JACKSTAN
Mechanical
- Oct 5, 2005
- 21
Hi.
I would like consult an expert.
I check the design of ball valve different types.
One of them is for preinsulated bonded pipe systems for directly buried hot water networks acc. to EN 488.
Mentioned standard says that valves shall withstand the load comes from axial forces (tensile stresses 163 MPa and compressive stresses 144MPa ) and internal pressure. These stresses exist in the part of system which is fixed through friction during heating or cooling the system by 60/ 70 Kelvin. These axial forces are indicated in the table 1 of mentioned EN 488 standard. The point is that mentioned forces and internal pressure generate longitudinal stresses in the section of valve equal Ret (in elevated temperature).
Acc. to EN13445-3 max. longitudinal stresses in the cylindrical shell/ part comes from external forces and internal pressure shall be lover than f = min (Ret/1.5, Rm/2.4). While EN 13480 in the part 12.3.4 (flexibility analysis) allows stress range sigma < fh + fa (=~ 1.6 – 1.8 Ret). Can we allow so big range of allowable stresses?
It’s common knowledge that pressure accessories like valves are consider as rigid components of piping.
What is your experience in this field and what advice would you give me.
I would like consult an expert.
I check the design of ball valve different types.
One of them is for preinsulated bonded pipe systems for directly buried hot water networks acc. to EN 488.
Mentioned standard says that valves shall withstand the load comes from axial forces (tensile stresses 163 MPa and compressive stresses 144MPa ) and internal pressure. These stresses exist in the part of system which is fixed through friction during heating or cooling the system by 60/ 70 Kelvin. These axial forces are indicated in the table 1 of mentioned EN 488 standard. The point is that mentioned forces and internal pressure generate longitudinal stresses in the section of valve equal Ret (in elevated temperature).
Acc. to EN13445-3 max. longitudinal stresses in the cylindrical shell/ part comes from external forces and internal pressure shall be lover than f = min (Ret/1.5, Rm/2.4). While EN 13480 in the part 12.3.4 (flexibility analysis) allows stress range sigma < fh + fa (=~ 1.6 – 1.8 Ret). Can we allow so big range of allowable stresses?
It’s common knowledge that pressure accessories like valves are consider as rigid components of piping.
What is your experience in this field and what advice would you give me.
