Chromatography Forum

Hallo -
We purchased two new Beckman System Gold HPLCs in 2008. Our lab mainly uses RP-columns, with phospate buffers (upto 0.1M) on pump A and organics like MeOH, AcN on pump B. These instruments are extensively used, as are our older Agilent (1100 series) HPLCs. Tonight, while conducting a routine run, the pressure on pump B spiked (300 bar) and then the pump shut off with a whirring sound. As this has previously been because of the high-pressure shut-off, and that in turn because of worn pump seals, I opened up the pump to replace the seals as per usual maintenance protocol, only to find that multiple cracks had developed in the piston head itself. Closer inspection of the cracks led, most unfortunately, to a clean break at one point. The piston also showed evidence that it had been rubbing forcefully against the pump seal for a while.
I was led to believe that Beckman pumps are basically unbreakable. What are we doing wrong? Or is this something that has happened to other people? ANY feedback would be greatly appreciated. I will be contacting the company when they open for business tomorrow, but in the meantime, does anyone have any input?
Thanks!

I can speculate that what you saw is consistent with a misaligned head. Could be a manufacturing machinine defect, or possibly the result of not tightening the bolts evenly.

But, as I said, that's only speculation.

Tom's answer is right on the money. If the piston is not centered (or head not square), then the piston will wear against the seal. *Usually a grove is created in the seal. Pistons usually snap rather cleaning from this type of stress.

BTW: You would not see this type of problem with your 1100-Series pump. It has 'floating' pistons so they distribute wear evenly around the seal. A great design feature that actually works. That is not to say that a piston will not break in an 1100 (1050/1100/1200 all the same). They just do not break due to this problem.