TOTAL PRESSURE DROP IN PIPE

Calculating Pressure Drop

  The total pressure drop in the pipe is typically calculated using these five steps.  (1) Determine the total length of all horizontal and vertical straight pipe runs.  (2) Determine the number of valves and fittings in the pipe.  For example, there may be two gate valves, a 90o elbow and a flow thru tee.  (3) Determine the means of incorporating the valves and fittings into the Darcy equation.  To accomplish this, most engineers use a table of equivalent lengths.  This table lists the valve and fitting and an associated length of straight pipe of the same diameter, which will incur the same pressure loss as that valve or fitting.  For example, if a 2” 90o elbow were to produce a pressure drop of 1 psi, the equivalent length would be a length of 2” straight pipe that would also give a pressure drop of 1 psi.  The engineer then multiplies the quantity of each type of valve and fitting by its respective equivalent length and adds them together.  (4) The total equivalent length is usually added to the total straight pipe length obtained in step one to give a total pipe equivalent length.  (5) This total pipe equivalent length is then substituted for L in Equation 2 to obtain the pressure drop in the pipe.

    One of the most basic calculations performed by any process engineer, whether in design or in the plant, is line sizing and pipeline pressure loss.  Typically known are the flow rate, temperature and corresponding viscosity and specific gravity of the fluid that will flow through the pipe.  These properties are entered into a computer program or spreadsheet along with some pipe physical data (pipe schedule and roughness factor) and out pops a series of line sizes with associated Reynolds Number, velocity, friction factor and pressure drop per linear dimension.  The pipe size is then selected based on a compromise between the velocity and the pressure drop.  With the line now sized and the pressure drop per linear dimension determined, the pressure loss from the inlet to the outlet of the pipe can be calculated.

The term

To obtain pressure drop in units of psi/100 ft, the value of 100 replaces L in Equation 2.

An Example

The fluid being pumped is 94% Sulfuric Acid through a 3”, Schedule 40, Carbon Steel pipe:

63,143

70

112.47 S.G. 1.802 Viscosity, cp: 10

127 Pipe ID, in: 3.068 Velocity, fps: 3.04 Reynold's No: 12,998

0.029851.308

0.018 Straight Pipe, ft: 31.5

The most commonly used equation for determining pressure drop in a straight pipe is the Darcy Weisbach equation.  One common form of the equation which gives pressure drop in terms of feet of head { hL} is given by:

is commonly referred to as the Velocity Head.

     Another common form of the Darcy Weisbach equation that is most often used by engineers because it gives pressure drop in units of pounds per square inch (psi) is:

Mass Flow Rate, lb/hr:

Volumetric Flow Rate, gpm:

Density, lb/ft3:

Temperature, oF:

Darcy Friction Factor, (f) Pipe: Pipe Line DP/100 ft.

Friction Factor at Full Turbulence (¦t):

Fittings Quantity Total K

20 5.1 0.36 2 10.23 0.72Branch Tee 60 15.3 1.08 1 15.34 1.08Swing Check Valve 50 12.8 0.9 1 12.78 0.9Plug Valve 18 4.6 0.324 1 4.6 0.324

822.685 57.92 1 822.68 57.92TOTAL 865.633

60.944

0.412

11.734

Leq/D1 Leq2, 3 K1, 2 =¦t

(L/D)Total Leq

90o Long Radius Elbow

3” x 1” Reducer4 None5        

1. K values and Leq/D are obtained from reference 1.

2. K values and Leq are given in terms of the larger sized pipe.

3. Leq is calculated using Equation 5 above.

4. The reducer is really an expansion; the pump discharge nozzle is 1” (Schedule 80) but the connecting pipe is 3”.  In piping terms, there are no expanders, just reducers.  It is standard to specify the reducer with the larger size shown first.  The K value for the expansion is calculated as a gradual enlargement with a 30o angle. 

5. There is no L/D associated with an expansion or contraction.  The equivalent length must be back calculated from the K value using Equation 5 above. 

