When does it start to make sense

[otterdive]

Hi everybody, it's my first time to this section of the forum. I run a small, but rapidly growing dive school, serving children's summer camps in the northeast. I currently work with a local dive shop for fills. They are fantastic, and they give me a very good price per fill. I am considering buying a compressor, but I need to know a bit about the magic point at which that makes sense.

I currently own 18 AL 80s. I use about 5 tanks per day, throughout the summer. Within the next summer or two, I'll probably be using about 10 tanks per day during the summer. Virtually no fills during the rest of the year. The local dive shop is about 45 minutes away. They bank air and can fill all my tanks in about an hour, so that's about a 3 hour turn around, once every couple of days. I have been doing all the teaching, and schlepping myself. This next summer I'll have a divemaster who can help drive, or fill if I buy a compressor.

So, what do you guys suggest? I have just started to think about this, so any ideas would be very helpful. I'll research any suggestions you guys make. Models, capacities, prices, maintenance costs, etc.

Thanks!

 

[veriqster]

run the numbers, liability insurance included, and, if it does not make sense to buy unit with warrannty than it most probably will not make sense buying anything, especially since you plan to run it for commercial purposes. with that many tanks i guess it would make sense to get a VIP course so you can inspect them yourself. also consider that any of these might ruin your relation with the diveshop.
p.s. a small compressor will fill an AL80 in 7-20min, assuming it's not completely automatic you would spend a lot of time filling. if it is than you would need a manifold and 5-10 whips so you can start it and go mind your business. things add up quickly.

 

[pickens_46929]

For a decent compressor, you'll end up spending $3000 to $5000 depending upon options plus annual maintenance and such. And yes you could even spend more that $5000.

Figure $5 air fills and $20 per hour time and $0.50 mileage... let's say 40 miles each way... 10 tanks per day x 5 days per week... 5 trips per week... 13 weeks for summer...

$5 @ 10 tanks = $50 per day
3 hours @ $20 per hour = $60 time value
80 miles round trip @ $0.50 per mile = $50 mileage

So basically $160 per day... $800 per week... $10,400 for the summer...

Sounds like it could be worthwhile for you to lease a decent compressor including support / maintenance contract.

Generally it's not a matter of cost but rather a matter of convenience in most cases.

Features... auto-drain and auto-shut off are good to have... as for speed, the faster in terms of cu.ft. per minute the more expensive the compressor gets...

If you do 10 tanks a day, assuming they are AL80 down to 500 psi, you'll be pumping about 65 cu ft. of air per tank... 10 tanks = 650 cu. ft. per day... at 5 cu.ft. per min you're looking at a total fill time of 2 hours and change... at 6.6 cu.ft. per min you'll get done in just over 90 mins.

 

[otterdive]

Sounds like it could be worthwhile for you to lease a decent compressor including support / maintenance contract.

I did not know that was an option. Do you have any links?

Generally it's not a matter of cost but rather a matter of convenience in most cases.

I would not mind having that 3 hours driving time back!

If you do 10 tanks a day, assuming they are AL80 down to 500 psi, you'll be pumping about 65 cu ft. of air per tank... 10 tanks = 650 cu. ft. per day... at 5 cu.ft. per min you're looking at a total fill time of 2 hours and change... at 6.6 cu.ft. per min you'll get done in just over 90 mins.

Thanks for the great information!

 

[Isaac-1]

Ok, there are a few more things to consider, first air fills are not free, cost of filtration and electricity is a good portion of the cost of an air fill maybe as much as $2-3 per tank. This will vary depending on a number of factors (how good you are at bargain hunting, how big your filters are, etc.). Where are you going to run this compressor? Having said this you DO NOT WANT a small portable 3-5 cfm compressor, these units are designed for limited personal use, most require cool down after filling just 1 or 2 tanks, are splash lubricated and have small filters that don't last long, their BIG advantage is weight, often in the 100 pound range, they can be moved easily by 2 people. If you are looking at the used market I would suggest looking for an older Bauer 5-9 CFM unit, these tend to be real workhorse beasts weighing in over 500 pounds, are pressure lubricated and will run nearly 24/7 for a long time, they often show up on the used market fairly cheap (under $1,000 maybe less), many are 4,000-4500 psi units that came out of fire stations when they went to higher pressure tanks. These are also small enough to run on standard household 240V power, anything much bigger will likely only be available with a 3 phase electric motor. As a rule of thumb your looking at just under 1HP per CFM when powered with an electric motor, the largest commonly available single phase motors are around 7.5 HP.

 

[rcontrera]

Yup ... pumping air ain't free!

I just did a price workup for a dive shop that was looking at one of our $9200 7.6 CFM "all inclusive" machines (auto drains, auto shutdown, electronic motor starter, external oil indication, etc.). The figures are based on filling an empty 80 (unrealistic I know, but easier for math purposes).

