Radon Hut Mini Status Report, Nov. 8, 1999

HGB, Mozumi/Japan, updated 11/9/99.

Water pump at tunnel ditch replaced with spare

The sump pump that was installed in spring last year had an electrical short when I arrived at SuperK approx. two weeks ago. Therefore the cooling water flow turned out to be pretty weak, since the water pump in the radon hut had to suck the stream water all the way over the 100-meter pipe from the ditch to the hut. From shift reports earlier in the summer I believe that the stream was probably dry or at very low level at a couple of days in the summer. I guess that the sump pump was therefore no longer cooled by the stream and it's motor must have overheated and melted the insulations of its AC wiring. The outlet fuse in the radon hut, where the pump's power was connected, was in off position, but no further instrument was affected by the fuse.

As reported in May, the new pump that Roy sent to SuperK failed my short test runs. It's not operational anymore. Secondly, to my judgement it's not suited for operation in the tunnel environment anyway due to a) it's open design of the motor case and drive shaft (not dirtproof!) and b) it's voltage/current requirements (e.g. it's specified for 50 Hz, but AC at Mozumi area is 60 Hz. and it requires more than 10 Amp current - too high for a 100-meter power cable).

I remembered a spare water pump that Peter left in the spare parts container on the big Atotsu parking lot. I tested it and found it almost perfectly suited for the tunnel ditch. The piping re-arrangement at the ditch was relatively simple since we had all parts on hand as spares.
My only concern was its high voltage requirement of either 460V AC 3-phase or 208V AC 3-phase. On the other hand at 460V it requires less than 1.5 Amps per conductor, which is easy on a 100-meter cable. Secondly, 460V doesn't need to be down-transformed in the radon hut like we need to do for getting 208V or 120V; it's directly available from the incoming power line. So, all I needed to do was to order a suitable 100-meter spool of 4-conducter power cord. Here's how the final installation of the pump looks like now:

Inside the radon hut, I hooked up the pump's power cable to the 460 V control relay at PLC relay channel 2 (click on picture at right for more detail). This channel was reserved for the regeneration blower, which also ran on 460V AC 3-phase. But since the regeneration mode is no longer needed, I decided the relay channel would be perfectly suited for the ditch pump.

Now the water outlet (picture at left) at the rear of the radon hut shows nice and strong water flow again.

Last-not-least: Currently, the pump is mounted at the ditch in an open tunnel environment. It's a rugged design (explosion-proof, humidity-proof, etc.) and the only open section (where the cooling fan sucks air) is facing to the tunnel wall, away from the road side. But nevertheless, some sort of protection cover should be added sooner or later to prevent dust and dirt from getting to the motor mechanics. E.g. a little wooden shag maybe? Suggestions?

Spare pump order recommended, soon...

The two water pumps of the radon system are almost identical. The original pump on the floor inside the radon hut is a 1.5 hp model, whereas the newly installed pump at the tunnel stream is slightly shorter and a 1 hp model. Otherwise they're fully exchangeable. So, a 1 hp pump as spare would be good enough for either of the two positions.
Both models consist of two joined parts made by different vendors, an electrical motor and a mechanical water pump driven by the motor. Here are their technical data:

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