Thermal Expansion of Metal Pipe

Related Resources: heat transfer

Thermal Expansion of Metal Pipe

Fluids Engineering and Design
Heat Transfer

Thermal Expansion of Metal Pipe

Temperature changes cause dimensional changes in all materials. Table 1.0 shows the coefficients of expansion for metallic piping materials. For systems operating at high temperatures, such as steam and hot water, the rate of expansion is high, and significant movements can occur in short runs of piping. Even though rates of expansion may be low for systems operating in the range of 40 to 100°F, such as chilled and condenser water, they can cause large movements in long runs of piping, which are common in distribution systems and high-rise buildings. Therefore, in addition to design requirements for pressure, weight, and other loads, piping systems must accommodate thermal and other movements to prevent the following:

Failure of pipe and supports from overstress and fatigue
Leakage of joints
Detrimental forces and stresses in connected equipment

An unrestrained pipe operates at the lowest overall stress level. Anchors and restraints are needed to support pipe weight and to protect equipment connections. Anchor forces and bowing of pipe anchored at both ends are generally too large to be acceptable, so general practice is to never anchor a straight run of steel pipe at both ends. Piping must be allowed to expand or contract through thermal changes. Ample flexibility can be attained by designing pipe bends and loops or by including supplemental devices, such as expansion joints.

Thermal expansion of pipe formula:

ΔL = a · L · ΔT

Where:

ΔL = change in length
a = Coefficient of linear expansion for the material.
L = Length of pipe
ΔT = change in temperature (t_i - t_o)
t_i = initial temperature
t_o = final temperature

End reactions transmitted to rotating equipment, such as pumps or turbines, may deform the equipment case and cause bearing misalignment that may ultimately cause the component to fail. Consequently, manufacturers’ recommendations on allowable forces and movements that may be placed on their equipment should be followed.

Table 1.0 Linear Thermal Expansion Pipe

Saturated Steam Pressure, psig	Temperature, °F	Linear Thermal Expansion, in/100 ft
Saturated Steam Pressure, psig	Temperature, °F	Carbon Steel	Type 304 Stainless Steel	Copper
-	–30	–0.19	–0.30	–0.32
-	–20	–0.12	–0.20	–0.21
-	–10	–0.06	–0.10	–0.11
-	0	0.00	0.00	0.00
-	10	0.08	0.11	0.12
-	20	0.15	0.22	0.24
–14.6	32	0.24	0.36	0.37
–14.6	40	0.30	0.45	0.45
–14.5	50	0.38	0.56	0.57
–14.4	60	0.46	0.67	0.68
–14.3	70	0.53	0.78	0.79
–14.2	80	0.61	0.90	0.90
–14.0	90	0.68	1.01	1.02
–13.7	100	0.76	1.12	1.13
–13.0	120	0.91	1.35	1.37
–11.8	140	1.06	1.57	1.59
–10.0	160	1.22	1.79	1.80
–7.2	180	1.37	2.02	2.05
–3.2	200	1.52	2.24	2.30
0	212	1.62	2.38	2.43
2.5	220	1.69	2.48	2.52
10.3	240	1.85	2.71	2.76
20.7	260	2.02	2.94	2.99
34.6	280	2.18	3.17	3.22
52.3	300	2.35	3.40	3.46
75.0	320	2.53	3.64	3.70
103.3	340	2.70	3.88	3.94
138.3	360	2.88	4.11	4.18
181.1	380	3.05	4.35	4.42
232.6	400	3.23	4.59	4.87
666.1	500	4.15	5.80	5.91
1528	600	5.13	7.03	7.18
3079	700	6.16	8.29	8.47
-	800	7.23	9.59	9.79
-	900	8.34	10.91	11.16
-	1000	9.42	12.27	12.54

Reference:

ASHRAE Fundamental Handbook, 2019