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64-514: Gold was first discovered in the area in 1866, but no mining took place until the 1870s when the area became known as the Moose River Gold District. Interest waned in the early 1900s but resumed in the 1930s and the mine was brought back into production in 1935. These historic workings produced some 26,000 troy ounces (810 kg) of gold, which was largely taken from quartz veins, but some also from open slate quarries. On April 12, 1936,

128-458: A geotechnical investigation or environmental site assessment (a so-called Phase II ESA). This includes holes advanced to collect soil samples, water samples or rock cores, to advance in situ sampling equipment, or to install monitoring wells or piezometers . Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants. Typically,

192-444: A geotechnical investigation , environmental site assessment , mineral exploration , temperature measurement, as a pilot hole for installing piers or underground utilities, for geothermal installations, or for underground storage of unwanted substances, e.g. in carbon capture and storage . Engineers and environmental consultants use the term borehole to collectively describe all of the various types of holes drilled as part of

256-442: A borehole used as a water well is completed by installing a vertical pipe (casing) and well screen to keep the borehole from caving. This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment. Oil and natural gas wells are completed in a similar, albeit usually more complex, manner. As detailed in proxy (climate) , borehole temperature measurements at

320-447: A bowl of mercury and raise the closed end up out of it, keeping the open end submerged. The weight of the mercury would pull it down, leaving a partial vacuum at the far end. This validated his belief that air/gas has mass, creating pressure on things around it. Previously, the more popular conclusion, even for Galileo , was that air was weightless and it is vacuum that provided force, as in a siphon. The discovery helped bring Torricelli to

384-530: A car drives up a mountain, the (gauge) tire pressure goes up because atmospheric pressure goes down. The absolute pressure in the tire is essentially unchanged. Using atmospheric pressure as reference is usually signified by a "g" for gauge after the pressure unit, e.g. 70 psig, which means that the pressure measured is the total pressure minus atmospheric pressure . There are two types of gauge reference pressure: vented gauge (vg) and sealed gauge (sg). A vented-gauge pressure transmitter , for example, allows

448-404: A column of fluid of height h and density ρ is given by the hydrostatic pressure equation, P = hgρ . Therefore, the pressure difference between the applied pressure P a and the reference pressure P 0 in a U-tube manometer can be found by solving P a − P 0 = hgρ . In other words, the pressure on either end of the liquid (shown in blue in the figure) must be balanced (since

512-472: A depth of a particular fluid ( e.g., inches of water). Manometric measurement is the subject of pressure head calculations. The most common choices for a manometer's fluid are mercury (Hg) and water; water is nontoxic and readily available, while mercury's density allows for a shorter column (and so a smaller manometer) to measure a given pressure. The abbreviation "W.C." or the words "water column" are often printed on gauges and measurements that use water for

576-405: A depth of several kilometers. Hydrostatic gauges (such as the mercury column manometer) compare pressure to the hydrostatic force per unit area at the base of a column of fluid. Hydrostatic gauge measurements are independent of the type of gas being measured, and can be designed to have a very linear calibration. They have poor dynamic response. Piston-type gauges counterbalance the pressure of

640-539: A few to several hundred boreholes, and in practice, depths have ranged from 50 to 300 metres (150 to 1,000 ft). Borehole drilling has a long history. By at least the Han dynasty (202 BC – 220 AD), the Chinese used deep borehole drilling for mining and other projects. The British sinologist and historian Michael Loewe states that borehole sites could reach as deep as 600 metres (2,000 ft). K.S. Tom describes

704-505: A fluid exists in a closed system , gauge pressure measurement prevails. Pressure instruments connected to the system will indicate pressures relative to the current atmospheric pressure. The situation changes when extreme vacuum pressures are measured, then absolute pressures are typically used instead and measuring instruments used will be different. Differential pressures are commonly used in industrial process systems. Differential pressure gauges have two inlet ports, each connected to one of

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768-419: A fluid with a spring (for example tire-pressure gauges of comparatively low accuracy) or a solid weight, in which case it is known as a deadweight tester and may be used for calibration of other gauges. Liquid-column gauges consist of a column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight (a force applied due to gravity) is in equilibrium with

832-426: A gas, and felt that this applied even to solid matter. More condensed air made colder, heavier objects, and expanded air made lighter, hotter objects. This was akin to how gases really do become less dense when warmer, more dense when cooler. In the 17th century, Evangelista Torricelli conducted experiments with mercury that allowed him to measure the presence of air. He would dip a glass tube, closed at one end, into

