Intermittent Service? Say No More, We Have a SpiralTrac™ for You
- January 31, 2020
Pumps that are running intermittent service usually come with their own set of maintenance issues. The following application was no exception, but then a Version C (seal version) SpiralTrac showed up and changed the story.
The application we are discussing is in a Zinc mine. Pump is a Worthington M horizontal, single stage slurry pump, pumping sulfuric acid and manganese slurry. The product temperature is 100° F (≈38° C) and has 10% solid concentration. Manganese is a critical mineral for the global economy and an essential ingredient in steel production. 80% of the planet's manganese resources are found in South Africa, with the rest being heavily present in Australia, China and Brazil. The corrosive nature of sulfuric acid and the abrasive properties of the slurry makes this application quite hazardous and a big challenge to seal.
This pump is running in intermittent service. This means that unlike most process pumps running continuously 24 hours a day, 7 days a week, this specific pump doesn't "work" all the time. It is running in cycles, turned on and shut off when needed. When the pump is shut off and drained, the product cannot completely drain out of the stuffing box. This is just the nature of how stuffing boxes are designed. The leftover product can solidify and harden as it is sitting in the box. As the pump is being flooded and turned on again, this hardened leftover product can easily get embedded into the packing rings, eating away the packing and the shaft/sleeve. This Worthington pump had to be repacked every 4 months.
The pump was also a maintenance headache due to its hard-to-access location at the plant. When it was time to repack, a crane had to be used so the maintenance personnel could access the equipment.
Customer was looking to reduce or if possible, eliminate the 3 gpm flush that was utilized. It was also important that the pumped media could not be diluted!
The Chesterton specialist offered a SpiralTrac design that is pressed in from the impeller side.
The impeller side installation offers a clear unobstructed path for the spiral geometry. The solids entering the seal cavity are centrifuged to the bore during pump operation, and the axial flow sweeps them towards the SpiralTrac. As the particulates are caught in the spiral groove they increase in velocity, eventually being expelled through the exit groove towards the impeller. The majority of solids that would enter the cavity under the busing are caught and send back where they came from even before they could reach the seal cavity.
The Version C SpiralTrac has a special drain machined at the 6 o’clock position, allowing the product to easily drain from the stuffing box when the pump is turned off and the volute is drained. This prevents product residue from hardening in the box while the pump is not in operation. Now the Chesterton S10 seal can operate in a clean environment, staying cool and lubricated around the seal faces without even utilizing flush.
As of writing this article (Jan 2020), this solution has been running flush free for over three years without any issues! That is at least 12 times the pump didn’t have to be repacked, saving the customer on material, maintenance and flush water costs!