Zimmark Service Technician Micheal Burgess received a minor shock on April 11th 2018 when he reached down to test a tether float in the Gravity Filter Tank at our PRA site in Alabama. Micheal immediately informed his supervisor (Ken Attard). The customer was informed of the incident and the incident was recorded under their HSE Requirements. Micheal was not injured and did not require any medical attention.
ZIMMARK CAUSAL NUMBER: PRA-184-359
Treated, recycled Wash Water gravity drains from a 3000G into a 75G filter tank and circulates back to the tank via additional filtration. Floats were recently installed on the filter tank to shut off the gravity follow automatically. Michael was demonstrating the float operation to a new employee when he felt the shock. Power was immediately disconnected from the floats following the incident. The system is being operated manually pending an on site investigation to be conducted by David Nelson during week of April 23.
The floats were installed 2 weeks prior. A new model tether float had been used as it permitted operation within a shorter operating range. The float has not been used in any other Zimmark application.
NOT YET DETERMINED.
Power was from float was disconnected.
Pending further investigation, Zimmark’s equipment department has suspended use of Dayton Float Switch, Mechanical, Normally Closed, Zoro part no G1845313.
APPLICATION COMPATIBILITY CHECKED:
The 115VAC 10A float was used in a non hazardous fluid (pH 9.1) at approx 120˚F. The max temp for the unit is listed as 140˚F.
WAS IT FULLY TESTED:
Yes. The floats were tested repeatedly by David Nelson following initial installation
WHAT WE LEARNED:
An incident like this has never happened before. Zimmark uses commercially available control systems.
The investigation may identify preventative measures we can take following the install to ensure there is never any risk of electrical exposure.