Clearance question on stuffing box gland?

I have a stuffing box on a piece of equipment which needs replaced. It's a simple brass stuffing box with string packing and a brass gland. A new one is not available.

I'd like to put a bushing in the worn gland, but I don't know the clearance required between the gland and the SS shaft which runs through it. The shaft turns about 150 rpm.

Equipment is no longer made. The shaft size is 1.200"

Could someone please advise on the suggested radial clearance between the shaft and gland? In other words, what bore size would you recommend for the gland i.d.?

And one other question please. Is is customary where the staff goes through the stuffing box to have the same i.d. as the gland? In other words, is it customary for the smallest i.d. of the stuffing box to be the same as the i.d. of the gland?

Three relevant dimensions. Shaft diameter, stuffing box ID, and what I would call gland minor diameter.

Stuffing box ID needs to be larger than shaft diam by twice the size of the packing...if you are using 1/4" packing, then the stuffing box ID would be 1/2" larger than your shaft or approx 1.7" in your case.

What I am calling gland minor diameter is the size of the hole at the back of the stuffing-box that the shaft comes through. About the same as the packing follower bore. As long as the gland is rigidly concentric and coaxial with the shaft bearing, the smaller the better as long as there is no contact with the shaft. If the clearance is large, you will rapidly extrude your packing out the bottom of the gland. I would try .010"

Thank you very much.

One other question if you please.

Is it generally the case that the minor diameter of the stuffing box is the same as the minor diameter of the gland? If this is the case, I would know the exact size to bore the hole in the bushing to repair the gland.

Here drawing of what my stuffing box/gland looks like. Just two pieces and packing.

Build question stuffing box gland

I had another question regarding this stuffing box gland, if anyone has any thoughts on this?

I plan to make a new one, instead of repairing the current one with a bushing. The current one has some grease grooves which would be hard to replicate using a bushing, as it would leave the wall thickness of the original part thinner than I'd like.

I plan to make a new one out of 304 for good corrosion resistance weldablity. I've ordered some 1.75" round (for the cylinder portion) and some .375" plate for the flange portion.

However, I'm not sure of the best way to connect the flange to the cylinder portion of the gland.

As I'm seeing it, the options would be:

1. Overbore the flange and leave a shoulder on the cylinder portion allow for a press fit of the cylinder portion and the flange

2. See number 1, but also tack weld them together.

3. Finish bore the i.d. of the flange to match the finish i.d. of the cylinder portion, then butt weld the two together.

4. Butt weld the flange and cylinder portion together then machine the finish i.d. together.

The wall of the cylinder portion is 1/4" thick. The flange is 3/8" thick. I figured out the original clearance between the o.d. the the shaft, and the i.d. of the gland is .004"

Any thoughts on which would be the best way to build this, or does it make a difference?

Here are some pics of the old gland, which needs to be replaced.

I would use follower ID clearance similar to the clearance at back of gland. I am not so comfortable with SS for any of the pats, because of the likelihood of galling if something gets even a little out of line.

What kind of equipment?

more information and pictures usually get you better results...

using your numbers...

1.200" x .2617 = .314.............. .314 x 150 rpm = 47 fpm

if your rpm is wrong re-figure accordingly....

Disclaimer, use at your own risk

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From Marks mechanical engineers hand book 4th edition....

under 600 fpm ( .001 x diameter in inches) + .001.......I have done this with squirrel cage fans at 700 rpm ...

..depending on your application .0015 per inch..

over 600 fpm (.002 x diameter in inches) + .002.

call a pump company or driller for a bronze gland.....

probably a 1.1875 gland bored / modified to your required size would work.....

Depending on the length of the bearing I would go with the larger clearance....

If cutting a groove in the bushing for grease stay way from the ends of the bushing ...

.If application is horizontal ...Groove goes in the 12 o clock position...

if vertical put a circular groove in the middle.....


Is there anything that prevents an upgrade from packing to a lip seal?....or seals?

A tacky grease goes along way with bronze bearings...

Thanks very much for the helpful information.

JS said:

using your numbers...

1.200" x .2617 = .314.............. .314 x 150 rpm = 47 fpm

if your rpm is wrong re-figure accordingly....

Click to expand...

That's actually very close. I haven't measured the pulley assembly, but I'd estimate the 1.2" SS shaft turns at about 120 rpm.

JS said:

From Marks mechanical engineers hand book 4th edition....

under 600 fpm ( .001 x diameter in inches) + .001.......I have done this with squirrel cage fans at 700 rpm ...

..depending on your application .0015 per inch..

over 600 fpm (.002 x diameter in inches) + .002.

Click to expand...

