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Grove boom transducer zero

steve waldner

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Jul 5, 2017
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192
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huron sd
image.jpg image.jpg grove tms 700b , I got the hoses off the transducers (weight indicators) and when I go into pat monitor and set them to zero . It shows -7 thousand . When I pick the boom up it says I have 4000 . Can someone explain or give me some advise with this ? The reason I zeroed them they seamed to give way higher readings than my load chart . Like it will say I have 3000 lbs on when all I got is the big and small ball not more that 1500 . I need to understand this a little better . Thank you
 

crane operator

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Mar 27, 2009
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8,275
Location
sw missouri
Your transducer will read all load on the boom, which will include your stowed jib. If you pay attention, the "preload " will change based on boom angle, more when flat, less when boomed up, this is mostly stowed jib. Removing the jib will take out that as load on the scale. If you totally zero out that preload, you can overload the crane with the lmi still showing load available, because it won't be deducting the stowed jib and block and ball. 1,500 -2,000 isn't a unusual preload amount. My 700rt is about that.
 

steve waldner

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Joined
Jul 5, 2017
Messages
192
Location
huron sd
So it’s normal for the sensor to show -7 when the hoses are off from transducer ? Should I bleed the air from the line before I tighten or will they be accurate enough with air in the line ?
 

crane operator

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Mar 27, 2009
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You can't get accurate numbers with the transducers unhooked. Hook them back up and bleed the air out of the lines. Then you adjust the preload/ accuracy with no load , and a known weight load. I usually like my known load to be over 10, 000 lbs. Pick up a flatbed semi trailer or something that's been across a scale. You adjust the weight in the grey rectangular lmi/ pat box. The procedure is in the lmi portion of the service manual. If you don't have that, I think I've got a copy.
 

crane operator

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Messages
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As far as the -7,000 on the lmi with it unhooked. The pressure transducers read all pressure on the boom cylinder. You have to "deduct" out of that amount, the weight of the main boom. Its applying force on the boom cylinder, but its weight has been calculated out of the load chart. The lmi needs to account for this weight, so it has to automatically take the weight of the main boom out of the lmi readings.

You can't have the jib taken out of that amount, because it is a load, and isn't calculated out of the lmi reading, because you can run without the jib mounted.

I've actually removed the jib for certain jobs where I knew I was going to be right up to chart, and needed that extra amount, but didn't need jib. You'll notice with jib removed, probably 1/2 to a little more of your 3,000 lbs preload, would disappear.

You'll also find, that your "preload" amount will be much less at a higher boom angle than a lower boom angle, that's showing the effect of the stowed jib, its effective weight will change based on boom angle.

If you watch really close too, you can see the weight go up and down, based simply on whether you are booming up, no booming but just winching, or booming down. You can pick a load up with just the winch and be just inside chart, and then start booming up to bring it to you, and have the overload alarm go off. The weight of the load didn't increase, but the hyd pressure on the transducer did when you started to boom up the load.

Just make sure you don't get carried away and remove all the preload up to the amount of just your block and ball, it has to include the stowed jib.
 

steve waldner

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Jul 5, 2017
Messages
192
Location
huron sd
If I add the main block , headache ball, stowed 56’ jib, together I get 1800 lbs , that should be my preload . I went into Lmi display , info clr, password , I can adjust boom cyl load percent , I adjusted it to where I had a 5900 lb object on the and the total should of been 7700 , and the lmi showed around 8000 , stayed perty accurate even if I boom all the way up with boom extended . And angle down . Of course when I boomed up it showed 9-11,000 but when stable showed 8200 ,when boom down to release some pressure it showed 7500-8000 .1A9094BE-A191-4EEB-9DD7-76175F3FA39E.png
 

crane operator

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Mar 27, 2009
Messages
8,275
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sw missouri
If you are within 300lbs, that's about as good as it gets. I usually figure at least 500lbs one way or the other in accuracy.
 
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