Process Water Filtration

[Jaydubblazer]

I am at a newer facility and we get our process water directly from the river. Over the last two years we have had several failures due to what I describe as wear in our process water system, i.e. progressive cavity pumps, check valves, centrifugal rotors, and other equipment. We had a analysis done in the past on a separate issue and it was found that there is a large amount of diatomaceous earth.
First question can river water have enough suspended solids that it can severely score a 316 SS progressive cavity rotor. Secondly, how do I go about spec'ing out a proper filtration system to ensure that the equipment will last an appropriate amount of time. We use at max 400 gpm and this water does go through cooling and heating loops.

 

[bimr]

Diatomaceous earth is sometimes used as a filter medium. Diatomaceous earth is a mineral that is mined from deposits, but is not something that is normally present in river water.

River water treatment typically consists of a clarifer followed by multimedia filtration. That treatment will produce a zero solids water.

 

[stanier]

Mono pumps make a ceramic coated rotor that is used for seage applications. The key is running the PC pump at < 300 rpm. There are many PC pump suppiers who sell you a cheap small higher speed pump for a low price. then they make a killing on the spares.

Wear is proportional to velocity to the power 2.5 to 4.5. thus the lower the rotor velocity the less the wear.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[Jaydubblazer]

It is a chrome plate stainless steel rotor by seepex. The company didn't go cheap on the pump. It is a simular pump pump that other plants use when pulling river/bay water for the process. It does run between 200-300 rpm and the pressures are in the 60-70 psi range. We are having this issue on other pieces of equipment. We have lost two gear pumps(granted they were the best choice of pump for the applications), several butterfly valves and other misc equipment due to the water eroding metals.

 

[micalbrch]

Stanier is right with his advice but a ceramic rotor is very expensive. 316SS isn't a very hard material (even when coated) and in combination with a rubber stator it wears out when fine, abrasive particles are present. My advise is a diaphragm or a peristaltic pump. Depending upon flow and pressure it is not more expensive than a progressive cavity pump and if correctly sized it will last much, much longer. A gear pump is a rotating positive displacement pump, too. For this medium a rotating pump should not be first choice.

 

[SNORGY]

Jaydubblazer:

I always thought that a progreeive cavity pump would generally not be recommended for relatively non-lubricious fluids - such as river water. I might be wrong, since the technology may have advanced since 10-15 years ago.

If you wanted to keep a PC pump, maybe I'd try a hardened rotor and viton stator and see how that goes for a while.

Regards,

SNORGY.

 

[bimr]

Most raw water supply applications use centrifugal pumps. Progressive cavity type pumps are normally used for waste solids pumping.

Are you sure that it is diatomaceous earth and not just river sand?

You asked about water treatment. River water treatment typically consists of a clarifer followed by multimedia filtration. That treatment will produce a zero solids water.

 

[Jaydubblazer]

Changing all of the equipment really isn't feasible. A couple of you mentioned getting a clarifier and multimedia filtration, do you know of a good company that I can contact to determine what equipment may be needed to purify the water?

 

[quark]

I saw couple of references which consider suspended silica in surface water as diatomaceous earth. I didn't have any experience with suspended silica in water eroding flow components as we treat it by clarification and filtration as suggested by Bimr.

We do have applications where product is being filtered in module filters using diatomaceous silica (slippage is very minimal). All the components are of SS316L, still found scoring of vessel impellers over a period of time.

What level of suspended silica we are talking about here?

 

[bimr]

Siemens is one of the major players in water treatment:

http://www.water.siemens.com/en/industries/Pages/default.aspx

 

[stanier]

The rotor is ceraamic coated and is not that much more costly than a 316ss rotor.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[JavaMoose]

Try giving Harmsco a call. I've dealt with them for a 200gpm filtering application very similar to yours, though it was sea-water, they were very helpful and have a great product. They can even do a fully skidded system, if need be. Worst case, it will give you an idea of what size/type of system and the costs associated with it.

Link:

http://www.harmsco.com/

 

[Pumpsonly]

First question can river water have enough suspended solids that it can severely score a 316 SS progressive cavity rotor

.

This question can only answer by your self. You should take a sample and analyse it.

Secondly, how do I go about spec'ing out a proper filtration system to ensure that the equipment will last an appropriate amount of time. We use at max 400 gpm and this water does go through cooling and heating loops

.

You did not give a schematic of your existing system. Is the PC pump drawing water direct from the river and pumps through the cooling and heating loop and dump back to the river?
If you want to protect your process equipment,the basic arrangement would be using a low RPM centrifugal pump to draw the river water, filter it and use another pump to pump the clean water to the process. You will need a storage tank in between.

 

[bimr]

With all due respect, the problem seems to be that the original poster has been attempting to resolve issues with inadequate facilities supplied by firms that are not familiar with pumping and treatment of river water. River water treatment is accomplished with clarification and filtrations processes and harmsco does not make this type of equipment. They make cartridge filters that are used for polishing of water downstream of the river water treatment.

 

[AtlasPumps]

A Progressive Pump would be much better to use than a Diaphragm Pump. At 400 GPM, most processing facilities recognize that a Trash Pump would be the better fit for the application. I'm talking about a Hydromatic brand pump. If you want "ideal" configuration, a Hydromatic at the River inlet sending flow to a PC pump, that's what I would go with.

Here's a thought: Go to your local golf course......one of the nice courses. Most of the time they're getting irrigation water from a river, stream, or lake. Most of the time, they're using a trash pump to break up debris like sand, dirt, sticks, diapers, cans, etc.....before this fluid gets in the system. Then they'll send it to vertical turbines to increase pressure.

 

[Jaydubblazer]

OK guys, I have found three different manufactures of dual media filters that will handle the 400 gpm. We are now in the process of developing a capital authority for the equipment and going through the necessary permitting to allow for the backwashing of the material. I appreciate all of the responses.