Waters 2695 Torpedo Spring
Posted: Fri Jul 27, 2018 6:41 pm
Hello,
I'm using an older Waters 2695 HPLC. All was well with it until I began having pressure drops when the accumulator piston would retract & the primary was to be providing the system pressure. Once the accumulator began its compression stroke, system pressure would begin to rebuild. Static leak check revealed the primary pump was not building any pressure. After new check valves, pistons, and seals did not remedy the issue, I began swapping parts between the primary & accumulator (check valves, pump heads, transducers, torpedoes). The only part to make a difference was the torpedo/drive assembly itself, so I focused my attention there. Interestingly, having the torpedoes swapped resulted in pressure spikes rather than pressure drops. Both pumps built pressure in this configuration. After removing the manifold from the front of the [original] primary torpedo, I found the return spring in three pieces. It seems this was resulting in only a partial return of the piston driver during the return stroke, so the subsequent initial movement of the stepper motor was not building any pressure (there was a gap between the ball screw & the piston). Everything else in the LC is fine. I was wondering if any of you may know where I could source a replacement spring, or if I am stuck sourcing a new torpedo. The spring seems to have somewhat odd dimensions (2.7" free length, 1.7" OD, 0.105" gauge wire, and compressed length of a mere 0.75", with 5.5 coils) and made of stainless steel wire . I have never needed to source a compression spring before, so any guidance is appreciated.
I realize this is a somewhat odd question, so if nothing else, hopefully this helps someone else in the future diagnose a periodic pressure drop on their 2695.
Many thanks
I'm using an older Waters 2695 HPLC. All was well with it until I began having pressure drops when the accumulator piston would retract & the primary was to be providing the system pressure. Once the accumulator began its compression stroke, system pressure would begin to rebuild. Static leak check revealed the primary pump was not building any pressure. After new check valves, pistons, and seals did not remedy the issue, I began swapping parts between the primary & accumulator (check valves, pump heads, transducers, torpedoes). The only part to make a difference was the torpedo/drive assembly itself, so I focused my attention there. Interestingly, having the torpedoes swapped resulted in pressure spikes rather than pressure drops. Both pumps built pressure in this configuration. After removing the manifold from the front of the [original] primary torpedo, I found the return spring in three pieces. It seems this was resulting in only a partial return of the piston driver during the return stroke, so the subsequent initial movement of the stepper motor was not building any pressure (there was a gap between the ball screw & the piston). Everything else in the LC is fine. I was wondering if any of you may know where I could source a replacement spring, or if I am stuck sourcing a new torpedo. The spring seems to have somewhat odd dimensions (2.7" free length, 1.7" OD, 0.105" gauge wire, and compressed length of a mere 0.75", with 5.5 coils) and made of stainless steel wire . I have never needed to source a compression spring before, so any guidance is appreciated.
I realize this is a somewhat odd question, so if nothing else, hopefully this helps someone else in the future diagnose a periodic pressure drop on their 2695.
Many thanks