Sealless (API 685)

Petrosadid: Sealless (API 685)

On principle, a centrifugal pump pumps a liquid by forcing it through an impeller while giving it a rotating motion and thus an hydraulic power. A centrifugal pump hydraulic driven by a standard motor, must have at the end of the shaft a sealing system. Yet, 75% of the pumps’ failures are due to mechanical sealing.

A pumping system that does not have a dynamic sealing is thus very attractive for the users of dangerous, toxic, instable, expensive, radioactive… liquids. API 685 covers the minimum requirements for sealless centrifugal pumps for use in petroleum, heavy duty petrochemical, and gas industry services. Petrosadid can supply both magnetic drive and canned motor types with wide range of material.

For more information please contact our
Customer Support Center:
Customer Support Center

Common Services

• Acetic Acid

• Ammonia

• Benzene

• Caustic Soda

• Chlorosulphonic Acid

• Chromic Acid

• Ferric Chloride

• Hydrochloric Acid


• Methyl Ethyl Ketone

• Nitric Acid

• Oleum

• Phosphoric Acid

• Sodium Hypochlorite

• Sulfuric Acid



Petrosadid: Sealless (API 685)

75% of pump breakdowns are caused by mechanical sealing problems.

• Health dangers

• Risk of industrial accidents in case of hazardous fluid leak

• High maintenance costs

• Risk of industrial process disruptions



Petrosadid: Sealless (API 685)


1) Security:

• Totally hermetically sealed assembly (no dynamic seals)

• With double containment in case of stator liner failure

2) Reliability:

• Best MTBF (Mean Time Between Failure) of centrifugal pumps

• Maximal limitation of wearing parts

3) Simplicity:

• Best MTBF (Mean Time Between Failure) of centrifugal pumps

• Easiness of preventive maintenance operation


The Canned Motor Pump is composed of a traditional centrifugal hydraulic, connected to a special motor through a one piece assembly. The stator is canned in the air gap, confining the liquid in the rotor chamber. The pump liquid circulates through the rotor chamber, cooling the motor, and lubricating the slide bearings that support the rotor. The casing of the chamber forms a sealless enclosure that confines the liquid without any dynamic sealing.

Petrosadid: Sealless (API 685)

Moreover, in case of stator liner rupture, the liquid remains confined in the motor’s shielded shell (able to resist to explosions), and thus cannot leak externally. It is what we call the double security or double confinement. This gives the sealless canned motor pumps a decisive advantage against the magnetic drive technology which, in case of air gap hood, presents an immediate external leak.

Finally, the mechanical simplicity of the one piece canned motor pump, gives it many important technical advantages: Mechanical balance, Space benefit, No alignment, Low maintenance requirements, Silent functionning, Operationnal in explosive areas, Easy & effective surveillance, Various possibilities of motor cooling systems …

Petrosadid: Sealless (API 685)


• No mechanical seal = optimal MTBF.

• Low maintenance costs, long running life.

• No expensive and complex lubrication or cooling systems necessary.

• “One-piece” design = gain of space.

• Low sound level.

• Easy to assemble and disassemble.

• No clamping tie-rod (security in case of fire).

• Interchangeability: a given motor can be adapted on any hydraulic.

• Complete Flushing by the flushing hole, without disassembling the pump.

• Hydraulic balancing of the axial thrusts.

• Automatic degassing.

• Stator liner not submitted to the traction efforts created by the pressure or by differential dilatations.

• Intense circulation of the liquid in the motor, allowing an effective cooling.

• Possibility to install on the pump a liquid presence and/or a temperature sensor.

Petrosadid: Sealless (API 685)

How can we help you?

If you have questions, comments or feedback, please feel free to contact us. We are ready to help!