Komptec KT90 Compressor Track Record?)

[CraigAClark]

Lots of history here on the Mohnsam company and designs, that no longer exist. Komptec did license the Mini design from Mohnsam. The KT-70/90 is a modern design based on the mini described earlier. But it is all new. And it is designed to be a reliable breathing air compressor, also suitable for industrial applications, up to 4500 psi working pressure. It is equally suitable for the Air Gunner market, which also enjoys benefits of a breathing air quality compressor.

The Mohnsam design CraigAClark mentioned was not the mini block, but was a different block (the Joker) that Komptec was never engaged with. The 100 unit build that went bad was even further removed. Details of who built that and why it was bad are the responsibility of a different set of actors.

The Mini (a 70 lpm design rated to 300 bar) was last built in 2005, and was replaced by the KT-90. Today many of the Mini are still in service. Komptec still provides spares. We still list filters on our web site. On the KT-90, we increased the capacity, lowered the RPM, changed all the dimensions, and adopted designs that have proven to be very reliable. We updated the design again 2 1/2 years ago to further improve manufacturability / reliability.

If you're looking at a good portable compressor, in the class of the JR or MCH6, you should look at Komptec too. Look at the thousands of units deployed in the Mini / KT-90 product line, and the fact you can still get parts for the Minis last sold over a decade ago.

Back in our ancestry, our roots come from the Mohnsam company. But We were never involved with the Mohnsam block called the Joker which appears to be the root of some of the bad experiences discussed here.

Take a look a the specs, and at the documentation for the current Komptec compressors. We have one repair center already in place in the US, and will get more in place as we expand. We look forward to supporting the KT-90 series with the same longevity we support the Mini, last built in 2005.

Bill Woodruff

That is interesting since the one, my then employer, purchased at DEMA came in a carrying case that had "Mini" written on it. This is the first mention of a "Joker" reference I've ever heard. Well good luck with your series and I hope it doesn't have the problem we experienced.

 

[Bill_Komptec]

Iain,

Working on the data you suggested I pulled together info from a number of sources, some of which were you. So I did the table below and left the Bauer and Coltri columns blank since I can’t directly pull them from published data sheets.

Sitting with my Chief Engineer, I got some clarification on the Komptec unit. The Mini (last made in ’05) was a 70 lpm unit and had the 60mm 1st stage, and turned at 1850 rpm. The KT-70 (70 lpm) grew the 1st stage to 65mm, and lowered the speed to 1650 rpm. 2nd and 3rd stages remained unchanged. KT-90 (90 lpm) is the same block, at a 2100 RPM speed. The KT-70/90 now has over a decade of field experience.

Your earlier post postulates that the crank loading is higher with these changes. Yes, but the Mini was overdesigned so we used the same crank and bearings. Our field data bears out the validity of that choice. You also comment that gas temperatures increase, as they do. The jug and head designs we did for the KT-90 comprehended this, as did the redesigned interstage cooling coils, and the fan with 50% more swept area, and 6 vanes instead of 5.

Our predecessor Mohnsam had two other units, the Pilot and Joker. Joker was a unit that never really went to production. The Pilot was the unit that CraigAClark was referring to. But neither of these have any bearing on the current Komptec KT-90 design.

I’ve tried to keep my comments limited to responding to questions posed by members of the forum. I’ll try to give answers to any other questions you would like clarification on.

(sorry, table did not cut and paste well..)

KT-70
KT-90
Capacity
70 LPM
90 LPM
RPM
1650
2100
Motor
1.5KW
2.2KW
Stroke
17mm
17mm
1st Stage Dia
65mm
65mm
1st Stage Pressure
7.2 bar
7.2 bar
Ratio
7.2x
7.2x
2nd Stage Dia
22mm
22mm
2nd Stage Pressure
48 bar
48 bar
Ratio
6.7x
6.7x
3rd Stage Dia
10mm
10mm
3rd Stage Pressure
330 bar
330 bar
Ratio
6.9x
6.9x

 

[CraigAClark]

Iain,

Working on the data you suggested I pulled together info from a number of sources, some of which were you. So I did the table below and left the Bauer and Coltri columns blank since I can’t directly pull them from published data sheets.

Sitting with my Chief Engineer, I got some clarification on the Komptec unit. The Mini (last made in ’05) was a 70 lpm unit and had the 60mm 1st stage, and turned at 1850 rpm. The KT-70 (70 lpm) grew the 1st stage to 65mm, and lowered the speed to 1650 rpm. 2nd and 3rd stages remained unchanged. KT-90 (90 lpm) is the same block, at a 2100 RPM speed. The KT-70/90 now has over a decade of field experience.

Your earlier post postulates that the crank loading is higher with these changes. Yes, but the Mini was overdesigned so we used the same crank and bearings. Our field data bears out the validity of that choice. You also comment that gas temperatures increase, as they do. The jug and head designs we did for the KT-90 comprehended this, as did the redesigned interstage cooling coils, and the fan with 50% more swept area, and 6 vanes instead of 5.

Our predecessor Mohnsam had two other units, the Pilot and Joker. Joker was a unit that never really went to production. The Pilot was the unit that CraigAClark was referring to. But neither of these have any bearing on the current Komptec KT-90 design.

I’ve tried to keep my comments limited to responding to questions posed by members of the forum. I’ll try to give answers to any other questions you would like clarification on.

(sorry, table did not cut and paste well..)

