Komptec KT90 Compressor Track Record?)

[CraigAClark]

If this block is the same as the Mohnsam from the '90's, I have had nothing but bad experiences with them. I'm talking around 100 blocks that all failed and no support from the block manufacturer. At the time I was working as a department head for HP machines and equipment. The owner spent thousands of dollars creating a compact package around these blocks. We ended up having to modify the design to accept a Bauer J-II block, swapping all units with the Mohnsam block for the Junior block. The loss was tremendous.

 

[Guy Kuo]

Yikes, what went awry with all those old Mohnsam blocks?

Has Komptec changed things to prevent this from being a problem today?

 

[CraigAClark]

My understanding, that after the Mini was introduced to us at DEMA and we bought in, it was discovered that the block was only rated to 1800 psi and they were used as pneumatic backups for aircraft hydraulic systems.. The oil sightglass blew out of every one of those blocks.

As far as something being done to correct the problem, the only correction we came up with were replacement Bauer blocks. As far as this new brand name for this machine, unless they have figured out a conversion from 1800 to 3000 psi, nothing has changed.

 

[Guy Kuo]

Thanks for the info. They are about to come into North America.

 

[Bill_Komptec]

Lots of history here,

The current KT-70 / KT-90 is a design that is about 10 years old. Yes, it has roots that go back further, but this design is a modern design, with solid reliability. The specific design received some improvements a couple of years ago. It is designed for operation at 300 bar / 4500 psi, with all components rated for high pressure air operation.

I'll be in Germany next week, and will get more detail from the Chief Engineer who's been around for this whole time, to put some distance from what sounds like a painful history.

Regards, Bill Woodruff.

 

[Bill_Komptec]

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

 

[iain/hsm]

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. Bill Woodruff

Bill

This is interesting stuff in that If they have lowered the RPM and at the same time increased the capacity.
The big question however is how?

In order to achieve this engineering wise they would have had to increase the diameter of the pistons, and or increase also the piston stroke by increasing the crankshaft throw. Now as I don’t think they can increase the stroke of that old design so this may be all on the pistons.

If so by increasing the piston diameters on such a little compressor you also increase the rod loading on the con rod bearing and the crankshaft, But you also unfortunately increase the gas temperature on the discharge side and on the valves and increase the oil film lubrication temp dramatically.

Further this in most cases breaks the oil down sooner than expected, increases interstage cooling requirements and puts huge additional rod loading stress so much that it lowers the life expectancy on the lower end bearing and the con rods.

Now what would be interesting is to know both the old piston diameters and stroke for the Joker and Mini and these new piston diameters for the KT70/90 and then we can work out the increase in rod loading and temperature by compression ratio etc.

Basically run the tribology out the thing and see where they are,
Also say with a comparison to the likes of Bauer and Coltri to see how they stack out as well.

I know pretty much all the small compressor manufacturers are reluctant now to disclose both the piston diameters and the piston stroke and I guess its dive forum groups like scubaboard that have driven this reluctance. And as the calculation don’t look good for a long happy life.

But that’s where we are, with your piston diameters and stroke we can prove just how good the design claim is and without them I can’t and its down to the sales and marketing guys to say all they like.

But running small three stage compressors at 300 bar with such small motors is also well above the normal operating conditions, and once we get these piston diameters it may also be that the interstage balance is also off ideal and as I suspect they have done this by pushing the compression ratio up onto the final stage to achieve the sales and marketing requirement of a 300 bar ticket.

 

[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

 

[iain/hsm]

The Bauer Junior II is a 90 l/min 3 stage pump with a 60/28/12mm piston set on a 24mm stroke
CR is 1st at 6-7 barg 2nd 30-60 barg, 3rd at 225 to 300 barg
Oil sump 360 ml synthetic diester Change at 2000 hours
2.2 Kw power supplied
RPM: 2300

 

[Bill_Komptec]

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.