Pumping heavy grease

I want to pump very heavy grease along a tube that could be around 10mm inside diameter. The grease would be in a tube about 100mm diameter (a plastic drainpipe actually) and I hope to pressurise that by winding a piston down on a thread. I'll have a valve at the end of the pipe to control the flow. It would be bit like an ordinary grease gun on a large scale. The grease merely has to dribble out the end, so no pressure is needed after that. So, will the grease move in the small tube before the large tube bursts?

Ideally I would like to pump the grease at a variable rate using a rotary pump, but that looks a bit hard to make.

Reply to
MattyF
Loading thread data ...

Depends on length of 10mm tube, viscosity of grease, and pressure limits of the large tube.

Is it marine fuel? The usual trick is to heat it with the engine.

NT

Reply to
meow2222

It's environmental friendly grease for rails. Extremely viscous. I could make the small tube bigger. The big tube would be plastic, but I could use steel but that would be getting rather heavy to carry for several kilometres!

Reply to
MattyF

Sounds like a case of "suck it and see"!

Could you do an experiment - with a pressure gauge fitted to the large tube near where the small tube connects? First measure what pressure is required in order to achieve the maximum desired flow rate through the small tube. Then block up the small tube, and again apply pressure until the large tube (presumably expendable?) bursts or until the pressure is (say) twice the first measurement. That will tell you what margin of safety you have.

Reply to
Roger Mills

Plastic pipe comes in various grades, so you need to know what you are using. 4" BS3505 PVC pipe ranges from 6 Bar rating (Class B 3.4-4.0mm wall) to 15 Bar (Class E 7.3-8.4mm wall).

Reply to
Nightjar

I expect that doubling the diameter of the small tube will reduce the pressure requirement by a factor of 4 or 8.

Google Reynolds Number? (That comes to mind from over 40 years ago, but I could be barking.)

Reply to
GB

Archimedes screw rather than piston?

Reply to
Adam Aglionby

And making the transition from big to small a cone shape rather than a step. Can't decide if there would be much difference between a plain cone, bulgey out cone or bulgey in cone. Gut feeling is that a bulgey in one might be better.

Reply to
Dave Liquorice

In message , MattyF writes

Reinventing the wheel here, Matty. Googling grease dispenser gets zillions of hits.

You could ask a commercial supplier if the viscosity of your grease is a problem for their system. Compressed air driving a reciprocating pump is commonly used and could perhaps be adapted for your variable rate.

Most farms will have a dispenser which replaces the lid on steel 20/25L grease containers.

Medium pressure plastic gas pipe might be better than PVC drain:-)

Reply to
Tim Lamb

So you want the reservoir and pump part for this type of system:

formatting link

Could it be done with a small inline piston-pump on the outlet side of the reservoir?

And a well fitting cap on the top of the grease acting as a piston under atmospheric to prevent air voids forming in the grease?

Basically how a grease gun works... Suck from the reservoir and push to the delivery point.

Reply to
Tim Watts

Large bore metal tube, piston head with a nut welded on a small hole in the middle, mounted on a motor driven threaded stud.

Reply to
Tim Watts

This reference gives the formula for the flow rate. Just plug in the numbers and estimate the pressure drop needed for a particular flow rate and tube diameter/length.

formatting link

Reply to
GB

It *probably* isn't, but can I warn you that it can be difficult to pump molybdenum disulphide grease through small pipes; the oil and solids tend to separate and you can end up with a very effective plug of nearly pure molybdenum disulphide. It's an issue with relatively long pipes: at 10 mm diameter you would probably be OK for ~ 30 cm.

Reply to
newshound

If you want a ready made one look for a marine stern tube greaser, such as this one:

formatting link

Reply to
pcb1962

Yes that is exactly what I was thinking of making. Perhaps I will do some experiments. The small tube only has to go from the reservoir to a circular felt disk on a wheel, so it could be only an inch or two long, once I have invented some sort of tap to control the flow of grease.

Reply to
MattyF

Why arent you controlling the pump instead?

NT

Reply to
meow2222

I thought the easiest thing for me to make was a grease reservoir that could be pressurised by occasionally winding a piston down. Then a trigger could be pressed to let a small amount of grease out as needed. Otherwise if I could devise a way of using a wheel to drive a variable pump, that would be better. At the moment an ordinary grease gun is used. That means walking along trying to hold the applicator on the track while pumping the lever all the time. That is difficult and messy.

One day I may be asked to make an automatic device for every curved bit of track. However there is lots of curved track, so it's cheaper to have a volunteer to walk along every few weeks with a grease gun.

Reply to
MattyF

BUY! This is MattyF, more likely to machine something out of solid block of steel with only an angle grinder than BUY something.

Reply to
Dave Liquorice

I think that will happen with the pressure required and a plastic master cylinder. Certainly happens with me and silicone sealer things, flow continues from the nozzle unless you release the piston.

Which raises the question does the mechanism have to be a screw? Couldn't the ratchet mechanism from a sealant gun or a clamp be "borrowed"? The pressure coming from the slightly deformed cylinder?

And how is this grease delivered, filling the "gun" might be interesting and messy. A bit of trapped air would compress but help supply the pressurisation.

Reply to
Dave Liquorice

Was thinking about feed on injection moulding nachines:

formatting link

Perhaps with an auger or wide drill bit in a tube.

Reply to
Adam Aglionby

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.