BOILER SAFETY MEASURES

INTRODUCTION

Section 2(a) of Indian Boiler Act, 1923 defines “Accident” as follows:

“Accident means an explosion of Boiler or steam pipe or any damage to boiler or steam pipe which is calculated to weaken the strength thereof so as to render it liable to explode.”

The root cause of majority of the accidents is non-following of the safety norms and safety procedures.

Therefore, the explosion of Boiler and the secondary combustion in boiler is of prime concern as it resulted into severe accidents.

Coal Combustion is a function of turbulence and air distribution. Normal residence time of coal particle inside the furnace is 3-5 seconds & the particle to the exit from chimney is 22 seconds. As a result, incombustibles will remain inside the boiler for 22 seconds. Falling of heavy high temperature bonded deposited clinker to the bottom ash hopper leads to furnace pressurization and resulted into explosion of furnace and escaping out of the flue gases from the weakest portions of the boiler and this is the main cause of severe accident.

If a steam boiler is properly operated and maintained, including performance of all the necessary routine preventive maintenance, the likelihood of a explosion is virtually eliminated.

Improper purge can leave a combustible mixture in a boiler. Many explosions occur during attempts to relight a burner after it has tripped because of another problem and will be resulted into large unburnt combustible gases in the furnace which leads to explosion.

This scenario can be avoided by investigating the cause of the trip and allowing the furnace to purge thoroughly before any attempt to relight up. Therefore, safety practices are required to be monitored, controlled and implemented at various pressure part components during operation, maintenance and erection of boiler also.

Safety practices during Erection of boiler

Top girder jack up, structure erection, installation of pressure part components, and hydrostatic tests are the crucial activities as far as erection is concerned.

  • Prior to the commencement of the girder jack up and structure erection work, the management team will ensure HSE (Health Safety and Environment) Plan and pep talk procedure which are to be applied.
  • All workers together with frontline supervisor shall conduct safety task assignment every day before commencement of the work.
  • Supervisors shall make sure that all workers under his supervision understand and shall fully comply the assigned job and all requirements mentioned in the standard procedure.
  • No welding is to be carried out during jack up operation and will be allowed without proper checking of earthing and welding equipment.
  • Lifting equipment must be with valid certification.
  • Additional assisting crane should be prepared in good condition with certified crane operator.
  • All open holes should be well protected.
  • No lifting allowed under harsh weather condition.
  • Movement should be stopped if instructions are not clear.
  • There should be good communication with handy walky-talky of special frequency.
  • Working platform should be as per standard and with sound material.
  • Height work permit is required.
  • All structure erection must be finished as per requirement including bolt tightening.
  • Experienced riggers are required to be deputed to handle rigging.
  • Load being lifted in equilibrium position and constant load.
  • Approved critical lift plan must be available in hand prior to lifting work.
  • Only the competent and trained jack up operator will be allowed to operate the equipment.
  • Protection from sling’s sharp edge to be provided.
  • No unauthorized persons to be involved.
  • Full body harness (IS 3521) and safety belts must be used while working at height.
  • Before commencement of hydrostatic test, specification sheet of the equipment and pipeline which mentions pressure and temperature must be available.
  • Hydrostatic test pressure and temperature should be clearly defined in the document.
  • Supporting drawings must be available during hydrostatic test.
  • Hydrostatic pressure test planning must be distributed to all relevant sections in plant site at least two days before execution date.
  • Make good coordination among the related sections that involve in the test.
  • All test equipment and tools shall be inspected for wear and damage.
  • The pressure gauges used in the test are recommended to have 150% maximum allowable working pressure.
  • Pressure gauges must be installed at proper location so that it can be easily read and do not create additional hazards to the hydrostatic test or expose personnel to the vessels being tested.
  • All the temporary tools such as valve, fittings, hoses, flanges, and blind plate have to be rated more than maximum hydrostatic pressure.
  • Isolate other equipment and pipelines that do not include in the hydrostatic test.
  • Check the vent line before testing and make sure that it is not blocked.
  • Isolate the test area and surround it with safety line. Put appropriate safety signal at that area.
  • Do not start the test if problem is identified.
  • Issuing of work safety permit by authorized personnel is compulsory.
  • Proper illumination in and around boiler and temporary system has to be ensured.
  • Please ensure that before commencement of tests, no work is going on inside the boiler. Clearance certificate shall be signed off by all parties before the test.
  • All the hangers should be in locked position.
  • All turbine equipment like HP heaters and condensers are to be isolated, normalized for boiler hydro test and clearance to conduct hydro test is to be obtained from turbine group prior to commencement of boiler hydro test.
  • Housekeeping is done in boiler area particularly on top of boiler, stairway, platform, ground level, furnace, corner water wall, superheater, reheaters, economizers, etc.

