Thermal expansion on pipeline/expansion loop design

Thermal Expansion & Contraction

Compensating for Thermal Expansion & Contraction
Thermal expansion and contraction compensation can be accomplished by utilizing the inherent line flexibility of the system. A rule of thumb for temperature variations ±25 to 30°F is to install the system with offsets, bends or expansion joints as for a 100 psi steam line.

Example:
Type I Grade I PVC 60°F - 120°F installed at 90°F ±30°
Expansion/100' = (2.9 x 10^{- 5}) (12"/ft) (100') (60° FΔT) = 2.09"
Type IV Grade I CPVC 80°F - 130°F
Expansion/100' = (3.4 x 10^{- 5}) (12"/ft) (100') (50° FΔT) = 2.04"
Steel steam line installed 80°F - 100 psi (338°F)
Expansion/100' = 2.07"

Change in Length (inches) of a 10' Length of Pipe

*NOTE: The data furnished herein is based on information furnished by manufacturers of the raw material. This information may be considered as a basis for recommendation, but not as a guarantee. Materials should be tested under actual service to determine suitability for a particular purpose.

No rigid or restraining supports or connections should be made within the developed length of an expansion loop, offset, bend or brand. Concentrated loads such as valves should not be installed in the developed length. Piping support guides should restrict lateral movement and should direct axial movement into the compensating configurations. Calculated support guide spacing distances for offsets and bends should not exceed recommended hanging support spacing for the maximum temperature. If that occurs, distance between anchors will have to be decreased until the support guide spacing distance equals or is less than the recommended support spacing. Use of the rule of thumb method or calculated method is not recommended for threaded Schedule 80 connections. Properly cemented socket cement joints should be utilized.Expansion loops, offsets and bends should be installed as nearly as possible at the mid point between anchors.Values for expansion joints, offsets, bend and branches can be obtained by calculating the developed length from the following equation:

*L =

1 12

3E P

1 2

(doe)

1 2

where
L = Developed length in feet.
P = Maximum allowable fiber stress in psi.
do = Nominal O.D. pipe in inches.
E =Tensile Modulus of Elasticity in psi.
e = Elongation due to temperature rise in inches.

Coefficient of linear expansion: Type IV Grade I CPVC 3.4 x 10- 5 in/in/°F. Type I Grade I PVC 2.9 x 10- 5 in/in/°F. Values for Type I Grade I PVC and Type IV Grade I CPVC are: Modulus = E Maximum Stress = P
	Temperature	E	P	*L =
PVC	73°F	400,000	2,000	2.04 (doe) 1/2
	90°F	375,000	1,500	2.28 (doe) 1/2
	110°F	333,000	1,000	2.63 (doe) 1/2
	120°F	312,000	800	2.85 (doe) 1/2
	140°F	270,000	440	3.58 (doe) 1/2
	160°F	-	-	-
	180°F	-	-	-
CPVC	73°F	365,000	2,000	1.95 (doe) 1/2
	90°F	-	-	-
	100°F	356,000	1,600	2.15 (doe) 1/2
	120°F	346,000	1,300	2.35 (doe) 1/2
	140°F	330,000	1,000	2.62 (doe) 1/2
	160°F	308,000	750	2.92 (doe) 1/2
	180°F	280,000	500	3.42 (doe) 1/2

Thermal Compensation

A = Anchors	SG = Support Guide
EXPANSION LOOP: 2" pipe 2.375 O.D. nominal, expansion loop at mid point, 200' between anchors. Install at 80°F, operating temperature 140°F. For CPVC e = (3.4 x 10- 5) (200') (12"/ ft) (60°FΔT) = 4.89" L = 2.62 (2.375 x 4.89)1/2= 8.93' R = 8.93 5 = 1.8' = 1' 10" approx. For PVC e = (2.9 x 10- 5) (200') (12"/ ft) (60°FΔT) = 4.18" L = (3.58) (2.375 x 4.18)1/2= 11.3 R = 11.3 5 = 2.26' = 2' 3" approx.	Support guides for expansion loops should not exceed 12" - 18". Small diameter pipe 12" maximum.
OFFSET: 2" pipe 2.375 O.D. nominal, offset at mid point, 200' between anchors. Install at 80°F, operating temperature 140°F. For CPVC e = (3.4 x 10- 5) (200') (12"/ ft) (60°FΔT) = 4.89" L = 2.62 (2.375 x 4.89)1/2 = 8.93' R = 8.93 4 = 2.23' = 2' 3" approx. 140°F support spacing 2" Sch 40 5', 2" Sch 80 6' support guide distance more than satisfactory. For PVC e = (2.9 x 10- 5) (200') (12"/ ft) (60°FΔT) = 4.18" L = (3.58) (2.375 x 4.18)1/2= 11.3'  R = 11.3 4 = 2.83' = 2' 10" approx. 140°F support spacing 2" Sch 40 3', 2" Sch 80 3 1/2 support guide spacing satisfactory.	If the offset distance exceeds the calculated 2R, the offset should be treated as 2 bends.
BEND: (Examples are shown for CPVC only) 2" pipe 2.375 O.D. nominal, bend at mid point. Line A = 20'. Line B = 20'.Install at 80°F, operating temperature 140°F. e = (3.4 x 10- 5) (20') (12"/ ft) (60°FΔT) = .49" L = (2.62) (2.375 x .49) 1/2 = 2.83' = 2' 10" approx. Support guide distance = R1 = R2 = 2' 10" 140°F support spacing Sch 40 5', Sch 80 6', support guide distance more than satisfactory. 2" pipe 2.375 O.D. nominal, bend at mid point. Line A = 60'. Line B = 60'. Install at 80°F, operating temperature 140°F. e = (3.4 x 10- 5) (60') (12"/ ft) (60°F∆T) = 1.47" L = (2.59) (2.375 x 1.47) 1/2 = 4.8' = 4' 10" approx. Support guide distance = R1 = R2 = 4' 10" 140°F support spacing 2" Sch 40 5', 2" Sch 80 6'. Support guide spacing lines A & B just adequate for 2" Sch 40, satisfactory for 2" Sch 80.	R1 = L (For Line A) R2= L (For Line B) If a bend is centered between anchors the drawing applies directly. If a bend has one leg shorter than L, the first support guide on the longer leg should be at least:
BRANCH: 2" pipe branch 2.375 O.D. nominal, main run 3" pipe, 3.500 O.D. 20'. Install at 80°F, operating temperature 140°F. For CPVC (3.4 x 10- 5) (20') (12"/ ft) (60°FΔT) = .49" For 2" Branch L = 2.62 (2.375 x .49) 1/2 = 2.83' = 2' 10" approx. Reference: http://www.harvel.com/technical-support-center/engineering-design-data/thermal-expansion-contraction	L= Minimum length branch in ft. (Short branches relative to main line rung. Long branches treat as a bend.