  Typical Equivalent

Length Method

K Value Method

Straight Pipe DP, psi Not

applicable

Total Pipe Equivalent Length DP, psi

Not Applicable

6.82811.734 7.24

Final Thoughts - K Values

Valves and Fittings DP, psi

Not applicable

Total Pipe DP, psi

     The line pressure drop is greater by about 4.5 psi (about 62%) using the typical equivalent length method (adding straight pipe length to the equivalent length of the fittings and valves and

using the pipe line fiction factor in Equation 1).

     One can argue that if the fluid is water or a hydrocarbon, the pipeline friction factor would be closer to the friction factor at full

turbulence and the error would not be so great, if at all significant; and they would be correct. However hydraulic

calculations, like all calculations, should be done in a correct and consistent manner.  If the engineer gets into the habit of

performing hydraulic calculations using fundamentally incorrect equations, he takes the risk of falling into the trap when

confronted by a pumping situation as shown above.

     Another point to consider is how the engineer treats a reducer when using the typical equivalent length method.  As we saw above, the equivalent length of the reducer had to be back-calculated using equation 5.  To do this, we had to use ¦t and K.  Why not use these for the rest of the fittings and apply the calculation correctly in the first place?

     The 1976 edition of the Crane Technical Paper No. 410 first discussed and used the two-friction factor method for calculating the total pressure drop in a piping system (¦ for straight pipe and ¦t for valves and fittings).  Since then, Hooper2

suggested a 2-K method for calculating the pressure loss contribution for valves and fittings.  His argument was that the equivalent length in pipe diameters (L/D) and K was indeed a function of Reynolds Number (at flow rates less than that obtained at fully developed turbulent flow) and the exact geometries of smaller valves and fittings.  K for a given valve or fitting is a combination of two Ks, one being the K found in CRANE Technical Paper No. 410, designated KY, and the other being defined as the K of the valve or fitting at a Reynolds Number equal to 1, designated K1.  The two are related by the following equation:

K = K1 / NRE + KY (1 + 1/D)

     The term (1+1/D) takes into account scaling between different sizes within a given valve or fitting group.  Values for K1 can be found in the reference article2 and pressure drop is then calculated using Equation 7.  For flow in the fully turbulent zone and larger size valves and fittings, K becomes consistent with that given in CRANE. 

     Darby3 expanded on the 2-K method.  He suggests adding a third K term to the mix.  Darby states that the 2-K method does not accurately represent the effect of scaling the sizes of valves and fittings.  The reader is encouraged to get a copy of this article.

     The use of the 2-K method has been around since 1981 and does not appear to have “caught” on as of yet.  Some newer commercial computer programs allow for the use of the 2-K method, but most engineers inclined to use the K method instead of the Equivalent Length method still use the procedures given in CRANE.  The latest 3-K method comes from data reported in the recent CCPS Guidlines4 and appears to be destined to become the new standard; we shall see.

Pressure losses distributed in the pipes

Determine the total length of all Determine the number of valves and fittings in the pipe.  For example, there may

Determine the means of incorporating the valves and fittings into the Darcy equation.  To accomplish this, most engineers use a table of equivalent lengths.  This table lists the valve and fitting and an associated length of straight pipe of the same diameter, which will incur the same pressure loss as that valve or fitting.  For

elbow were to produce a pressure drop of 1 psi, the equivalent length would be a length of 2” straight pipe that would also give a pressure drop of 1 psi.  The engineer then multiplies the quantity of each type of valve and fitting by its

The total equivalent length is usually added to the total straight pipe total pipe equivalent length is then substituted for L

An Example

The fluid being pumped is 94% Sulfuric Acid through a 3”, Schedule 40, Carbon Steel pipe:

The calculation of the linear pressure loss, that corresponding to the general flow in a rectilinear conduit, is given by the following general formula:

Dp = pressure loss in PaL = friction factor (a number without dimension)

p = density of water in kg/m3V = flow rate in m/sD = pipe diameter in mL = pipe length in m

The expression above shows that calculations of pressure losses rest entirely on the determination of the coefficient L.

