Knife type mechanical seal
Mechanical seal for CNP pumps, used in 2 CNP series and listed in SC/TC.
- Ø d shaft (sleeve) diameter the seal fits
- Ø D largest outside diameter of the seal
- L installed (working) length
What it is
A mechanical seal closes the gap where the rotating shaft leaves the pump, so the pumped liquid stays inside without a leaking packing. It is the part that wears most in service and is the most frequently ordered spare.
How it works
A hard rotating ring (carried by the shaft) is pressed by a spring against a stationary ring fixed in the pump. A micro-thin film of liquid between the two polished faces cools them and limits leakage to almost nothing.
- Part group
- Mechanical Seals & O-Rings
- Used in
- 2 CNP series
- Materials
- SC/TC
- Supply
- Quoted per pump model
Signs it needs replacing
- Drip or steady leak at the shaft after start-up
- Squealing or dry-running noise from the seal area
- Black dust (carbon wear) around the shaft
- Overheating or vibration at the shaft end
Selection & fitting tips
- Match the shaft diameter and the seal length of your pump model, not only the pump size
- Face pair decides life: carbon/ceramic for clean water, silicon carbide / tungsten carbide for hot, dirty or abrasive liquids
- Elastomer (NBR, EPDM, FKM) must suit the liquid and temperature
- Never run the pump dry, even briefly
What to send us to order
Pump model code, shaft diameter, face materials and elastomer if known, quantity.
We identify the exact part for your pump and reply with price and delivery.
Request a quotationSeries that use the knife type mechanical seal
| Series | Listed as | Material | Standard | Fits sizes | |
|---|---|---|---|---|---|
| LLT (coaxial) | Knife type mechanical seal | SC/TC | — | All sizes | |
| LLTS (extended shaft) | Knife type mechanical seal | SC/TC | — | All sizes |
Catalogue dimensions
Seal-face materials: typical use (5 rows)
| Face pair | Typical use | Notes |
|---|---|---|
| Carbon / ceramic | Clean water, general duty | Economical; avoid abrasives and dry running |
| Carbon / silicon carbide | Hot water, mild chemicals | Better thermal shock and chemical resistance than ceramic |
| Silicon carbide / silicon carbide | Abrasive or dirty liquids | Very hard faces; tolerates solids better |
| Tungsten carbide / tungsten carbide | Abrasive liquids, higher pressure | Tough and hard; common on multistage and submersible pumps |
| Tungsten carbide / carbon | General industrial water, higher pressure | Good all-round combination |
General engineering guidance; the face materials actually fitted to each series are listed in the series table above.
Elastomer guide: typical temperature range (3 rows)
| Elastomer | Typical range | Typically used for |
|---|---|---|
| NBR (nitrile) | -30 to +100 °C | Water, oils, glycol mixtures |
| EPDM | -40 to +130 °C | Hot water, steam condensate, mild alkalis (not mineral oil) |
| FKM (Viton) | -20 to +200 °C | Chemicals, hydrocarbons, high temperature |
Typical compound ranges; confirm the exact grade and the liquid with the supplier.