Type CK 725 Vessel & Agitator Seals | Mechanical Seals | John Crane

Type CK 725 (W,D)

Mixer and Agitator Cartridge Seal to Vessel Seal Standard DIN 28138 for Steel Chemical Reaction Vessels — No Bearing Integrated

The Type CK 725 is a dual-pressurized, cartridge seal for top-entry mixing and agitating equipment. The seal is lubricated with a liquid or gas barrier. The seal has a value-engineered design, with a high level of standardization and a broad range of material options making this seal a cost-efficient solution for general-duty applications in the chemical and pharmaceutical industry. Standard versions are compliant with vessel seal standard DIN 28138 Parts 1 and 3. They are designed for use on steel-made agitated chemical reaction vessels to DIN 28136, to fit on a mounting flange to DIN 28141 and agitator shaft end dimensions to DIN 28154. The seals are also available to fit to non-DIN equipment.

By exchanging the seal faces, a Type CK 725 wet seal can easily be converted from a liquid lubricated, to a contacting dry-running seal. Type name then changes from Type CK 725W to Type CK 725D. Advantages of contacting dry running seals include freedom from contamination by barrier liquid and a low face wear rate, together with a cost-efficient, easy-to-install (gas) supply system. To simplify inventory, seal components are standardized with the other seal types of this family Type CK 726(D) and Type CK 736(D).

The seal is suitable for operation in potentially explosive atmospheres. Depending on individual explosion protection requirements, the seal operating limits may differ from the values given in the parameters section. Furthermore, additional monitoring devices may be required.

For undemanding applications, the wet seal versions can be operated without pressurizing the barrier liquid. Please consult John Crane.



  • California Residents: PROPOSITION 65 WARNING
  • Dual-cartridge seal without bearing to DIN 28138 for stainless steel vessels.
  • Fits mounting flange to DIN 28141 and shaft ending to DIN28154.
  • Back-to-back seal arrangement with unbalanced faces.
  • Reversed pressure capabilities inboard.
  • Liquid-lubricated (CK 725) or dry-running (CK 725D) face versions available.
  • Non-standard sizes, special designs and material options are available on request.
  • Debris well and cooling flange options available.
  • Suitable for application in explosive areas. Certificates of conformity according to European Directive 2014/34/EU (ATEX) Cat. 1, 2, or 3 on request.
  • Limits of operation without pressurized barrier fluid are available upon request.

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