896-400: A gauge pressure. Atmospheric pressures are usually stated using hectopascal (hPa), kilopascal (kPa), millibar (mbar) or atmospheres ( atm ). In American and Canadian engineering, stress is often measured in kip . Stress is not a true pressure since it is not scalar . In the cgs system the unit of pressure was the barye (ba), equal to 1 dyn·cm . In the mts system, the unit of pressure

960-433: A highly linear calibration. They have poor dynamic response because the fluid in the column may react slowly to a pressure change. When measuring vacuum, the working liquid may evaporate and contaminate the vacuum if its vapor pressure is too high. When measuring liquid pressure, a loop filled with gas or a light fluid can isolate the liquids to prevent them from mixing, but this can be unnecessary, for example, when mercury

1024-461: A negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 4 inHg, calculated as 30 inHg (typical atmospheric pressure) − 26 inHg (gauge pressure). Atmospheric pressure is typically about 100  kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when

1088-463: A particular pressure. For example, a water pump can be controlled by a pressure switch so that it starts when water is released from the system, reducing the pressure in a reservoir. Pressure range, sensitivity, dynamic response and cost all vary by several orders of magnitude from one instrument design to the next. The oldest type is the liquid column (a vertical tube filled with mercury) manometer invented by Evangelista Torricelli in 1643. The U-Tube

1152-484: A series of different depths can be effectively " inverted " (a mathematical formula to solve a matrix equation) to help estimate historic surface temperatures. Clusters of small-diameter boreholes equipped with heat exchangers made of plastic PEX pipe can be used to store heat or cold between opposing seasons in a mass of native rock. The technique is called seasonal thermal energy storage . Media that can be used for this technique ranges from gravel to bedrock. There can be

1216-450: A vacuum or to some other specific reference. When distinguishing between these zero references, the following terms are used: The zero reference in use is usually implied by context, and these words are added only when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures , deep vacuum pressures, and altimeter pressures must be absolute. For most working fluids where

1280-421: Is a mechanical device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is used to measure pressures lower than the ambient atmospheric pressure , which is set as the zero point, in negative values (for instance, −1 bar or −760  mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading

1344-435: Is also a category of pressure sensors that are designed to measure in a dynamic mode for capturing very high speed changes in pressure. Example applications for this type of sensor would be in the measuring of combustion pressure in an engine cylinder or in a gas turbine. These sensors are commonly manufactured out of piezoelectric materials such as quartz. Some pressure sensors are pressure switches , which turn on or off at

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1408-461: Is always changing and the reference in this case is fixed at 1 bar. To produce an absolute pressure sensor , the manufacturer seals a high vacuum behind the sensing diaphragm. If the process-pressure connection of an absolute-pressure transmitter is open to the air, it will read the actual barometric pressure . A sealed pressure sensor is similar to a gauge pressure sensor except that it measures pressure relative to some fixed pressure rather than

1472-489: Is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer ; it generates a signal as a function of the pressure imposed. Pressure sensors can vary drastically in technology, design, performance, application suitability and cost. A conservative estimate would be that there may be over 50 technologies and at least 300 companies making pressure sensors worldwide. There

1536-560: Is defined as equal to one tenth of a bar. The unit used in the US is the foot sea water (fsw), based on standard gravity and a sea-water density of 64 lb/ft . According to the US Navy Diving Manual, one fsw equals 0.30643 msw, 0.030 643   bar , or 0.444 44   psi , though elsewhere it states that 33 fsw is 14.7 psi (one atmosphere), which gives one fsw equal to about 0.445 psi. The msw and fsw are

1600-451: Is desired, except when measuring differential pressure of a fluid (for example, across an orifice plate or venturi), in which case the density ρ should be corrected by subtracting the density of the fluid being measured. Although any fluid can be used, mercury is preferred for its high density (13.534 g/cm ) and low vapour pressure . Its convex meniscus is advantageous since this means there will be no pressure errors from wetting

1664-408: Is measured in millimetres of mercury (see torr ) in most of the world, central venous pressure and lung pressures in centimeters of water are still common, as in settings for CPAP machines. Natural gas pipeline pressures are measured in inches of water , expressed as "inches W.C." Underwater divers use manometric units: the ambient pressure is measured in units of metres sea water (msw) which

