tool must be known. There is no such rating because it is intermittently cycled, 1,2 ... times by the operator, in one minute. Bottled gas, unlike a compressor, has a finite amount of gas, so nothing will be replaced, until the tank is recharged. I was also warned of the toxicity of the exhausted nitrogen. Well our atmosphere is 78% Nitrogen so I doubt this small amount in a large space would be of significant concern.

I'm hoping some of the sages here are more knowledgeable and can help with a reasonable estimate.
At the worse case, we'll fill the tank, lash it up, and count the cycles! :!:

Thanks
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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Externet
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Re: How Many Cycles?

Post by Externet » Sat Feb 25, 2017 8:53 am

Len, am sorry. Wrote a long elaborated reply and this fu%$n" board lost everything written and requested re'logging taking me nowhere to a blank. Am furious. :x

Remember about 1500 crimps from the cylinder. Am too pissed off to rewrite now.
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Re: How Many Cycles?

Post by ShopRat » Sat Feb 25, 2017 11:54 am

I'm not an engineer, but this seems workable. First, how many cu.ft. at 120 psi equal 40 cu.ft. @2200 psi? (I don't know, but Nitrogen is quite compressible) Subtract 40 from that (tank still full of N @120 psi), then divide by 40 cu.in. and you should have a fairly close estimate. My quick SWAG is a minimum of several thousand cycles, and I would guess that 28K is surprisingly close!

Some years ago in a stamping press factory, we still had one or two old presses with "compressed air cushion" systems (no longer used), but the many die sets that needed consistent "spring pressure" used Nitrogen cushion systems (basically one-way cylinders pressurized with N) plumbed to a standard junction box with a quick-connect, valve, and guage. If repair work required relieving pressure, I believe they simply bled N to the air, I don't remember any N recovery pump system. I do remember the supply "truck", basically a rack of those cylinders hooked to a manifold hooked to a "whip" which plugged into the quick-connect on a die (I think 500 psi may have been common in die cushions). And, don't some places inflate tires with Nitrogen for "premium service?" So I wouldn't worry about toxicity (worry about ignorant government inspectors? Yes! :D ).

Of course, don't try this without safety precautions :smile: ; NEVER use oxygen for this, always secure N cylinder before removing the valve protective cap, etc.

Good luck, and enquiring minds want to know how it works out!

Dale

P.S. I think SCUBA tanks are around 2500 psi, do you know any dive-shop owners?

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Lenp
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Re: How Many Cycles?

Post by Lenp » Sat Feb 25, 2017 4:41 pm

I found an online gas calculator here http://www.cmwelding.com/technical/gas- ... -gas-phase


Tank 40 Cu Ft / 2200 PSI
Tank Data
Temperature (STP): 70 deg F (at Standard Temperature & Pressure)
Product: Nitrogen (N2)
Pressure: 2200 psig
Water Volume: 40 cu.ft.
Temperature: 70 deg F
Density: 10.67126 lbm/ft3
Density (STP): 0.07244 lbm/ft3
Compressibility: 147.306
Product Volume: 5892.25 scf
Product Weight: 426.85 lbs

Cylinder = 3" bore, 3" stroke, Dual acting
Cylinder Data
Temperature (STP): 70 deg F (at Standard Temperature & Pressure)
Product: Nitrogen (N2)
Pressure: 120 psig
Water Volume: .2 cu.ft.
Temperature: 70 deg F
Density: 0.66512 lbm/ft3
Density (STP): 0.07244 lbm/ft3
Compressibility: 9.181
Product Volume: 1.84 scf
Product Weight: 0.13 lbs

Cycles = Tank Product Volume / (Cylinder Product Volume*2)
Cycles = 5892 scf / (1.84scf*2) = 1601 Cycles Approximation!

Opinions!?
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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Re: How Many Cycles?

Post by ShopRat » Tue Feb 28, 2017 6:22 am

Len,

First, I calculated my previous "SWAG" by comparing 40 cu.in. per cycle fed from 40 cu.ft. tank. So, a simple ratio of inch to foot, cubed, gives 1728 cycles from one full tank @120 psi drained to zero (theoretical). Seat-of-the-pants engineering and the pressure differential makes me think I can round that up and throw in some "fudge factor" for a "first pass" answer. Then I could ask myself if it's pass-or-fail financially or worth deeper investigation/calulation (I already doubt your lowest answer from the engineering site), and tells me to re-check wildly different detailed calculation answers (brain fade and fat fingers?).

