We considered several factors, how could we lift the pump more easily than I had with a friend last year, and how we could monitor levels, as it is extremely hard to measure the amount of fluid going into the system obviously.
While I looked thoroughly at the electrical installation - Andy and Puck scrutinised the pumping.
I started out by first measured the average current to three phase pump, approx 1.8 Amps on a single phase, I also tested the pump under startup load, no problems either so the pump looks like it is electrically sound.
What was surprising was that after 8 years of maintenance, and pump specialists looking at the pump, nobody had realised that the pump itself had not been earthed, and the armoured cable to the control box had been linked to the contactor with a piece of 3 core mains flex! Whilst this would be ok in some situations, if the pump is double insulated and IP rated for immersion, the pump is actually suspended on a steel chain connected to the body of the steel pump outer casing. This means that should a fault develop inside the pump electrically, anyone touching the chains would most likely be electrocuted or at least get a very nasty 415 Volt shock - and with an open manhole that is 5 metres deep - thats a very dangerous situation!
I also discovered that there was a fault with the earth spike for the building, as when I put in a temporary earth, the motor tripped out, which made me realise someone had previously made a decision to not attach an earth to the pump rather than spending 5 pounds on an earth spike and making off the armoured cable sheath properly (which is an earth!)
Andy started to fit a ratchet chain block kindly supplied by Puck and tackle and a frame to support it, to enable us to raise and examine the pump more easily while I started to investigate the best way of fitting a time-switch onto the system.
I switched the pump on at 1.30am and it was switched off in the morning at 7.30am - At 10:30am on Sunday further investigation was made (removal of the outlet hose outside the building) proved that the pump was doing very little, with black sludge coming up - a trickle, rather than gushing out of the 2 inch pipe. This explained why the level in the sewer wasn't moving. Andy calculated 2 cubic metres had been shifted overnight. It was quite clear that the pump isn't doing its job, as a 2kw pump should shift that sort of quantity in an hour - even a pond fountain 400Watt pump would do better than that!
We lifted the pump, which of course with the right kit is now pretty easy thanks to our collective expertise and equipment - we discovered that the position of pump vertically is crucial to flow, if the pump is positioned too low, then it can't cope with the "black sludge" - and does very little. As soon as the pump was raised a few inches, and started again, we had a full flow outside.
I replaced the old timeswitch, which I had fitted yesterday - which didn't seem to advance, over to a low-cost plug in version, which will be more easy to replace in the event of a fault, and re-wired the previous control box so that the emergency stop button would function again.
The timeswitch has now been set to run from 1.30am to 5.30am in the morning, so we can take advantage of night electicity rates (economy 7). As the pit was still quite high, we decided to override the timeswitch from 2pm onwards to reduce the pit's fluid levels and get the manholes down the road back to a sensible low level.
Andy will look at the old pump unit and attempt to refurbish it, and my next job next weekend will be to fit a proper earth spike and run an earth cable to the pump connection in the control box to make it completely safe.
We also discussed investigating the flow rate at the end of the pipe at the sewage works, so we will investigate that in due course.
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