Engine rpm

[james n]

I have a 9 year old prochem apex. 31Hp has kabota Manual says Engine idle 1500 Rpm.
2740 rpm high speed pump on.
Water pump 965-1000
Vacuum pump 3100 Rpm
My question is how can the vacuum blower run 3100 if the high speed on the engine is 2740 ? I measured the engine rpm full throttle and it seems to be running at 1800 Rpm now. Performs well but I’m wondering if it can perform better since the rpm is lower then spec.

 

[SRD]

Different size pullys

 

[Anderson]

most all the big 3 and others make their blowers to run at around 75-80% or 3000 rpm.

why do they do this when the specs show they can actually run these blowers at 4000 rpm.
make the blower last longer ?????

I run 1 of my blowers around 3800-4000 rpm
and it makes a big difference, but industry has been doing this for 30 years and my guess is they aren't gonna change.

 

[james n]

I have the 408 tri lobe blower and it has great vacuum. I have to change the throttle cable on the machine so it got me thinking about the rpm. I’ve been running it this way for 9 years 8000 hours. Didn’t adjust anything from when I got it. Figured it was set up correct now I’m wondering if it has been underperforming all these years.

 

[Anderson]

yes probably...
but like i say it is industry standard...

unless you go with a custom build...a non BIG 3...
AND EVEN MOST OF THEM UNDER PERFORM...
here is a chart of the tri-lob fro denver...
file:///C:/Users/ander/Downloads/TriFlow%20Series%20PS%20(3).pdf

notice the 408 can be run at 4000 rpm....
if I am correct the big 3 run it at 3000 rpm....
which shows about 400 CFM.....
which is about what they list on their TM specs....

 

[james n]

Well it might be underperforming because they are keeping the rpms under the max. But I’m thinking mine was set up even under the limits prochem sets. I just assumed my distributor set it up to spec. I did a tach test on my engine and it’s running at 1800rpm full throttle. Idle was 900. It is way off what prochem recommends.

 

[mrotto]

it was probably set at the factory specs when it was new. Things dont happen all at once and over the years you probably didnt notice the change because it happens so slow. Thats one of the advantages of taking it to JD or IL to have annual maintenance done on it. They check RPMs and would have caught it right away.

 

[RVR]

I have had my engine speed drop over time a few times. Finally put an electronic tach/hour meter on it so I can adjust as needed.

 

[james n]

That’s true. I do have it set up 4 to the door so it doesn’t seem like I’ve lost vacuum. Only started doing that for a year now. But I’d think if my rpms dropped that much I’d notice the difference in performance. When I turned the throttle to 2700 it sure sounds a lot different though. I don’t think it ever was set that high.

 

[JDARNOLD]

most all the big 3 and others make their blowers to run at around 75-80% or 3000 rpm.

why do they do this when the specs show they can actually run these blowers at 4000 rpm.
make the blower last longer ?????

I run 1 of my blowers around 3800-4000 rpm
and it makes a big difference, but industry has been doing this for 30 years and my guess is they aren't gonna change.

They are running the blower at the lower rpm in order to make heat in the HX bx. plus they open the gap of the lobes of the blower for the same purpose.

 

[seagrtj]

They are running the blower at the lower rpm in order to make heat in the HX bx. plus they open the gap of the lobes of the blower for the same purpose.

Why do you say they are opening the gap of the lobes? Those blowers are just dropped in straight from the mfg.

There will always be a difference in recommended specs between the mfg of the blowers, pumps, & engines. Those mfg's make those products for several various applications. They can only set specs for that particular piece of equipment. The TM mfgs have done their own testing and found the optimal performance for their configuration.
For instance, Gardner Denver says that you only need to change the oil in the blower about every 4,000 to 5,000 hrs. Would you wait that long with your blower?

The pump and blower put a huge load on the engine. running them out of their spec can cause undue damage to the engine. Just like running the engine at anything but full throttle will cause damage because it can't handle the load. IMO, that really only applies to the 2 cyl engines

 

[Anderson]

probably true that they dont have a big enough engine to turn the blower past 3000 rpm....

it probably has to do with $$$$$...imo

Another reason I believe is because many if not most of these engineers have never been behind a wand on a job and do not appreciate the extra 100-200 cfm that can produce amazing results for extra cleaning and dry times.

 

[JDARNOLD]

Why do you say they are opening the gap of the lobes? Those blowers are just dropped in straight from the mfg.

There will always be a difference in recommended specs between the mfg of the blowers, pumps, & engines. Those mfg's make those products for several various applications. They can only set specs for that particular piece of equipment. The TM mfgs have done their own testing and found the optimal performance for their configuration.
For instance, Gardner Denver says that you only need to change the oil in the blower about every 4,000 to 5,000 hrs. Would you wait that long with your blower?

The pump and blower put a huge load on the engine. running them out of their spec can cause undue damage to the engine. Just like running the engine at anything but full throttle will cause damage because it can't handle the load. IMO, that really only applies to the 2 cyl engines

Straight from hydramaster school they are not straight from the factory they are to Prochem and hydramaster, Siphire scientific spec's. I've been to hydramaster certified school 4 times Prochem 3 times and SS once that's how and why I said it.

 

[Joe cool]

My 408 has the 1.6 Hyundai
Plenty of power . I would like a extra 2 HG's but its very efficient.

 

[JDARNOLD]

The thing is that you can 17hg of lift but without air flow you don't have suction. 14hg is generally the industry standard, but in the last few years there are several units running 13.5hg. Steamaction is one of the few that are set up for 17hg. But look at their waste tank it's a 3/16 SS tank. I've seen several aluminum tanks that have been cracked from the flexing high vac pressure.

 

[JDARNOLD]

Why do you say they are opening the gap of the lobes? Those blowers are just dropped in straight from the mfg.

There will always be a difference in recommended specs between the mfg of the blowers, pumps, & engines. Those mfg's make those products for several various applications. They can only set specs for that particular piece of equipment. The TM mfgs have done their own testing and found the optimal performance for their configuration.
For instance, Gardner Denver says that you only need to change the oil in the blower about every 4,000 to 5,000 hrs. Would you wait that long with your blower?

The pump and blower put a huge load on the engine. running them out of their spec can cause undue damage to the engine. Just like running the engine at anything but full throttle will cause damage because it can't handle the load. IMO, that really only applies to the 2 cyl engines

I change my customers blower oil and pump oil every 500 hours or 6 months which ever comes first. And make sure that you use a oil that meets or exceeds the manufacturer's recommended oil.

 

[gborris]

I run 3600 rpm direct coupling to blower