Thursday, August 29, 2013

Lime Silo Bottom Outlet Screw Feeder Isolation

Paper Mill Lime Silo Valve
Paper Mill Lime Silo Valve
Customer: Paper Manufacturer
Service: Lime Silo Bottom Outlet Screw Feeder Isolation
Process: Lime Powder at 1800 F.

Problem:
Lime Silo Outlet Valve. Existing valve was a 14” RoValve through port knife gate with a Rotork electric actuator. Valve gate had galled badly and actuator could not stroke the valve with out the help of a sledge hammer driving the gate as well.
Valve must function reliably to allow for isolation of the screw feeder at the bottom of the silo. Screw feeders are high maintenance equipment and it was taking longer to isolate the feeder than it would take to actually repair the feeder.

Solution:
Install a custom fabricated Hilton 290B knife gate valve designed for high temperature powder service. Valve has a displacement pocket design that is self clearing and allows the lime powder to freely drain from the valve body into the feeder, preventing lime powder from jamming or galling the valve. By using a bonneted type valve the required thrust was reduced and gate wear due to packing was eliminated. This allowed the use of a pneumatic cylinder actuator further reducing cost.

The valve was fabricated to fit in the allowed space and required no spacers or transition pieces for installation. The valve was fabricated from 310SS material to ensure long life at the high operating temperature of 1800 F.

Result:
A severe service application was solved with innovative thinking and close work with both the end user and manufacturer engineering staffs. Valve was installed and fit perfectly. Valve strokes reliably ensuring the safety of maintenance personnel and reducing outage times for maintaining the screw feeder.