The development of the Support Rod Analysis Program is a direct result of research conducted by Bolttech Mannings in conjunction with major generating stations throughout the United States.
Discoveries have been made indicating that boiler hanger rods have been loaded in two or even three times their design setting. This can cause improper loading during initial installation and non-uniform temperature gradients within the support structure.
Though this overloading does not cause immediate problems — the rods are not highly loaded relative to their proof strengths — but as loads get excessively higher, the creep lives are greatly reduced.
On-site inspection has revealed that heat and corrosion can reduce the effective cross-sectional areas of support rods by up to 50% over the years of boiler operation. All these factors — boiler hanger rod overloading, reduced creep life, and corrosion — could lead to boiler hanger rod failures.
Bolttech Mannings has developed a “complete package” for support-rod load monitoring and analysis. Our turnkey boiler Support Rod Analysis Program and specialized hydraulic tools help power station engineers to fully adjust out-of-balance hanger rods to OEM specifications.
By specifying Boiler Hanger Rod Analysis, Bolttech Mannings can monitor and balance an entire support structure and reduce the possibility of failure or collapse.
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Flexible Pipe Support Evaluations
The principle operation of this procedure is to transfer the gravitational and/or thermal load from the spring hanger to our specialized hydraulic test fixture.
Extensometers used in conjunction with digital readout gauges define the “zero” load point of the pipe hanger support by measuring the strain as it is removed. At this point, the actual load has been transferred to the Bolttech Mannings lifting apparatus. The hydraulic pressure, multiplied by the effective cylinder area, gives the true load carried by the particular hanger being weighed.
All test equipment and ancillary materials are selected based on the design load of each hanger to ensure system integrity and safety.
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Load Distribution Analysis
Bolttech Mannings offers a turnkey Boiler Support Rod Analysis Program. We arrive on site with all necessary equipment and labor to perform the analysis. This process is usually conducted in two parts:
- Determine boiler weight distribution.
- Balance the structure to OEM and/or power station specifications.
The first part of the program is the boiler weigh. Every rod is individually “weighed” by the use of our specially designed hydraulic boiler tool. A graph is then plotted for each rod, which gives the rod’s loading and an indication of the support structure’s flexibility.
The graph is plotted by recording the amount each rod is lifted at various induced load levels. As the nut just lifts from the bearing surface, the hydraulic lifting device captures the entire load. This transaction is illustrated on the graph as a linear relationship between the applied load and rod displacement. Finally, the actual load is extrapolated from the curve. These results are then analyzed by Bolttech Mannings in close liaison with power station engineers. Details of correct boiler hanger rod settings are discussed in detail prior to adjustment.
The “out-of-balance” boiler hanger rods are adjusted once the load distribution of the support structure is known. The rods can be adjusted singularly, in pairs, or in complete rows, depending upon the design of the boiler.
Boiler weighing tools are placed on all rods that are to be balanced simultaneously. They are linked by means of a flexible hydraulic manifold, then pressurized simultaneously. The tools are isolated, and the proper adjustment is made at the nut once the correct load has been applied to each rod.
Bolttech Mannings’ experience demonstrates the importance of balancing rods in groups, especially on flexible structures. It is of prime importance to prevent any load transfer from taking place on rods already balanced.
Bolttech Mannings’ specialized equipment is manufactured to strict specifications and is designed to easily accommodate a wide range of boiler configurations.
Experienced Bolttech Mannings engineers can monitor and adjust the rods in a support system during a boiler outage or while the unit is on-line.
