Centrifugal Pump - Unique Venting Arrangement

Looking for automatic venting arrangement to aid running of a centrifugal pump with single partly-open vane impeller:

1. Medium - 90% water 10% sediment (25 years of corroded mild steel / aluminium alloy) SG 1.05 - Viscosity like 'milk' e.g. 3 Centipoise. Contains radioactive products.

2. Prior to starting pump, flood a horizontal suction line from clean water tank as pump must lift medium from storage tank. Anti syphon valve fitted between horizontal and vertical sections.

3. With stationary pump must have automatic venting of casing and displaced air from suction line. ( Operators have no access to pump and cannot use valves with chambers (e.g. kinetic, combined ) or bled block valves.))

4. Vent line returns vapour and small amount of carry over liquor to a catch pot.

5. Option of using fluid sensors to shut valve or de-energise pump should liquor enter catch pot.

6. Running pump can cope with 3% air.

And to where to you wish to vent this pump to?

Atmosphere?

It contains radioactive material. Is this NORM or from another source?

Sounds like a homework assignment coming from an AP

This whole process seems to have too much carryover liquor.

Plumb the pump so that the volute is always flooded.

Or, use an automatic air vent valve.

If fluid is hazardous make sure you have a system to contain the vented fluids.

Using the running pump to flood the stand-by pump is interesting.

With a centrifugal pump will the impeller turn the shaft and affect the electric motor on stand-by pump set?

How was the orifice selected?

These pumps' vent lines are connected to a collection vessel that will hold any liquid carry over. Liquid is returned to the storage tank by operating a remote operated valve fitted to the collection tank. Vapours are exhausted naturally from the collection vessel via a vent U-pipe into the enclosed un-manned compartment surrounding both the storage tank and collection vessel.

A picture might be worth 1000 words.

I am trying to attach an image to support my explanation to your question, but the image is not getting in, not even the emotion icons:(

Can some one help me on this?

try using a "pinch" valve (AKO / Paladon manufacture these) they are pneumatically operated and allow a full bore uninterrupted flow characteristic, on demand or signal they are instant actuation, many types of liner are available, dependant on wetted fluid / metallic conditions.

you can also energise these to normally closed in failsafe mode to suit the control functionality of your system

hope this helps.

Pinch valves work by squeezing a flexible tube closed. That will not work for the OP because his system has an abrasive radioactive fluid. Plastic tubing will not work in that service. Because of the abrasive fluid, he will need materials that can stand up to abrasion as well as the radioactive nature of the fluid.

Something else we need to know: how much air is entrained prior to pump startup? The OP says the pump can stand 3% air (assume he means by volume). We need to know how much air is entrained because if there is too much air at first, a vent valve must be located upstream of the pump inlet. If this is the case, a second valve may be needed to vent the pump casing.

Gentlemen

before we start giving the solutions to this question, my BIG concern is the radioactive bit.

Not a very big word, but has a huge impact on all we do.

Where does this source come from, if vented where will it go, what are the protocols for containment and disposal, does the OP and the operation understand the environmental impact, which country, and finally do they know the type of isotope?

I STRONGLY suggest we stop answering until this VITAL point is covered.

I agree that the radioactivity level / source / radiological protocols need to be verified, it could be LLW, ILW or HLW - I suggest that once this has been confirmed, then further reference is drawn from C4/5 R4/5 containment principles from say NVF/DG001:July 2009, which will cover issues of the 'vented' nature, rather than wetted surfaces from any direct radioactive liquor / particulate solids contact - which I assume (at this point) would be handled by other downstream 'systems' evaporators, scrubbers etc. whereas it appears as if this application is a system venting contam air, this would need to be via HEPA filtration and an assessment of any particulate held within the containment identified & subsequently designed accordingly. This seems to be developing into a far more critical application & should be given the respect of seeking a nuclear containment specialist?

This system is within a self contained unmanned area with no emissions & regulated. Discharges & vented air remains within this area.

Some good ideas given. Much appreciated.

The OP clarified that this venting system is a closed loop, and implied the vented air/fluid mixture was recirculated to a catch tank.

But you make an excellent point....the more I see of this system, the less I like it.

An automatic vent valve may be had for less than £15GBP. Why is CR4 to be bothered with this thread? <sigh>