FLUID PARAMETERS

PIPE PARAMETERS

Allowance in Equivalent Length of Pipe for Friction Loss in Valves and Threaded Fittings

3/8 1 0.6 1.5 0.3 0.2 8 1/2 2 1.2 3 0.6 0.4 15 3/4 2.5 1.5 4 0.8 0.5 20

1 3 1.8 5 0.9 0.6 254 2.4 6 1.2 0.8 355 3 7 1.5 1 45

2 7 4 10 2 1.3 558 5 12 2.5 1.6 65

3 10 6 15 3 2 8012 7 18 3.6 2.4 100

4 14 8 21 4 2.7 1255 17 10 25 5 3.3 1406 20 12 30 6 4 165

Diameter of fitting in inches

90° std. ell, ft.

45° std. ell, ft.

90° side tee, ft.

Coupling or straight run of tee,

ft.Gate valve,

feetGlobe

valve, feet

1  1/41  1/2

2  1/2

3  1/2

Absolute Pipe Roughness

micron

drawn brass 5 1.55 1.5

150 45wrought iron 150 45

400 120500 150

cast iron 850 260wood stave 600 to 3000concrete 0.3 to 3 mmriveted steel 0.9 to 9 mm

Included here is a sampling of absolute pipe roughness e data taken from Binder (1973). These values are for new pipes; aged pipes typically exhibit in rise in apparent roughness. In some cases this rise can be very significant.

Pipe Material

Absolute Roughness,

e

x 10-6 feet (unless noted)

drawn coppercommercial steelasphalted cast irongalvanized iron

0.2 to 0.9 mm1000 to

10,0003000 to 30,000

Relative pipe roughness is computed by dividing the

Example:

Friction Loss Charts

P.S.I. Per 100' Single LineHose

1" 1½" 1¾" 2½" 3" 4"U.S. GPM

30 26 4 1.5 --- --- ---60 --- 9 6 1 --- ---95 --- 22 14 2 --- ---

125 --- 38 25 3.5 1 ---150 --- 54 35 5 2 ---200 --- --- 62 8 3.5 ---250 --- --- --- 13 5 1.5

Add 5 P.S.I. Per Storey

P.S.I. Per 100' Dual Line Kpa Per 30 Meter Dual LineHose

2½"3"WI

3"Hose

65mm76mm

U.S. GPM 2½" CPL L/Min. 65mm CPL500 13 3 2 1900 90 20750 32 6 4 2850 220 40

1000 56 10 7.5 3800 390 701250 87 15 12 4750 600 100

Add 5 P.S.I. Per Siamese or Wye Add 30 Kpa Per Siamese or Wye10 P.S.I. Per Portable Monitor 70 Kpa Per Monitor

FIRE HOSE

Back to Top

Allowance in Equivalent Length of Pipe for Friction Loss in Valves and Threaded Fittings

Angle valve, feet

48

1215182228344050557080

The Reynolds number is defined is:

According to kinematics viscosity According to dynamics viscosity

(kg/m.s = One tenth of a poise = 10 poises)

Reynolds number is inversely proportional to kinematics viscosity.

Kinematics viscosity in m2/s

Loss pressure

Laminar flow (Re £ 2000)

The loss pressure is determined by the following function:

V = flow rate in m/s p = density in kg/m3d = pipe diameter in mm V =speed in m/s

v = viscosity of water in mm²/s (or centistokes) D = hydraulic diameter of the pipe in m

µ = dynamic viscosity in Pa.s (or kg/m.s)(legal System (S.I) in m²/s = 1000000 centistokes or mm²/s)

The viscosity of a fluid is a characteristic which makes it possible to determine resistance to the movement of the fluid. The higher kinematic viscosity will be and the more difficult it will be to move the fluid in the pipe.

Kinematics viscosity (v is the ratio of dynamic viscosity on the density of the fluid.

kinematics viscosity in mm²/s (or centistokes)

v = kinematics viscosity in mm²/s (or centistokes) - (legal system (S.I) in m²/s = 1000000 centistokes)

µ = viscosity dynamic of water Pa.s or (kg/m S)

p = density of water in kg/m3

In rate of laminar, the nature or the surface quality of the interior walls of the lines does not intervene in the calculation of the pressure loss.

