Hi

I was wondering if anyone else out there using the Graseby 500 had experienced the 'no flow above pump' problem only to find cleaning and re-adjusting did not cure the problem.

This problem relates to horizontal elongation of the sleeve that carries the upper piston rod - but it is not a sleeve you can replace... it's part of the pump engine!!!

There is little or no wear in the vertical axis so I can only conclude that the wear has been caused by a constant but slight sideways bias from the cam as it rotates - as the piston slides in and out it wears the sides of the sleeve / carrier.

This is incurable - despite trying to clean it all up - try re-adjustment - the piston just sticks ....lubrication of the piston rod just causes stiction and delays the movement of the piston in the return stroke.

The only cure now seems to be a new pump engine at £550 + !!!

I have been working on these units for over 5 years and familiar with most faults but only recently finding more and more of the older G500s are comming down with this problem... problem is we have 100+ of these devices

Is this a time bomb?

How old are these pumps, Rich?

Hi Geoff

This particular pump is 6 years old - the others that are playing up are between 5 and 7 years old.

Interesting that they are that "young". Have they had a "hard life", would you say ... or just the normal sort of thing? Anyway, let's hope that you get some feedback from others with this pump on inventory.

It isnt something they are cleaning them with as we dont have a problem with ours.

Or have they gotten some sticky fluid in there.

I haven't seen that one yet, do you see other indications of wear such as problems during the motor torque test?

Lee

I'm wondering what they are pumping ... gear oil at SAE 140?

It is not something as simple as not having the bag high enough over the pump? The bottom of the bag needs to be 15-30cm above the top of the pump.
This gives the same error message.
Robert

Having the bag not high enough will produce the same error message but this is a similar scenario where the head height of water is not enough to overcome the excess friction of the piston rod against the sides of the sleeve.

To answer previous questions on the thread

The pumps are in use every day, some twice a day so they do get a fair battering.

I am using water but as you can imagine the problems when these pumps are used for blood.

A tempory fix to the problem is a carefull application of scilicon spray but I'm not happy to progress in this manner.

How about the condition of the giving set? We've had problems with testing for the correct 'no flow' minimum head height, when the plastic of our test giving set had got stiff with age. A new set (or warm water) cleared the apparent fault. Now the only issue for us is those exposed wire 'no flow' contacts getting dirty; I use a bit of switch cleaner on a long cotton bud ;-)