Boiler Weighing
Boiler Weighing
The development of the Support Rod Analysis Program comes as a direct result of research carried out by Bolttech in conjunction with major generating stations throughout the U.S.
It has been discovered that boiler hanger rods have been loaded in two or even three times their design setting. The causes for this condition are improper loading during initial installation and non-uniform temperature gradients within the support structure.
This overloading does not cause immediate problems since the rods are not highly loaded relative to their proof strengths. However, as the loads are excessively higher than design, 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 of these factors – boiler hanger rod overloading, reduced creep life, and corrosion – could certainly lead to boiler hanger rod failures.
Bolttech has developed a “complete package” for support rod load monitoring and analysis. By using the turnkey boiler Support Rod Analysis Program, and specialized hydraulic tools (designed by Bolttech), the results are analyzed with power station engineers to fully adjust to out-of-balance hanger rods to OEM specifications.
By specifying Boiler Hanger Rod Analysis, Bolttech can monitor and balance an entire support structure and reduce the possibility of failure/collapse.
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, in conjunction with digital readout gauges, are used to define the “0” 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 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 selected are based on the design load of each hanger to ensure system integrity and safety.
Load Distribution Analysis
Bolttech offers a turnkey Boiler Support Rod Analysis Program. We will arrive on-site with all the necessary equipment and labor to perform the analysis, which is normally conducted in two parts:
- Determine boiler weight distribution.
- Balance the structure to O.E.M. and/or power station specifications.
The graph is plotted by recording the amount each rod is lifted at various induced load levels. When the nut just lifts from the bearing surface, the entire load has been captured by the hydraulic lifting device. This transition 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 in close liaison with the power station engineers. Prior to adjustment, details of correct boiler hanger rod settings are discussed in detail.
Once the load distribution of a support structure is known, the “out of balance” Boiler Hanger Rods are adjusted. 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. When the correct load has been applied to each rod, the tools are isolated and the proper adjustment is made at the nut.
Bolttech’s 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’s specialized equipment is manufactured to strict specifications and designed to easily accommodate a wide range of boiler configurations.
Experienced Bolttech engineers can monitor and adjust the rods in a support system during a boiler outage or while the unit is on-line.
