Salient Features of Steam Distribution System In Process Plant

A Steam Distribution System inside any Plant plays a crucial role in performance improvement and efficient operation of Plant. To keep the Plant equipment healthy, to maintain their effective working and to maintain the high Production, the efficient distribution of Steam is necessary which accounts to the supply of steam of most appropriate quality (Pressure & Temperature) and quantity.

The Process of Steam Distribution starts with the Central Source where the Steam is being generated, either in a Boiler or Co-Generation Plant then outflow towards the Point of use. The steam need to be passed down to the point of use through the Stream of Pipes or “Steam Mains” transferring the steam from Boiler to the operation center.

• Starting Load: During Startup, the condensing rate will be at its peak because this is due to the fact that the temperature difference between the steam and the pipework is at its greatest at the start. The condensing rate of steam during the startup is often termed as “Starting Load”.
• Running Load: After Startup, there is a slight temperature difference between the pipes and the steam, since the pipes have reached at a certain higher temperature, but some condensation will still happen since the pipework is still radiating heat into the surrounding air. This condensing rate is often termed as “Running load”.

Fig. 1 Typical Steam Distribution System

Due to the gradient in the steam main, which should be set up to fall in the direction of steam flow, the ensuing condensate falls to the bottom of the pipe and is carried along by the steam flow. The steam main will then need to have the condensate emptied from a number of key locations.

Once the product and equipment are warmed up (starting load), the steam sends its energy to the process to continue heating it (running load).

The Losses in the Steam Distribution System are due to following reasons:-

• Leakage of steam from High Pressure Components like Valves and Piping
• Flash steam loss through high-pressure condensate receiver vents.
• High-pressure steam trap leakage
• High-pressure steam piping heat loss

At higher pressures, a kilograms of steam takes up less space than it does at lower pressures. Therefore, for a given heat load, the size of the distribution mains will be less with a high-pressure system than a low-pressure system if steam is created in the boiler at a high pressure and also supplied at a high pressure.

• Higher pressure steam generation takes up less space than lower pressure.
• Smaller steam distribution lines are needed for transporting steam under higher pressure.
• Smaller diameter steam lines call for less capital expenditure on insulation, supports, flanges, and pipes.

For the purpose of preventing entrained and ensuring that high-quality steam passes through, a PRV is mounted upstream of the reducing valve. If the PRV malfunctions, a safety valve on the downstream side protects the system.

Thus efficient steam distribution is critical in improving the plant and process efficiency and performance.