The Speedy Moisture Meter is a portable system
The Speedy Carbide test is a portable system for measuring the moisture content of a wide range of materials including soils, aggregates, dust and powders (and liquids). The system consists of a rugged plastic case containing a low-pressure vessel fitted with a pressure gauge and an electronic scale and ancillaries.
Moisture measurements are made by mixing a weighed sample of the material with calcium carbide reagent in the sealed pressure vessel. The reagent reacts chemically with water in the sample, producing acetylene gas that in turn increases the pressure within the vessel. As the pressure increase in the vessel is proportionate to the amount of water in the sample, the
moisture content can be read directly from the calibrated pressure gauge
What is calcium carbide
Calcium carbide has three main uses:
- The manufacture of acetylene,
- Reaction with nitrogen to give cyanamide
- The desulfurisation of hot metal, cast iron, and steel.
Steps to use Speedy Carbide test
- Clean the Speedy vessel: Prior to using the Speedy tester, ensure that the inside of the Speedy cap and vessel are
empty and clean. Use the bristle brush to remove any residues from previous tests. - Select and prepare the sample: Ensure that the sample to be weighed and placed in the Speedy is representative of the material that is under investigation. Some materials, such as free-flowing powders and sands, need no preparation, whereas others may need to be ground prior to testing.
- Weigh the sample: Place the empty measuring beaker on the electronic scale and zero the scale (refer to the electronic scale user instructions for further details). Add small amounts of material from the sample until the correct sample weight until 6g is reached.
- Add the sample to the Speedy vessel: Pour the sample into the chamber of the Speedy vessel.
- Add the reagent to the Speedy cap: Using the metal scoop, add a minimum of two full scoops of calcium carbide reagent to the Speedy cap cavity.
- Seal the Speedy: Hold the Speedy horizontally. Then swing the stirrup into position and
tighten the top screw to seal. - Mix the sample with the reagent: Hold the Speedy vertically with the pressure gauge facing the ground and shake vigorously for five seconds. Rotate the Speedy through 180° so that the pressure gauge faces the sky, tap the sides of the Speedy to ensure the sample falls into the cap cavity and prop or hold the Speedy in this position for 1-2 minutes.
- Take the reading: Hold the Speedy horizontally and at eye level and take the moisture content reading directly from the pressure gauge.
- Release the pressure: Hold the Speedy vertically with the pressure gauge facing the ground. Locate the arrow on the flange of the cap and point this away from yourself and other people in your vicinity. Unscrew the top screw slowly to vent the gas that may have been generated within the Speedy.
- Remove the sample and reagent: Tip the contents of the Speedy directly into a clean and dry open container and dispose of in accordance with Section 13 of the Calcium Carbide Material Safety Data Sheet.
- Clean the Speedy: Clean the Speedy vessel, cap and measuring beaker in preparation for the next moisture measurement.
Special Considerations for Speedy Carbide test
Use the instructions in this section to adapt your test procedures to special measuring conditions.
Applying the Proportional Test Technique
If the moisture content of the material exceeds the measurement range of the Speedy being used, then the Proportional Test Technique may be used to obtain measurements. This involves halving the normal sample weight and doubling the gauge
value. For example:
- Assume a Speedy with a measurement range of 0-20 H2O% W/W is being used to test soil with a nominal moisture content of 30%
- The sample is prepared as required and half the normal weight (i.e. 3g) is placed in the Speedy.
- The normal test procedure is followed and a gauge value of 14.7% is recorded.
- This value is then doubled to give the actual moisture content of 29.4%.
The Proportional Test Technique may also be used to obtain clearer readings in very dry material by doubling the sample size and halving the gauge value.
Compensating for Non-Standard Temperature
For optimum performance the Speedy tester and sample should be at 20°C (68°F) when used. If this is not practical, take at least three tests in quick succession to equilibrate temperatures as much as possible. Ignore the first and second test results and record the later results.
Establishing Correction Factors
When compared with oven test results, Speedy readings may be low if the material under investigation contains volatile components other than water, as these may evaporate with the water at elevated temperatures. Correction factors for given materials can be established by plotting graphs of Speedy test results against oven test results.
Measuring Moisture Content in Liquids
Speedy testers may be used to measure the moisture content of certain liquids (most commonly oils) by adapting the test
procedure as follows:
- Weigh the liquid sample as in the standard procedure.
- Place the liquid in a clean mixing vessel and add two to four scoops of dry sand. Mix the contents thoroughly and place the
mixture in the Speedy vessel. - Continue with the test as detailed in the standard Moisture Test Procedure.
Converting Wet Weight to Dry Weight
The pressure gauges used with the Speedy testers are calibrated to give the moisture content expressed as a percentage of the sample’s wet weight. If required, the measured value (MWW) can be expressed as a percentage of the sample’s dry weight (MDW) by using the following formula:
100 x MWW
MDW = 100 – MWW