Second, I found my "apprentice" calculator in my toolbox and started crunching numbers from your last post, when something seemed "off." Either I'm really lost, my calculator battery is dying, or there's a misplaced decimal in your cylinder volume number. I'll try to cut and paste your table, and corrected data (from your linked website).

Tank 40 Cu Ft / 2200 PSI
Tank Data
Temperature (STP): 70 deg F (at Standard Temperature & Pressure)
Product: Nitrogen (N2)
Pressure: 2200 psig
Water Volume: 40 cu.ft.
Temperature: 70 deg F
Density: 10.67126 lbm/ft3
Density (STP): 0.07244 lbm/ft3
Compressibility: 147.306
Product Volume: 5892.25 scf
Product Weight: 426.85 lbs

Cylinder = 3" bore, 3" stroke, Dual acting
Cylinder Data
Temperature (STP): 70 deg F (at Standard Temperature & Pressure)
Product: Nitrogen (N2)
Pressure: 120 psig
Water Volume: .2 cu.ft. should be .0123 cu.ft.
Temperature: 70 deg F
Density: 0.66512 lbm/ft3
Density (STP): 0.07244 lbm/ft3
Compressibility: 9.181
Product Volume: 1.84 scf should be .11 scf
Product Weight: 0.13 lbs should be .01 lbs

I think that worked! Anyway, I got sidetracked by the Arduino program problem and haven't yet crunched the new numbers. I think you're on the right track, and I'll try to get back to the calculator later today. Also, double those numbers for a full cycle (as before).

Dale

P.S. I'll second Externet's first line (above). I've learned to "save draft" a lot, and still get bit. The "timeout" seems erratic, but apparently just part of using a "work computer."

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Lenp
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Re: How Many Cycles?

Post by Lenp » Tue Feb 28, 2017 7:35 am

Thanks Dale, but look at the tank's calculated 'product weight' ! The gas plus the tank and the regulator are a one hand carry
Something is still buggy :sad:
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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Externet
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Re: How Many Cycles?

Post by Externet » Tue Feb 28, 2017 7:37 am

This goofing of the web site when posting must be fixed. Heard posted versions the text is not lost when submitted, but a board cannot have a time-out when logged without autosaving. And the autosaving must appear when resuming after time out and re-logging.
I believe it is the option for staying always logged (option for lazy people to avoid typing the log-in every time coming here, leaving my connection alive on the web for spammers to enjoy)

Yes, Shoprat. The figure I got was also around 1700 crimps but because of Murphy's law, I conservatively downgraded to 1500 accounting for leaks and losses.

Len: do not be derailed by this:
Trying to remember my elaborated lost first response, remember something like
"There is room for confusion : 40 cu ft of N fitted at 2200 psi in a cylinder is not the same as N fitted at 2200 PSI in a 40 cu ft tank" Has to be the first.
A cylinder rated 2200 psi capable of storing 40 cu ft should be smaller than a scuba cylinder which is 80cu ft at 2200 psi being almost 2 feet tall, 8" diameter.
Miguel, scuba diver since 1972.
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Re: How Many Cycles?

Post by ShopRat » Tue Feb 28, 2017 8:01 am

Len,

Sorry, I didn't recalculate anything on the tank. Wait! 40 cu.ft.? That can't be one-hand carry! Maybe 40 cu.ft. of "standard pressure" N? I admit, I was thinking 40 gal. (probably also wrong) and picturing the "chest-high" industrial tanks (similar to dad's Oxygen tank on a cart beside the Acetylene tank). Yours must be closer to the Oxy-Acetylene torch I can buy (and exchange tanks) at my local TSC with a molded plastic carrier. If you can get some clarification, I'm still game to try calculations. Maybe more research on a welding site?

Dale

edit; Typing while Externet was posting.

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Lenp
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Re: How Many Cycles?

Post by Lenp » Tue Feb 28, 2017 8:42 am

That must be 40 cuft at STP. Nothing else would be right because the gas volume depends on the pressure. The cylinder itself is about 20"overall, and is listed on welding sites as a 40 CuFt cylinder.

The devil is in the details!
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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Re: How Many Cycles?

