Hobart wash arm Split open

[whirlykenmore78]

The Hobart AM-14 Dishwahser at my work was spitting out water at the side doors today. I pulled out the upper wash arm to find that the SS had split where it is crimped and took it to be welded. Mind you this is no small wash arm. I took the photos against the steering wheel of my car for size comparison.

 

[whirlykenmore78]

Hobart wash arm

This is not a small or flimsy part.

 

[whirlykenmore78]

hobart arm

These jets will get em clean

 

[jetcone]

how old is that

DW??

 

[stevet]

I have seen worse!

Those wash arms sure DO throw lots of water all over the dishes and a split seam is not all that uncommon especially if the machine was used heavily and if the users did not clean the arms on a regular basis(meaning at least after each meal period during the day). If the holes clog up, you can just imagine the pressure the seams are exposed to. The smaller arms on the LX Series will also split due to clogged holes in the wash arms. This is quite prevalent in the Starbucks stores where the arms are seldom cleaned out. When they call to report leaks out the door or poor washing results, the first thing I do is take out the arms and show the managers what has been going on. They are quite amazed that the arms can split like that.But when you have a 3/4 hp motor pumping water into those arms in that undercounter machine, the pressure will find the weakest spot and open a seam.

On the AM machines, you can probably get away with leaving the arms in place until a replacement comes in and not really notice too much of a wash difference but on the undercounter machines, if the the split seam is on the bottom arm, water will usually spray right out under the door or else it will spray downwards into the water in the bottom of the tank and literally blow the water all over the place and create waves of water which will go out the door in large volume.

In the case of the undercounter machine, if the top arm is okay, you can buy time by transferring the bottom arm to the top position and vice versa. But you need to replace it so you do not lose washing ability.

 

[stopmeister72]

Speed of lxi washarms

Steve, do you know what the rpm of the wash arms should be on a lxi machine. The new one at my school last year seemed to turn very fast and didn't wash well, my 20 plus year old wm5h does much better. I would estimate by the rhythm that the lower arm was turning close to 120 rpm which seems like that would be too fast. ( and by trying to take a peak) They weren't clogged but didn't examine the seams. Wished the holes were bigger.

 

[stevet]

I'm working on it, people!

I put it out there to tech support to get me the specs on the speed of the washarms and have to call them tomorrow(9-22) to discuss it with my buddy. Will report what I learn as soon as I hang up with him.

 

[jetcone]

Just downloaded the install

manual, how does the rinse arm work with the wash arm? Are they fed by different water supplies?

 

 

 

[stevet]

Wash arm Speed

Installment #1:

Optimal washarm speed in LX series machines is from 50-100 rpms. It sure does go around pretty fast and is dependent on water charge in tank and as we know, how much detergent and foaming there may be, though most machines use a metered amount of almost non foaming liquid detergent.
Also. that is with none of the holes blocked by debris and the sump filters clean and not limed up or covered by food and other particles,which will restrict the intake of the pump.

Still waiting on the SR series specs. Will report back when in!

 

[stevet]

Wash and Rinse

Jon, to answer your question about wash and rinse in these machines, the AM Series uses separate plumbing to supply the rinse arms on the top and bottom of the wash chamber which supplies the individual rinse arms. Total water delivery varies depending on the style of rinse arms that the machine came with when originally built. The AM 14 series had 2 different rinse arms and the wash arms are like you see in the picture above.
The AM 15 has a completely different washarm with smaller holes shown to be able to scrub the dishes better than the older style arms as well as a different rinse arm.
In all cases, there is rinse piping which connects to the manifold housings that the washarms ride on and the rinse water is delivered thru internal passages in that housing. That is the way it is done in nearly every manufacturer's machine of this type. The theory is the same, the look and specifics are all slightly different.

The LX does it basically the same way with a manifold supplied by the washpump that runs up the back of the machine to supply the upoper washarm and at the top and bottom of the pipe, the manifolds have internally molded passageways for the rinse water to be delivered to the rinse arms.
There are certain models in the LX series which are fill and dump machines which deliver the water for wash and rinse thru the normal fill air gap we are all familiar with. Those units have only the single washarm on the top and bottom and lack the rinse arms as they machine drains the wash water and then refills with the rinse water.
SR24 machines are like the KD18 series and are fill and dump units as well.They have the single washarm on the bottom and a smaller one up on top, similar in size to the original 18 arm used under the top rack but not identical to it, feeding water down on to the dishware.

Hope this helps.
Steve

 

[stevet]

SR Washarm speeds

Just got the answer to the SR24 washarm speed specs, which would be the same arm I put in my KDS18 to repalce the 4 way Hydro-Sweep Arm.

The design specs on the SR24 are 30-53 rpms for the lower arm and 10-25 rpms for the upper arm which,as I mentioned, looks like the original 18 series upper wash arm, only it is mounted on the top of the tank and delivers its water straight down on to the dishes in the single rack.
Pump delivery is rated at 45gpm.

FYI, the design specs on the the 18 series was for rotation speeds of approx 35rpms for both arms delivering 50 gpm from the pump.

I would definitely say that the single arm in the 18 I have does turn faster than the 4way arm and the manner in which it mounts to the washarm support just about eliminates the wear on the arm bushing and the sealing ring that could cause problems with the way style arm.This will also help it deliver consistent pressure out of the arm to wash the dishes.

 

[stopmeister72]

thanks, and I am going to have to get a new empeller

Thanks for the information Steve. Those rotation speeds sound about right for my wm5h. I would think the newer dishwashers would do a better job of washing if the arms didn't turn as fast as they do. Just about two days ago was washing dishes and the pump sounded a little funny, then came back in and my partner opened the door to turn it off and said it was making some funny noise. Latched the door again, and the water was barely spraying, thought my motor was going bad (a kitchenaid replacement motor with a seperate relay - not a hobart motor). Come to find out, the top of the empeller is stripped so it was slipping on the motor shaft. There are no more groves for that washer to lock into, so I guess I get to take a trip to Hobart tomorrow if they have it in stock. Wonder why it stipped? It's only 20 years old or more. I've got the part numbers so going to call tomorrow morning.