Two times in a Row or Another Insdustrial Hydraulics Mishap

     This is the kaboom story I've been craving to share for a long time, but having no pictures to illustrate it with forced me to wait patiently for the day X... Finally - the right pump popped up, and now I have the visuals to tell you the sad story called "twice in a row".

   The pump in question is a Rexroth A7VO55 open loop unit, and the pictures to the left are actually form my last week's post about this model (A7VO55LR3E). Unfortunately I have no images of the scrap (this tragedy is from the old days - when I wasn't carrying my camera everywhere I went), but it's still a nice story to tell, so I kind of hope that your imagination will provide you with the missing details.

     Once upon a time a machine owner appeared at our doorstep, and he brought a A7VO pump with him (exactly like this one). The complaint was - it makes a very strange noise, and the machine won't work... We opened the pump and discovered a completely trashed rotary group inside. The damage pattern suggested that something very hard got jammed in between the barrel and the valve plate, leaving a deep scar on the brass surface, and pretty much mutilating everything else. It wasn't difficult to determine what it was since the torque limiter pin was missing. When the man saw the parts - he recalled that the torque limiter was dripping oil, so he gave the order to dismount it and replace the o'rings. Of course, when the valve assembly was removed, the person who performed the task wasn't aware of the small pin behind it, nor he was aware that this pin wasn't atached to it - so it fell directly into the inlet, causing the complete destruction of the ill-fated unit! What's done is done, so the man cursed, stiffened up his upper lip, and paid for the expensive rebuild....

    About a year and a half later, the same guy, with the same pump appeared at our shop... When I said something like "don't tell me that you removed the valve to replace the o'rings again..." he looked at me, surprised and puzzled at first, and then - and this was the most interesting moment of all - he didn't utter a single word, but for about five seconds his facial expression clearly read (in the following order):

"but how did you know..?!!!"
"wait a minute, don't I know you from somewhere..?"
"oh, you're that fellow who repaired one of my pumps last year, aren't you..?"
"now hold on just a second, wasn't it the pump that..?
"don't tell me that once again I..."
"I can't beleive that I..."
"I am f#cked, ain't I?..."

   The last phrase was pronounced out loud (in Portuguese), and I agreed with the man that he indeed was in a pickle...again... The following disassembly confirmed the diagnosis, and in the end the man had to stiffen up his upper lip for yet one more time...

    I am really sorry that I took no pictures - the damage was extensive and picturesque.

    I've been carrying this story for a long time, waiting for the right example pump. Many A7VO pumps with torque summation controls passed through our shop, but all of them had the connecting rod attached to the spool with a small spring pin - so I couldn't use them for proper illustration...

    FINALLY I can take this load off of my chest and pass this story to the privileged circle of IH readers.