Industrial boilers are known as the beating heart of production lines in factories, food industries, petrochemical, pharmaceutical, textile and hospitals. Due to the extensive establishment of mother industries, numerous industrial towns in Shiraz, Morvdasht, Zarghan, Kazerun and Fasa, maintaining the thermal efficiency and safety of steam equipment is of great importance. In the structure of all types of boilers, two vital parts called Tube Sheet and Furnace play a key role in heat transfer and bearing mechanical loads. Erosion, corrosion, formation of hard sedimentary layers, thermal shock and material fatigue over time lead to serious damage to these parts. In case of any failure, stopping the production process will cause heavy financial losses; Therefore, the use of specialized tube sheet and boiler furnace repair services in Fars by registering a quick and unmediated request from an experienced and qualified standard is the most important step in maintaining production lines.
The importance and position of sheet tube and furnace in firetube boilers
In firetube boilers, which are the most common type of boilers in the industries of Fars province, the furnace is the main place for burning the burner fuel and exchanging radiation heat to the surrounding water. The heat from the flame first hits the furnace wall and then the combustion gases enter the tubes. The round and strong plate that holds the ends of the tubes in place and separates the pressurized water from the hot gases is called a tube sheet. The tube sheets are located in the front (Front Tube Sheet) and the rear (Rear Tube Sheet) and based on the design, they may be Wetback or Dryback.
Due to the very high temperature difference between the gases coming out of the furnace and the water inside the boiler drum, the sheet tube is under continuous thermal stresses and cyclical pressures. Due to direct contact with the tip of the flame and strong radiation, the furnace is exposed to creep stresses, deformation and sedimentation. Disruption in any of these two parts immediately leads to a severe drop in efficiency, water leakage into the smoke path, burner shutdown and irreparable explosive risks. Therefore, continuous monitoring and the use of expert teams to repair tube sheets and boiler furnaces in Fars is a guarantee of the health of thermal facilities.
Common signs and symptoms of boiler sheet failure
Early recognition of signs of failure is the difference between a simple repair and a costly industrial disaster. In many factories located in the industrial towns of Fars province, not paying attention to the early signs has caused the complete destruction of the piping network and damage to the boiler shell.
The first obvious sign is a rapid drop in the water level of the boiler without external leaks in the taps or plumbing lines of the hall. A leak from the expansion area or the welding of pipes to the tube sheet causes water to drip into the combustion chamber or smoke box, which is usually accompanied by the formation of white steam from the exhaust. Another sign is the accumulation of lime and white or brown salt deposits around the pipe junction on the outer surface of the tube sheet. Ligament cracks are one of the most dangerous side effects of extreme thermal stresses, which require non-destructive inspection and immediate engineering action. In such a situation, stopping the boiler and filing an expert request with Sepehr Industrial Group is the safest management decision.
Causes of common defects in boiler furnace
Fire tube boiler furnace absorbs the most amount of heat flux. Therefore, any inconsistency in the water supply system or burner ignition adjustment can cause critical damage to the furnace. The most important furnace damage is deformation and geometrical shape change known as Sagging or Collapse. The main reason for this phenomenon is the formation of a thick layer of sediment on the surface of the furnace water intake. Calcium and magnesium deposits have very low thermal conductivity; As a result, the metal of the furnace is not able to transfer heat to the water and the temperature of the steel shell reaches more than the design temperature. Steel succumbs at high temperature and under the pressure of ambient steam, it sinks inwards.
Another cause of damage is the non-adjustment of the torch flame angle and so-called "Flame Impingement". The physical contact of the flame tip with the furnace wall creates local hot spots, which over time causes wear, local oxidation and reduction of the thickness of the furnace. Also, the use of untreated water with inappropriate hardness and the lack of regulation of the amount of chemical injection of the boiler accelerates severe oxidation, cavitation and pitting in the furnace shell.
The specialized steps of boiler sheet tube repair in Fars by experts
Sheet tube repair needs to comply with ASME BPVC Section I standard guidelines and Iranian national standards (Standard 4231). Experienced technicians with no knowledge of metallurgical engineering usually create dangerous residual stresses with non-basic welds on the cracks, which completely destroys the performance of the tube sheet. Sepehr Industrial Group carefully implements the following steps in the tubesheet repair process:
First of all, after the complete cooling of the boiler and draining the water, all the soot and deposits on the surface of the tube sheet are cleaned with high-pressure water jet devices and mechanical brushing. Then, non-destructive tests such as penetrating liquid test (PT) and magnetic particle test (MT) are performed to determine the depth and extent of microscopic cracks in the tube sheet. If there is a leak from the place where the pipes are waltzed, first waltzing is done again with standard torque. If the pipes are not able to be rolled due to their long life or insufficient thickness, the defective pipes are cut and removed.
In cases where the crack has spread in the distance between the tubes (ligament), the engineers of Sepehr Industrial Group empty the root of the crack with specialized grinding operations, apply precise pre-heating and perform multi-pass welding operations under the control of the input heat using special electrodes suitable for the tube sheet material (usually heat-resistant alloy steels such as 17Mn4 or A516 Gr 70). In more extensive damage, the complete replacement or the damaged part of the tube sheet is performed by re-sheathing with high dimensional accuracy.
