Bulletin 61

The symbols on the left side of the charts below may help you to select the hydrometers you should order. Hydrometers and thermohydrometers marked with these symbols have special ranges that avoid the need to purchase two instruments to cover the range for aviation fuels. ASTM has assigned special numbers and has officially approved them. For example, most jet fuels have an API gravity range that requires ASTM S555HL but there are some fuels that need ASTM S554HL to reach 37° API. So the new ASTM S561HL, with a range of 37-49°, covers all jet fuels. ASTM S562HL covers Avgas. Each symbol also indicates additional qualities as described below:

GTP-1857 is shown. Other models may vary in appearance.

These hydrometers are thermometers have been shortened so they will fit in Aljac JM-3001 samplers when the lid is closed. Graduated spacings remain the same as ASTM instruments but the ranges have been shortened in some cases.

GTP-3312-1GB is shown. Other models may vary in appearance.

Graduated to 0.01, 320mm length. No thermometers are included.

Any of the hydrometers in this brochure may be furnished with a NIST Traceable Certificate of Calibration at extra cost, upon request. This certificate shows actual data at three test points as required by ASTM E-100 (for hydrometers) or the test points required by ASTM E-1 (for thermometers). Actual readings are resolved to 1/10 of the smallest scale division. The test methods and NIST standards that are used, as well as uncertainties of measurement and all other necessary data to maintain full traceability are provided.

This calibration is performed by an independent calibration laboratory which is accredited to the international standard ISO/IEC 17025. Copies of the laboratory’s ISO 17025 Accreditation are available upon request for your qualified vendor files. To order this certificate, add the suffix “C” to our GTP number. There is an additional charge for this service.

These circular calculators eliminate the need for books of tables for making gravity or density corrections to standard temperature. Easy to use and very fast – about half a minute.

There are two methods that you can use. The best way is by cooling. The more difficult way is by using heat. The object of both methods is to get the broken pieces of mercury into a chamber where they can rejoin. The bulb at the bottom is large enough to hold all of the mercury in the capillary when it is cooled in dry ice. If there are pieces of mercury left in the capillary after cooling, carefully tap it vertically on a padded surface. Allow the thermometer to warm naturally (do not heat it) in a vertical position, and observe the mercury column as it ascends into the capillary to be certain it is intact.

If dry ice is not available, you must use heat. Thermometers and thermohydrometers that are offered by Gammon Technical are made with an “expansion chamber” at the top of the capillary tube. The purpose of this chamber is to provide over-range protection in case the thermometer is heated beyond its scale range. This chamber may be used to rejoin separations provided that the amount of separated mercury is very small (not more than a few scale divisions in length). The thermometer should be heated in water that is warmed only slightly higher than its maximum reading. The objective is to apply only enough heat to urge the broken pieces of mercury into the expansion chamber, followed by a small portion of the main (intact) column. DO NOT USE FLAME! Great care must be taken to not fill the expansion chamber more than halfway, because the developed pressure can break the glass. Remove the thermometer from the heat, maintain it in a vertical position, and observe the mercury column as it retreats into the capillary to be sure it is intact.