Special offer for TPS, TPP

We offer the range of works that take place in the course of recovery heat treatment (RHT) with preliminary fault finding, subsequent repairing and setting up of the hanger-support system of TPS, TPP pipelines normalizing the loading onto HP and MP cylinder bases and eliminating bending and vibration of collectors and steam pipelines of TPS, TPP.

We have currently accumulated considerable experience in discharging and setting up of the hanger-support system of TPS pipelines which is mandatory during RHT. By "discharge" we shall hereinafter understand additional restraining and force action (variable or fixed) of pipelines in order to avoid axis distortion in the areas of RHT procedures.

Modern pipeline systems have complex three-dimensional configurations. The advantage of the technology currently in use is to execute RHT without technological dismantling of pipelines and as a rule with minimum required cutting. This solution is the most cost-effective. It allows getting more uniform metal texture along the length of the pipes and bringing the falls of lines in conformity with accepted standards. However, RHT execution without pipelines dismantling causes considerable difficulties to discharge them.

In the course of heating up to some 1000°С pipe steels considerably change their physical properties (modulus of elasticity and linear expansion coefficient), metal yield point considerable decreases and there is a danger that heated areas can "sag" when executing RHT. On the other hand, in each section of pipelines there are their own internal forces and moments conditioned by the self-weight of the pipes, reactions of the hanger-support system, as well as mounting and repair negative allowances. Thus, it is required to limit the impact of moments and forces of the cold part of the pipeline on to the area heated for RHT. That is the basic goal of discharging.

In some cases the position of pipelines elastic axes is substantially different from the position of its primary mounting axes (for the pipelines as such it is generally necessary to adjust the hanger-support system after mounting). Therefore, before executing RHT of such pipelines they must be reduced to the position of mounting axes (in whole or in part). The decision on whether or not this operation is required must be made by estimating the mass load effect of the pipeline in question.

Preliminary works are of great importance. It includes studying all the existing technical documentation to the pipeline. It is intended for gathering information on the initial project, cold negative allowances, real conditions of the pipeline operation and the faults detected earlier. Then in order to identify apparent faults the pipeline and hanger-support system of its fastenings (in running order) is examined. The identification of springs in other supports is carried out. We perform the measurement of spring supports load (in running and cold condition of the pipeline). The geometry of lines and location of the hanger-support system elements are specified, and the deviations from the initial projects are found. This information is required further to carry out checking calculation of the pipeline of strength and self-compensation of thermal expansion, and to define calculated load on the HP and MP cylinder bases, as well as to calculate load operations when executing RHT.

Subsequent to the results of the inspection performed we develop recommendations on the elimination of detected faults and on the technology of joining pipelines to the cylinders. The faults must be eliminated prior to the start of all further RHT procedures.

Recommendations on remounting and elimination of all the non-project “cold” negative allowances, pipeline drainage, on cutting obstructive auxiliary pipelines and metalware, and safe disconnection from running pipelines. There on the chilled pipeline (with temperature not hire than 50°С) spring suspensions are fixed with rigid bracing. Straightness error and other apparent faults that appeared while mounting and operating are recorded in the acceptance certificate before starting RHT procedures.

In order to reduce the forces from thermal extension cold spring was executed on many pipelines including those that spent their design life. This can greatly confuse the initial stress state of the pipeline which considerably complicates all the pipeline discharge operations predicting angular deformations in any possible directions. In this case cutting of the pipeline in preparation of RHT is necessary and it can be used for internal stress relieving and removing off-design forces that are transferred to the cylinder bases.

After defining the scope of works and specific conditions regarding RHT procedures, the pipelines are calculated for strength and self-compensation. In addition, a discharge variant is chosen by calculation which is the most effective in terms of man-hours.

The beginning of RHT execution is set on the areas farthest from the places of pipeline cutting. This choice allows us if it is necessary to straighten the final position of the pipeline axis after some intermediary overcastting.

When executing RHT without using noble gases or air extraction, a specialized organization carries out acid washing and pipeline purging in order to remove scale and then to conserve the equipment after fulfilling all the operations.

Pipeline condition monitoring in the course of heating operations includes inspection of the pipe, registration of thermal fields and shifts of the pipe, and the comparison of the received data with the designed data; checking of the rod tightness of the temporary supports and the state of supports in the are of RHT execution.

