The expansion joints always must be mounted with pre-tension. The amount of pre-tension must be calculated considering the mounting temperature and a distance must remain in order to leave mounting space by adding the free length of the expansion joint. Loose Expansion Joints are used to absorb the thermal expansion parallel to the axis of the straight pipelines. Long piping systems are divided into shorter expanding sections, and isolated by main anchors. Thus the movements in the individual expanding sections are absorbed by the KRS-13 axial expansion joints in this section.
Calculation
Minimum temperature=-10 °C
Maximum temperature= 93 °C
Difference between fi xed points= 20 °C
Operation pressure= 2 bar
Temperature difference = 103 °C
Pipe Weight (see table section) At -10 °C -10 mm. compression
At 93 °C 25 mm. expansion
ΔX =ΔXmax – ΔXmin= 25-( -10)= 35 mm..
ΔTmax=ΔTmax – ΔTmin=93-(-10)=103 °C
PN= PW/AP
From the gradient factor table 103 °C AP=0,9 and PN=2,2 bar
ΔK= Δb/Af From the gradient factor table Af=1
ΔK=ΔX = Δb ΔK= Δb/Af
For pretension amount P, use the following formula.
P=ΔX/2 + ΔE/4 ΔE=Expansion joint label value as mm.
ΔE=40 mm. (for example)
P= 35/2 + 40/4 =27,5 mm
