How do you measure the water pressure in a pipe?
pressure as it is usually measured in pounds per square inch (psi)can also be measured in feet (head0; for water with density of 62.4pcf, 1ft of head = 0.43psi so if you fix a hose into a faucet opened at full throttle, lift the hose vertically until you can no longer see water coming out, the height measure from the faucet to the tip of the hose is the equivalent pressure. however, you will need a hose 23 feet long if you expect a pressure of 10psi. since pressure is directly proportional to velocity, which means the higher the pressure is, the greater should the velocity be, and the greater the velocity is, the higher it can push water up in the air. so if you adjust a faucet facing horizontally and open it at full throttle, then you can measure the distance from the faucet to the point in the ground where water hits. if you do this again at a later time when you think there is substantial difference in pressure, the difference in the distance measurement will prove which time has lesser or greater pressure. though the measured distance does not register the actual pressure.
Is it possible to use another liquid instead of mercury in measuring pressure?
Sure, mm H2O is a widely used measure of pressure. H2O is the chemical name for water. Being a lot less dense than mercury, the equivalent head is much higher. The handy thing is that it tells that the height of the water column gives you the underwater pressure at that depth. It can also be given as meters of H2O or inches of H2O or feet of H2O.e.g. 100 feet H2O is the near equivalent of pressure 100 feet underwater (good for fresh, off a couple of percent for salt water)But you can use any liquid that’s not too viscous (thick).
If a pressure gauge is installed downstream a centrifugal pump, will it measure static head or total dynamic head which is indicated on the pump curve?
TDH is the pressure difference between the outlet and the inlet of the pump expressed as a head (equivalent depth of water). A differential pressure gauge connected between the inlet and the outlet would measure TDH.If you connected a typical pressure gauge to the outlet, it would measure the pressure difference between the outlet and the surrounding atmospheric air pressure. If the inlet is sucking in from atmospheric pressure, then that gauge would read TDH. But it’s quite possible that the inlet is at some other pressure. If you have two regular gauges connected to the outlet and inlet, and if both were measuring pressure relative to the surrounding air pressure, then you could subtract their two readings to get TDH.Similarly, if both gauges were measuring absolute pressure (with the reference being a vacuum instead of the surrounding air), you could take their difference and get TDH.If the outlet of the piping connected to the outlet of the pump were discharging water at some point where the pressure is equal to atmospheric pressure (an open tank, for instance), then a normal gauge connected to the outlet of the pump would be measuring the sum of the static lift head (the height from the pump outlet to the piping outlet) PLUS the frictional losses in the outlet piping.So the answer to your question depends on what kind of gauge(s) you are using and whether in the inlet or outlet are operating at atmospheric pressure.
What is pressure head?
Suppose you have a glass cylinder, you put it upright and it’s closed at the bottom and open at the top. Then you pour some water in it. This water column will apply some pressure at the base of the tube. This pressure’s corresponding height (i.e. height of water column in our case) is called pressure head.It is to be noted that it doesn’t matter whether you use a cylinder of 1 km diameter or a cylinder of 2 cm diameter; in both cases, for same heights of water columns (that is, for same pressure heads), you will have same magnitude of pressure acting at the base of the cylinder.
How calculate pressure from u-tube manometer ?
1) Pressure is equivalent to the height of water. 2) greater height difference is greater pressure difference across the manometer. Also vice versa. 3) Definition of a pascal is 1 newton per square meter. Consider a volume of water one meter cubed. If this has a mass of 1000kg, that is on a surface area of 1 square meter, and gravity is 9.81m/s/s. The force is mass * g. The pressure is (1000kg * 9.81m/s/s) / 1 square meter = 9810 pascals. Thus a 1m head of water represents 9810 pascals, and 0.23m is 9810 * 0.23 = 2256Pa. The actual conversion factor is just more accurate, and is taken to be 9806.65Pa per meter of water. A bar is 100,000 pascals. Towards understanding the head of water, the pressure is force per unit area, so the force on the whole area changes with changing area (e.g. tube diameter) but the pressure does not. Pressure is like the force with the area taken into account.
If we convert pump head into pressure, will it be absolute or gauge pressure?
Neither. The pump head is the differential value of pressure between the delivery and the suction sides of the pump. If there’s a water pump with pump head 10 metres, it doesn’t mean the delivery has a pressure of 10*1000*9.81 Pa (1 kg/cm^2). It means that the difference in pressure between delivery and suction sides is 1 kg/cm^2.Easing it up, in an ideal frictionless pipeline, the pump deliver the fluid to a height of 10 metres from the level of the suction. If there’s friction, the height which it can deliver reduce by the head loss due to friction which is calculated from the pressure losses due to friction.“If there’s a water pump with pump head..”-Why pumps are specified with head and not pressure?
