Ejector for pump out water 5

[vedranpetro]

Hi!

I have ethylene pumps installed under ground level in a pit because of NPSH . The pit dimensions are 6x4m and the pit is 4m deep.There is no drainage so all rain finishes on the bottom of it, and you can't walk in a 20cm deep water

The problem is :because of explosion zone i can't install any electric pump to pump out the water,so my idea is to install some ejector(i have 5 bar compressed air available to use). Is it possible to pump out water with ejector(5 bar air) from 4m deep pit and if not what would be best solution?
tnx in advance

 

[DLite30]

How about an air-operated diaphram pump? Say from Wilden...

http://www.wildenpump.com/

 

[zdas04]

It is possible to use an ejector (i.e., a thermocompressor with a compressible power fluid) and air, not terribly efficient, but possible. Problem is that ejectors and eductors (i.e., a thermocompressor with an incompressible power fluid) are mass-tansfer devices and it takes something like twice as much motive mass as you are trying to pump. Compressed air is a couple of orders of magnitude less dense than water so you have to run a bunch of air through it.

For pumping out water I'd use an eductor with water as the power fluid. It sounds like you could do this one with a garden hose and a plastic water-bed pump. Total cost around $30 (call it 20 Euro's) if you have to buy new hoses. Since it is inside a plant, you'll have to add a bit to comply with safety standards and regulations, your new cost should be under $30,0000 (call it 20k Euro's). The hose and blue plastic water bed pump would actually be safer, but that is not one you are going to be able to sell to the Nanny Society.

David

 

[vedranpetro]

DliteE30
yes ,i also thaught about this since we already have wilden pumps on plant,but for this purpose it would be not the best option because it also has moving parts and you need that to be certified for zone ,expensive,complicated,i need simpler solution

zdas04
i didn't understand completely, why waterbed pump if i take eductor? Of other medium available for ejector/eductor power fluid on plant i have 3bar steam,air already mentioned,and water,why i need waterbed pump if i install eductor with water from piping as a power fluid?i want to avoid any electric motors or pumps if it is possible
yes solution with waterbed pump is simple but regulations made it different

tnx for your answers

 

[zdas04]

If you have a water source with adequate pressure and flow rate (neither have to be terribly high), then a simple eductor (I'd set it physically in the tank to avoid having to change height very much on the suction) would probably be the best and least expensive option (and it won't have any particular explosion issues. At the end of the day, this is basically a water pump and a hose, built to plant specs.

David

 

[micalbrch]

I know that some airports in Spain (Barajas/Madrid and Valladolid definitely) use electrically driven diaphragm pumps with submersible motors and in full compliance with explosion proof standard (ATEX) for exactly the same application. I'm sure it is not a cheap piece of equipment but an alternative in case David's advise is not practicable.

 

[tr1ntx]

If you don't need to get all of the water, but can tolerate 1 to 1.5cm, you can just use a pipe loop with a free-floating check valve in the bottom run.

Using 1.5cm pipe or smaller plastic tubing, route it down one pit wall, across the floor, and then up the other side and to a drain. In the section of pipe running along the floor, have a "T" fitting with a short stub of pipe. Put a free-floating check valve on it, oriented so that it allows flow into the pipe. Connect your compressed air to the end of the piping with a valve.

With the air valve closed, water will flow into the pipe along the floor. When you open the air valve, the initial flow out will push the check valve closed, then the water will be forced up and out to the drain. Keep cycling until the water level is all the way down. This won't get all the water though. You could even use a float switch and automate the valve.

If you would like, you can use very small tubing and run it back-and-forth across the pit floor several times in order to capture as much water as possible each cycle. I don't know how small of a floating bean check valve you can get, but 6mm thin-wall plastic tubing would only leave 2mm or so water in the bottom. If you use small tubing, use several check valves to get a higher inflow rate.

In my sketch, I was thinking of a swing check valve, but you probably can't get them is small enough sizes so that they allow in the most water and leave the least depth. The drain must be open to the atmosphere, or you will need a standpipe type vent so that the water can flow into the pipe. If you use a pneumatic valve on the air-control, you can use a 2-way and let that be your vent.

 

[dcasto]

so, what do your existing ethylene pumps run on, gas engines? Come on, why can't you use an explosion proof sump pump.

 

[kacarrol]

I used diaphragm air pumps to empty oil barrels in a gas turbine engine testing facility. I'm pretty sure you can get them explosion proof without a problem.

 

[vedranpetro]

fistly tnx everyone on answers

micalbrch,dcasto,kacarrol

it' s not a question ,all those pumps exist in explosion proof version but it's much more expensive solution than some eductor. And that's what i want :cheap but good enough solution .

tr1ntx
interesting idea,tnx for drawing

Finally i see two solutions :
-eductor with water
and second one which is most interesting and simplest solution

-"mamooth pump principle" -you have only two pipes ,one with compressed air and other one for pumping out water out

if anyone has any experience with these pumps, or know where you could find instructions for sizing that system? it would be very helpful to me
i mean how to determine size of pipe for water ,height of tie in of air piping?
my conditions are 3.5 m height of sump and water level in it is max. about 0,5m,air pressure 5 bar