There usually are upstream causal factors or circumstances that contribute to most failures. In the science of failure analysis, they are known as failure modes. Many failure mode contributions are associated with detectable forewarnings. Many others are not. Warning examples: A blinking warning light, a threatening alarm, reviewing a panel of pilot lights and spying a blank pilot light that should be shining brightly, opening a hatch and finding water in a bilge, hearing a motor that is presenting with an unusual hum, vibration or sound… All of these and many others can signal a perceptive boater that the breakdown of a system is close at hand. Of course… there are many times when no overt signaling occurs…
While we are out cruising, and in particular, during a passage, we perform serial engine room checks every hour. Most equipment throughout the boat is in use to some extent so we usually discover when something is amiss and can take steps to remediate the issue and arrest the downward spiraling cascade that may have led to a failure.
In contrast to our overtly active cruising surveillance practices, while anchored for long periods of time, and when we are in port wintering in place for months at a time, we perform monthly inspections and testing to make sure all is well. Being diligent boaters, we have a long list of contraptions to monitor. I was following our list. All was well. In SECTION 5, ELECTRONICS, there is the following: (oh yes, there are many sections on the list)
10. Press the display button on each “Water Witch Bilge Counter”. The display should read “000”.
11. Go to each bilge pump area” “FWD”, “MID”, “AFT” and lift the float switch to determine if the bilge pump is working appropriately.
12. Lift the high water float switch to determine if the switch will generate an alarm.
When I lifted the float switch in the engine room bilge sump, the pump failed to engage. Malas hierbos!!! Les and I put on our headsets. She positioned herself in the pilothouse and I went back to the engine room. While I had my head close to the pump she set the pump switch to “MAN” (manual). The pump emitted a loud buzzing noise. “Turn it off! Turn it off!” I serenely and tranquilly declared into my headset microphone and into her appreciative ears. That is my story version, and I am the one writing the account of my articulations. I have been informed that her recollection of that moment significantly varies from mine. Be that as it may… that unruly hum signaled an induction into the kingdom of Woe”.
It sounded like the pump was locked up. That is a very bad thing. If the armature in a pump stops moving, the windings in the pump heat up very quickly. That can result in a pump meltdown. The worst case scenario is an electrical fire in the bilge. Other things can happen depending on the cascade of ongoing events. I noted that there was no fuse on the hot lead going to the pump. Interesting. I had not perceived that before. Nor had the three marine surveyors that have spent time on Great Northern looking for things that go bump in the night. Hmmm…
I removed the pump. While removing the pump the hose that leads from the outlet of the pump to the overboard stopcock… cracked, split, and broke off. Turns out It was quite brittle. Good to know. I tested the pump on my Victron power supply. It tested fine. That’s nice because a new one is quite expensive. I replaced the overboard hose, reinstalled the pump, replaced the pilothouse control switch, the float switch and updated all the wiring. Upon attachment of the new negative lead wire, I noticed a slight hum. The pump worked just fine. But… it had a slight hum at rest. That is one of those failure mode contributions, a detectable forewarning I was alluding to above. A resting pump should not present with an unusual hum. I removed the negative wire from the pump to inactivate the circuit.
I broke out my voltmeter and placed the electrodes between the negative lead and the pump. I noted a 2.04 Volt current load. It should have been zero or close to it. I traced the negative wire back to its source in the electrical panel and replaced it. The source seemed fine. But I noted… that a few of the negative wiring posts were carrying a positive current: 2.04 volts. Well… it could be the pump. It could be the switch. It could be something in the panel. It could be something buried deep within a wiring harness. One of many harnesses. It could be cosmic rays.
There is another detectable forewarning. When we place the switch activating that pump on Auto… the LED light that indicates that the pump is pumping… wass glowing. It was a slight glow, but it shouldn’t glow unless the pump motor was running. The light signals that current is flowing through the switch. It shouldn’t do that unless the float switch is lifted by the ingress of water in the bilge or an enquiring finger lifts it up to actuate the switch.
I spent the next day inspecting the other two bilge pumps and ended up replacing their float switches and adding appropriate fusing. I reattached the negative wire to the engine room bilge pump. No hum detected. The float switch activated the pump when lifted. The bottom LED light on the switch was still glowing. That might signify that there is not enough current flowing to make the pump hum, but enough current to dimly light the LED. I will spend more time with my voltmeter coaxing it to unearth the issue. And… I contacted an electrically savvy expert to geek out the causal factors. Good thing I happen to know several of them. I sense a failure mode effects analysis is in order.
Just another day in spent working on a boat in an exotic location…
Salish Sea Cruising With Blair, Les, Leo, and Bliss 