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irrigation implement
Looks like an OK product. There may be some things to think about. The unit looks a bit like the wigglers (at least that's what I call them) on our township portable fire fighting pumps. The wigglers have course-screens and a foot valve. They're called wigglers because the pump is primed by submerging the wiggler and wiggling it back and forth until the suction fills with water. Trying to prime a pump by pouring water into a small port through a funnel isn't good in fire-fighting situations. A finer filter may have a large surface area and may contain quite a bit of water, which might complicate priming.
The suction line screens on the township pumps are only fine enough to stop anything large enough to damage or clog the pump. Use of a filter has potential of stopping the pump if it clogs, and that may not be a good idea for unattended operations. In fire fighting, you know quickly if a pump stops working and the pumps have safety devices.
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irrigation implement
Paul: The wiggler, apparently AKA a foot valve and strainer, at this site http://www.cascadefire.com/cgi-bin/cfcart/cart.cgi?partno=23951 isn’t quite like the ones we have but it’s the same idea. It might be interesting to nose around the cascade site to see what else is available even if fire fighting equipment is pretty expensive (right up there with tractor parts).
This site also has wildfire fighting equipment but it seems like they took their catalogue off-line http://www.forestry-suppliers.com/index1.asp The catalogue has all sorts of clothing and personal equipment for forestry workers, including fire fighting.
This site http://www.wildfire-equipment.com/WildfireMain.html carries Mark 3 pumps. I forget if we use Mark 2 or Mark 3 pumps, but they aren’t exactly new and shiny. This site probably has suction line accessories as well but I couldn’t get the list of accessories to work on their site.
The safety equipment on our Mark 3 pumps is a governor. The governor shuts the engine down if it over revs. It doesn’t work like a tractor governor at all. The idea is that the engine speeds up if it looses its load. I wondered why it just didn’t throttle back like a tractor. I figured out that when a pump looses its load something needs to be fixed, so the engine is shut down. It’s curious that the engine also revs when a hose is clamped to add another length but not enough to trip the governor. You’d think that there would be more rather than less load when the hose is off, but I guess it’s actually less work if no water is being moved.
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Yep, cavitation seems to be the explanation for many things. I still wonder though if it might be less work for the motor to work against cutoff pressure than moving high a volume of water through hose at lower pressure. Never the less, when the hose is clamped the pump is sure going to cavitate.
The safety switch on our Wajax pumps works off air pressure. High rpm trips a switch, and I know that loss of prime definitely trips it. I don't know if leaving a hose clamped for a long while would eventually trigger the switch, but our instructor did say not to leave them clamped for long. Our target for clamping, adding or removing a hose section and releasing is 15 seconds. If we're doing it right the pump doesn't get much time to do anything other than pump.
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