Force Main Comminutor Application

[bbonner]

Does anyone know of an application with respect to a comminutor inline AFTER a submersible pump station?

I am currently involved with a small WWTP project (already designed) that includes a comminutor in a valve vault, after a submersible pump. After talking to the sales rep, he tells me he has never seen (nor have I) a comminutor placed after a pump in a presssure situation, as the comminutor will typically work only with gravity. My thinking is that is was originally desinged to run only when the pump was pumping, and not continuously.

Just curious is anyone knows if this will work.

Brian

 

[jgailla]

This doesn't make sense. The purpose of a comminutor is to protect the pump. If it is downstream, the pump will clog and seize up.
Of course, there may be unusual design contraints that would require this, but I can't think of anything off the top of my head.
Also, the comminutor would be used for gravity flow, so if you put it downstream of a pump, the force main would go to gravity flow at the comminutor and the pump would have no effect on the downstream force main.
I suppose you could design a comminutor that could be sealed and used in pressure flow, but I don't know why this would be useful in a typical sanitary lift station and force main system.

 

[bbonner]

Thanks for the reply- I think we will be looking at moving the comminutor to the gravity portion of the line. The previous engineer (the third person to touch this project) never picked up on it. There was supposedly a decision made based upon a grinder pump not being able to handle to small flow situation, so they went with a solids handling pump instead. Why, I don;t kow -a s the notes on the project are pretty sketchy, at best.

Brian

 

[sjohns4]

I've seen in-line grinders for full pipe flows like you're describing, but under normal circumstances I dont know why you'd use one?

That is some odd logic...usually grinder pumps are best at low flow situations. I'd definately be sanity checking that whole setup.

 

[SteveWag]

Actually, despite my dislike for comminuting, I have placed 10 or 12 of these in force mains or equipment supply piping. A very common use is in supply piping to a belt filter press or vacuum filter. (Wow, I guess that dates me!) If a recessed impeller or screw impeller style pump is used, the pump will pass rags and stingy material (and live fish). Putting the grinder after the pump oftentimes results in a more easily maintained grinder, and may remove it from a classified area. As deeper submersible pump stations become popular, I have been placing the Headworks, screening and grit removal, after the main pumps feeding a treatment plant. By using Wemco Hydrostal pumps with hardened impellers, I can place the Headworks at grade.
Steve

 

[bimr]

I stay away from comminutors as well. If you have to remove the materials anyway, what value is it to grind the materials up before you remove the materials.

If the comminutor has been in this application for some time without maintenance, the comminutor may not be working anyway.