15 Mixing Valve Rotation
Valve rotations for the Digester Mixing System are performed each day at 3:00 p.m. (even months = day shift crew, odd months = swing shift crew). A schedule is posted on the wall of the Solids Building.
In general, the operator will switch the current suction/discharge valve settings on both digesters. Each digester is equipped with two pairs of discharge valves (top and bottom) that are rotated on a daily basis. (The middle discharge valves {tag nos. 1505VLV5272H & 1505VLV5274H are always open and are not adjusted in this SOP.) Each digester is also equipped with one pair of suction valves (top and bottom) that are rotated on a daily basis. No adjustments are made to the Hi-Rate Mixing Pumps.
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.
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,
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- Key or other tool to open/close valves.
- Record activity to log book.
Valve rotations for the Digester Mixing System is performed each day at 3:00 p.m. (even months = swing shift crew, odd months = day shift crew). A schedule is posted on the wall of the Solids Building.
This SOP is performed in conjunction with the Sludge Feed Valve Rotation SOP at 3:00 p.m. each day. Click here for the Sludge Feed Valve Rotation SOP.
In general, the operator will switch the current suction/discharge valve settings on both digesters. Each digester is equipped with two pairs of discharge valves (top and bottom) that are rotated on a daily basis. (The middle discharge valves {tag nos. 1505VLV5272H & 1505VLV5274Hare always open and are not adjusted in this SOP.) Each digester is also equipped with one pair of suction valves (top and bottom) that are rotated on a daily basis. No adjustments are made to the Hi-Rate Mixing Pumps.
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 system valves are open and closed before making any changes.
1. Rotate Mixing Dischargevalves located at front exterior of Digester 1:
Locate the discharge valves at the front of the digester {tag nos. 1505VLV5272G& 1505VLV5272J}.
a. Determine which discharge valve is currently open.
b. Open the other discharge valve.
c. DO NOT adjust the middle valves {tag nos. 1505VLV5272H& 1505VLV5274H}.
2. Rotate Mixing Suction valves located at exterior of Digester 1:
The Digester suction piping is labeled” TOP” and “BOTTOM”. Each Digester Tank is equipped with a “bottom” suction valve {tag no. 1505VLV5100} and a “top” suction valve {tag no. 1505VLV5100A}.
a. At Digester 1, verify which suction valve (top or bottom) is currently closed. Open that valve.
b. At Digester 1, close the other valve.
3. Rotate Mixing Dischargevalves located at back exterior of Digester 1:
One set is located on the back of the Digesters and includes a top and a bottom valve {tag nos. 1505VLV5272E, 1505VLV5272F}.
a. Rotate the “back” Mixing Discharge valves at Digester 1.
I. At the back of Digester 1,verify which discharge valve (top or bottom) is currently open. Open that valve.
II. Close the other valve.
4. Rotate Mixing Dischargevalves located at front exterior of Digester 2:
Locate the discharge valves at the front of the digester {tag nos. 1505VLV5274G &1505VLV5274J}.
a. Determine which discharge valve is currently open.
b. Open the other discharge valve..
c. DO NOTadjust the middle valve.
5. Rotate Mixing Suction valves located at exterior of Digester 2:
The Digester suction piping is labeled” TOP” and “BOTTOM”. Each Digester Tank is equipped with a “bottom” suction valve {tag no. 1505VLV5200} and a “top” suction valve {tag no. 1505VLV5200A}.
a. At Digester 2, verify which suction valve (top or bottom) is currently closed. Open that valve.
b. At Digester 2, close the other valve.
6. Rotate Mixing Dischargevalves located at back exterior of Digester 2:
One set is located on the back of the Digesters and includes a top and a bottom valve {tag nos. 1505VLV5274E, 1505VLV5274F}.
a. Rotate the “back” Mixing Discharge valves at Digester 2.
I. At the back of Digester 2, verify which discharge valve (top or bottom) is currently open. Open that valve.
II. Close the other valve.
- Update log book.
- Update maintenance records (if applicable).
- Report any maintenance or attention that is required.
EQUIPMENT NAME | TAG NUMBER |
Digester 1 Mixing Discharge Valves (front exterior) | 1505VLV5272G & 1505VLV5272J |
Digester 1 Mixing Suction Valves | 1505VLV5100 & 1505VLV5100A |
Digester 1 Mixing Discharge Valves (back exterior) | 1505VLV5272E & 1505VLV5272F |
Digester 2 Mixing Discharge Valves (front exterior) | 1505VLV5274G & 1505VLV5274J |
Digester 2 Mixing Suction Valves | 1505VLV5200 & 1505VLV5200A |
Digester 2 Mixing Discharge Valves (back exterior) | 1505VLV5274E & 1505VLV5274F |