Filter cartridges are expensive but can process up to 9000 cubic feet of air. The cost per fill works out to anywhere from $ .62 to $ .97 depending on humidity.

Synthetic oil is also expensive compared to mineral oil. However the cost per fill runs about $ .10.

So your costs for consumables is about $.72-1.07 per fill.

Scheduled maintenance is also a few bucks. A 500 hour kit runs about $330 so that adds another $ .13 to the cost per fill.

So operating expenses so far is about $1.20 per fill. Now, comes the hard part.

Electricity is a big expense in operation. Single phase is a LOT more expensive than three phase but isn't available to most home businesses. And single phase limits the size of compressor you can get ... the biggest we have is 14 CFM. The amperage on the 220 single phase is 24 so you will have to have your electrical guru do the calculations for cost based on your local electrical costs. In my area, electricity is cheap so filling a tank here is about $.38.

Then figuring in the cost of the compressor itself is tough as well. Most people count on a compressor lasting about 3000-5000 hours before major work is due ... depending on how well you take care of it. That means the cost per fill is anywhere from $2 to over $4 per fill.

So the grand total varies from $3.23 to about $5.58 per fill.

Of course you can drop the cost per fill a bit by going with cheaper compressor systems. But as has already been posted, don't get anything that doesn't have auto drains or an auto shutdown.

One additional note that has already gotten me in trouble with some of my other compressor dealers. Times are tough right now. So the temptation to buy used is huge. However, times are tough for compressor distributors as well so it might be worth your while to try to get some concessions and go new. Of course, if you don't go with me, don't tell the dealer I said anything.

 

[pickens_46929]

Leasing is always an option. Support / maintenance is generally something that's location dependent. If you have a number of nearby fire departments, they will sometimes use a shop for maintenance but not all the time.

As Issac says don't look for the cheap 3 cu ft. "portable" compressors, they just won't fill fast enough or have the duty cycles you are going to need.

You can get gas or diesel powered compressors as well. I go out with a charter on the St. Lawrence and he's got a 7.5 cu.ft. per min Bauer that runs on a small gas engine. Does great job filling tanks.

 

[veriqster]

I did not know that was an option. Do you have any links?



I would not mind having that 3 hours driving time back!



Thanks for the great information!

I know nothing about leasing, but i can tell you that unless you get a "fully loaded" unit or LARGE bank capacity your 3 hours drive will just transform into 3 hours of filling tanks.
If you have 3phase you should be able to pick up a decent surplus unit. they pop on govliquidation from time to time and big 3 phase compressors usually command no interest.
the least that you will need to add to almost any compressor you get will be a manifold and a decent bunch of whips, almost no unit comes with more than 1-2 whips.

 

[rjack321]

Ok, there are a few more things to consider, first air fills are not free, cost of filtration and electricity is a good portion of the cost of an air fill maybe as much as $2-3 per tank. This will vary depending on a number of factors (how good you are at bargain hunting, how big your filters are, etc.). Where are you going to run this compressor? Having said this you DO NOT WANT a small portable 3-5 cfm compressor, these units are designed for limited personal use, most require cool down after filling just 1 or 2 tanks, are splash lubricated and have small filters that don't last long, their BIG advantage is weight, often in the 100 pound range, they can be moved easily by 2 people. If you are looking at the used market I would suggest looking for an older Bauer 5-9 CFM unit, these tend to be real workhorse beasts weighing in over 500 pounds, are pressure lubricated and will run nearly 24/7 for a long time, they often show up on the used market fairly cheap (under $1,000 maybe less), many are 4,000-4500 psi units that came out of fire stations when they went to higher pressure tanks. These are also small enough to run on standard household 240V power, anything much bigger will likely only be available with a 3 phase electric motor. As a rule of thumb your looking at just under 1HP per CFM when powered with an electric motor, the largest commonly available single phase motors are around 7.5 HP.

I want to know where I can get a 5cfm Bauer for $1000!!!

 

[Isaac-1]

They turn up in all sorts of places, craigslist and other classified ads, keep an eye out on the classified section here and on the deco stop, etc. I ran across a 2-3 month old ad for a late 1970's Bauer Capitano (maybe full size Utilus) a year or two ago about 250 miles from here, assuming it was already sold, I enquired about it, turns out it was still available, asking price was $750, it was set up and running in garage, I passed on buying as my wife does not see the need in having more than 2 compressors. Government liquidation is another place to buy compressors cheap, but be a dice roll as everything is sold as is, I bought my 12 CFM diesel powered Davey from GL a couple of years ago for under $400. I have seen a number of nice looking Bauers sell on GL, some cheap, most have been too far away for me to consider buying. I also have a little 30 year old Mako rebranded Bauer Purus that I bought 3rd hand off ebay for $250 about 6 years ago, it spent most of its life at a small volunteer fire department, and was rebuilt just a few years before I bought it.