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Field Service Bulletin 31: Cycle-PO4 and HydroCycle-PO4 Product Problems and Service-time Update

Service times for Cycle-PO4 and HydroCycle-PO4 have become significantly affected by instrument component issues and a growing backlog of instruments in for service. Service times are currently around 3-4 months for Cycle. We realize the time an instrument is in service and downtime due to sensor problems means that users are not collecting much needed data. We sincerely apologize for our current difficulties and wanted to update users on the status, details, and path forward.  

The issues are 1) swelling duckbill check valves in the pumps, 2) increased baseline noise and 3) pump pressure compensation at low temperatures.  

1) Swollen Duckbill Check Valves: Swollen duckbill check valves have been found primarily in warmer waters and where users are needing to bleach clean more frequently (e.g., every 2 weeks rather than 6-8 weeks). We tested this change before making it, but we now think this change could be related to the baseline noise quality issue.

2: Increased baseline noise) A few months after the duckbill valve material change a noisy baseline was observed for some units in our 5-m deep “silo” mock deployment. This test uses tap water, rather than the lab water used in most factory testing. We did not have test criteria around the silo noise, but an experienced service technician noticed unusually noisy pump performance, raised flags, and we have evolved our test criteria to set limits for baseline pumping noise during this test. We sincerely apologize for this error and if your recently serviced unit is affected by increased baseline noise please contact (see example raw data below). We have yet to fully identify the root cause of the baseline noise and will continue to investigate this issue until we have a solution.  

3) Pressure compensation at low temperatures: While instruments undergo extensive temperature testing during development, periodic temperature testing found that ~1/6 units can experience pump “skipping” at low (<10⁰C). The root cause of this issue is the viscosity change of the pump pressure compensation fluid. A new fluid was tested and in early March of 2017 we started switched fluid for both service and new builds. Since this change we have not had any internal testing issues or customer issues associated with the change.