Thanks for that. That's exactly some of the info I was looking for. I do notice that the new stuffing box has a minor i.d. diameter of 1.204". That's why I assumed the new gland follower should be made with the same clearance?

JS said:

If cutting a groove in the bushing for grease stay way from the ends of the bushing ...

.If application is horizontal ...Groove goes in the 12 o clock position...

if vertical put a circular groove in the middle.....


Is there anything that prevents an upgrade from packing to a lip seal?....or seals?

A tacky grease goes along way with bronze bearings...

Click to expand...

Perhaps it should be made of bronze. The other end of the shaft rides inside a SS bushing, so I assume the gland follower could be made of SS? The current gland follower stuffing box is made of cast. Since I can't easily manufacture a gland from cast, I thought I'd use 18/8. It really doesn't come in contact with the tank water, except for a possible weep through the cord packing, but it is outside, so thought it would be an upgrade to go with SS?

I'm not married to the idea though. I've ordered enough SS to make the parts, but I could use something else. I'm thinking I need to be able to weld it, or press fit. I'd rather not try to machine the gland in one piece. I don't have the CNC equipment for that.

JS said:

What kind of equipment?

more information and pictures usually get you better results...

Click to expand...

Here's some more info.

The stuffing box and gland is off a 400 gal. ag sprayer. The sprayer has wheels and pulled behind a tractor. Runs off PTO. The sprayer is over 50 years old, but has been completely rebuilt with all SS parts. Tank, fittings, etc. all SS. The pump and frame are about the only thing original. I rebuilt the pump a few years ago. This gland and stuffing box are one of the few original things left, but it has lasted 50 years, so thought the design OK for my needs. I certainly won't live another 50 years.

I was able to purchase a new (old stock) stuffing box, but there is no new gland available. I was able to purchase a used worn one. I had originally planned to bore and bush the worn one, as a a replacement part, when I am ready to disassemble the sprayer and drop the replacement parts in place. Then when I saw the grease grooves would prevent bushing the gland, I thought the easiest was to make a new gland.

I have a manual Bridgeport mill, but no lathe. I have a Criterion boring head, with internal and external boring bars (with carbide inserts). I also have a Hardinge dividing head with a dead center I've used in conjunction with the mill, to turn parts. I think I can make the part, but maybe not.

Here are some more pics:

This is the a pic of the new (old stock) stuffing box and gland. The stuffing box doesn't have a lantern ring. It's just a simple one packed with graphite cord. The stuffing box screws into a SS 2" female couple. The SS couple is welded on the tank.



Here is a pic of the other side.



Here is the stuffing box and gland disassembled.



Here is a "stick man" drawing to give an idea of the layout of the tank and part in question.



As I mentioned the 1.2" shaft rides inside a SS bearing/bushing on one end and rides inside the cast iron stuffing box and gland on the other.

Btw,

If bronze is recommended for the gland, what type of bronze would be most suitable? Probably a dumb question, but I'm assuming bearing bronze?

Also what type of joint would be recommended to fit the flange and cylinder together (i.e. press fit, butt braze, press and braze)?

Probably make both parts from Dura-Bar cast Iron...class 30 and never mess with it again.....

My go to when dealing with anything non potable is SAE 660 or C93200 same material different designation.......

Mid America pump in Hasting Nebraska could possibly have a gland save you some effort...or any driller might be able to find you one...

or Flowserve / Ingersoll Dresser pumps out of Hastings Nebraska........

Spent roughly a decade manufacturing pumps & parts......Not for either of them .....Good people though...

From your drawing the gland serves the purpose of a seal and a bearing. Consider compatibility of chemicals with your choice of materials. I would machine the base of the stuffing box as if it was a bearing, .0015 to .003 clearance. The stuffer can be a bit looser. Stuffing boxes are meant to drip a small amount so don't tighten too much. Teflon stuffing worked well for me on water pumps turning at 1750 rpm.

Thank you for the helpful tips.

deltap said:

From your drawing the gland serves the purpose of a seal and a bearing.

Click to expand...

That's exactly right.

deltap said:

I would machine the base of the stuffing box as if it was a bearing, .0015 to .003 clearance. The stuffer can be a bit looser.]

As I understand what you are communicating, the gland follower (pictured here)



are commonly manufactured with a smaller i.d. than the minimum i.d. of the stuffing box? (The piece painted in green above.)

Or are you just saying I should machine this gland follower with an i.d. smaller than the minimum i.d. of the stuffing box because it acts as both a seal and a bearing?

Click to expand...

I had pictured the part with studs that screws into the tank would have more of a bearing surface behind the packing. Looks like it doesn't. So the part with the grease fitting would serve as bearing if machined to a bearing fit to the shaft and the bore. You can make that part in the milling machine using a boring head. Hand cut the grease groove.