Calibrating a Type B Concrete Pressure Meter (HM-30, HM-30S)

Calibration of the Gilson Type B concrete pressure meter.
This presentation does not demonstrate the calibration of the sample chamber volume or of the calibration vessel, which must be completed before calibration of the Gilson Type B concrete pressure meter.
Once the lid assembly has been removed, our base is ready to be filled with room temperature water to begin the calibration process.
Pick up the lid assembly and thread the straight calibration tube into the only threaded hole on the underside of the lid - directly beneath the petcock.
Then place the lid assembly on top of the base and make sure there is solid contact around its circumference, assuring that the meter is airtight once the lid is clamped to the base.
Now, secure the two opposite clamps simultaneously. And Repeat until all four clamps have secured the lid to the base.
Both petcocks are now open so that water can enter and exit the bowl freely without trapping air.
To complete the filling the meter with water and expel all remaining air, fill the blue syringe with water from the water bucket and place the end of the syringe inside the petcock with the straight calibration tube attached to it.
The base is full when water flows out of the opposite petcock.
Please note that verification of the Initial Pressure line should be performed initially and performed periodically thereafter to confirm performance.
Once you’re sure the air has been removed AND the base is full of water, pump the unit up until the dial comes around to the pre-determined initial pressure reading, visible at approximately the 5 O’clock position, and then close both petcocks.
Next, make small adjustments to assure that the needle is aligned to the proper initial pressure mark, by lightly tapping the gauge body to stabilize the needle.
And if too much air is pumped into the meter, loosen the air bleeder valve cap to reduce the pressure. Be sure to tighten the valve cap before resuming.
When the gauge at the outset reads the pre-determined initial pressure, press down on the needle valve lever to inject the air into the base.
As you hold down the lever, lightly tap the gauge body again to make sure that the gauge rests on zero.
If two or more determinations show the same variation from zero percent, then the initial pressure line will have to be adjusted.
Once the initial pressure is verified, screw the bent calibration tube into the top side of the petcock that already has the short tube fixed to it, making sure that the tube opening faces down.
Now place the empty calibration vessel directly under the bent tube. Next, Open the bent calibration tube petcock and slowly press down on the needle valve lever to fill the calibration vessel completely full with water.
Once the calibration vessel is exactly full, stop the flow of water by releasing the needle valve lever. Next, Discard the water in the vessel and set it aside.
If determinations are to be made at higher air contents, then multiple calibration vessels can be removed to achieve the desired air content.
To check air meter accuracy for mixes with higher air content, repeat the filling of the calibration vessel to verify accuracy at 10% ±0.1
Now open the opposing petcock to allow water from the bent calibration tube back into the base. Once the water flows back into the base, we can open the opposite petcock, and remove the bent calibration tube and set it aside.
The air content in the sample chamber is now at the value determined by the previous calibration of the calibration vessel, nominally 5.0%.
In you case, refer to the value determined previously during the calibration of the calibration vessel for the proper air content.
Pump the unit back up to the pre-determined initial pressure mark, making sure to lightly tap the gauge body until it stabilizes and then close both petcocks.
Next press down on the needle valve lever to exhaust the air into the base, making sure to hold the lever DOWN while AGAIN lightly tapping the gauge body until the reading stabilizes.
The gauge should read plus or minus 0.1% from the correct air content as determined by the calibration of the calibration vessel. In this demonstration the value is 5%.
If two successive readings show a variation greater than 0.1% from the correct air content, you’ll have to adjust the gauge needle to read appropriately.
This adjustment is performed by unscrewing the gauge glass and using a small screwdriver to move the gauge to the proper position.
Once the adjustment is completed, reinstall the gauge glass and repeat the calibration procedure at least twice to ensure that the initial pressure line has not changed, and that the air content readings are accurate to within 0.1%.
After two successive readings confirm that the gauge reading is within 0.1% of the correct air content, then the pressure meter is properly calibrated.
Unclamp the lid assembly, remove the small calibration tube and finally remove the water from within the base.

[@jesusglopez8430]

Thanks for sharing, very Educative and Informative.

[@GilsonCompanyInc]

Our pleasure!