In many systems, spring cans support portions of the pipe. Spring cans perform the same function as spring hangers, except that they are below the pipe, pushing up or compressing down. The relative movement between the pipe, trunnion, shoe, or cradle and the top plate of the spring creates frictional forces on the piping system.
The Spring Can with Friction Builder provides simple and comprehensive modeling methods for spring cans.
Comprehensive Method
Specifies a detailed design of the spring can assembly and considers the spring can components and the insulation.
Rigid elements
Element 5-10
A rigid element from the pipe center to the pipe outer surface, where length equals the outer pipe radius.
The rigid element dimensions and process parameters match the parent pipe at the spring can assembly location node (SL).
Element 10-15
A rigid element from the pipe outer surface to the top of the can at the hanger node (HN). The element length, h equals:
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The trunnion or shoe height for hot insulated and non-insulated pipe.
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The cradle height for cold insulated pipe.
The rigid element dimensions match the parent pipe at the spring can assembly location node (SL), but the process parameters are ambient temperature and zero pressure. Other parameters, such as fluid density, mill tolerance, corrosion allowance insulation thickness, and insulation density are set to zero.
Element 25-30
A rigid element representing the available installation space, H, of the spring can with or without a stanchion.
The rigid element dimensions match the parent pipe at the spring can assembly location node (SL), but the process parameters are ambient temperature and zero pressure. Other parameters, such as fluid density, mill tolerance, corrosion allowance insulation thickness, and insulation density are set to zero.
Restraints to account for friction
Node 15 with CNode 20
Hanger with horizontal restraints X and Z (when the Y-axis is vertical).
Node 20 with CNode 25
Vertical restraint +Y with the coefficient of friction, µ.
Node 30
Restraint anchor node, ANC. The anchor node represents equipment, a platform, or structure.
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While the restraints account for spring can friction, they do not carry piping loads. When the pipe, trunnion, shoe, or cradle slides on top of the spring can, the frictional loads at Node 20 are FX and FZ.
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Element 25-30 can be omitted by retaining the +Y restraint with µ provided on node 20 and then deleting CNode 25.
Simple Method
Specifies a simplified, generic design applicable to any hot-insulated, cold-insulated, or non-insulated condition. Rigid elements are not created.
Restraints to account for friction
Node 45 with CNode 55
Hanger with horizontal restraints X, Z (when the Y-axis is vertical).
Node 55 CNode 60
Vertical restraint +Y with the coefficient of friction, µ.
Node 60
Restraint anchor node, ANC. The anchor node represents equipment, a platform, or structure.
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While the restraints account for spring can friction, they do not carry piping loads. When the pipe, trunnion, shoe, or cradle slides on top of the spring can, the frictional loads at Node 55 are FX and FZ.
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The software bases spring can selection on the height, H. ANC at node 60 is defined at the distance H from the bottom surface of pipe, even though there are no elements between nodes 55 to 60.