15 Sludge Feed Valve Rotation
Valve rotations for GT/DAF Sludge Feed, Sludge Recirculation, and FOG Feed are performed each day at 7:00 a.m. (day shift crew), 3:00 p.m. (even months = day shift crew, odd months = swing shift crew), and 11:00 p.m. (swing shift crew). A schedule is posted on the wall of the Solids Building. Recirculation valves and GT/DAF sludge feed valves arelocated inside the Digester Building. FOG feed valves are located on the exterior of the digesters.
The temperature and contents of the digester sludge is consistent.
Watch for open tanks and high elevations. If working on or near equipment, watch for rotating parts. Watch for tripping hazards and overhead piping while manipulating the valves.
Use caution when rotating valves. Valves must be opened and closed in a particular order. The first step should always be to open a valve. If the operator’s first step is to close a valve, there is a risk that two valves on that pressure system may be closed. If this happens, pressure sensors should signal an alarm. The worst case scenario is that the high pressure created in the closed pressure system would cause damage and/or failure of the system. Warning: always verify which valves are open and closed before making any changes.
Valve no. 1505VLV5277F is on a permanent Lock Out so it cannot be mistaken for a GT/DAF Feed Valve. This valve is to remain open. Incorrect manipulation of this valve could result in pumping the contents of one digester to another via the heat exchanger recirculation pump, drawing down one digester, and overfilling the other digester.
The Operator must be aware of the different process streams and their associated valves while performing this SOP. Incorrect valve manipulation could reduce the efficiency of the Digester System. In a worst case scenario, incorrect valve manipulation could create a high pressure situation in a closed pressure system and the potential failure of that systen,
Operator I, knowledge of digestion process and equipment controls.
- Key or other tool to open/close valves.
- Record activity to log book.
Valve rotations for GT/DAF Sludge Feed, Sludge Recirculation, and FOG Feed are performed each day at 7:00 a.m. (day shift crew), 3:00 p.m. (even months = swing shift crew, odd months = day shift crew), and 11:00 p.m. (swing shift crew). A schedule is posted on the wall of the Solids Building. Recirculation valves and GT/DAF sludge feed valves are located inside the Digester Building. FOG feed valves are located on the exterior of the digesters.
This SOP is performed in conjuction with the Digester Mixing Valve Rotation SOP each day at 3:00 p.m. Click here for the Digester Mixing Valve Rotation SOP.
Warning: Use caution when rotating valves. Valves must be opened and closed in a particular order. The first step should always be to open a valve. If the operator’s first step is to close a valve, there is a risk that two valves on that pressure system may be closed. If this happens, pressure sensors should signal an alarm. The worst case scenario is that the high pressure created in the closed pressure system would cause damage and/or failure of the system. Warning: always verify which valves are open and closed before making any changes.
Each digester is equipped with one sludge feed valve, as summarized below.
· 1503VLV5685: Digester 1 GT/DAF sludge feed
· 1503VLV5685A: Digester 2 GT/DAF sludge feed
Each digester is equipped with one pair of Recirculation valves. One valve recirculates flown to the center of the digester and the other valve recirculates flow to the side of the digester, as summarized below.
· 1505VLV5277D: Digester 1 recirculation center feed
· 1505VLV5277E: Digester 1 recirculation side feed
· 1505VLV5277K: Digester 2 recirculation center feed
· 1505VLV5277L: Digester 2 recirculation side feed
Note: If a digester is receiving GT/DAF sludge feed, the recirculation flow for that digester should be through the center. If a digester is not receiving GT/DAF sludge feed, the recirculation flow for that digester should be through the side.
1. Determine which digester IS NOT currently receiving GT/DAF sludge feed. This SOP will start GT/DAF sludge feed to that digester. Begin valve rotation at piping for that digester.
a. Rotate valves to recirculate flow to the center of the digester.
i. Open the center recirculation valve {tag no. 1505VLV5277D or 1505VLV5277K}.
ii. Close the side recirculation valve {tag no. 1505VLV5277E or 1505VLV5277L}.
b. Begin GT/DAF Feed. Open the sludge feed valve {tag no. 1505VLV5685 or 1505VLV5685A }.
2. Determine which digester IS currently receiving GT/DAF sludge feed. This SOP will stop GT/DAF sludge feed to that digester. Begin valve rotation at piping for that digester.
a. Stop GT/DAF Feed. Close the sludge feed valve {tag no. 1505VLV5685 or 1505VLV5685A }.
b. Rotate valves to recirculate flow to the side of the digester.
i. Open the side recirculation valve {tag no. 1505VLV5277D or 1505VLV5277L}.
ii. Close the center recirculation valve {tag no. 1505VLV5277E or 1505VLV5277K}.
Note: Valve nos. 1505VLV5277F and 1505VLV5277M are on a permanent Lock Out so it cannot be mistaken for a GT/DAF Feed Valve. This valve is to remain open. Incorrect manipulation of this valve could result in pumping the contents of one digester to another via the heat exchanger recirculation pump, drawing down one digester, and overfilling the other digester.
Each digester is equipped with one FOG feed valve, as summarized below.
· 1505VLV5682: Digester 1 FOG feed
· 1505VLV5682D: Digester 2 FOG feed
Note: GT/DAF sludge feed and FOG feed should not be fed to the same digester. If a digester is receiving GT/DAF sludge feed, the FOG feed should go to the other digester.
3. Go to the FOG valve for the digester that IS NOT receiving GT/DAF sludge feed.
a. Start FOG Feed. Open the FOG feed valve {tag no. 1508VLV5682 or 1508VLV5682D}.
4. Go to the FOG valve for the digester that IS receiving GT/DAF sludge feed.
a. Stop FOG Feed. Close the FOG feed valve {tag no. 1508VLV5682 or 1508VLV5682D}.
- Update log book.
- Update maintenance records (if applicable).
- Report any maintenance or attention that is required.
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