1728-457: Is neither gauge nor absolute; it is a differential pressure. While static gauge pressure is of primary importance to determining net loads on pipe walls, dynamic pressure is used to measure flow rates and airspeed. Dynamic pressure can be measured by taking the differential pressure between instruments parallel and perpendicular to the flow. Pitot-static tubes , for example perform this measurement on airplanes to determine airspeed. The presence of

1792-589: Is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very low pressures, a gauge that uses total vacuum as the zero point reference must be used, giving pressure reading as an absolute pressure. Other methods of pressure measurement involve sensors that can transmit the pressure reading to a remote indicator or control system ( telemetry ). Everyday pressure measurements, such as for vehicle tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to

1856-480: Is still in widespread use in the US and Canada, for measuring, for instance, tire pressure. A letter is often appended to the psi unit to indicate the measurement's zero reference; psia for absolute, psig for gauge, psid for differential, although this practice is discouraged by the NIST . Because pressure was once commonly measured by its ability to displace a column of liquid in a manometer, pressures are often expressed as

1920-434: Is the measurement of an applied force by a fluid ( liquid or gas ) on a surface. Pressure is typically measured in units of force per unit of surface area . Many techniques have been developed for the measurement of pressure and vacuum . Instruments used to measure and display pressure mechanically are called pressure gauges, vacuum gauges or compound gauges (vacuum & pressure). The widely used Bourdon gauge

1984-480: Is used as the manometer fluid to measure differential pressure of a fluid such as water. Simple hydrostatic gauges can measure pressures ranging from a few torrs (a few 100 Pa) to a few atmospheres (approximately 1 000 000  Pa ). A single-limb liquid-column manometer has a larger reservoir instead of one side of the U-tube and has a scale beside the narrower column. The column may be inclined to further amplify

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2048-431: Is very similar, except that atmospheric pressure is sealed on the negative side of the diaphragm. This is usually adopted on high pressure ranges, such as hydraulics , where atmospheric pressure changes will have a negligible effect on the accuracy of the reading, so venting is not necessary. This also allows some manufacturers to provide secondary pressure containment as an extra precaution for pressure equipment safety if

2112-593: The Russian island Sakhalin . The Chayvo Z-44 extended-reach well took the title of the world's longest borehole on 27 August 2012. Z-44's total measured depth is 12,376 metres (40,604 ft). However, ERD wells are more shallow than the Kola Borehole, owing to a large horizontal displacement. In July 2023, China began drilling deep boreholes, one at the Sichuan Basin expected to reach 10,520 metres (34,510 ft) into

2176-462: The Touquoy zone, after a former mine owned by Damas Touquoy. DDV Gold Ltd. applied to operate an open pit gold mine in 2007. Deposits at the project named Touquoy hold an estimated 635,000 troy ounces (19.8 t) of gold, worth $ 700 million in 2012. The surface operation will involve drilling, blasting, and gold cyanidation to process the ore. The Moose River Gold Mines site will also process ore from

2240-415: The ambient atmospheric pressure (which varies according to the location and the weather). For much of human history, the pressure of gases like air was ignored, denied, or taken for granted, but as early as the 6th century BC, Greek philosopher Anaximenes of Miletus claimed that all things are made of air that is simply changed by varying levels of pressure. He could observe water evaporating, changing to

2304-407: The atmospheric pressure. Both mm of mercury and inches of water are common pressure heads, which can be converted to S.I. units of pressure using unit conversion and the above formulas. If the fluid being measured is significantly dense, hydrostatic corrections may have to be made for the height between the moving surface of the manometer working fluid and the location where the pressure measurement

2368-414: The borehole is lined with materials like bricks, stones, or concrete rings. This reinforcement maintains the integrity of the borehole's structure and helps to prevent contamination. A concrete platform or slab may be installed at the bottom to prevent sediment from entering the water. The top of the borehole is capped to protect it from debris and contamination. Piezometer Pressure measurement

2432-440: The burst pressure of the primary pressure sensing diaphragm is exceeded. There is another way of creating a sealed gauge reference, and this is to seal a high vacuum on the reverse side of the sensing diaphragm. Then the output signal is offset, so the pressure sensor reads close to zero when measuring atmospheric pressure. A sealed gauge reference pressure transducer will never read exactly zero because atmospheric pressure

2496-426: The company's mine at its Beaver Dam deposit, 37 km away, which has an estimated yield of 426,600 troy ounces (13.27 t). This will save the construction of a second tailings pond, and an old bush road will be upgraded to facilitate transport. The Moose River mine will have a life of five years and Beaver Dam just three. There are more deposits at Cochrane Hill and Fifteen Mile Stream, 57 km away. Despite

