Hot Recycled Oil Pumping

[Mendit]

We have a High Pressure Barrel pump (7 stages) It is used to pump waste oil at Recycled oil plant. Before the oil enters the pump it is preheated to approx 650 C. This is causing coking problems and very rapid wear of the pump. All case, and impeller wear rings, center bushing and throat bushings are Coated with Tungsten Carbide, to resist wear. Pump only lasts about 5 months. Coked product jams the inlet of the 1st stage impeller. Suggestions please to either extend pump life or modify the process ?

 

[BrianatLiquiflo]

Need more details...

What flow rate and size of pump?

What are the inlet conditions? Low NPSHA could cause solids to flash out of solution in the eye of the first impeller.

The duty cycle is key - This fluid needs to be flushed prior to any shut down. I suspect that this is not done and the pump is started cold. This will cause excessive wear and tear as the viscosity of the cold oil would be orders of magnitude higher than the 650deg C working temperature.

Is the pump heat jacketed? It should be.

Brian Atherton at LiquifloInc.com

 

[TD2K]

At 650C, I'm not surprised the oil is coking and breaking down, why this high of a temperature before you try to pump it?

 

[RotaryG]

650 C? 650 F?

Regards,

Guru

 

[Mendit]

Sorry guys,
Oil temp is 650F as guru questioned, more details pump is 7 stages 3600 rpm inlet pressure is 125psi discharge is 550psi. Operation is continuous 24 hrs / day 168hrs /wk.
Pump is insulated but not heat jacketed. The pump is never started cold, product is preheated before any start up. I will have flow rates later. Mendit

 

[RotaryG]

Since, insulation cannot remelt the solidfied stuff you are pumping, can you heat trace the existing pumps - steam or electricity? Next batch of pumps when you buy, ask for full jacket.

Also ensure that with the new pumps full dia impellers are used. This apparently maximises particles are pumped out of the casing rather than some getting settled in the casing.

Wear rings should be flushed with clean oil. You may get other suggestions from our friends on this forum once you come back with more information.




Regards,

Guru

 

[Mendit]

Flow rate for pump is 167GPM, should the need be to shut down, the pumped cleaned oil is recycled back in to the pump. But the product is always heated before start up.
Along with the pump problems, the mechanical seals also have limited life (6 months at best)

 

[25362]

Modify the process. Pass the cold oil thru coarse filters (2 in parallel) with 3 mm holes in baskets before dewatering, heating and pumping. Please comment.

 

[RotaryG]

Do u have bellow type seals or spring type?

Regards,

Guru

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