As you are operating a Vac2Go vacuum truck, air is flowing throughout the truck. As air is leaving the microstrainer, it flows past an air-operated butterfly valve. The purpose of the air-operated valve is to relieve the system vacuum during normal operation. Excessive vacuum can be caused by a clogged suction hose or boom. A loss of vacuum air flow at the hose can result when the debris tank is full; the vacuum relief valves are opened or the float balls have risen, shutting off air flow to the vacuum system.
There are two types of relief valves on a Vac2go vacuum truck. There is an air actuated relief valve as well as a manual relief valve.
Air Actuated Relief Valve
The air actuated vacuum relief valve is designed to relieve vacuum in the system. The air activated vacuum relief valve is activated through either the “vacuum” switch on the master control panel, or the pendant. The “master switch” on the master control panel must be turned on in order for the “vacuum” switch or the pendant to operate.
Manual Relief Valve
The manual vacuum relief valve is located near the master control panel. The manual relief valve is used in instances where the automatic relief valve fails to operate properly or it can be used to provide relief in addition to that provided through the automatic relief valve. The valve is open when the handle is in line with the valve. To close the valve, squeeze the trigger lever handle and rotate so that the handle is perpendicular to the valve. The handle can be placed anywhere along this 90 degree arc depending on how much vacuum relief is needed.
Note: All Vac2Go vacuum trucks are equipped with a minimum 27″ blowers. There is no automatic relief valve because the vacuum is too high for an automatic relief valve to work. If you are operating a vacuum truck that has a 15″ or 18″ blower, continue reading below for information on the automatic vacuum relief valve as well as a step by step guide on how to test the valve.
Automatic Vacuum Relief Valve (Knuckle Valve)
The automatic vacuum relief valves provide for the inlet of air when it reaches a preset vacuum level. These valves are standard on the units with 15″-18″ blowers. Depending on the unit, the number of automatic vacuum relief valves can range from two to three. In order to operate the valve manually using the remote pendant, the master switch on the main control panel must be turned on.
Testing of Vacuum Relief Valves
As a safety precaution, the automatic vacuum relief valve should be tested every day before operation to ensure it is operating properly. The following steps should be followed:
- Start the truck engine and engage the hydraulics.
- Allow the engine to reach 1500 rpm.
- Raise the debris body approximately two feet.
- Open the manual relief valve.
- Place a sturdy board on the opening of the microstrainer. It should be large enough to cover the entire opening of the microstrainer.
- Slowly close the manual relief valve until a whistling or clattering sound is heard coming from the vacuum relief valves.
- Check the vacuum relief gauge on the master control panel. It should be 1″ or less below the vacuum rating of the pump.
- If it is not 1″ or less, or the valve fails to open, the valve should be preset or replaced.
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