The pressure gauge has been calibrated to plus or minus ¼ psi (mid-range) and the thermometer tested to plus or minus ¼ degree prior to shipment of the instrument. If after a period of use there is a question of gauge and thermometer accuracy, the following checks should be performed on the unit:
- The gauge should be checked and calibrated using the Zahm & Nagel tester (series 8000), a “dead weight” tester or a digital test gauge. The most accurate range of the gauge is the midrange, and the gauge should be calibrated to this area. The needle can be re-set by removing the face cover and inserting a small screwdriver into the slotted brass screw located at the 5 o’clock position of the gauge. Turn the screwdriver clockwise or counterclockwise to match the pressure established on the gauge tester or dead weight tester. A “zero zone” is located on the gauge face and the needle may occupy any place in this zone and still be in calibration-do not attempt to calibrate the gauge back to this zone.
- The thermometer liquid column may become separated due to rough handling and may be rejoined as per enclosed instruction sheet-“separated columns.” If the thermometer is broken please refer to replacement instructions sent with the instrument.
- The piston (1005) may become stuck in the piston body (1006)-if this condition occurs, unlock the piston locking pin (1008) open the inlet valve (1020-B) and pull the piston out to full open position. Apply a small amount of “o” ring lubricant to the piston and work the piston up and down to lubricate the internal “o” ring (1009) located inside the piston body. This should be done at frequent intervals as part of the routine maintenance of the instrument.
Warning: Operator must wear eye protection while operating this instrument.
Note: Before operating, cool the volume meter to the approximate temperature of the beer being tested.
- Close the lower inlet valve (1020-B) and lock the expansion piston (1005) in the “in” position.
- Open the top vent valve (1020-B) and establish counter pressure with aspirator bulb (1042) (or other convenient pressure source) up to the approximate counter pressure plus hydrostatic head pressure existing in the tank to be sampled and then close the top vent valve. (1020-B)
- Attach the volume meter to the trycock of the tank by opening the clamping device screw (1024) and sliding the clamping device yoke (1023) over the boss of the trycock. Turn the clamping device screw clockwise so that the clamping device gasket (1025) makes a tight seal between the try cock and clamping device assembly (1021).
- Open the inlet valve (1020-B) and then fully open the trycock.
- When the gauge pressure is steady, remove the aspirator bulb (1042) and partially open the top vent valve (1020-B) so that the pressure on the gauge drops about 1 psi. Allow the volume meter to fill until beer overflows at the gooseneck (1045).
- Fully open the vent valve (1020-B) so as to allow the beer flow to sweep out any air bubbles
- Close the inlet valve, vent valve and the trycock. Remove the volume meter from the trycock on the tank.
- Partially open the vent valve (1020-B) to reduce the false pressure reading and allow the gauge pressure to drop to approximately the equilibrium pressure expected in the test, and then close the vent valve (1020-B)
- Turn the piston handle (1007) counterclockwise to the release position. Do not pull the handle out but allow the bottle pressure to force the piston out as the sample is shaken. Pulling the handle out will result in damage to the gauge.
- Vigorously shake the volume meter until equilibrium temperature and pressure is established and record the readings. Refer to the chart accompanying the instrument for the corresponding gas volumes. Equilibrium is achieved when, after shaking, the temperature and pressure remain constant. Do not allow your hands to touch the metal body of the volume meter when shaking as this will cause a rise in temperature of the beer. Hold the volume meter by the handles-if the volume meter is not equipped with handles hold it by the base shield (1003) and the neck shield (1004a).
Note: the volume meter chart (1049) gives solubility of CO² gas in average beer, and will be found to give lower readings than charts based on solubility in water.