15 Heat Exchanger Start Up
The two Heat Exchangers {tag nos. 1505EXR5861 & 1505EXR56825} are typically fueled by the Cogeneration System, which is managed and operated by Cal Power. (If the Cogen System needs to be taken offline, Cal Power must be contacted).
When the Cogen System is down, the Heat Exchangers can be fueled by either digester gas or by natural gas. Of the two, digester gas is most commonly used and the piping for that utility is red. Natural gas is considered the secondary gas source and the piping for that utility is orange.
During normal Cogen fueled operation, the Digester Gas Isolation Valve {tag nos. 1505VLV51885} and Natural Gas Isolation Valve {tag nos. 1505VLV5187} are closed. Heated water enters each Heat Exchanger near the floor on the west side of the equipment and exits from the top of the Heat Exchanger through a butterfly valve. The heated water is then piped through a flow meter {tag nos. 1505FE/FI5278 & 1505FE/FI5278A}, which balances flow between the two Heat Exchangers. Gauges monitor the pressure {tag nos. 1505PI5278 & 1505PI5278A} and temperature {tag nos. 1505TI5278 & 1505TI5278A} of the system.
Several different valve scenarios provide flexibility in how the Heat Exchangers function. During normal operation, the Heat Exchangers operate in a parallel configuration. It may be necessary to operate the Heat Exchangers in a series condition is a pipe breaks, a digester is below temperature, or some other abnormal condition presents itself.
Successful operation of the heat exchangers keeps the digested sludge heater for optimal treatment.
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.
Be aware of the gas piping and their locations. When the Cogen System is down, the Heat Exchangers can be fueled by either digester gas or by natural gas. Digester gas is piping is red. Natural gas piping is orange.
The Heat Exchangers are typically fueled by the Cogeneration System, which is managed and operated by Cal Power. If the Cogen System needs to be taken offline, Cal Power must be contacted.
Operator I, knowledge of digestion process and equipment controls.
- Record activity to log book.
1. Locate and close the Digester Gas Isolation valve {tag no. 1505VLV5185}. 2. Locate and close the Natural Gas Isolation valve {tag no. 1505VLV5187}. 3. Locate and close the Bypass Valve {tag no. 1505VLV5278}. Closing the Bypass Valve will re-circulate the water back to the Cogen System for reheating. Abnormal Operation (Heat Exchangers Operate in Series): 1. Locate and close the Series Return Valve {tag no. 1505VLV5278A}. 2. Locate and close the Main Feed Valve to Heat Exchanger No. 2. {tag no. 1505VLV5190A}. Isolate from the Cogen Unit: Follow this SOP when the heated Cogen water is not required or if the operator needs to isolate a Heat Exchanger for maintenance. The configuration allows the water to circulate while bypassing the Cogen System (and Cal Power doesn’t have to be called to shut down the Cogen Unit). 1. Locate and open the Main Feed Valve to Heat Exchanger No. 2. {tag no. 1505VLV5190A}. 2. Locate and open the Series Return Valve {tag no. 1505VLV5278A}. 3. Locate and open the Bypass Valve {tag no. 1505VLV5278}.
Observe Digester Recirculation Pump Operation: 1. Listen for excessive noise or vibration. 2. Check for oil or process fluid leaks. Record Data to Operator’s Log Book: Record Digester Recirculation Pump Activities to the log book with other entries for the day. Include the following in the entry: · Operator(s) that performed the Digester Recirculation Pump SOP. · Note condition of equipment, piping, valves, etc. · Note any unusual conditions with flows, levels, odors or other process issues. · Note any damage, wear, or required maintenance on equipment. |
- Update log book.
- Update maintenance records (if applicable).
- Report any maintenance or attention that is required.
Sludge remains heated.