# Seals for a shaft with 24000 rpm

• Wasiq
Wasiq
Hi everyone! I am having a problem with the leakage through the hole between high high-rotation shaft and the wall of the case that is of 2.5 mm each point. Attached below is the pdf that show that the outer diameter is 12.5 mm while the diameter of the shaft is 12mm . There are some of the characteristics:

1. Shaft rpm= 24000 rpm
2. Linear velocity= 13.4 m/s
3. Temperature= Between 150-180
4. Exposed to tar and grease
I have used multiple types of solutions such as rotary shaft sealing but there is no solution. Can you tell me about the correct sealing through which the leakages will be minimum.

#### Attachments

• Fumecatch.pdf
144.1 KB · Views: 5
Is the fluid air?
We need a better picture of the structure and some idea of the pressure differences between chambers.

Have you considered a labyrinth seal?
A small disc attached to the shaft may throw out air and prevent flow along the shaft.

Is a sealed ball bearing insufficient?

Your PDF shows what appears to be a centrifugal blower, but does not show what we need to know:

1) A detailed drawing of the portion of the shaft around the seal, the blower housing around the seal, and the seal housing.
2) What are you sealing - is it a liquid or gas? What liquid or gas?
3) What is the temperature of the substance that you are sealing?
4) What is the pressure difference across the seal?
5) How long does it need to last - minutes, hours, days, months, years, or decades?
6) What is the shaft deflection at the seal location?
7) Discuss the "exposed to tar and grease". Is it a few drops splashing, or a high pressure stream aimed at the seal?
8) What is the allowable seal leakage? There is a huge difference between 1 cc/year and 1 cc/day, and zero leak seals can get very expensive.

Tell us exactly what seal designs you have tried. Why did each of those not work?

A 12 mm diameter shaft running 24,000 RPM will have a surface velocity of 15 m/sec, so what is moving at 13.4 m/sec?

Flyboy said:
Is a sealed ball bearing insufficient?
Do you think ball bearings can withstand 24000 rpm

Wasiq said:
Do you think ball bearings can withstand 24000 rpm
NSK 6801 - 12 mm ID x 21 mm OD x 5 mm wide.
open in oil = 38,000 RPM.
metal shield = 32,000 RPM.
non-contact sealed = 32,000 RPM.
rubber lip sealed = 20,000 RPM.

jrmichler said:
Your PDF shows what appears to be a centrifugal blower, but does not show what we need to know:

1) A detailed drawing of the portion of the shaft around the seal, the blower housing around the seal, and the seal housing.
2) What are you sealing - is it a liquid or gas? What liquid or gas?
3) What is the temperature of the substance that you are sealing?
4) What is the pressure difference across the seal?
5) How long does it need to last - minutes, hours, days, months, years, or decades?
6) What is the shaft deflection at the seal location?
7) Discuss the "exposed to tar and grease". Is it a few drops splashing, or a high pressure stream aimed at the seal?
8) What is the allowable seal leakage? There is a huge difference between 1 cc/year and 1 cc/day, and zero leak seals can get very expensive.

Tell us exactly what seal designs you have tried. Why did each of those not work?

A 12 mm diameter shaft running 24,000 RPM will have a surface velocity of 15 m/sec, so what is moving at 13.4 m/sec?

Baluncore said:
NSK 6801 - 12 mm ID x 21 mm OD x 5 mm wide.
open in oil = 38,000 RPM.
metal shield = 32,000 RPM.
non-contact sealed = 32,000 RPM.
rubber lip sealed = 20,000 RPM.
lemme have a check on it

Beyond 'labyrinths', consider eg 'magnetic bearings', where shaft does not extend through sealed enclosure ??
Okay, may also have 'trad' bearings to accommodate 'excursions'...

Nik_2213 said:
Beyond 'labyrinths', consider eg 'magnetic bearings', where shaft does not extend through sealed enclosure ??
Okay, may also have 'trad' bearings to accommodate 'excursions'...
The issue is that the objective is not just suspending the axle in space and reducing friction.

It’s also providing an air seal for the blower housing. A magnetic bearing would not provide that seal.

IIRC, there was a trick used in model-boating before modern materials such as ferro-fluids and PTFE to have a threaded prop-shaft so that its usual rotation acted as a screw-pump within stern-tube to drive inevitable ingress along shaft back outwards. Think 'lead-screw'...

You could not run in reverse for 'long', and the wary fitted a small, float-switched bilge-pump in reserve...
Think 'cellar sump-pump'...

Hmm: In your application, could you have a magnetic coupling so the blower shaft is entirely within the housing, and there are no through-housing axle seals to wrangle ?? Per oil-free air-compressors and 'hygienic' equipment...

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