Annoying Compressor fault....?

[normspanners]

Actually when the belt became slack on my Clarke it wouldn't start even on a warm day. As soon as the pump started pushing air into the tank the belt slipped and there wasn't enough momentum in the flywheel to carry the pump over TDC.

that is correct I have had that loads of times but that is akin to a worn out slipping clutch, when slack.

I was talking about normal tension you will find that a certain amount of belt slippage takes place and is inevitable that is similar to slipping the clutch to attain more torque, in the same way dragsters control the amount of tyre slip to attain maximum acceleration, without burning out the clutch they burn out the tyres instead. So that the engine is at maximum power whilst feeding in the load. a little like having a lower gear but for milli seconds or an automatic torque converter.

Engineering formulas A ratio is a proportional factor between two similar objects of different sizes. In a belt drive system, a ratio is used to determine the speed relation between two v-belt pulleys. The speed ratio would be stable if slippage did not occur; however as belt slip is inevitable, the ratio varies and is therefore only theoretical.

from http://www.baldor.com/mvc/DownloadCenter/Files/MS4050

 

[normspanners]

Starting a high capacity fan is very similar to a compressor and you very often hear belt slip until sync is reached because, for one, the faster a belt drive spins the more it will drive so at zero/very low rpm the drive is at its worst.
one large fan we needed to start with a 70hp motor would blow the trips because the supply was not really big enough causing massive volt drop and tripping the motor overloads untill I hit on the idea of slackening the belts slightly, then when the motor started there was a period of belt slip not enough to damage the belts, but once up to sync the drive was easily strong enough to drive it at full speed all day. the star delta changeover point was critical factor also and shortening it down, rather than lengthening it in conjunction with belt slip was desirable. The same with compressors a short star delta time helps stops unwanted tripping.

 

[normspanners]

why do your posts always make sense

You sure your talkin ta me??
I sometimes have to read what I write 3 times, for them to make sense to ME

 

[normspanners]

he just copies and pastes from google

4---- 'Cough'----------in fact I use that much paste my keyboard is a right mess.

 

[Mee]

My Clarke SE16C150 starts everytime no matter how much air is in the tank or what the ambient temperature is. I was going to buy the 50 Litre version, but bought the SIP instead. Wish I'd paid the extra £100 for the Clarke.

We all live and learn

 

[Mee]

It is 'ALL' about the oil, and is the main factor----------has been proved year after year time to go to new lower viscosity oil funny thing on saturday my standby tyre blower ( allways switched on 24/7) had tripped the amp switch and didnt start and was thinking I need to change the oil and thought I wonder when the first post would hit !

No, its not always about the oil, the biggest problem is cooler and more dense air, by trying to compress more dense air you push the motor a little harder and as most smaller compressors are poorly designed to fail to make you replace them more often you get the motor failing to start. Compressed air generates its own heat during compression and this translates to conducted heat through both the pump and motor on a coupled unit and in cold weather the motor loses some performance when it is cold, particularly if it cold and damp from a little condensation.

So we have several issues: a motor slightly down on power, denser air to compress, and a motor which needs a heat cycle through it to bring back its power.

 

[daleyd]

and here I was thinking that norm was some form of engineering savage savant

Fixed that for you

 

[normspanners]

the motor loses some performance when it is cold,

AFAIK motor loose efficiency, as temp rises, not gain it because of increased resistance, the only thing that causes a problem with cold motors is thick grease and that brings us back to general lubrication.

 

[normspanners]

and here I was thinking that norm was some form of engineering savant

More like servant , HEHE I've got broad shoulders I can take the stick (he says sobbing uncontrollably)

 

[normspanners]

Many years ago used to work on forklifts and we had two warehouses next door to each other with several identical new forks linde h30s deutz engined, one warehouse was full of tissue paper toilet rolls in plastic bags and the other full of ally ingots
there was a significant difference in feel between the two buildings whilst the ambient temp was obviously the same there was a different shiver factor to the place it was just MAYBE a couple of deg's colder in the ally side. Due to the massive cold radiators (ally blocks) staying cold after a freezing night any draft would pick up that cold and chill everything in there, down further.
We had difficulties with starting the trucks every winter with the ally warehouse and I came up with the idea to use a different oil 5/30 whilst the paper place still used the same summer oil 20/50 ! both warehouses shared the same roof and building design
it was all down to the fact as the temp dropped to sub 5deg.
we proved it by building a little open topped 'garage' to park the trucks in overnight in the ally w/house with pallets of tissue from next door and the trucks started with the same 20/50 oil but not as well as next door. linde would not believe it saying the trucks should be good to minus 5-10 on the same oil but stuck with us and allowed the thinner oil.

And what are engines ? essentially compressors, to begin with, till fuel is added then they become engines.

