API STANDARD 521 - Hydraulic Expansion(팽창)

 

 

4.4.12.3 Special cases

​

Two general applictions for which thermal-relieving devices larger than a DN 20 x DN 25(NPS 3/4 x NPS1) valve can be required are long pipelines of large diameter in uninsulated, aboveground installations and large vessels or heat exchangers operation liquid-full.

Long pipelines can be blocked in at or below ambient temperature; the effect of solar radiation raises the temperature at a calculable rate.

If the total heat transfer rate and thermal expansion coefficient for the fluid are known, a required relieving rate can be calculated.

See Parry for additional information on thermal felief.

​

If the fluid properties vary significantly with temperature, the worst-case temperature should be used. Alternatively, more sophisticated calculation methods that include temperature-dependent fluid properties can be used to optimize the size of the relief device.

​

For liquid-full systems, expansion rates for the sizing of relidf devices that protect ahainst thermal expansion of the trapped liquids can be approximated using Equation (2) in International System (SI) of units or Equation (3) in US customary (USC) units :

​

V = B × q / 998 × G × Cp

​

V : Volume flow rate at the relieving conditions, expressed(m3/h)

B : Cubic expansion coefficient for the liquid at the relieving conditions, expressed(1/℃)

q : Total heat treansfer rate, (kcal/h)

G : 15.6 ℃ 물의 밀도를 1로 보고 계산한 상대적 밀도로서 액체의 압축성은 무시

Cp : 액체의 열용량(kcal/kg·℃)

​

Table - Typical Values of Cubic Expansion Coefficient for Hydrocarbon Liquids and Water

API Gravity	Sp.Gr	B
Water	1	0.00018
3 ~ 34.9	1.052 ~ 0.851	0.00072
35 ~ 50.9	0.850 ~ 0.776	0.00090
51 ~ 63.9	0.775 ~ 0.725	0.00108
64 ~ 78.9	0.724 ~ 0.673	0.00126
79 ~ 88.9	0.672 ~ 0.641	0.00144
89 ~ 93.9	0.642 ~ 0.629	0.00153
94 ~ 100 & Heavy	0.628 ~ 0.611	0.00162
At 15.6 ℃(60℉); for other temperatures, Equation can be used to estimate the cubical expansion coefficient.

​

​

 

API STANDARD 521 - Hydraulic Expansion(팽창)