Turbulent flow (Re > 2000)

With:

Usual value index of roughness (k) in mmNature of interior surface Index roughness K

1 Copper, lead, brass, stainless 0,001 to 0,002

2 PVC pipe 0,00153 Stainless steel 0,0154 Steel commercial pipe 0,045 à 0,095 Stretched steel 0,0156 Weld steel 0,0457 Galvanized steel 0,158 Rusted steel 0,1 to 19 New cast iron 0,25 to 0,8

10 Worn cast iron 0,8 to 1,511 Rusty cast iron 1,5 to 2,512 Sheet or asphalted cast iron 0,01 to 0,01513 Smoothed cement 0,314 Ordinary concrete 115 Coarse concrete 5

L = friction factor (a number without dimension)Re = Reynolds number

The laminar flow meets in practice only in the transport and the handling of the viscous fluids, such as the crude oil, fuel oil, oils, etc.

In the critical zone, i.e. between 2000 and 4000 Reynolds the formula of computation employed will be treated in the manner that in situation of mode of turbulent flow.

In rate of turbulent, the factor of friction is translated by the formula of Colebrook considered as that which translates best the phenomena of flow into turbulent mode.

It is noted that this formula is in implicit form; consequently search can be done only by successive approaches (iterative calculation)

L = friction factor (a number without dimension)D = pressure loss coefficient.k = index of roughness of the pipe.d = pipe diameter in mm.Re = Reynolds number.

16 Well planed wood 517 Ordinary wood 1

Influence rate of antifreeze (glycol)

Pipe dia. [d mm.] = 50Flow Rate l/min = 120

Flow velocity [m/s] = #DIV/0!Viscosity [mm^2/s] =

50 mm PVC pipe, 120 l/min

Kpa Per 30 Meter Single LineHose

25mm 38mm 44mm 65mm 76mm 100mmL/Min.

130 180 28 10 --- --- ---225 --- 60 40 7 --- ---350 --- 150 95 14 --- ---475 --- 260 170 24 7 ---570 --- 370 240 35 14 ---760 --- --- 425 55 24 ---950 --- --- --- 90 35 10

Add 30 Kpa Per Storey

Kpa Per 30 Meter Dual Line

76mm

14285085

Add 30 Kpa Per Siamese or Wye70 Kpa Per Monitor

In the case of an addition of antifreeze (glycol) to water, kinematics viscosity (into centistokes) varies in the following way:

t = temperature at 0°Ca = percentage of glycol

Pipe Head Loss Calculator

Input Data Output DataFluid Parameters

Flow rate (Q) = 100 GPM Velocity (V) = 2.52 Ft/s

0.00001216 69527.96Pipe Parameters Velocity Head (Hv) = 0.1 Ft

Inside Diameter (D) = 4.026 Inches 0.021265Length (L) = 100 Ft

0.00015 Ft 0.625 Ft

Input Data Output DataFluid Parameters

Velocity = 2.52 Ft/s Flow Rate = 100 GPM

Kinematic Viscosity = 0.00001216 Reynold's Number = 69527.96Pipe Parameters Velocity Head (Hv) = 0.1 Ft

Inside Diameter = 4.026 Inches 0.021265Length = 100 Ft

Absolute Roughness = 0.00015 Ft 0.625 Ft 1. Friction head loss calculation based on Darcy-Weisbach equation.

Common Fluid Properties

Fluid0.000019310.000016640.000012160.000008690.000011180.00002583

0.0001

0.00004783

0.0001

0.00003161NOTE:

1. Aqueous solution, concentration in volume percent.

Common Piping Material Properties

MaterialSteel and wrought iron 0.00015

Cast iron 0.00085Galvanized steel and iron 0.0005

Copper and brass 0.000005Cast iron, tar coated 0.0004

Cast iron, cement lined 0.000008Plastic 0.000005

Fiberglass 0.000017

Visit us at

The information contained on this chart has been carefully prepared and is believed to be correct.SyncroFlo makes no warranties regarding this information and is in no way responsible for loss incurred from the use of such information.

