Views: 0 Author: Site Editor Publish Time: 2026-10-29 Origin: Site
A cross-section lands on the procurement desk with a column of English labels nobody asked for. Get it wrong and the order goes out wrong, then the seal leaks the day it sits in the pump. The drawing decides that step, not the catalogue. It shows where two faces close a gap and why they hold.
Start at the centreline. That chain-dotted line down the middle is the shaft axis, everything lines up to it. The sleeve wraps the shaft. The rotating face turns with the shaft, the springs sit behind it, and the stationary face locks in the gland and stays. Between the two faces is the film, that thin band, and the seal only does its work there. Process fluid pushes on one side, atmosphere on the other, and the micron film is all that stands between.
Read it in one pass, outside in. The order below follows the path a seal takes from the shaft to the air.
On the drawing | What shows | Why it matters |
|---|---|---|
Centreline, shaft axis | Chain-dotted line down the middle | Every dimension references it, find it first |
Sleeve | Tube around the shaft | Protects the shaft, its finish decides the dynamic O-ring |
Rotating face and springs | Ring that turns with shaft, springs behind | Springs hold the faces shut at zero pressure |
The film | Thin gap between the two faces | The real seal, too thick leaks, too thin burns |
Stationary face | Ring locked in the gland | Does not turn, usually the hard SiC or ceramic |
Gland plate | Plate bolted to the pump | Holds the stationary face, carries flush ports |
Secondary seals | Small O shapes in the drawing | Block the bypass paths, the usual leak spot |
Atmosphere side | Other side of the film | Where a lost film ends up, so the film stays |
The balance ratio on the drawing beats the part names. A figure near 0.7, or a balanced tag, and the seal takes high pressure. An unbalanced one suits low pressure only. The spring layout tells something too. One big coil wound round the shaft has a wind direction and unwinds if fitted backward. A ring of small springs fits either way and forgives a careless hand.
Tell the faces apart by whether they turn. The rotating face rides the shaft and moves. The stationary face locks in the gland and holds still. Those small O shapes scattered through the drawing earn their place. They are the secondary seals, and the one that slides along the shaft as the faces wear is the beginner's common failure. A scratch on that shaft surface tears it the first day.
A cartridge drawing boxes every part inside one outline. That frame says the whole assembly ships pre-set as one unit, no setting on the shaft. Keep bare hands off the lapped faces. Skin oil alone shortens their life, and a dropped ceramic ring goes in the bin even with no visible crack, because the fracture hides inside and fails within weeks. Match the drawing to the real shaft and duty before the order, not to the nameplate number.
FBU builds cartridge seals to the chamber and the duty, air tested before they leave. Send the cross-section or the shaft size. What arrives fits, not almost fits.
How to read a mechanical seal cross-section drawing?
Start at the centreline and read outward. The rotating face and the stationary face meet at the film, the only real seal. The sleeve, springs, gland and small O shapes are the parts that locate, load and bypass-proof the faces. Process fluid sits on one side of the film, atmosphere on the other.
What is the thin line between the seal faces on a drawing?
The fluid film, a fraction of a micron thick. It lubricates and cools the contact zone while it seals. Too thick and the faces lift and leak; too thin and they touch, overheat and crack. The whole seal lives or dies in that band.
How to tell the rotating face from the stationary face on a seal drawing?
By whether it turns. The rotating face rides the shaft and moves with it; the stationary face locks in the gland and stays still. In a cartridge the two are boxed together, but the motion difference still holds.