Methods of renovating and replacing boiler furnaces in Shiraz and other cities
When the boiler furnace is deformed beyond the standard limit or its wall thickness is reduced due to corrosion, it is vital to rebuild it. According to the standard, if the depression depth of the furnace exceeds the permissible limit, the use of mechanical jacking methods alone is not recommended, and the furnace must be replaced, or in limited conditions, after accurate local heating, it must be formed under the supervision of the supervising engineer.
The importance of hydrostatic testing and non-destructive testing after repairs
The end of welding operation does not mean the end of repairs. One of the most important safety requirements is to evaluate the quality of connections before starting the boiler. Sepehr Industrial Group performs detailed visual inspection (VT) and ultrasonic test (UT) or radiography (RT) of vital welds after completing tube sheet and boiler furnace repairs in Fars to ensure the absence of shrinkage holes, insufficient penetration or hidden cracks.
After confirming the health of the welds, the hydrostatic pressure test is performed according to the standard with a pressure equivalent to 1.5 times the design working pressure. During the hydrostatic test, the pressure of the tank with fully aerated water is monitored, and the absence of pressure drop and the absence of any leakage or deformation in the tube sheet and furnace is considered as the final condition for issuing a health certificate. The supervisors of the Labor Department and international inspection companies are accompanied with the documents of the Sepehr Industrial Group in order to issue a legal operating permit for the industrial unit.
The role of boiler water quality control in increasing the lifespan of the furnace and tube sheet
Many of the industries in Fars that are faced with successive furnace and tube sheet failures ignore the root of the problem in the water purification system. Water from wells and underground sources in the industrial areas of Shiraz, Marodasht, Abadeh and Larestan have high salts and hardness. If the boiler is not equipped with a suitable resin hardener, deaerator to remove oxygen and carbon dioxide gases, and an anti-fouling and anti-foam injection package system, the thickness of the furnace walls and sheets will quickly be affected by oxidation and stratification.
A layer with a thickness of only one millimeter of silicate deposit can reduce the heat transfer efficiency of the furnace by 10% and increase the temperature of the wall metal by hundreds of degrees beyond the permissible limit. In addition to physical repair, the experts of Sepehr Industrial Group provide expert advice in the field of boiler water chemistry, adjustment of blowdown courses and selection of standard chemicals to factory engineers in order to prevent the recurrence of breakdowns.
Why do Fars Industries choose Sepehr Industrial Group for boiler repair?
Different industries in Fars province have strict criteria for choosing a repair team; Because any delay in repairs or non-compliance with the standards of the Ministry of Cooperatives, Labor and Social Welfare has serious consequences. Based on the following features, Sepehr Industrial Group has established its position as the best option for tube sheet and boiler furnace repair in Fars:
Benefiting from an experienced technical staff consisting of metallurgical and mechanical engineers who have a long history in the construction and renovation of all types of steam boilers. Possession of specialized modern pneumatic and hydraulic rolling equipment with the possibility of accurate torque control, the use of standard alloy electrodes and materials with a valid analysis certificate, providing services throughout the cities of Fars province, including Shiraz, Kazeroon, Fasa, Jahorm, Abadeh, Darab, Euclid and Zarghan in the fastest possible time, and providing a written performance guarantee and official hydrostatic test, has made Sepehr Industrial Group a reliable name for technical and facility managers.
In addition, the high speed of action in response to the emergency situations of the factories, the dispatch of mobile teams in the shortest time and the possibility of providing standard spare parts from A516 sheets to ST35.8 seamless fireproof pipes, bring peace of mind to the production cycle of the province's industrial units.
Guide for registering requests for tube sheet and boiler furnace repair services in Fars
In order to prevent long-term stoppage of production lines, Sepehr Industrial Group has provided a direct communication system and application registration process without intermediaries for industries, hospitals and industrial centers of Fars province. The process of repairing tube sheets and boiler furnaces in Fars is very fast and transparent by registering a request:
The first step: communication with technical experts through the communication ports of Sepehr Industrial Group and sending basic information such as boiler capacity, model, steam production tonnage, working pressure and description of the problem that occurred (such as unusual noise, water leakage, torch fluctuation or blistering observation).
Second step: sending clear photos and videos of the state of the furnace, packings and front and back tube sheets to the engineering unit for preliminary evaluation and preparation of initial test equipment.
Third step: immediate dispatch of a senior expert to the project site throughout Fars province for field inspection, ultrasonic thickness measurement, accurate determination of the extent of damage and estimation of the exact timing of the operation.
Fourth stage: presentation of a clear pre-invoice, specification of consumables, immediate start of reconstruction operations and final hydrostatic tests and delivery of the boiler with technical health approval.
Summary
In order to optimize costs and ensure the continuity of boiler operation after repairs, maintenance and repair managers (NET) must apply periodical inspection protocols seriously. The first point is to turn on the boiler with a gradual heating rate. A sudden increase in furnace temperature after repairs can cause adverse thermal shocks in the place of newly constructed joints and rollers. It is necessary to accurately adjust the air-to-fuel ratio of the burner and ensure that the flame is placed in the center of the furnace so that there is no contact between the flame and the body of the furnace.
Also, it is recommended to develop a regular schedule for seasonal inspection of the tube network and to ensure the cleanliness of the tubes through mechanical soot removal; In addition to reducing heat transfer, the accumulation of soot increases the local temperature of the rear sheet and creates stress points. Using the support services of Sepehr Industrial Group will help you to implement specialized checklists for daily and monthly boiler monitoring in your facilities and to maximize the useful life of the furnace and tube sheet.