Compressor calculation
Hi Simon,
I am new in this scuba forum but been around a week or so in hunting forum. Just want to share some ideas on compressors because I have a few shared-units and my friends owns a few personaly.
Here in Indonesia, the most popular brand is Bauer from Germany. I am not familiar with other brands. In fact in South East Asia this is the leading brand. I maintain my group compressors and I can detail you on the cost of operation if you or any other readers really wants 2 know.
I dive almost all year round but less during the west wind season which occur 3 months a year. The reason I and my group owned a compressor is because our diving area has no refill station and without a comp, we need to bring too many tanks.
In Jakarta-Indonesia an average refill cost anything from US$ 3.50 to US$ 7.00 depending on location.
A 3.5 CFM Bauer JUNIOR selling at +- US$3,500. It fills an 80 Cf at 3000 psi in 23 minutes. This is a 3-4 divers comp. 5 HP Honda driven and operational speed of ( I forgot exactly ) +- 2,200 RPM crankshaft speed at the compressor and Honda speed at almost maxed out at 3,600 RPM. I don't reccomend this unit because not only it is slow ( but light weight at +- 50 kg ) it is also high speed operation in both the Honda & the comp itself. High speed means more wear & tear. A friend of mine has this and we almost never use it unless as back up. I hate this unit and I don't mess around with this often.
A 5.0 CFM Bauer CAPITANO. It fills 80 cfm/3000 psi in 16 minutes.
I share this unit between 9 divers. We bought it second ( almost 99% new condition ) hand at +- US$ 4,500. I think the retail is like US$6000 something. This unit I play a lot with. It used to come with a 5HP Honda. The comp operational speed is 1,300 RPM, while the Honda is nearly maxed out at 3,600 RPM. A 5HP Honda is way underpower. I replaced mine/ours with a 7 HP Honda and set bigger pulley so that Honda operational speed maintained at +- 2,700 RPM and still have enough torque to run the comp. Gas engines will be best to operate at 75% maximum RPM to last long. The comp is reliable, the Honda only weakness is the exhaust system. It corrode and grow loud within only 150 hours of operation. Is best to change it at max 200 hours if u want ur neigbours to love u. In Jakarta we can get it for US$75.00. The standard Bauer air cartridge filter retail at +- US$36.00 and in our 80% humidity and 30 * Celcius temperature, it can last up to a maximum of 120 air fills. I always refer to air fill as 80 cf tank at 3000 psi.
Based on my calculation, if I remember correctly, here are the cost to operate based on Honda driven, I have no experience with electric motors because our comp have to be mobile and independent of electric supply :
01. Air filter cartridge. US$ 36.00 for 100 average air fill. US$0.36 per tank.
02. Honda engine oil at 1.2 liters per 50 hours. Average oil quality US$ 9 per change. Average cost per tank = US$0.05.
03. Fuel at 0.8 liters per tank. Calculate ur own country rate. Mine is at US$0.23 per liter. US$0.19 per tank.
04. Bauer compressor oil at 1.6 liters per 300 hours or 6 months, I waste a bit here. Manual Book say more, but no way. Estimated cost US$ 50 for oil change. US$0.05 per tank.
05. Bauer air pre-filter. US$10-15 ( I forgot ), last hell of a long time. I think fair price is US$0.01 per tank.
06. Hate ur neigbours & change exhaust muffler of Honda at 300 hours. US$ 0.07 per tank.
07. Fan belts, spark plugs and overhaul Honda for all the way to 1,000 hours. Piston over size one step up, valve job & crankshaft bearings. In my country is only at US$ 250 maximum. US$0.07 per tank. Double this for any developed countries. At about 1,500 to 2,000 hours, best to buy a new Honda.
08. Bauer compressor service at 1,000 hours. Change all inlet & exhaust valves for three pistons and some other minor bullshit. Get US$ 1,000 to be safe. US$0.27 per tank.
Rough estimate for the first 1,000 hours of operation is about US$1.07 per tank, in my country for a 5.0 CFM Buer CAPITANO.
This is based on ideal operating condition and not bringing it on board a boat. Rust damage from sea salt spray is number 1 compressor killer.
By the time u hit 2,000 hours, expect to spend double this. One thing 4 sure you need a new Honda and your compressor overhaul will be more costly because pistons will be more worn out. It will be save to calculate that a 1,300 RPM compressor should last easily 5,000 hours if well maintaned and no bad luck for owner. Safer calculation is to double the purchase price
( brand new ) and divide by 5000 hrs of life span. Double is to take the per 1,000 overhaul expenses into consideration for the entire life of the compressor. So the actual total cost in my probably wrong calculation is at approx US$ 1.50 a tank.
In actual life scenario ur comp will get damage more often by sea water, rain, operation in unshaded area too long in the heat of the day, bumped around in the boat in bad weather, main pulley get hit during transport and so on. Only compressor immobile in a dive shop rather far away from the beach, will last long.
If you scuba to remote area, a compressor is better than a wife.
If you are within easy air fill area, not worth it.
I also shared another group a very old & used 1983 6.0CFM Bauer MARINER with 6 other divers. This baby has consumed about US$ 5,000 in the last 5 years. US$2,000 was rebuilding her from a sorry state & a new 9HP Honda purchase. US$ 3,000 was to maintain her in the last 5 years of abused usage .......not as per operational hours.
When u are doing airfill by the water, be very careful with the air suction hose. One of my friend's MARINER compressor suck in sea water when this hose fell into the water at a marina. All of the gasket blew apart, even the crankshaft was distorted because water is incompressible, it cost US$3,000 to repair. This unit is about US$8,500 brand new.
All in all I have 5 compressors within my core divers group either shared or individualy owned. It gave us big time convenience, dive anytime-anywhere but it sure blew a big hole in our pockets.
Well I hope the info is massive enough.
IYA
