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Case Study of IISCO

Advantages of Double Flanged Screwed Pipes Over Sand Cast Pipes For Sand Stowing Operations in Coal Mines :

Hi thereto double flanged C.I. Pipes cast in sand mould have been used for sand stowing operations in coal mines. With the commissioning of double flanged screwed Pipe plant at kulti 81 works, the Indian iron and steel company. Ltd (IISCO) is now in position to offer double flanged screwed pipes with spun barrels for sand stowing operations. The pipes are available in 150 mm dia with standard length of 5.3 meters and 10 mm wall thickness, confirming to IS: 1536, Class ‘B'.

Advantages of Screwed Pipes :

Some of the advantages of 150mm x 5.3 meters D/F Screwed pipes over 6” dia x2.75 meters sand cast pipes are enumerated below :

Price :

The F.O.R. Kulti price per meter (as on 1-2-83 ) of screwed pipes is 56.67% lower than sand cast pipes resulting in a substantial saving in cost of sand stowing operations.

Price of 6” dia x2.75 M sand-cast pipe Rs. 524.49 per meter
Price of 150 mm dia x5.3 M Class ‘B' Screwed pipe Rs. 226.58 per meter
Saving in price / meter Rs. 297.93 (56.80%)

Life of Pipes :

The centrifugally cast barrel of screwed pipes has a dense and homogeneous structure with superior wear resistant qualities resulting in longer life of pipe.

A trial was carried out at lay bed colliery of Bharat coking coal Ltd.(BCCL) between 25-12-77 and 26-4-78 when 12,050 cu meter of sand slurry was pushed through line having 6” dia x 2.75 meters sand cast pipe and 150mm dia x 5.3 meters Class ‘B' pipe. At the end of trial it was observed that the wear in the bottom portion of screwed pipe was 3.5 mm asa against 13 mm in case of sand cast pipe, Assuring that 3 mm pipe thickness is left before the same is rejected and pipe is rotated 3 times before rejections the life of screwed pipe will be 13% higher than sand cast pipe.

Sand Cast Pipe Screwed Pipe
Thickness of new pipe 26 mm. 10 mm
Wear after pumping 12050 cu.m of Sand slurry 13mm
Thickness of pipe before rejections 3mm 3mm
Slurry which be pumped before that Pipe is rejected 3x12050x(26-3)/13 = 63,958 cu.mi.e. 13% higher 3x12050x(10-3)/3.5 = 72,300 cu.m.i.e. 13% higher

Length :

Sand cast pipes are available in length of 9 ft (2.75 M) whereas screwed pipes are available lengths up to 5.3 meter. Longer lengths (92.7 % longer) means less number of flange joints and faster lying of pipe lines.

Also multiple lengths of sand cast pipes of shorter lengths can replaced small number of screwed pipes.

Weight :

Screwed pipe is lighter by 34.4% than sand cast pipe which means ease handling in underground mines.

Weight of 6” dia x 2.75 meter sand cast pipes 315 Kg (114.5 Kg/m)
Weight of 150mmx5.3 meters class ‘B' Screwed pipe 206.67 Kg (39.99 Kg/m)
Difference in weight 108.33 Kg
Screwed pipe lighter by 34.4%

Mechanical Properties :

The Centrifugally casting process imports to the screwed pipe barrels uniform sectional thickness, higher strength, higher resistance to bursting and transverse stresses and ensures freedom from blow holes and homogeneity of structure.

Being machined on sophisticated automatic special purpose machines highest quality of pipe is ensured. Before tightening of flanges on the barrel a suitable epoxy resin base sealing compound is applied on the threads ensuring leak proof joints.

Standardisation :

The screwed pipe confirms to Indian standard specification IS – 1538: 1976 whereas sand cast pipes are not covered by Indian Standard.

Availability :

The screwed pipes are available at short notice from The Indian Iron & Steel Co, Ltd, is Public Sector Company.

Conclusion :

For sand stowing operations in coal mines the double flanged screwed pipes are superior to sand cast pipes on account of advantage summarized below :

  • Price : 56.80% Cheaper Reduction in sand stowing cost.
  • Life : 13.0% higher Saving in sand stowing cost.
  • Length : 92.7% Longer Less number of joints and saving in jointing material.
  • Weight : 34.4% Lighter Ease handling.
  • Mechanical Properties : Far superior Durability.
  • Standardisation : Confirm to IS 1536 Standard pipe.
  • Availability : Short delivery from long term contract can be entered into public sector company.

Hence double flanged screwed pipes are ideally suitable for sand stowing operations.

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