KT-70
KT-90
Capacity
70 LPM
90 LPM
RPM
1650
2100
Motor
1.5KW
2.2KW
Stroke
17mm
17mm
1st Stage Dia
65mm
65mm
1st Stage Pressure
7.2 bar
7.2 bar
Ratio
7.2x
7.2x
2nd Stage Dia
22mm
22mm
2nd Stage Pressure
48 bar
48 bar
Ratio
6.7x
6.7x
3rd Stage Dia
10mm
10mm
3rd Stage Pressure
330 bar
330 bar
Ratio
6.9x
6.9x

Again interesting. You now say the unit we had problems with, that was clearly represented to my employer (at the time) and myself as the Mohnsam Mini, is now a "Pilot" as opposed to the "Joker" you claimed it to be in your last post. You must admit that is a bit confusing.

 

[Bill_Komptec]

Craig,

Not sure what happened 10+ years ago in a different company. I'll go into any detail you'd like on the Komptec product.

Regards, Bill

 

[iain/hsm]

To kick off
The K90 is a 90 l/min intermittant duty 3 stage pump with a 60/22/10mm piston set on a 17mm stroke
CR is 1st at 7 barg 2nd at 45 barg, 3rd at 330 barg
Oil sump 300 ml synthetic diester KL 751 at 500 hours
2.2 Kw power supplied
RPM: Not disclosed but can be worked out from the .5m/sec piston speed (1765 RPM)
Split crank design, spash lube with single oil slinger

Weird or what replying to your own post but I can't correct the dimentions given in my earlier post
To revise:
The K90 is a 90 l/min intermittant duty 3 stage pump with a 65/22/10mm piston set on a 17mm stroke
CR is 1st at 7.2 barg 2nd at 48 barg, 3rd at 330 barg
Oil sump 300 ml synthetic diester KL 751 at 500 hours
2.2 Kw power supplied
RPM: Now revised to 2100 RPM for the KT-90 (and 1650 RPM for the 70 LPM Model KT-70)
Split crank design, spash lube with single oil slinger.

The reason for all this Piston RPM stuff will become apparent when comparing varoius models when I finish it
and the reason for doing it in one place makes it easier for me to lift for a post on comparison of all compressor models. But these revised figures look much better and make much more sense now when doing the maths.

By increasing the 1st stage piston from 60 to 65mm more gas per stroke is delivered. As its on such a short piston stroke you therefore need a higer RPM to deliver the same rated flow. By doing this you also push up the interstage pressure and in turn lower the CR factor for the final stage. Also the rod loading is lowered and the work of compression may be shared between the pistons more evenly.

Comparison of all the "players" will come later on a separate post but the biger 65mm piston on a short 17mm stroke compared to say the Bauer smaller 60mm piston on a longer 24mm stroke compensates. With the trade off penalty of a little more power needed, and a little more heat generated to get rid of but the bonus is lower heat in the higher stages provided the approach temperature is kept as low (hence the fan modification I guess) which is better and also with a higher rod loading on the 1st stage again this resuts in lower loads in the 2nd and 3rd. Iain

 

[iain/hsm]

The Rix SA-3 is an 85 l/min 3 stage pump with a 57/25.4/12.7 mm piston set on a 24mm stroke
Designed for 250 Bar Pressure
An oil free oil less design there isn't an oil sump so no oil change periods
2.2 Kw power supplied
RPM: 2300
Weight 43 Kg

 

[iain/hsm]

Iain,

Love the thread, am traveling with the Chief Engineer next week and will work up the answers. We'll work the answers for 90 LPM for the Komptec unit. All data should be from publicly available data, I assume your data above on the Komptec is from our User Manual.

Bill

Thanks for the information good points well made and I would encourage you to consider continuing
with this vein of technical engineering thinking and presentation with your sales and marketing.

All too often buyers are being persuaded by brand names only without any clue as to
a good, moderate or plain poor design.

We are at a point in scuba stuff when the only question asked is “how long to fill and 80” and how much.

I trust by better education and a clear defined technical presentation with some educational pointers users could be educated more into making better informed choices about the compressors they buy.

Further if engineers who design them are taking note they also need to start designing better
more reliable better balanced pumps and stop mixing piston and hash sets up from other models just to reduce the inventory stock.

If they don’t then junk from China will take over and all we will get is the bleating how do I fix posts.

The continuing dive down to the cheapest denominator with the available brands in the small scuba compressor market is also a worrying trend and the damage caused by the silly paintball and the airgun market needs culling.

The reason for banging on about pistons RPM and the like is that I’m also working on a program to calculate out all the input parameters for pretty much all the small compressor in the market with a view to be able to work out the rod loading, temperature heat outputs etc for any particular brand or model together with the idea at some point to “design” the “perfect balanced compressor for diving if only on paper at least.

At present the plan is looking more like a bit like Engine heads meets Nascar but its a work in progress.

Your position on your cooling fan improvement is also well received. All to often the number of fan blades, pitch angle and stall speeds are knocked back by the compressor sales folk who complain on about how much more noise better cooling makes. Further complicated by most of the manufacturers not having a proper fan designed or built but buy something near enough off something else that they make fit and do.

Tribology is the other item I am looking to factor in, the wear friction and lubrication aspects as well as weight, service interval, spare parts costs, rust proof parts, also how long parts last and why oh why some manufacturers choose to supply service item parts only as complete “Sets” only and why no one supplies a complete spares price list to customers before they buy.