InsaneHydraulics - Sergiy Sydorenko © 2009-2011 All Ridghts Reserved
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
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
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
"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.