MPIL’s Structure to BHEL’s Bunker

By
Amol Bhalerao
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A Bunker Shell forms an integral part of any thermal power plant and MPIL Steel Structure was excited to be the part of BHEL’s prestigious project of a Bunker Shell for a 2 x 500 MW thermal power plant located at Tiruchirapalli. MPIL had successfully executed the Bunker Shell project in the given time frame. The bunker weighed 430 MT, reaching a height of 24.36 m from datum. The most challenging aspect of this project was the sheer size of the shell, hence the fabrication had to be planned as per the in house fabrication, pre assembly for quality check and site dispatch. Considering the challenges, the shell was divided into 4 parts which consisted of 23 sub-assemblies. There were more than 2,000 steel plates of varying sizes from 10 mm to 40 mm to be welded together. Each plate was cut to the size with the help of CNC multi nozzle gas and CNC plasma cutting machine. These plates were welded together as per the part drawings. They were assembled at the factory floor with the help of EOT cranes. Due to its sheer size, the assemblies and subassemblies were shifted to MPIL’s open fabrication yard where the company utilized its gigantic crane along with the hydras to assemble each part together for final quality inspection.
The Bunker Shell demanded for combination of high grade steel material to withstand high temperature required in Boilers for Power Plants. To meet the said requirements, the material used were as per -IS 2062 grade E 250 and E 350 for outer shell and inner liner of SS 304 SA 260. The bunker shell was composed of Mild Steel as well as Stainless Steel liner; hence, it was time consuming process for the welders to weld two dissimilar metals. Consumables like E7010, E8018, E6015, E308 and E309 were utilised. Each of the welded joint was thoroughly inspected with 100 per cent Radiography and Ultrasonic Test.
Each of the 23 sub-assemblies was given a specific part number for easy identification and tractability. This increased the efficiency of assembly process at the site. The subassemblies were then loaded on to the trailers according to their assembly sequence and were then dispatched to Tiruchirapalli.
MPIL has come long way and has successfully explored great expertise in domestic and international projects. The company has been exploring new horizons in the Steel Structure Industries to reach new heights.

Project – Bunker Shells (428 MT)

Project Details – BHEL-High Pressure Boiler Plant, Tiruchirapalli
For Neyveli Lignite Corporation (2X500 MW)

Trial Assembly Procedure

1 Bunker Shell- 4 Parts – Total 23 Nos. of Assemblies
Part 1 – 4
Part 2 – 4
Part 3 – 8
Part 4 – 7
Plate Thickness Details-  (Total 2000 Plates of varying profiles)

  1. MS E 350 C – 189 MT (Bunker Skin Plate with its Stiffeners – 1300 Nos. of Plates)
  2. SS 304 – 24.5 MT (Liner Material-704 Nos. of Plates)
    1. Bunker Skin Plate – 12 mm (E 350 C)
    2. Hopper Plate – 12 mm (E 350 C)
    3. SS Liner Plate – 4 mm (SA240 TP 304)

Bunker Stiffener Plate – 6mm to 50 mm (E 350 C)

Assembly of Bunkers

  1. Part 1 and Part 2 assembly will be in vertical position with only 4th hopper of Part 1.
  2. Part 2 and Part 3, Part 3 and Part 4 can be done Vertical or Horizontal as per suitability.
  3. Ensure the loose SS liner plate shall be laid with wall plates.
  4. Proper marking on loose SS liner Plates should be done with hard Punch and painted with white color.