Modern Trends of Erection of Boiler with utmost safety and minimum manpower

The assembly of Ceiling girders with pressure part assembly weighing 3050 MT load is to be carried out at ground level, and the same is to be lifted with 16 strand jacks of 300MT capacity each upto 85.5 mtrs.

The same is to be connected to the main columns on LHS and RHS of the boiler.

This exclusive erection technique was adopted by M/s L&T for erection of supercritical boiler of 660MW capacity at Koradi Thermal power stations, thereby reducing the chances of accidents during pressure part erections considerably.

Strand Jacks at top of boiler column seen from cavity

Nose block assembly
Economizer hopper assembly with secondary pass & Eco.inlet headers
Ceiling girders assembly being lifted from Boiler cavity with the help of strand jacks

IBR codes for safety of Boilers

Safety practices during maintenance of boiler
❖ Furnace

  • Using sky climbers ensure electrical connections reliability – Proper Fitting – Necessary Care
  • Ensuring proper safety rope
  • Avoid Water Washing
  • With Cup-lock scaffolding, Water Jetting should be with thorough checking electric connections, proper scaffolding arrangement.
  • Railings and Side Supports
  • Perfect walkways and safety platforms
  • Use of Safety Belts

❖ Platen Super Heater

  • While attending Boiler Tube leakage at P.S.H. zone scaffolding erection is critical
  • From II Pass, Erection is done & hanging platform is required to be erected.
  • It is full disk involved work & to be carried out with utmost safety and sturdiness.
  • Utmost care for erecting scaffolding from wrapper tube coil assembly to required elevation.

❖ Reheater

  • Work is generally required to be carried out on slant portion and therefore safety precautions must be taken.
  • Utmost Safety is to be followed due to Restricted Space.
  • High risk & proper holding supports required for carrying out repairs.
  • Access platforms to be erected by maintaining perfect distance.
  • Sometimes slant portion is full of ash. While attending BTL, care to be taken that ash is to be removed completely. Sudden severe burning of legs has been observed.

❖ Screen Tubes

  • Utmost Safety is to be followed due to Restricted Area.
  • Both Side slant and Narrow Passage- safety norms to be followed stringently
  • Tube Metal temperature must be ensured before commencement of the work.
  • Only 2-3 access modules for free movement
  • Access Platforms should be erected with proper distances.

❖ Economizer

While carrying out Eco Coil / LTSH Coil Assembly replacement

  • Rear steam cooled wall scaffolding must be made permanent.
  • Electrically operated switches & their supports must be proper.
  • PPE must
  • Safety Belts
  • More precaution is in the vicinity of Eco-hopper.

❖ APH

  • Fire in APH during II stage passivation is generally observed.
  • Best Maintenance Practice and preservation of CDS tubes to be maintained.
  • Ensuring healthiness of Oil carry over detectors is must.

