Skip to main content

Dear Vibration people

Am facing an issue with four of our fire pumps driven by engine with rectangle gearbox and 10-12 meters length suction column from the sea. All the four pumps having this oscillating problem and due to this the top side flanges getting damaged and the pump is hitting the walls of drum also the cathodic protection anodes at the bottom. Bump test conducted but couldn't find anything.



Please suggest me to reduce the oscillation and if you have faced any problems before like this please share

Video attached

Attachments

Videos (1)
VID-20210518-WA0004
Tags: Suction, Offshore, oscillating, column

Replies sorted oldest to newest

Sharath,

The suction lift you are trying to do is not fundamentally possible?

Theoretically, all centrifugal pumps can lift water not more than 10.33 m at sea level. If the liquid is below the pump datum, the vertical distance between the pump impeller and the surface of the liquid on the suction side of the pump is referred to as the suction lift.Apr 13, 2017

Are these newly installed? Are there more than 4 fire pumps? Do the each have their own suction pipe? What is the altitude of the pumps from sea level?

Possible solution

https://hydra-tech.com/overcoming-high-suction-lifts/

Dave

RM

Hey Dave thanks for your reply and ur time on this.

The sea level is approximately 15 to 17 mts from the right-angle gearbox and the pump is submerged in water ~5mts. And all the pumps are placed on different platforms with different suctions and we also have 2 jockey pumps with same height and length but there is no any oscillation in column as fire pumps. All the pumps are installed recently may be 20 months.

Suction lift and discharge pressure are getting as required but the only issue is with oscillation

RM

Sharath,

Not sure of your pumping drive or piping configuration, IF this is a self priming application, then read on. You state pump is submerged 5 meters under the water? What is design point, pressure/flow rates, pump manufacturer, model number etc

You do not address the fact that the suction lift for the pumps is not possible? 15 to 17 meters is 49 feet, ALL CENTRIFUGAL PUMPS follow the same laws of physics, the maximum amount of suction lift at sea level is 10.33 meters at sea level, unless other means have been provided to address the high suction lift.

This video talks of vortexing in suction pipe, this too is a real world problem, no matter how far submerged the suction pipe

https://www.youtube.com/watch?v=ltWFzjRNBaE

Is the suction line or discharge line air bound? Anywhere there is an upside "U" creates a potential air bubble, centrifugal pumps do not pump/move air, during commissioning if not all the air was removed from piping this too could create issues. Basically the highest point in the discharge piping system needs an air release valve

IF there is vortexing, I would assume the pressure/flow would oscillate with the noise you are hearing? Can you post a video of what you are seeing/hearing?

Dave

RM

Add Reply

×
×
×
×
Link copied to your clipboard.
×