Kinematic Viscosity (v) = Ft2/s Reynold's Number (Re) =

Friction Factor2 (f) =

Specific Roughness (e) = Friction Loss1 (Hf) =

Ft2/s

Friction Factor2 =

Friction Loss1 =

2. Friction factor calculation based on approximated Colebrook equation (Swamee-Jain equation) when Re>5000.

Kinematic Viscosity, v (Ft2/s)Water, clear (32°F)Water, clear (40°F)Water, clear (60°F)Water, clear (85°F)

Saltwater, 5% (68°F)Saltwater, 25% (60°F)

Propylene Glycol, 35% (20°F)1

Propylene Glycol, 25% (40°F)1

Ethylene Glycol, 35% (20°F)1

Ethylene Glycol, 25% (40°F)1

Specific Roughness, e (Ft)

http://www.syncroflo.com/

Copyright Ó 2003, SyncroFlo, Inc.

Inputs

Answers

Wall drag and changes in height lead to pressure drops in pipe fluid flow.

To calculate the pressure drop and flowrates in a section of uniform pipe running from Point A to Point B, enter the parameters below. The pipe is assumed to be relatively straight (no sharp bends), such that changes in pressure are due mostly to elevation changes and wall friction. (The default calculation is for a smooth horizontal pipe carrying water, with answers rounded to 3 significant figures.)

Note that a positive Dz means that B is higher than A, whereas a negative Dz means that B is lower than A.

  Pressure at A (absolute):  Average fluid velocity in pipe, V:

  Pipe diameter, D:  Pipe relative roughness, e/D:

  Pipe length from A to B, L:  Elevation gain from A to B, Dz:

  Fluid density, r:  Fluid viscosity (dynamic), m:

  Reynolds Number, R: 1.00 × 105  

Select desired output units for next calculation.

  Friction Factor, f:  0.0180  

Hint: To Calculate a Flowrate

Equations used in the Calculation

  Pressure at B:  95.5  kPa  Pressure Drop:  4.50  kPa

  Volume Flowrate:  7.85  l/s  Mass Flowrate: 7.85  kg/s

You can solve for flowrate from a known pressure drop using this calculator (instead of solving for a pressure drop from a known flowrate or velocity).

Proceed by guessing the velocity and inspecting the calculated pressure drop. Refine your velocity guess until the calculated pressure drop matches your data.

Changes to inviscid, incompressible flow moving from Point A to Point B along a pipe are described by Bernoulli's equation,

where p is the pressure, V is the average fluid velocity, r is the fluid density, z is the pipe elevation above some datum, and g is the gravity acceleration constant.

Bernoulli's equation states that the total head h along a streamline (parameterized by x) remains constant. This means that velocity head can be converted into gravity head and/or pressure head (or vice-versa), such that the total head h stays constant. No energy is lost in such a flow.

For real viscous fluids, mechanical energy is converted into heat (in the viscous boundary layer along the pipe walls) and is lost from the flow. Therefore one cannot use Bernoulli's principle of conserved head (or energy) to calculate flow parameters. Still, one can keep track of this lost head by introducing another term (called viscous head) into Bernoulli's equation to get,

where D is the pipe diameter. As the flow moves down the pipe, viscous head slowly accumulates taking available head away from the pressure, gravity, and velocity heads. Still, the total head h (or energy) remains constant.

For pipe flow, we assume that the pipe diameter D stays constant. By continuity, we then know that the fluid velocity V stays constant along the pipe. With D and V constant we can integrate the viscous head equation and solve for the pressure at Point B,

where L is the pipe length between points A and B, and Dz is the change in pipe elevation (zB - zA). Note that Dz will be negative if the pipe at B is lower than at A.

The viscous head term is scaled by the pipe friction factor f. In general, f depends on the Reynolds Number R of the pipe flow, and the relative roughness e/D of the pipe wall,

The roughness measure e is the average size of the bumps on the pipe wall. The relative roughness e/D is therefore the size of the bumps compared to the diameter of the pipe. For commercial pipes this is usually a very small number. Note that perfectly smooth pipes would have a roughness of zero.