Post by ShopRat » Wed Mar 01, 2017 10:11 am

Len,

I can guess where you're headed with this project now, but it beats doing real work :grin: so I'll post version 3 of your data table and crunch some numbers to see where it goes.

ver. 3
Tank 0.27 Cu Ft / 2200 PSI
Tank Data
Temperature (STP): 70 deg F (at Standard Temperature & Pressure)
Product: Nitrogen (N2)
Pressure: 2200 psig
Water Volume: 0.27 cu.ft.
Temperature: 70 deg F
Density: 10.67126 lbm/ft3
Density (STP): 0.07244 lbm/ft3
Compressibility: 147.306
Product Volume: 39.77 scf
Product Weight: 2.88 lbs

Cylinder = 3" bore, 3" stroke, Dual acting
Cylinder Data
Temperature (STP): 70 deg F (at Standard Temperature & Pressure)
Product: Nitrogen (N2)
Pressure: 120 psig
Water Volume: .0123 cu.ft.
Temperature: 70 deg F
Density: 0.66512 lbm/ft3
Density (STP): 0.07244 lbm/ft3
Compressibility: 9.181
Product Volume: 0.11 scf
Product Weight: 0.01 lbs

And, "theoretically empty" tank
Tank 0.27 Cu Ft / 120 PSI
Pressure: 120 psig
Water Volume: 0.27 cu.ft.
Compressibility: 9.181
Product Volume: 2.48 scf
Product Weight: 0.18 lbs

So, full tank minus unusable (in this application) portion divided by use per cycle gives:

Cycles = Full scf - Empty scf / (Cyl. scf * 2)
Cycles = 39.77 - 2.48 / (0.11 * 2) = 170 Cycles approximation!

I've tried a few "other directions" and got similar results (within "rounding error" range -- 10 cycles).

If you haven't completely given up this idea yet, I have questions for the "other side" of this project. Is 120 psi the working pressure or maximum recomended pressure? Factory "shop air" is running about 100 psi, and I think I've heard 90 psi for their minimum (during normal operations; huge distribution network). Do you need to regulate to some lower pressure, depending on the wire and terminals you're crimping? A quick search only found pictures and little data on the AM-10, and a working pressure of, say, 60 psi would change both consumption per cycle and unusable remainder. 120 psi to a 3 in. cylinder gives about 850 lbs. force to the end of the piston rod, which seems high for the pictured crimper.

If I can confuse you any more, feel free to ask :smile: !

Dale

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Lenp
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Re: How Many Cycles?

Post by Lenp » Wed Mar 01, 2017 5:24 pm

Hi Dale,
I certainly appreciate all your efforts, and I think the numbers look pretty realistic. I will probably still go forward and do a real test since I have located an available cylinder with a partial fill, and go from there. In the benefit of the cycle count, the crimper cylinder is actually smaller than the numbers I gave since they were outside measurements, and are not actual bore/stroke and no rod deduction was used.

Plus you may also be correct in that the crimper may work well with lower applied pressure. Unfortunately there is not much information regarding this unit, and there seems to be no real source. The manufacturer is obscure, even though there are a ton of them online all with different labels and colors.

The piston's rod operates linkage inside the unit to close the jaws and because of the mechanical advantage, they state a force of 3.5 Kn (3000 psi +/-). The terminals, we crimp most often are Molex 2.54mm and 3.96mm terminals for nylon connectors. Not much force is needed to crimp them so a lower pressure would probably work, also increasing the cycle yield.

I tried crimping these little terminals with a hand crimper; holding the terminal, placing the wire and squeezing the crimper, leaves you one hand short. It is possible, but counterproductive with erratic results.

On the the plus side, the machine uses universal dies and there are numerous models available from many suppliers. I robbed a die set from my Ideal crimpers and they were a drop-in fit. Another die set, for .25" flag terminals, was ordered from China and it was less than $7 delivered with China Post. Really hard to say no!

In the next couple of weeks I'll try the bottled gas and see how many cycles I can get from what's left in that tank and let you know the results.

Also, the idea of using a refrigeration compressor as the pump with an appropriate tank may be a quiet and viable option. The CFM of refrigeration compressors is low, around 1CFM, but since it is so quiet, it could run all day to keep up. There will be some down time to change wire colors and terminals plus packing the finished connectors so that is all slack time for the compressor to catch up. We have a suitable refrigeration compressor, and as time permits, I will hook it to a tank to see how well that option works out.

Again thanks!
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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