0t---salvage pumps
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  1. #1
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    Default 0t---salvage pumps

    so i reviewed builder records of salvage pumps--aka trash pumps--and found an interesting factoid
    pertaining to ability to handle solids
    so a one inch discharge trash pump handles solids up to 0.5 inch
    two inch discharge solids up to 1 inch
    4 inch discharge ---2 inch solids
    6 inch discharge==== 3 inch solids---and there is no advancement in solid diameter capability
    in pump sizes larger than 6 inches

    therefore--12 inch discharge pump has 3 inch solid handling capacity

    i found no explanation in literature as to the three inch limit---but today--in process of
    parting out a 10 inch barnes us navy pump--discovered the limiting geometry-- impeller
    dimensions

    the 10 inch pump was powered by 80 hp detroit 3-53 heat engine
    flow volume an excepitional 3000 gpm--typical for 80 hp would be 1800 gpm
    likely explanation is dedicated to naval ship pump out with low discharge pressure head requirement
    therefore--increased discharge volume at tradeoff of lower discharge pressure

    the critical measurement is height of impeller blisk--3 inches
    blisk clearance from stationary pump frame is 0.010 in

    therefore--no object larger than 3 inches in any dimension should be introduced into pump
    cavity

    my conjecture is probability of cavitation with suction feed limits pumps of this category
    to 3 inch or less impeller blade height--comments welcome
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    Default

    I want to say most shipboard seawater pumps are 100 HP electric motor driven. Small ships have atleast four of them.

    Dewatering a flooded/flooding space is not done with pumps, it's done with eductors. Every space with a bilge has built in eductors and many spaces have spare modular eductors ready for use. The eductors use firemain pressure to create a venturi and suck many times the water they use.

    I don't know what the eductors were rated for, but I gaurantee it's way way more than 3000 GPM. Probably like 20k or 50K GPM depending on the firemain pressure.

    I got to use the eductors frequently. I was firefighting teamleader on my ship and I was also in charge of the engine room. When we were at sea I would have the engine room guys powerwash all the nasty crap and train everyone in my division on how to align the eductors. They would empty a 10 foot deep bilge in an instant.

    Had a 6" pipe break off at a seachest about 10 ft below the waterline. Not full flow, but there was a 1/2" gap or so. Lots of water. Eductor kept up with it just barely cracked open.

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    Lincoln electric published a series of books from the 1970's in which they awarded
    companies that re-designed products using welding.

    One job was dredging pumps, and they handle IIRC 12" rocks.
    The article had very good pix of the impellers and housings as well.

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    In well pumps the eductor would be part of a system called a jet pump. I had no idea they would be used for dewatering, but an excellent solution for low head discharge.

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    The Eductor is the very same principle as a Penberty Injector used to recharge feedwater of a steam boiler... and the same principle used to draw detergent into a pressure washer. Works great, no moving parts, save for the stuff flowing through 'em!

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    eductor apparatus is new to me

    this Dept of Navy film introduces sobering fact---12 inch square penetration in ships hull 15 ft below water line
    introduces 14,000 gpm ----how to survive this event is one part of damage control lecture you dont want to snooze thru



    "UNWATERING FLOODED COMPARTMENTS" 1950 U.S. NAVY DAMAGE CONTROL FILM 12984 - YouTube
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