What is normal atmospheric pressure at sea level?
Atmospheric pressure at sea level is approximately 100,000 pascals (101,325 Pa by definition.) Air pressure is usually measured in hectopascals (hPa), the hecto prefix corrsponding to 100 (a hecatre is a square with 100m sides), so 1 atmosphere is approximately 1000 hPaA pascal is the SI unit for pressure, defined as 1 newton per square metre.Earth's gravitational acceleration on the surface is approximately 10 m/s^2, so atmospheric pressure is roughly equivalent to 10,000 kg, or 10 tonnes per square metre!Because water is about 1000 kg per cubic metre, you would need 10 cubic metres of water over 1 square metre to be equivalent to one atmosphere, which would be about 10m deep (10.34m more precisely). You can change the width and length to anything you want, but as long as you keep the depth the same, the force per unit area (the pressure) will stay the same. This means that if you dive down 10m in water, you are experiencing 1 extra atmosphere of pressure. This is also why it is physically impossible to suck water up a straw longer than 10m. As you remove the air from the straw, the pressure of the atmosphere pushes the water up to fill the partial vacuum. as you suck more air out, the vacuum gets stronger until there is no air left, and the water reaches a height of 10.3m. because there is no more air to remove, there is no way to raise the water any more without adding more pressure at the bottom.This is the basis of a pressure gauge. If you create a high tube, and remove all the air at the top, the water will be pushed up to a certain point by the atmospheric pressure. If you change the pressure at the bottom, the level of the water wil change. If a low pressure storm goes over, there is less pressure pushing the water up the tube, so the water level will drop. If a nice high passes over, there will be more pressure, so the water level will rise. It is possible to do this with any liquid, and it is preferable to use a more dense liquid for convenience, because 10m is fairly large! Mercury is about 13.5 times as dense as water, so you would only need 1/13.5 times the depth to create the same pressure. This is about 760mm, or 30 inches. This is where the term 'inches of mercury' comes from.
Air Pressure: What is the difference between the units psi and psig?
For you to know the difference between these two things that measures the pressure in air, then all you need is to take note of the fact the other is greater in terms of value which is why it was differentiated. This can often be checked if you actually apply the air pressure on a tire of your car if you want to add up more air to it again. Psi means pounds per square inch, while the psig is the same, but with gage on the last part. These two are different despite of the fact that it has almost the same units due to some circumstances. If you know how to measure these two properly, then you can convert psi to psig, or vice-versa in an easy way indeed.If you want to learn how to do this propery, then take note that there is an additional amount if you want to remove the gage pressure once you want to measure it as psi. The sea level pressure is known to be exactly 14.7 psi, and that is widely used for converting the amount to psi if there is a gage that’s to be removed. For example, if you happen to have 15 psig, then the inside pressure of it will be added with 14.7 in order to get 29.7 psi. Also, if you encounter another unit called psia, then take note that this is only an indication that it’s the final result – wherein a means “absolute”. So if you encounter these, for sure you can measure it properly this time!Reference article: THE DIFFERENCE BETWEEN PSI, PSIA & PSIG
Converting and Finding Pressure Given Specific Gravity and Depth?
Pfluid = ρgh Pfluid is pressure in Pa or N/m² ρ is the density of the fluid in kg/m³ density of water at 20C = 0.998 g/cm³ = 998 kg/m³ density of seawater = 1.025 g/cm³ = 1025 kg/m³ g is the acceleration of gravity 9.8 m/s² h is the height of the fluid above the object in m Ptotal = Patmosphere + Pfluid Patmos = 1.01e5 N/m² or 101 kPa One bar is 100 kPa 13 ft = 3.96 meters density oil = 0.75 x 998 kg/m³ = 739 kg/m³ for 13 feet of water, P = (998)(9.8)(3.96) = 38730 Pascals for oil 38730 = (739)(9.8)(h) h = 5.35 m or 17.5 feet easier method: (water) ρgh = (oil) ρgh 13 = 0.75 h h = 17.3 feet
Why are SI units used for scientific measurement?
Two things:“SI” is the abbreviation for Le Système International d'Unités. This is not just the name of the system of units, it is a fact. The World has agreed upon the SI system of units. Contrary to popular belief, the SI system of units is the standard system of units everywhere including the United States of America. In the event that quantities are measured in U. S. English units or Imperial English units, those units are defined in terms of SI. There are no independent definitions of non-SI units.in the US, the vast majority of scientific measurements are supported by grants and contracts from the Federal Government. Whether or not scientific work is supported by the Federal Government, it is published in professional journals that are dominated by work that is supported by the Federal Government. We understand that SI is the International Standard system of units. However, that is not the reason that all scientific measurements use SI. The reason is that the Federal Government requires SI units for all Government proposals, grants, and contracts.