Measuring Devices (Miscellaneous)

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Dairy Manometer | Hydrometer | General References

Dairy Manometers

Description: Milking systems used on dairy farms have vacuum lines that remove and transport the milk from cows' udders to bulk cooling tanks. Vacuum gauges, or dairy manometers, are an important part of the milking system and are used to measure the pressure in the vacuum line. The mercury dairy manometer is one type of gauge that has been used in milking systems. Mercury dairy manometers are usually a U-shaped tube containing about 12 ounces of liquid elemental mercury. One end of the tube is connected directly to the milking pipeline by a vacuum hose. The other end of the U-tube is open to the atmosphere so that when the pump is running the farmer reads the height difference between the two columns of mercury.

Purpose of the Mercury: The mercury level in a dairy manometer rises or falls in response to vacuum changes in the milking system. The vacuum pressure is important to maintain for the optimum

Click image for a larger view Source: Cuoco & Cormier Engineering Associates Inc., (mercury dairy manometer)

operation of the milking process and must be accurately measured - less vacuum leads to longer milking time and greater energy consumption; a high vacuum leads to mastitis among the dairy cattle. The vacuum pressure in a mercury-added dairy manometer is read from the side of the mercury-containing tube. Non-mercury manometers display the vacuum pressure on a dial or a digital display.

Potential Hazards: Even with proper use, continuous releases of mercury occur as the mercury vaporizes from the end of the open U-tube manometer to the atmosphere. Mercury spills may also occur during routine servicing of the mercury in the manometer. During servicing, the manometers are often emptied and filled with new mercury. Farmers that do this on-site end up with a lot of elemental mercury waste that must be disposed of as hazardous waste and/or recycled.

The large amount of mercury contained in dairy manometers, combined with the fact that they often have an "open-system" (one end of the U-tube containing the mercury is open), creates a high potential for a mercury release or spill. Such a spill would present a significant risk of exposure as well as extensive cleanup costs. Spills greater than one pound of elemental mercury (about two tablespoons) must be reported to the appropriate state environmental agency. Persons that have been exposed to a mercury spill should contact the public health department or poison control center.

Recycling/Disposal: Because of the amount of mercury in dairy manometers, they are prohibited from being disposed of in landfills and must be managed as hazardous waste. Some states, including Connecticut, Maine, Massachusetts, Minnesota, New Hampshire, New York, Vermont, and local municipalities have offered a mercury collection program specifically for farmers to dispose of their old mercury dairy manometers.

When replacing an old mercury-containing dairy manometer, farmers should also check with the vendors to see if they will accept the old manometer when they install the new mercury-free gauge. Licensed hazardous waste professionals should collect, transport, and recycle mercury from the manometers. The mercury collected from the dairy manometers should be sent to a reclamation facility for recycling.

Statutes and Other Information: Many states, including Connecticut, Louisiana, Maine, Minnesota, Rhode Island, and Vermont, have phased-out the sale and distribution of mercury dairy manometers. Minnesota also banned the use of mercury dairy manometers and required all mercury manometers to be removed from service in 2000. Other states, including California, Illinois, Massachusetts, and New York prohibit the sale of mercury-containing measuring devices, including dairy manometers. These states, however, do allow manufacturers to apply for an exemption, which, if approved, would allow them to sell these products in the state after the effective phase-out date.

Other states have focused on outreach and education programs for dairy farms that encourage the proper disposal of mercury manometers and the use of non-mercury devices, such as bourbon gauges, aneroid, electronic, or digital manometers. Some state and local agencies have even initiated specific collection programs for ensuring proper disposal of mercury dairy manometers, and many include an exchange program, where farmers can exchange their old mercury dairy manometer for a non-mercury replacement device.

Links to these specific outreach and education programs and other useful information can be found in the "General References" section at the bottom of the page.

Related Link:
http://www.epa.state.oh.us/opp/manometer_web.pdf

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Hydrometers

Description: A hydrometer is an instrument used to measure the specific gravity of a liquid - the ratio of the density of the liquid to the density of water. Hydrometers are often used in cooking, especially in beer and wine making. They are typically made of glass and consist of a cylindrical stem and weighted bulb, which makes the device float upright in the liquid solution. Historically, elemental mercury was used in hydrometers as a weight. The amount of mercury was small - often less than one gram, depending on the size of the instrument. Non-mercury hydrometers that use lead ballast for the weight are now used.

Click image for a larger view Source: NEWMOA, (mercury hydrometer – bulb shape)

Hydrometers are also used in laboratories and in school science classrooms to measure soil particle size distribution in a soil suspension. Non-mercury soil hydrometers are available that use lead for the ballast.

Purpose of the Mercury: The mercury was used in hydrometers as a weight so that the device would be buoyant in a liquid solution. For example, a hydrometer is used when making wine because it floats to a certain height depending on the amount of sugar in the wine - the more sugar in the wine, the denser the liquid and the higher the hydrometer "floats." As the wine ferments, and the yeast turns the sugar into alcohol, the wine becomes less dense and the hydrometer "sinks" or floats lower. Using a hydrometer allows the winemaker to monitor the progress of fermentation.

Potential Hazards: Hydrometers are usually made of glass, making a mercury hydrometer susceptible to breakage. If a leak or break occurs, persons should immediately contact their state environmental agency for instructions on proper clean-up and disposal. Persons that have been exposed to a mercury spill should contact the public health department or poison control center.

Recycling/Disposal: Mercury hydrometers must be disposed of as hazardous waste through a licensed hazardous waste facility. The mercury collected from the hydrometer will be sent to a mercury recycler for reclamation.

Click image for a larger view Source: NEWMOA, (mercury hydrometer)

Statutes and Other Information: Depending on the amount of mercury in the hydrometer (greater than 10 milligrams), this product may be subject to sales restrictions in certain states, including Connecticut, Louisiana, and Rhode Island. Other states, including California, Illinois, Maine, Massachusetts, New York, and Vermont prohibit the sale of hydrometers under the category of mercury-containing measuring devices. These states do allow manufacturers to apply for an exemption, which, if approved, would allow them to sell these products in the state after the effective phase-out date. However, research indicates that mercury hydrometers are no longer produced or available for sale.

Related Links:
http://www.ec.gc.ca/MERCURY/SM/EN/sm-mcp.cfm#HD
http://www.pressedforwine.com/equipment/hydrometer.shtml

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General References

The links below are general references that provide information pertaining to all mercury-containing measuring devices:

General Information about Mercury in Measuring Devices:
http://www.newmoa.org/prevention/mercury/imerc/FactSheets/measuring_devices.pdf

Mercury Product Phase-outs, Sales Prohibitions, and Exemptions:
http://www.newmoa.org/prevention/mercury/imerc/productban.cfm
http://www.newmoa.org/prevention/mercury/imerc/phaseoutinfo.cfm

Dairy Manometer Outreach and Replacement Programs:
http://www.deq.state.mi.us/documents/deq-ead-p2-mercury-agmercbr.pdf
http://www.vermontagriculture.com/2001report.htm
http://www.uwex.edu/erc/pdf/hhw/manometer_summary.pdf
http://www.mntap.umn.edu/intern/projects/mano.htm
http://www.des.state.nh.us/press/archive/2006/press08042006Hg.htm

Spill Clean-up Guidance:
http://www.mass.gov/dep/toxics/stypes/spill.pdf

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