Greasing and sizing the packing rings

How big do packaging rings need to be? Is there some recommendation (a graph perhaps) showing the relation between the shaft diameter and the size of the packing rings? Or do all of them work pretty much the same, as long as let's say, three rings are fitted ("three rows")?

Also, I've noticed that some shafting installations have ... ugh, I don't know what is the exact term in english, so I'll try to describe it ... a small "greaser" for inserting some more grease into the ... this I've not seen on smaller installations, but starting from 100mm diameter upwards. Is there a rule of thumb, when it should be fitted, let's say in relations to outer shaft velocity?

 

The packing ring goes around the shaft. The relation is that the outside diameter of the shaft is the same as the inside diameter of the ring.

 

Naturally,

but it was my understanding that nowadays often packing rings are sold as ... how to describe it, "rope" ... wait a min, I'll find a link ... http://www.directindustry.com/industrial-manufacturer/braided-packing-76655.html

and you cut it accordingly. So I can put "larger" or "thinner" rings around the shaft.

 

The square section rope has been in the market for many decades. You need to install the size that fills the gap between the shaft and the tube.

 

Gonzo, hi ... I'm aware of their function.

I don't have any catalog with me (btw, where can you buy them over the internet, rings for boat shafting?) and that's why I'm asking about their sizes.

As for the shaft/tube I'm just drawing it for a certain project, that's why I don't have the inner diameter of the tube still determined.

 

Packing is sold by the meter in various thickness's. Typically You cut it into " C" pieces and fill the stuffing box. Offset the "c" sections.

This is a popular brand I see in ship stores.

http://www.europeanmarine.co.uk/Duramax Ultra-X Compression Packing.pdf

 

Yeah although he knows the function he is not aware that you buy in length and cut .

Its just greasy string you must have seen it but not knew that it was. you need up to 5 rings and you can buy low friction.

The only size needing consideration is will it fit in the the slot ie the gap between the shaft and inside of the stuffing box. When fitted you should be able to turn it by hand.

 

Zerk fitting or grease nipple are the terms you're looking for (my assumption).

 

www.tss.trelleborg.com/

www.europeanmarine.co.uk/Duramax Ultra-...

www.mjengineering.com.au/.../Propeller_Shaft_Seal_System_Brochu...

The modern Duramax or similar have no need for greasing.

FF

 

Thanks to all for their help, I found some of the links a very useful read.

However, I still can't find in there a simple table that would tell me (in metric units), what would be the appropriate size of rings for a shaft of let's say 70mm in diameter?

10mm? 9mm?

Or should I say, what would need to be the clearance between the shaft and the shafting tube to enable a good "flow of water" for cooling the seals and the bearings?

 

It's not the size of the shaft - it is the clearance between the OD of the shaft and the inside of your packing gland. You don't want the packing to rattle around - it should be a just push in by hand fit fit.

 

Quote by saildude --- ( It's not the size of the shaft - it is the clearance between the OD of the shaft and the inside of your packing gland. You don't want the packing to rattle around - it should be a just push in by hand fit fit.)



Me again-- I think that I said that above, is there an ecko in here.

 

Ugh, we've been over this before ... (it is somewhere in the posts above).

I have the shaft diameter. Everything else is at this moment unknown and mine for choosing. I can determine the tube inner diameter, I have the option of several bearings each with different thicknesses, and have the option to put let's say, 8mm packing rings in a smaller shafting tube, or 10mm packing rings in a larger shafting tube.

I imagine, packing rings of 5mm would not be good for a shaft with OD=150.

That's my dillema. I need an approximation of what would be the right size.

 

Ok lets try a different tack on the OP question...

The size of gland seals is determined by the stern tube stuffing box. The stuffing box is delivered with the shaft through hole drilled. Clearence for the shaft is ~ 1mm (1/32). The stuffing box itself has a radial clearence of ~4 - 10mm (3/16-3/8) with larger diameter shafts having more clearence. Into this radial clearence space is driven the greased/soaped/lubed flax/hemp/poly gland packing. The gland seal is sold in various base diameters/square sizes4,6,9 mm (3/16, 1/4, 3/8) in various stock lengths and then cut to length at installation (cut the end at a 45 then wrap it around the shaft and cut it at a 45 to overlap the splice for each ring but some oldtimers just taper the starting end then use the whole length of packing as one piece). Some manufacturers sell them in pre-formed rings to their specific stuffing boxes, but industry wide standardization is not in place. Then the gland cap/nut is installed and as frosty says, tightened down until the drag of the packing can just be felt. In normal operation, the seal should leak a drop or two per minute. When stopped at moor, the seal should be tightened slightly and the drops should stop. Before getting underway you should back off the seal slightly.

And yes the grease cup/fitting is a shaft velocity consideration. Grease cups can be self tending if you use tallow rather than synthetic grease.

 

Note the xpost with Idigas

Ok; this is a scary turn, as you don't use flax packing with 6" shafts they are engineered using a seal system consistant with the application. I take it you do not have a degree in Marine Engineering. This is one of those thing you should take to a professional as you can kill people real fast with a shaft that big.