2560-629: The composition of the gas, since the interpretation relies on the sample compressing as an ideal gas . Due to the compression process, the McLeod gauge completely ignores partial pressures from non-ideal vapors that condense, such as pump oils, mercury, and even water if compressed enough. 0.1 mPa is the lowest direct measurement of pressure that is possible with current technology. Other vacuum gauges can measure lower pressures, but only indirectly by measurement of other pressure-dependent properties. These indirect measurements must be calibrated to SI units by

2624-400: The conclusion: We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight. This test, known as Torricelli's experiment , was essentially the first documented pressure gauge. Blaise Pascal went further, having his brother-in-law try the experiment at different altitudes on a mountain, and finding indeed that the farther down in

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2688-428: The controversy of land expropriation, production is expected to begin in 2015 or 2016. Borehole A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well ), other liquids (such as petroleum ), or gases (such as natural gas ). It may also be part of

2752-502: The conventional units for measurement of diver pressure exposure used in decompression tables and the unit of calibration for pneumofathometers and hyperbaric chamber pressure gauges . Both msw and fsw are measured relative to normal atmospheric pressure. In vacuum systems, the units torr (millimeter of mercury), micron (micrometer of mercury), and inch of mercury ( inHg ) are most commonly used. Torr and micron usually indicates an absolute pressure, while inHg usually indicates

2816-575: The course of fifty-six hours, and was picked up by the BBC and broadcast to Europe . It was the first live 24-hour radio coverage of a breaking news story in Canada. The following year a Hollywood movie, Draegerman Courage , was made about the events in Moose River and cave-in at the mine, trapping three men. The 'Draegerman' that the title refers to is a man whose job it is to clean up cave-ins in mines and rescue

2880-597: The drilling process: "The Chinese method of deep drilling was accomplished by a team of men jumping on and off a beam to impact the drilling bit while the boring tool was rotated by buffalo and oxen." This was the same method used for extracting petroleum in California during the 1860s (i.e. "kicking her down"). A Western Han dynasty bronze foundry discovered in Xinglong, Hebei had nearby mining shafts which reached depths of 100 metres (330 ft) with spacious mining areas;

2944-425: The drilling rig. Especially in developing countries many boreholes are stull dug by hand. The digging begins with manual labor using basic tools such as shovels, picks, and crowbars. Workers excavate the soil layer by layer, often using a circular motion to create a well-shaped hole. The process is slow and demanding, requiring teamwork and coordination. To prevent the walls from collapsing and to ensure water quality,

3008-415: The flow direction, while having little impact on surfaces parallel to the flow direction. This directional component of pressure in a moving (dynamic) fluid is called dynamic pressure . An instrument facing the flow direction measures the sum of the static and dynamic pressures; this measurement is called the total pressure or stagnation pressure . Since dynamic pressure is referenced to static pressure, it

3072-418: The glass, though under exceptionally clean circumstances, the mercury will stick to glass and the barometer may become stuck (the mercury can sustain a negative absolute pressure ) even under a strong vacuum. For low pressure differences, light oil or water are commonly used (the latter giving rise to units of measurement such as inches water gauge and millimetres H 2 O ). Liquid-column pressure gauges have

3136-470: The ground and the other at the Tarim Basin with a planned depth of 11,100 metres (36,400 ft). Drillers may sink a borehole using a drilling rig or a hand-operated rig. The machinery and techniques to advance a borehole vary considerably according to manufacturer, geological conditions, and the intended purpose. For offshore drilling floating units or platforms supported by the seafloor are used for

3200-602: The holes varied, the drilling of a single well could last nearly one full decade. It was not up until the 19th century that Europe and the West would catch up and rival ancient Chinese borehole drilling technology. For many years, the world's longest borehole was the Kola Superdeep Borehole in Russia. From 2011 until August 2012 the record was held by the 12,345-metre (40,502 ft) long Sakhalin-I Odoptu OP-11 Well, offshore

3264-403: The liquid is static), and so P a = P 0 + hgρ . In most liquid-column measurements, the result of the measurement is the height h , expressed typically in mm, cm, or inches. The h is also known as the pressure head . When expressed as a pressure head, pressure is specified in units of length and the measurement fluid must be specified. When accuracy is critical, the temperature of

