Steam boilers are imperative in the process and manufacturing sector to generate high-quality steam. Plant managers monitor various factors to ensure hassle-free operations. One of such important factors is steam pressure. An oversized steam boiler utilizing saturated steam opt for reducing the steam pressure. Steam pressure is determined by the factors like the maximum safe working pressure of the steam boiler and condensation within the pipe.
What do you mean by Reducing Steam Pressure?
Steam pressure reduction means reducing steam pressure of the boiler through the pressure control included in the steam boiler. Reducing steam pressure impacts the high-pressure part of the boiler. The pressure-reducing valves (PRV) adjust the pressure at lower levels within acceptable limits. Therefore, it can be concluded that reducing steam pressure results in considerable savings in the high-pressure section of the steam boiler.
Why Reduce Steam Pressure?
Listed below are some of the energy losses in steam boiler systems that can be decreased by reducing steam pressure,
- Combustion Loss:
Reducing steam pressure results in lowering the stack temperature that consequently leads to improved combustion efficiency. The ideal method to determine the temperature reduction and savings for a steam boiler is by conducting a combustion test at different pressure and constant load.
- Boiler Blowdown Loss:
Reducing steam pressure leads to a reduction of blowdown loss in a steam boiler. If the energy is recovered through a blowdown heat recovery system, it hinders any chances of further savings through reducing steam pressure. On the other hand, draining of blowdown water and venting of flash steam result in savings from reducing steam pressure.
- High-Pressure Steam Piping Heat Loss:
Heat loss from steam and condensate piping occurs in two stages. Initially, the heat is conducted from the hot steam through the walls and insulation surrounding the pipe to the outer surface. Later, the heat is lost by radiation and convection to the ambient air.
- Steam Leaks from High-Pressure Components like Valves, Piping, and Other Components:
External steam leaks take place in piping, joints, valves, and other components for various reasons. The degree of leakage varies on the maintenance of the steam boiler. It is mainly caused due to corrosion, erosion, water hammer, faulty design, or poor installation. Reducing steam pressure decreases the leakage rate in the high-pressure part of the steam boiler system.
- High-Pressure Steam Trap Leakage:
Poor steam trap maintenance is a major contributor to losses in the steam boiler system. Although reducing steam pressure is not an alternative for regular trap maintenance, it can result in savings of 0.6% of fuel input. Some of the other factors that impact the steam loss that should be considered are,
- Leakage of only a partial opening of the trap orifice, as compared to a “blow through”
- Steam trap flow coefficient
- Condensate passing through the leaking orifice
- Pressurized condensate return line
- The usual reduction of trap inlet pressure when variable process loads are involved
The combination of the factors leads to additional resistance to the flow of steam through the leaking trap orifice. It results in leak calculation for an individual trap to vary between 10% and 100%. Reducing steam pressure eventually reduces the leakage in high-pressure traps.
- Flash Steam Loss through High-Pressure Condensate Receiver Vents:
A large steam boiler includes multiple local condensate receivers that collect hot condensate and pump it back to the boiler plant. Flash steam losses will be decreased directly by reducing the steam pressure in the high-pressure section of the steam boiler.
- Steam Supplied to the Deaerator:
The steam quantity used for the deaerator is decided by the energy required to heat a mixture of hot condensate and cold makeup water to the saturation temperature at the operating pressure of the deaerator. The reduction in the steam leak, steam trap leak, and flash vent loss leads to a reduction in the boiler makeup water rate. It consequently leads to a reduction in the steam supplied to the deaerator.
- The Enthalpy Savings Effect:
The energy supplied to steam loads comes from the latent energy in the steam. Steam utilized at the pressure it is being generated requires less steam to supply the required latent energy at a lower pressure than at a higher pressure. Condensate from reduced steam pressure loses less energy from flash than condensate from high-pressure steam. At lower pressure the steam boiler must supply less energy to the condensate to raise it from the feedwater condition to the saturation point.
- Problems and Limitations with Reducing Steam Pressure:
- Boiler Carryover Steam Boiler
- Boiler Circulation Leading to Tube Overheating
- Boiler Performance at Highest Rated Load and Rated Pressure
- Steam Velocity, Pressure Drop, and Temperature in Piping
- Impact of Steam Pressure Reduction on Flowmeters
- Steam Traps
Rakhoh Boilers are leading boiler manufacturers in Pune, with more than 3000 steam boiler installations in over 26 countries worldwide. We manufacture efficient and reliable steam boilers, waste heat recovery systems, thermic fluid heaters, and boiler accessories and provide the best boiler services to boost the overall efficiency and performance of the steam boiler.
To learn more about our products and services, visit www.rakhoh.com