Diaphragm Pump & Centrifugal Pump in Series

[ekschwab]

We are designing a system that uses an air operated double diaphragm pump for pumping wastewater through some filters and a demineralizer. The problem is the diaphragm pump does not have enough output pressure to pump all the way through the demineralizer at the required flow. (The plant air supply pressure will limit this pump’s output.)

We are thinking of using a centrifugal pump to boost the pressure. It would be located downstream of the filters but before demineralizer. Are there any concerns with operating a centrifugal pump in seried with a diaphragm pump? Could the pulsations from the diaphragm pump cause a problem on the centrifugal pump)? We can add a pulsation dampener if needed.

Use of the diaphragm pump is a given and cannot be changed. Any comments would be appreciated.

 

[Montemayor]

ekschwab:

You haven't stated the order you propose to put the equipment in. I have to presume you are going to install the centrifugal pump upstream of the diaphragm pump (also assuming the diaphragm pump is a positive displacement pump). In other words, the centrifugal would feed (or boost) the positive displacement diaphragm pump. This should work OK, as long as you match up with the centrifugal pump's max. TDH and the diaphragm pump's max. inlet allowable pressuren as well as the flow capacity of both pumps.

You don't want to boost (or feed) a centrifugal pump with a positive displacement device. That's not a logical way to hook both up since one of them has a limited head and the other doesn't - at least not under nominal process conditions. That's why there should be no problem with pulsations from the diaphragm pump causing a problem on the centrifugal pump and no pulsation dampener is needed.

 

[ekschwab]

Thanks Montemayer. I should have made it clearer. The order as currently designed (but not built) is:

waste tank --> diaphragm pump --> filters --> demin

We want to put the centrifugal pump between the filters and demins.

 

[Ashereng]

Another solution to a dampener, in case it isn't sufficient, is to use an intermediate tank.

The diaphram pump sends it through the filters to an intermediate tank. The centrifugal sucks from the tank and sends it to the demin.

In our gathering systems, the LACTs usually use PD pumps to send it to the main gather lines. The booster station on the main gathering lines use centrifugal. And we have tankage.

 

[ekschwab]

Thanks Ashereng. I like the tank idea and have suggested it to the system engineer.

 

[Ashereng]

You're welcome.