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3328-410: The liquid movement. Based on the use and structure, following types of manometers are used A McLeod gauge isolates a sample of gas and compresses it in a modified mercury manometer until the pressure is a few millimetres of mercury . The technique is very slow and unsuited to continual monitoring, but is capable of good accuracy. Unlike other manometer gauges, the McLeod gauge reading is dependent on

3392-569: The manometer. Fluid density and local gravity can vary from one reading to another depending on local factors, so the height of a fluid column does not define pressure precisely. So measurements in " millimetres of mercury " or " inches of mercury " can be converted to SI units as long as attention is paid to the local factors of fluid density and gravity . Temperature fluctuations change the value of fluid density, while location can affect gravity. Although no longer preferred, these manometric units are still encountered in many fields. Blood pressure

3456-412: The measurement fluid must likewise be specified, because liquid density is a function of temperature . So, for example, pressure head might be written "742.2 mm Hg " or "4.2 in H 2 O at 59 °F" for measurements taken with mercury or water as the manometric fluid respectively. The word "gauge" or "vacuum" may be added to such a measurement to distinguish between a pressure above or below

3520-448: The measuring instrument inevitably acts to divert flow and create turbulence, so its shape is critical to accuracy and the calibration curves are often non-linear. A pressure sensor is a device for pressure measurement of gases or liquids . Pressure sensors can alternatively be called pressure transducers , pressure transmitters , pressure senders , pressure indicators , piezometers and manometers , among other names. Pressure

3584-462: The ocean of atmosphere, the higher the pressure. The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N·m or kg·m ·s ). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N·m . When indicated, the zero reference is stated in parentheses following the unit, for example 101 kPa (abs). The pound per square inch (psi)

3648-408: The outside air pressure to be exposed to the negative side of the pressure-sensing diaphragm, through a vented cable or a hole on the side of the device, so that it always measures the pressure referred to ambient barometric pressure . Thus a vented-gauge reference pressure sensor should always read zero pressure when the process pressure connection is held open to the air. A sealed gauge reference

3712-419: The pressure differential between the two ends of the tube (a force applied due to fluid pressure). A very simple version is a U-shaped tube half-full of liquid, one side of which is connected to the region of interest while the reference pressure (which might be the atmospheric pressure or a vacuum) is applied to the other. The difference in liquid levels represents the applied pressure. The pressure exerted by

3776-589: The roof of the mine collapsed, trapping three men, Herman Magill, David Robertson, and Alfred Scadding, 150 feet (46 m) down for 11 days. The men were reached by drilling a borehole on the sixth day to bring food, water and a telephone until the rescue was completed. Robertson and Scadding survived and Magill died on the seventh day. The event was broadcast by J. Frank Willis of the Canadian Radio Broadcasting Commission (CRBC) to more than 650 radio stations throughout North America over

3840-411: The shafts and rooms were complete with a timber frame, ladders and iron tools. By the first century BC, Chinese craftsmen cast iron drill bits and drillers were able to drill boreholes up to 1,500 metres (4,900 ft) deep. By the eleventh century AD, the Chinese were able to drill boreholes up to 900 metres (3,000 ft) in depth. Drilling for boreholes was time-consuming and long. As the depth of

3904-403: The survivors. Today, there is a provincial park with a cairn and there was a plaque where the borehole was drilled, and there is a museum portraying the history of the gold mine. The plaque was stolen sometime before June 28, 2006. It has yet to be recovered. In the 1980s, drilling exploration in the area of the earlier slate workings found significant gold deposits in what became known as

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3968-421: The volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings. Moderate vacuum pressure readings can be ambiguous without the proper context, as they may represent absolute pressure or gauge pressure without

4032-427: Was invented by Christiaan Huygens in 1661. There are two basic categories of analog pressure sensors: force collector and other types. A pressure sensor, a resonant quartz crystal strain gauge with a Bourdon tube force collector, is the critical sensor of DART . DART detects tsunami waves from the bottom of the open ocean. It has a pressure resolution of approximately 1mm of water when measuring pressure at

4096-567: Was the pieze , equal to 1 sthene per square metre. Many other hybrid units are used such as mmHg/cm or grams-force/cm (sometimes as kg/cm without properly identifying the force units). Using the names kilogram, gram, kilogram-force, or gram-force (or their symbols) as a unit of force is prohibited in SI; the unit of force in SI is the newton (N). Static pressure is uniform in all directions, so pressure measurements are independent of direction in an immovable (static) fluid. Flow, however, applies additional pressure on surfaces perpendicular to

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