The enthalpy of the high-pressure feedwater entering the boiler system.

The enthalpy of the superheated steam leaving the boiler.

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IBR fittings are used in any industrial facility that operates high-pressure steam boilers and pipelines. Specifically, they are legally required under the Indian Boiler Regulations for any steam-containing pipe, valve, or fitting that exceeds specific pressure and capacity thresholds (generally above 1 kg/cm² or 14.2 psi).

Here is exactly where you will find them installed:

Critical Steam Circuits

Main Steam (MS) Lines

This is the primary artery of a thermal power plant. It carries superheated, high-pressure steam directly from the boiler to the high-pressure (HP) turbine. Fittings Used: Heavy-wall butt-weld elbows and tees are heavily utilized here. These fittings must be perfectly radiographed to ensure there are no internal microscopic cracks, as a failure in the main steam line is highly destructive.

Hot and Cold Reheat (HRH & CRH) Lines After steam expands through the HP turbine, it loses pressure and temperature. To maximize efficiency, this steam is routed back to the boiler via the Cold Reheat line, reheated, and sent to the intermediate-pressure (IP) turbine via the Hot Reheat line.

Fittings Used:Large-diameter IBR reducers and elbows. Because the volume of the steam expands as its pressure drops, reheat piping is significantly larger in diameter than main steam piping.

Boiler Feed Water (BFW) Systems Before water can become steam, it must be pumped into the boiler at a pressure higher than the operating pressure of the boiler itself. Fittings Used: High-pressure forged flanges (especially weld neck flanges) and heavy-duty check valves. These systems deal with immense hydraulic pressure and require robust, leak-proof joints.