For laminar flow (R < 2000 in pipes), f can be deduced analytically. The answer is,

For turbulent flow (R > 3000 in pipes), f is determined from experimental curve fits. One such fit is provided by Colebrook,

The solutions to this equation plotted versus R make up the popular Moody Chart for pipe flow,

The calculator above first computes the Reynolds Number for the flow. It then computes the friction factor f by direct substitution (if laminar; the calculator uses the condition that R < 3000 for this determination) or by iteration using Newton-Raphson (if turbulent). The pressure drop is then calculated using the viscous head equation above. Note that the uncertainties behind the experimental curve fits place at least a 10% uncertainty on the deduced pressure drops. The engineer should be aware of this when making calculations.

Area

To convert Into Multiply by

square meters (m²) 10000

square meters (m²) square feet (ft²) 10.763911

square kilometers (km²) 0.386109

square kilometers (km²) 0.291181

square kilometers (km²) acres 247.105381

acres 640

acres square yards (yd²) 4840

acres square feet (ft²) 43560

hectares(ha) acres 2.47105381

Length

>> Unit Conversion Guide

square centimeters (cm²)

(statute) square miles (mi²)

nautical square miles (nm²)

(statute) square miles (mi²)

To convert Into Multiply by

meters (m) centimeters (cm) 100

meters (m) inches (in) 39.37008

meters (m) feet (ft) 3.28084

meters (m) yard (yd) 1.093613

kilometers (km) (statute) miles (mi) 0.621371

kilometers (km) nautical miles (nm) 0.539612

feet (ft) inches (in) 12

Mass

To convert Into Multiply by

kilograms (kg) grams (g) 1000

kilograms (kg) pounds (lb) 2.204627grams (g) ounce (oz) 0.035274

Pressure

To convert Into Multiply by

atmospheres (atm) millibar (mb) 1013.25

atmospheres (atm) feet of water (at 4°C) 33.9

atmospheres (atm) 29.92

centimeters of mercury 76kgs/cm² 1.0333

lbs/in² 14.7

tons/ft² 1.058

inches of mercury (at 0°C)

atmospheres (atm) atmospheres (atm) 

atmospheres (atm) 

atmospheres (atm) 

Speed

To convert Into Multiply by

kilometers/hour (km/h) meters/second (m/s) 0.277778

kilometers/hour (km/h) miles/hour (mi/hr) 0.6214

knots(kn) meters/second (m/s) 0.514444

Temperature

To convert Into Multiply byFahrenheit (°F)-32 Celsius (°C) 9-May

Fahrenheit (°F)+459.67 kelvin (K) 9-MayCelsius (°C)+17.7778 Fahrenheit (°F) 1.8Celsius (°C)+273.15 kelvin (K) 1

Volume

To convert Into Multiply by

cubic meters (m³) cubic centimeters (cm³) 1,000,000cubic meters (m³) cubic feet (ft³) 35.31467cubic meters (m³) U.S. gallons (gal) 264.1721liter(l) U.S. gallons (gal) 0.2641721

Plumbing Conversions

For questions and comments, please contact: Dr. L. Charles Sun, Email: Charles.Sun@noaa.gov

To Change To Multiply By

Atmospheres Pounds per square inch 14.696Atmospheres Inches of mercury 29.92Atmospheres Feet of water 34Btu/min. Foot-pounds/sec 12.96Btu/min. Horsepower 0.02356Btu/min. Watts 17.57Centimeters of mercury Atmospheres 0.01316Centimeters of mercury Feet of water 0.4461Cubic inches Cubic feet 0.00058Cubic feet Cubic inches 1728Feet of water Atmospheres 0.0295Feet of water Inches of mercury 0.8826Gallons Cubic inches 231Gallons Cubic feet 0.1337Gallons Pounds of water 8.33Gallons per min. Cubic feet sec. 0.002228Gallons per min. Cubic feet hour 8.0208Horsepower Foot-lbs/sec. 550Inches Feet 0.0833

