Senin, 06 September 2010

CALCULATION OF USING TRUST BLOCK ON UNDERGROUND PIPING

Di bawah ini adalah contoh dari calculasi terhadap penggunaan trust block dalam suatu system pmipaan
yang dipasang di bawah tanah.
Dan kebanyakan trust bloc ini dipasangkan ke pipa PVC .
Untuk itu , dengan mengambil info dari http://www.engineeringtoolbox.com/ , kami uraikan perihalnya di bawah ini:

TRUST BLOCK


The resulting force on a thrust block or anchor depends on the fluid mass flow and flow velocity and the pressure in the bend.

Resulting force due to Mass flow and Flow Velocity

The resulting force in x-direction due to mass flow and flow velocity can be expressed as:

Rx = m v (1 - cosβ) (1)

= ρ A v2 (1 - cosβ) (1b)

= ρ π (d / 2)2 v2 (1 - cosβ) (1c)

where

Rx = resulting force in x-direction (N)

m = mass flow (kg/s)

v = flow velocity (m/s)

β = turning bend angle (degrees)

ρ = fluid density (kg/m3)

d = internal pipe or bend diameter (m)

π = 3.14...

The resulting force in y-direction due to mass flow and flow velocity can be expressed as:

Ry = m v sinβ (2)

= ρ A v2 sinβ (2b)

= ρ π (d / 2)2 v2 sinβ (2c)

Ry = resulting force in y direction (N)

The resulting force on the bend due to force in x- and y-direction can be expressed as:

R = (Rx2 + Ry2)1/2 (3)

where

R = resulting force on the bend (N)

Example - Resulting force on a bend due to mass flow and flow velocity

The resulting force on a 45o bend with

• diameter 114 mm = 0.114 m

• water with density 1000 kg/m3

• flow velocity 20 m/s

can be calculated by as

Resulting force in x-direction:

Rx = (1000 kg/m3) π ((0.114 m) / 2)2 (20 m/s)2 (1 - cos45)

= 1196 (N)

Resulting force in y-direction:

Ry = (1000 kg/m3) π ((0.114 m) / 2)2 (20 m/s)2 sin45

= 2887 (N)

Resulting force on the bend

R = ((1196 N)2 + (2887 N)2)1/2

= 3125 (N)

Note - if β is 90o the resulting forces in x- and y-directions are the same.

Resulting force due to Static Pressure

The pressure and the end surfaces of the bend creates resulting forces in x- and y-directions.

The resulting force in x-direction can be expressed as

Rpx = p A (1- cos β) (4)

= p π (d / 2)2 (1- cos β) (4b)

where

Rpx = resulting force due to pressure in x-direction (N)

p = gauge pressure inside pipe (Pa, N/m2)

The resulting force in y-direction can be expressed as

Rpy = p π (d / 2)2 sinβ (5)

where

Rpy = resulting force due to pressure in y-direction (N)

The resulting force on the bend due to force in x- and y-direction can be expressed as:

Rp = (Rpx2 + Rpy2)1/2 (6)

where

Rp = resulting force on the bend due to static pressure (N)

Example - Resulting force on a bend due to pressure

The resulting force on a 45o bend with

• diameter 114 mm = 0.114 m

• pressure 100 kPa

can be calculated by as

Resulting force in x-direction:

Rx = (100 kPa) π ((0.114 m) / 2)2 (1 - cos45)

= 299 (N)

Resulting force in y-direction:

Ry = (100 kPa) π ((0.114 m) / 2)2 sin45

= 722 (N)

Resulting force on the bend

R = ((1196 N)2 + (2887 N)2)1/2

= 781 (N)





Menghitung berat steel pipe

If the outside diameter and the wall thickness of a steel pipe is known, the weight per foot can be expressed as:

m = 10.68 (do - tw) tw (1)

where

m = weight per foot (lbs/ft)

do = outside diameter (inches)

tw = wall thickness (inches)

Example - Weight of 4" Schedule 40 Steel Pipe

The outside diameter (do) of 4" Schedule 40 Steel Pipe is 4.500 inches. The wall thickness is 0.237 inches. The weight per foot can be calculated using (1) as:

m = 10.68 ((4.500 in) - (0.237 in)) (0.237 in)

= 10.79 lbs/ft

Bila bingung, pelajari sekali lagi dan bisa sudah pandai , ajari saya ........

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