Mechanical seals for WITTE gear pumps

Mechanical seals for chemical pumps

A variety of seal variations are available for WITTE CHEM chemical pumps. In addition to mechanical seals - depending on the process - magnetic couplings or radial shaft seals are also installed. In individual cases, chemical pumps from the CHEM series can also be sealed threaded shaft seals. The use of seals is determined by the suction pressure, viscosity and temperatures.

Example structure of a WITTE mechanical seal (AD)

  • Wedge
  • Radial shaft seal ring
  • Stationary seal ring
  • Spring element
  • Rotating seal ring
  • Entrance of buffering medium
  • Release of buffering medium
  • Packing ring

  • Wedge

    The spring element presses the wedge into a wedge-shaped groove between shaft and rotating ring. By that the wedge serves as secondary, stationary seal inside the rotating unit of the mechanical seal.  

  • Radial shaft seal ring

    The shaft seal ring seals the external mechanical seal from the atmosphere outside. A radial spring presses its seal lip onto the surface of the rotating shaft. As to guarantee a long lifetime despite abrasion and wear the ring has to be made of material of considerable surface quality and hardness.       

  • Stationary seal ring

    The stationary seal ring is mounted on the pump cover and therefore is part of the stationary unit of the mechanical seal. The dynamic seal point is located between it and the rotationg seal ring. Since the spring element permantly presses the rotating seal ring against the stationary one, the latter must be made of material that can withstand wear and heat over a long period of time.

  • Spring element

    The spring element consists of a combination of discs, springs and pins. It belongs to the rotating unit of the mechanical seal. With even force it presses the rotating seal ring against the stationary one.

  • Rotating seal ring

    The rotating seal ring is part of the rotating unit of the mechanical seal. It is mounted on the rotating shaft. The spring element presses it against the stationary seal ring with an even force. For that reason the rotating seal ring is exposed to permanent wear (and heat). It must be made of a material that can withstand these conditions over a long period of time.

  • Entrance of buffering medium

    The interior of an external mechanical seal is separated from the internal chamber of the pump. For that reason it is not lubricated by the conveyed medium. Instead an external buffer fluid is added to the seal chamber. It does three things

    • it lubricates the dynamic seal point
    • it dissipates heat
    • is seals the pump chamber airtight from the outer atmosphere

    As to avoid bubbles in the buffer fluid system the inlet must be located below the outlet.

  • Release of buffering medium

    See inlet buffer fluid. As to avoid bubbles in the buffer fluid system the outlet must be located above the inlet.

  • Packing ring

    The packing ring serves as a stationary seal and seals the mechanical seal against the pump cover.

[Translate to English:] Chemiepumpe mit Vakuum Gleitringdichtung

Variations of the WITTE mechanical seal

Single-acting mechanical seal (ED)

The single internal mechanical seal (ED) is the standard seal for WITTE CHEM chemical pumps. It can be used for viscosities of up to 50,000 mPas.

Can be used for the following pump types:

  •     [CHEM]
  •     [PURO]

Operating parameters

Pressure suction side:
from Vacuum up to 15 bar(a)
Viscosity:
0,2 – 50.000 mPas
Temperature:
max. 300 °C

Quenched internal mechanical seal

 

The quenched, internal mechanical seal (EQD) is an affordable alternative to classic double seals if the actual operating parameters allow for a single-acting seal, but the medium must be hermetically separated from the atmosphere. Examples include applications according to TA-air or media that reacts to oxygen or moisture.

Can be used for the following pump types:   

  • [CHEM]
  • [PURO]

Operating parameters

Pressure suction side:
from 1 up to 3 bar(a)
Viscosity:
0,2 – 50.000 mPas
Temperature:
max. 250 °C

Vacuum mechanical seal (AD), locked pressureless

The single external vacuum mechanical seal for chemical pumps (AD) is locked without pressure. The locked mechanical seal is specially designed for vacuum conditions on the suction side. It can be used for viscosities of up to maximal 100 Pas.

 

Can be used for the following pump types:

  •     [CHEM]
  •     [PURO]

Operating parameters

Pressure suction side:
Vacuum up to max 2 bar
Viscosity:
0 - 100,000 mPas
Temperature:
max. 250 °C

Double mechanical seal, locked (DD)

The double mechanical seal (DD), locked can be used for viscosities of up to max. 1,000 Pas, because the moving parts of the mechanical seal cannot come into contact with the product. All moving parts are lubricated through the buffering medium. The GLRD (DD) can be used for incoming pressures that may amount to vacuum conditions of up to max. 15 bar.

Can be used for the following pump types:

Operating parameters

Pressure suction side:
Vacuum up to max 15 bar
Viscosity:
0 - 1,000,000 mPas
Temperature:
max. 300°C

Other seals

Querschnitt einer Magnetkupplung
Magnetic coupling
Einfache Gleitringdichtung
Mechanical seals
Gewindewellendichtung für Zahnradpumpen
Threaded shaft seal
Radialwellendichtung für Zahnradpumpen
Radial shaft seals
Dichtung für eine Zahnradpumpe
Seals from other manufacturers
CHEM Doppelte Stopfbuchse
Stuffing box