14 DPS Surge Tank

Low or Failed System Pressure Condition:  The fastest way to get the system back in service is to re-pressurize the Surge Tank with the portable Smith compressor and manually run the DSPS pumps.  Sometimes re-pressurizing the Surge Tank alone will not re-pressurize the entire system.

When the Surge Tank water level falls below 10”, the pressure sustaining valve closes. The pressure sustaining valve is located at the bottom of the Surge Tank and is a butterfly valve that is controlled by a three-way air solenoid. During normal pressure conditions, the solenoid switch is in the middle position.

1.     Re-Pressurize the System to 80 psi:

a.     Place one of the DSPS variable speed pumps {tag no. 1404PMP/VSD4100 & 1404PMP/VSD4200} in manual control by turning the HOA switch {tag no. 1404HS4100 & 1404HS4200} to HAND.  Depending on the current system demand, the operator may need to run one variable speed pump and one constant speed pump {tag nos. 1404PMP4200, 1404PMP4400 & 1404PMP4500}.  If Phase 2 is filling or there is a leak in the system, etc., more pumping will be required to restore pressure in the system.

b.     Monitor the Reclaimed Water system pressure on the local PLC screen. Manually increase the variable pump speed and/or run a constant speed pump if more flow is required to meet the target pressure.

2.     Re-Pressurize the Surge Tank:

a.     Move the portable Smith Compressor to the DPS Surge Tank {tag no. 1404TNK4691}.  The portable Smith Compressor is typically stored in the Sludge Pump Room.  If the Smith compressor is unavailable, substitute the Emqlo DPS Compressor {tag no. 1404CMP4841} (located in the DPS Control Room) to re-pressurize the Surge Tank. Please note: output from this compressor is very low and it can take 3 – 4 hours to resume system pressure.    

b.     Connect the compressor air hose to the Surge Tank connection, which is located overhead.

c.     Force air until the Surge Tank pressure equals the Reclaimed Water system pressure.   

d.     Once the Surge Tank pressure and the Reclaimed Water system pressure are aligned, re-open the Pressure Sustaining Valve {tag no. 1404FY4691} by turning the 3-way switch.  This will equalize the Surge Tank pressure and system pressure.

3.     Re-Pressurize the System to 120 psi:

a.     When the Reclaimed Water system pressure and Surge Tank pressure are equalized at 80 psi, place the DSPS pumps back in AUTO control at the HOA switch.

b.     As the Reclaimed Water system pressure increases to 120 psi, refer to the Surge Tank Operation Table for further instructions.  The Surge Tank Operation Table is taped to the front of the DSPS control panel.  Click here for a copy of the Table.

DPS Compressor Operation:

If the Smith Compressor is unavailable, substitute the use Elmqo Compressor and perform the following SOP. Under normal conditions, the Elmqo DSPS Compressor {tag no. 1404CMP4841} runs in AUTO mode. The typical functions of the DSPS Compressor are the following:

·         Provide air to the Pressure Sustaining Valve {tag no. 1404FY4691} on the Surge Tank.

·         Provide a direct air source to the Surge Tank {tag no. 1404TNK4691}.

·         Maintain a pressure of 120 – 160 psi in order to maintain a DPS system pressure of 120 psi.

Under normal conditions, the Air Supply Valve {tag no. 1404VLV46825} is closed.  When the Surge Tank water level reaches 31 inches (an abnormal condition), the Air Supply Valve automatically opens and the Compressor {tag no. 1404CMP4841} forces air into the Surge Tank {tag no. 1404TNK4691} until the water level lowers to 26 inches.  The Air Supply Valve will automatically close when the Surge Tank water level reaches 26 inches.

When the Surge Tank water level falls below 26 inches, the following SOP should be performed.

1.     Open Air Supply Valve.

a.     Locate the Air Supply Valve Switch {tag no. 1404HS4841}, which is located on the side of the main DPS Control Panel, below the blue keypad.  During normal operating conditions (when the Surge Tank water level is at 26 inches) the Air Supply Valve is closed and the Switch is in the OFF position.

b.     Flip the switch to OPEN.  You should hear the air release as the valve is opened and air is pushed back into the Surge Tank {tag no. 1404TNK4691}.

The Surge tank control valve toggle switch should be in ON (auto) position.  The switch is equipped with a safety feature that automatically closes the switch during a power outage. This feature saves air in the surge tank during power outages.