❖ Coal Mills

  • Care if burning reject is observed.
  • Check on Alpha Quartz Particle
  • Ensure Sulphur quantity in coal, otherwise allied effects –omitting, headache and unconsciousness.
  • Checking of breaker perfectly in “OFF” condition
  • Necessary care during start of mill at local/remote level

SAFETY PRACTICES FOR SAFE REMOVAL OF CLINKER

Ministry of commerce and Industry, department of industrial policy and promotion constituted a three-member committee under chairmanship of technical advisor(boiler) and secretary. The committee has submitted its report which has been approved by the hon’ble commerce & industry minister. As per this report, following recommendations are made to all Power plants for follow-up of the safe practices:

  • Opening of the man-hole doors/scaffolding doors during operation is prohibited and should not be resorted to at any cost.
  • Water injection for dislodging the ash in S panel should be avoided.
  • Whenever there is problem in ash handling system, the problem should be addressed and rectified fully before resorting to the normal operation.
  • Permission/Protocol shall be obtained from relevant departments as per prescribed norms, before taking up maintenance of equipment
  • If the system is not fully rectified due to constraints, the same is to be explicitly recorded and a timeline for further work to be indicated by maintenance.
  • If the problem is not fully resolved, the boiler should be stopped for undertaking maintenance.
  • Accumulation of ash should be controlled and continuous ash removal to be ensured without blocking the furnace bottom opening and the ash hopper.
  • Operational person should monitor the various equipment conditions and report to the operation-in-charge and also to mention in the logbooks about the condition of the equipment and corrective action if required, should be taken.
  • Proper communication should be made and insisted upon for shutting down the unit to avoid such incidents in future to save lives and equipment.
  • The Usage of coal of high ash quality should be studied for its effect in the boiler system & ash handling system.
  • It is mandatory that qualified BOE should be engaged in boiler operation always to ensure safe operation of the boiler.
  • Only such quality of coal is to be used for which the boiler has been designed.
  • Whenever people attend to any problem during boiler operation, there should be clear practice of having a checklist for safe practice to be adopted. This should be approved by committee of operation and maintenance/safety departments with final approval of the head of the plant. The persons working in ash handling area to be provided with thermal wear which can withstand high temperature and flame proof clothing for people working near the furnace area.
  • There should be a permit system for people working in other areas around the boiler also depending upon the activities being performed in the pressure parts, pulveriser systems, boiler operating floor, safety valve floating, boiler start up etc, which should be endorsed by safety department apart from operation and maintenance. This also to be notified by plant head.
  • All power plants are advised to follow the recommendations as above for prevention of accidents.

Safety practices during operation of boiler

Furnace explosion is the main cause in severe boiler accidents that leads to escaping out of flue gas and ash from the furnace and allied pressure part components & resulted into fatal accidents. Therefore, utmost safety is required to be taken while working on boiler and boiler mountings. Other critical parameters like ensuring wind box to furnace DP, complete combustion, flame intensity, availability of clinker grinders, soot blowing as per schedule, mill fineness, furnace temperature mapping and O2 grid measurement are also required to be monitored for prevention of explosion of furnace.

CONCLUSION

Hazard Identification & Risk Assessment study of each and every critical and crucial activity of carrying out the repairs of boiler is to be carried out for critical appraisal of all potential hazards involving personnel, plant, services and operation methods and to prepare a Risk Register that will help in continuously monitoring these risks and to identify the existing safeguards available to control the risks due to the hazards.

Thus, the safety practices are required to be implemented, monitored and controlled during erection, commissioning, operation and maintenance of the boiler to minimize the accidents.

Shri Pramod P Kate, Boiler Technical Consultant

  • Avinash Adhau
    May 25, 2021 at 5:07 pm

    Sir,very well elaborated boiler safety precautions during operation and erection,very helpful for personnel working in boiler operation, maintenance and erection.

  • Sunil wate
    May 26, 2021 at 5:16 am

    Very deep guidance given regrading safety concept of boiler.

  • Rajesh Ranjan
    May 26, 2021 at 8:16 am

    Very useful guidence on safety on and during boiler erection and operation. knowledge imparted is most important for the o&m officials. Hat’s off for sharing this information.

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