Inches of water Pounds per square inch 0.0361Inches of mercury 0.0735

Inches of water Ounces per square inch 0.578Inches of water Ounces per square foot 5.2Inches of mercury Inches of water 13.6Inches of mercury Feet of water 1.1333

Inches of mercury Pounds per square inch 0.4914Ounces (fluid) Cubic inches 1.805

Pounds per square inch Inches of water 27.72

Feet of water 2.31

Pounds per square inch Inches of mercury 2.04

Pounds per square inch 0.0681

Inches of water 

Pounds per square inch

Atmospheres 

Length (Unit of length of S.I. = meter)

US & Imperial >>: Metric system Metric system >> US & Imperial

1 Inch (in) - US 25.40005 mm 1 millimeter (mm) 0.03937 in (US)

1 Inch (in) - Imp 25.39996 mm 1 millimeter (mm) 0.03937 in (imp)

0.3048006 m 1 meter (m) 3.28083 ft (US)

0.3047995 m 1 meter (m) 3.28083 ft (imp)

0.9144018 m 1 meter (m) 1.093611 yd (US)

0.9143984 m 1 meter (m) 1.093611 yd (imp)

1.609347 km 1 kilometer (km)

1.609341 km 1 kilometer (km)

1.853181 km 1 kilometer (km)

Surface (the unit of area of S.I. = square meter)

US & Imperial >> Metric system Metric system >> US & Imperial

1 Acre - US 0.4046873 ha 1 hectare (ha)

1 Acre - Imp 0.4046842 ha 1 hectare (ha) 2.4711 acre (imp)

0.1550 sq.in (imp)

10.7639 sq.ft (imp)

1.1960 sq.yd (imp)

0.3861 sq.mi (imp)

Volume (the unit of volume of S.I. = cubic meter)

----- -----

1 Foot (ft) = (12.in) - US

1 Foot (ft) = (12.in) - Imp

1 Yard (yd) = (3.ft) - US

1 Yard (yd) = (3.ft) - Imp

1 Mile (mi) = (1760.yd) - US

0.6213699 mi (US)

1 Mile (mi) = (1760.yd) - Imp

0.6213724 mi (imp)

1 Nautical mile (imp)

0.5396127 n.mi (imp)

2.471044 acre (US)

1 Square inch (sq in) - US 6.451626 cm2

1 Square centimeter (cm2)

0.1549997 sq. in (US)

1 Square inch (sq in) - Imp 6.451578 cm2

1 Square centimeter (cm2)

1 Square foot (sq ft) = 144 sq in - US 0.09290341 m2

1 Square meter (m2)

10.76387 sq.ft (US)

1 Square foot (sq ft) = 144 sq in - Imp 0.09290272 m2

1 Square meter (m2)

1 Square yard (sq yd) = 9 sq.ft - US 0.8361307 m2

1 Square meter (m2)

1.195985 sq.yd (US)

1 Square yard (sq yd) = 9 sq.ft - Imp 0.8361245 m2

1 Square meter (m2)

1 Square mile (sq mi) = 640 acres - US 2.589998 km2

1 Square kilometer (km2)

0.3861006 sq.mi (US)

1 Square mile (sq mi) = 640 acres - Imp 2.589979 km2

1 Square kilometer (km2)

US/imp >> Metric system

Metric system >> US/imp

Volume ----- ----- -----

16,3871 cm3

16.38698 cm3

28.31702 dm3

28.31670 dm3

----- ----- -----

33.814 fl oz

35.195 fl oz

1 Bushel (US)

1 Bushel (imp)

1 Gallon (US)

1 Gallon (imp)

1 Liquid pint (US)

1.759803 pt (imp)

Attention not to confuse mass and weight.

