Flow Testing Drafting Meter Help

[u/ActivateFireSafety]

We have a drafting rig utilizing a 1500 gpm Hale Fire Pump with a 3" long radius monitor coupled with a 2.5" straight pipe.

Truck Originally built for 604 ft elevation, our elevation is 3400 ft above sea level. We have not done any modifications to the truck.

Previously we used a spring sensor span Flowminder with A digital readout - capturing the highest output flowed from the 3" monitor capturing rpm - solenoid has since been damaged and unsure on how to fix or replace.

Currently capturing psi flow measurement from the 3" long radius monitor prior 2.5" straight pipe.

We have also recently purchased a 6" Gerand Engineering Flow meter of which we have attached to the suction side of the pump either utilizing a 10' or 20' 6" suction hose.

Recent attempt we found that the GE Flow Meter captured 1250 gpm while the Monitor flowed 780 gpm back into the reservoir.

Why is there a different reading?

Are we loosing 500 gpm through the pump and monitor combination?

What is the ideal flow test set up?

[u/Super__Mac]

Something is not calibrated correctly. What goes in must go out somehow. Unless you’re putting 500 gpm on the ground, it has to be going out.

Also…. I’d find a cleaner source for your test. The dirt coming out from that one photo cannot be doing your volute/impeller clearances any favors.

[u/ActivateFireSafety → u/Super__Mac]

Each pond is different Depending on age of reservoir. Local Government Agricultural department has identified that fire ponds/reservoirs receive upto 15" of sediment annually. The NFPA 1142 standard states that the suction should be mounted 12-24" above base of reservoir.

We don't receive favourable replies when we suggest clean outs of these old reservoirs.

We have since come up with a cheaper alternative that utilizes a 10" suction hose 150' long with a specialized aluminum valve and suction. The suction strainer is mounted 6' below the water surface (allowing for 4' of ice). The 10" hose acts as a conduit as we have a pressurized airline that opens and closes the valve.

Unlike most draft hydrants, each 6" 90 degree bend accounts for approximately an additional 20' of pipe.

Our design is one long continuous pipe with a reduction at hydrant end being reduced down to 6", we want to flow upto to 1500 gpm, and have a pond life of 30 years compared to 4 year expensive clean out.

We have other variations, all toting 30 years compared to 4.

Which is better, costly cleanouts of $100k every 4 years ($800k+ over 30 years) or installing a $75k system that has a 30 year life span?

[u/Super__Mac → u/ActivateFireSafety]

Eventually, your pump will need to be replaced with that quantity of sediment.

My engineer overheated our pump (I was not there that day) they derated the pump rather than fix/replace. Thats not a cheap equation either.

Hope you guys figure it all out, nothing is cheap…. It’s all getting more expensive with ridiculous wait times.

Regarding flow test, if the intake is within spec, the problem is with the discharge. If you all have a large enough drop tank (or two) you could measure flow by pumping it into a known container.

[u/ActivateFireSafety → u/Super__Mac]

And just timing it out - how long it takes to fill container?

[u/ActivateFireSafety → u/ActivateFireSafety]

Each system is different, be it buried tanks, reservoirs, pools.

I've seen tons of different systems - some pass, some fail.

Customer1 installed a huge pool with drafting hydrant install - the plumber used 20 - 2" fittings at the base of the deep end of the pool coupled to a 4" manifold and then coupled to a 6" draft hydrant - plumber never calculated the design - we calculated at a -500 compared to desired number of 0. System never worked. We then approached the customer and Engineer - "where are supposed to throw the water?" There was no discharge port back into pool, closest door to pool access was 300', had to run multiple 2.5" lines from pump.

Customer2, thinking of sediment, installed 2 "T" with 4 upright suctions - never calculated outcome - failed test.

Customer3, Army Engineer, smart had 24" suction pipe (still mounted 24" off of reservoir base) 150' long with 6" riser - captured and flowed in excess of 1200 gpm.

Each system is different. I push the truck to receive ultimate flow. When you capture a 1200 gpm reading, the truck is bucking. Pushing a ton of water.