According to the results of repair and adjustment of the hanger-support system the following technical documentation is drawn:

  • Reports on technical state of pipelines and the hanger-support system of their fastenings;
  • Registers of faults of pipelines and the hanger-support system with the note of their elimination;
  • Axonometric design model of the pipeline refined as a result of the examination with indication of design joints and sections;
  • Feasibility study of the chosen variant of the strength calculation (if in the design diagram there are areas that work with different temperatures or have different operating time);
  • Characteristics of the supports that specify the type of springs, their rate, output capacity, number of chains, free height of the springs, as well as loading unbalance for separate supports and for the hanger-support system on the whole;
  • Justification of various decisions made in the course of calculating;
  • Voltage table in design sections of pipelines;
  • Supports and hangers load chart;
  • Table of the designed visible shifts of pipelines in the places thermal expansion indicators are installed;
  • Conclusions on the basis of the results of the calculations made;
  • Concentrated loads of equipment or reinforcement weight;
  • Values of displacement of joints to connect with the equipment, as well as cold springs;
  • Key physical constants and safety factors (modulus of material elasticity in operating and cold states; coefficient of linear expansion; admissible stress in operating and cold states; overload factor; reduction factors related to the weld joints; coefficients related to the stress relaxation).

The volume of works on adjusting the hanger-support system and RHT is to be preliminary approved by the customer.

List of the Works Performed

1. Technical diagnostics of the power equipment

1.1. Technical assistance at commissioning and primary adjustment of steam mains and the steam pipelines of TPS reheat.
Work objective is to increase the safety of steam pipelines and their operation level.

2. Experimental and adjustment work.

2.1 Setting-up of the running steam pipeline (pipeline).
Work objective is to improve reliability of steam pipelines (pipelines).
In accordance with the complexity and volume the works are performed in 3 (three) categories:

  • Category I – pipeline with nominal diameter more than 350 mm;
  • Category II – pipeline with nominal diameter from 225 to 325 mm;
  • Category III – pipeline with nominal diameter to 200 mm.

The cost of works depends on the number of spring fastenings on 1 (one) line of the steam pipeline (pipeline).

2.2 Calculation of strength and self-compensation of the running steam pipeline (pipeline).
Work objective is to ensure reliability of steam pipelines (pipelines).
2 (two) variants of calculation are provided.
The cost of works depends on the number of design units on 1 (one) line of the steam pipeline (pipeline).
Computerized calculations are not included in the scope of works.

3. Operation Level Increase.

3.1 Calculation of strength and self-compensation of the redeveloped (designed) steam pipeline (pipeline).
Work objective is to ensure reliability and safety of steam pipelines (pipelines).
2 (two) variants of calculation are provided.
The cost of works depends on the number of design units on 1 (one) line of the steam pipeline (pipeline).
Computerized calculations are not included in the scope of works.

3.2 Organization of the monitoring of the steam pipelines movements.

Work objective is to implement a set of actions on thermal movements of one branch of the steam pipeline from the boiler to the turbine.

The cost of works depends on the power plant capacity, for для 1 (one) branch of the steam pipeline (pipeline).

TPS steam pipeline (pipeline) setting-up provides for the works on examining pipeline layout and adjusting the hanger-support system of steam pipelines: direct steam, hot reheat (HRH), cold reheat (CRH), PRDS steam pipelines, fast-response PRDS, high pressure bypass pipes of HPC, bleed steam pipelines connected with HPC, IPC, LPC and the pipeline with feed water (FW), outlet valve taps of direct steam and HRH, heating and devaporation of HRH, exhausting of steam from seals, etc.

We perform the following works:

  • Examination of steam pipelines and hanger-support system in order to define the pipeline layout, absence of bends and jammings, as well as conformity to the project.
  • Check-out if the installed springs meet the requirements of the project, their location and design.
  • Calculation of loading of steam pipelines hanger-support system.
  • Due to the replacement of HPC and IPC we perform some groups of technical actions for joining the pipelines to the external HPC, IPC of the turbine with consequent performing of cold negative allowances and adjustment of fastenings load.
  • Calculation of the tightness of springs of spring suspensions and defining of real value of the loads in cold state with working out notes and recommendations for adjusting.
  • Adjusting of springs of spring suspensions factoring admissible and design loads.
  • Multistage adjustment of steam pipeline hanger-support system connected with HPC and IPC in order to normalize and balance the loading on the HPC and IPC bases.
  • Making-out and issuing of log books of spring pretension of spring suspensions of direct steam, HRH, CHR, feed water pipelines bleeding, etc.
  • Analyzing thermal movements of steam pipelines of direct steam, HRH, CHR pipelines according to the data of thermal movements log books.
  • Compilation of reports on the works performed.