Specific mass = quotient of the mass of a body by its volume

US/imp >> Metric system Metric system >> US/imp

1 Cubic inch (cu in) - US

1 Cubic centimeter (cm3)

0.06102509 cu in (US)

1 Cubic inch (cu in) - Imp

1 Cubic centimeter (cm3)

0.0610241 cu in (imp)

1 Cubic foot (cu ft) - US

1 Cubic decimeter (dm3)

0.03531544 cu ft (US)

1 Cubic foot (cu ft - (Imp)

1 Cubic decimeter (dm3)

0.0353148 cu ft (imp)

1 Cubic yard (cu yd) - US 0.7645594 m3 1 Cubic meter (m3)

1.307943 cu yd (US)

1 Cubic yard (cu yd) - Imp 0.7645509 m3 1 Cubic meter (m3)

1.307957 cu yd (imp)

Measure of capacity

1 fluid ounce (fl oz) - US

29,5735 cm3 (or ml)

1 Cubic decimeter (dm3)

1 fluid ounce (fl oz) - Imp

28,4131 cm3 (or ml)

1 Cubic decimeter (dm3)

35.23829 dm3 (or litre)

1 Cubic decimeter (dm3)

0.0283782 bu (US)

36.36770 dm3 (or liter)

1 Cubic decimeter (dm3)

0.02749692 bu (imp)

3.785329 dm3 (or liter)

1 Cubic decimeter (dm3)

0.2641779 gal (US)

4.545963 dm3 (or liter)

1 Cubic decimeter (dm3)

0.2199754 gal (imp)

0.4731661 dm3 (or liter)

1 Cubic decimeter (dm3)

2.113423 liq.pt (US)

1 Pint(pt) = 20 fl oz - Imp

0.5682454 dm3 (or liter)

1 Cubic decimeter (dm3)

Mass (the unit of mass of S.I. = kilogram)

The mass (kg) is a intrinsic characteristic of the body and is measured in kilogram.

Masse spécifique ou volumique = quotient de la masse d'un corps par son volume.

Weight is a force which depends on terrestrial attraction and it is the equivalent of the mass of a body by the acceleration of gravity (9.80665 at the sea level) and is measured in Newton [ N ].

For example a man of 75 kg (it is its mass, and not its weight contrary to the current expression), has a weight of: 75 * 9.80665 = 735,5 N on the sea level.

1Grain (gr) - US 64.79892 mg 1 milligram (mg)

1Grain (gr) - Imp 64.79892 mg 1 milligram (mg)

1Ounce (oz) - US 28.34953 g 1 gram (g)

1Ounce (oz) - Imp 28.34953 g 1 gram (g)

0.4535924 kg 1 kilogram (kg)

0.4535924 kg 1 kilogram (kg)

45.35924 kg 1kilogram (kg)

1Cental (imp) 45.35924 kg 1 kilogram (kg)

1.016047 t 1 ton

1Ton (imp) 1.016047 t 1 ton

Specific Gravity

0.01543236 gr (US)

0.01543236 gr (imp)

0.03527396 oz av. (US)

0.03527396 oz av. (imp)

1Pound (Ib) = 16 oz - US

2.204622 lb av. (US)

1Pound (Ib) = 16 oz - Imp

2.204622 lb av. (imp)

1Short hundredweight(sh cwt)= 100 Ib - US

0.02204622 sh.cwt (US)

0.02204622 ctl (imp)

1Long ton (l tn) = 2240 Ib - US

0.9842064 l.tn (US)

0.9842064 tn (imp)

The density of gas, relative to air, is called specific gravity. The specific gravity of air is defined as 1. Since propane gas has a specific gravity of 1.5, propane-air mixtures have a specific gravity of greater than 1.

Design 1: (1) Determine the total length of all horizontal and vertical straight pipe runs.

(3) Determine the means of incorporating the valves and fittings into the Darcy equation.

(5) This total pipe equivalent length is then substituted for L in Equation 2 to obtain the pressure drop in the pipe

2) Determine the number of valves and fittings in the pipe.  For example, there may be two gate valves, a 90o elbow and a flow thru tee.

(4) The total equivalent length is usually added to the total straight pipe length obtained in step one to give a total pipe equivalent length. 

(5) This total pipe equivalent length is then substituted for L in Equation 2 to obtain the pressure drop in the pipe

2) Determine the number of valves and fittings in the pipe.  For example, there may be two gate valves, a 90o elbow and a flow thru tee.

(4) The total equivalent length is usually added to the total straight pipe length obtained in step one to give a total pipe equivalent length.