Sodium Hypochlorite Injection 1

[kauhi]

Does anyone have any suggestions for injecting hypochlorite at a pump station with 112 psi back pressure? We started with LMI chlorine metering pumps, but they constantly need repair and replacement of the pump diaphragm and other pump parts at quite an expense. We then tried a Pulsafeed peristaltic pump that is suppose to be good for 125 psi, but are having a decay in the pump output. Over the last 3 months we have had a steady decline in the pump output even though we have changed the peristaltic hose. Our suction line looks good, no leaks. We are also having back pressure leakage through the peristaltic pump, even though we shouldn't, back into the feed drum. We have gone to liquid hypochlorite because of gas regulations, but have had nothing but trouble and higher maintenance costs. Any suggestions?

 

Kauhi:

You engineer should have cought the fact that you were going to operate at that fringe pressure, it's disapointing to hear he missed it. The pumps you talked about definately won't hold up very well to pressures in your system since non-demand pressures are probably higher than 125 for some period of time. How did your old Cl gas system work? I would assume it was a side stream type system, which is what you are probably going to have to consider for this application.

Good Luck....

 

[Fiscalizador]

The LMI pumps are Diaphragm type pumps. The diaphragm is driven by a solenoid atached to its center. The mechanical stress can become quite high.

For high pressure applications you should consider Hydraulic Diaphragm pumps (DOSAPRO Milton Roy, the owner of LMI, has this kind of products).

These pumps have a piston that pressurizes a hydraulic fluid against the diaphragm. The force is distributed over the full surface, which reduces the maintenance problems. Other advantage is that the hydraulic system avoids problems in case of blockage in the pressure side of the pump.

Note: this pumps are designed to operate in flooded suction.

Hypochlorite is difficult to dosage, due to the degassing. You should include a timed valve in the pressure side that allows to remove the gas (along with some liquid !) back to the dosing tank.

Comments on Bob PE answer: a Chlorine Gas dosing system for 125 PSI is possible. Be aware that you need a special high pressure injector and a booster pump around 200 psi.

 

[rodesign]

Why not dose the NaOCl on the suction side of the booster pumps, and avoid this high pressure issue?

ProMinent makes pumps that are driven by electric motors rather than trying to use solenoid drives. Several of these pumps are capable of this operating pressure.

 

[MechanicalJoint]

ditto on the ProMinent pumps....

 

Hello Kauhi!!

That feed should really not be a problem. Try Watson Marlow peristaltic pumps.

http://www.watson-marlow.com/watson-marlow/

Make sure you get the high pressure head for the pump and the high pressure tubing. These pumps are rated up to 230 psi as far as I know.

We feed hypochlorite into a pressurized line, the pump speed is controlled by SCADA through the 4-20 mV output. Very nice setup, just change the tubing on a regular basis.

I don't sell these pumps, but I would not buy anything else for this application.

JJ

 

[Patnaik]

Hi

Can someone suggest a suitable material for Na-hypochlorite soultion. The dosing tank level switch float(Titanium) is attached with SS316 wires. The 316SS wire gets corroded and breaks. Any suggestions please--I think SS316 is not the suitable material for this service.

 

[quark]

Patnaik!

Use rod supports (or tube) for float for hypochlorite level switch. This is widely in use. Or a costlier option is ultrasonic level controller.

 

[Chris73]

patnaik,
of course does 316 SS not resist highly oxidizing media. If SS I would specify SS out of ferritic stainless steel series 29-4 SS. Even 26-1 or 26-1S might last for a while as well.

 

[anylev]

could someone suggest a suitable plastic material for tieing on the switch? But don't even think "cable-ties" - some have a little stainless clip blade inside that will rot like buggery!

With apologies for using the word "cable-ties" twice in one day.

anylev

 

[assco]

Use a hydraulically actuated diaphram pump, Milton Roy, Brann & Lubbe etc... A peristaltic pump will be a maintenance headache. There is no degassing valve required, however you must have a positve suction head. Raise your feed tank on a platform, slope your suction line downward to a standpipe then slope your suction pipe up to the pump. the slope of the suction line will remove all gas on the suction side and your done. You will find this arrangement will be trouble free for years. I know I've installed several.

 

[hace]

What flex hose might be used to connect a sodium hypochlorite feed tank to a metering pump? I have looked at "chlorine feed" flex hoses, but they seem to have monel threaded ends which would not be suitable for a 12.5% liquid feed. So I am thinking of using Kynar barb fittings, but would like suggestions on the actual hose material(s). Pressure requirement is less than 25 psi, and feed rates are low (0.5 to 1 gph), and a 0.25" to 0.5" ID hose would be ideal.

Thanks,
HACE

 

[ch81pc]

Is the dosing lance that you use changed regularly? I operate a plant that used to show a tailing off in dosage rate as you describe. Hypochlorite will react with any hardness in your water and begin to build up scale. We currently change our lances on a weekly basis and this has helped to reduce our maintenance and down time. Hope this helps.

Paul

 

[glennpan]

A couple of suggestions here:

First for the person asking about what type of floats to use. PVDF should work fine. Definitely go with plastic materials for this application.

As far as the pumps go, I would definitely agree to get away from the solenoid driven pumps at that pressure. I do like the peristaltic pumps, but I prefer not to use them over 60 PSI. Either a motorized mechanical pump (as a Prominent) or even better a hydraulically metering pump (like an Alldos) is a good selection.

What is the flow rate that you are trying to dose?

 

[guvs]

Would recommend the solenoid driven pumps with the self de-gassing hads fromm ProMinent (see

http://www.prominent.co.uk)