 

[normspanners]

I did a old 3ph ingersol rand one last week, at another garage I do work for belts squealing on start up, changed oil to thinner grade all good, no belt squeal running like a new one ( well better in fact, better because IMO modern compressors are crap)

 

[Mee]

Modern compressors are not engineered as such, they are designed to be marginal in every area; that's commerce for you, why sell a compressor every 20 years when you can sell one every 3 years.

As for the oil being the major issue, this is merely a peripheral issue as even the manufacturers themselves admit air density due to temperature is the main issue and the reason they tailor them to different temperature regions, and as far as motors losing performance goes it is not a motor gaining performance it is an issue of motors losing slight performance when they are stood in the damp as it is the damp itself which penetrates the motor.

 

[daleyd]

...as it is the damp itself which penetrates the motor.

This is a joke, right??

 

[Crater Creator]

Modern compressors are not engineered as such, they are designed to be marginal in every area; that's commerce for you, why sell a compressor every 20 years when you can sell one every 3 years.

As for the oil being the major issue, this is merely a peripheral issue as even the manufacturers themselves admit air density due to temperature is the main issue and the reason they tailor them to different temperature regions, and as far as motors losing performance goes it is not a motor gaining performance it is an issue of motors losing slight performance when they are stood in the damp as it is the damp itself which penetrates the motor.

Can you provide a link to the source of the manufacturer's statement that you are quoting?
Denser air does not increase the pressure acting on the top of the piston...

 

[the snooper]

Modern compressors are not engineered as such.

are they formed from modeling clay by hand, by a class in primary school then ?

 

[the snooper]

Modern compressors are not engineered as such, they are designed to be marginal in every area; that's commerce for you, why sell a compressor every 20 years when you can sell one every 3 years.

As for the oil being the major issue, this is merely a peripheral issue as even the manufacturers themselves admit air density due to temperature is the main issue and the reason they tailor them to different temperature regions, and as far as motors losing performance goes it is not a motor gaining performance it is an issue of motors losing slight performance when they are stood in the damp as it is the damp itself which penetrates the motor.

This is a joke, right??

Can you provide a link to the source of the manufacturer's statement that you are quoting?
Denser air does not increase the pressure acting on the top of the piston...

another load of joke posts from Mee, like the, how to save money on your enegy bills thread me thinks

 

[rtbcomp]

... the reason they tailor them to different temperature regions...

I've just looked through three instruction manuals, SIP & Clarke belt drive and Clarke direct drive, and none of them give an ambient operating temperature range.

Interestingly, the Clarke compressors (which start OK when cold), use SAE30 oil and the SIP (which gives problems) uses SAE40.

 

[brightspark]

I've just looked through three instruction manuals, SIP & Clarke belt drive and Clarke direct drive, and none of them give an ambient operating temperature range.

Interestingly, the Clarke compressors (which start OK when cold), use SAE30 oil and the SIP (which gives problems) uses SAE40.

so try sae 30 oil in it when its cold and see if it makes a difference . it would be easy to see if u used a clamp meter on the motor on a cold day whether it made a difference on the current draw it probably would . I posted on here a couple of years ago on my comp start up current on cold and start up on warm and there was a difference on current draw

 

[rtbcomp]

...
Denser air does not increase the pressure acting on the top of the piston...

If you push a piston into a cylinder that has a vacuum (density = 0) in it you'll get no resistance, then if you force air into the cylinder the higher the pressure means increased density and at the same time the piston would be more difficult to push.

It's the pressure rather than the density that gives rise to the resistance, but you can't have higher pressure without higher density (at a given temperature/volume).

So perhaps sucking higher density air into the cylinder and then compressing it would take more effort.

But in the context of the original topic, I reckon the effect of denser air is insignificant compared to the effect of thick oil. What we need to do is try to start a problematic compressor on a cold day whilst feeding it with hot air.

so try sae 30 oil in it when its cold and see if it makes a difference . it would be easy to see if u used a clamp meter on the motor on a cold day whether it made a difference on the current draw it probably would . I posted on here a couple of years ago on my comp start up current on cold and start up on warm and there was a difference on current draw

I was going to give that a try at the next oil change.

 

[Crater Creator]

If you push a piston into a cylinder that has a vacuum (density = 0) in it you'll get no resistance, then if you force air into the cylinder the higher the pressure means increased density and at the same time the piston would be more difficult to push.

It's the pressure rather than the density that gives rise to the resistance, but you can't have higher pressure without higher density (at a given temperature/volume).

So perhaps sucking higher density air into the cylinder and then compressing it would take more effort.

But in the context of the original topic, I reckon the effect of denser air is insignificant compared to the effect of thick oil. What we need to do is try to start a problematic compressor on a cold day whilst feeding it with hot air.



I was going to give that a try at the next oil change.

Yes, you're right, the density is higher because of the pressure, which is what creates the load.
In my opinion pumping losses due to denser intake air would be negligible, at the low flowrates we're talking about.
I'm ready to be wrong though, if Mee can provide a link to the source of his wisdom.
I think the weight of the oil when very cold is 99% of the problem.