When steam is output from the boiler at high pressure and transported to various equipment points, it is generally necessary to control the pressure by using back pressure valve. Why is pressure reduction required for steam? The main reasons are as follows:
Boilers typically produce high-pressure steam, which allows for smaller boiler sizes, reduces the occurrence of wet steam, improves steam dryness, and facilitates long-distance transportation.
Steam density changes with pressure. High-pressure steam has higher density, allowing for the transport of a larger quantity of high-pressure steam through pipes of the same diameter. Using high-pressure steam reduces the size of the pipelines and saves costs.
Condensation occurs when steam is used. Reducing the pressure of steam decreases the pressure of the condensed water, avoiding losses caused by the generation of flash steam during condensate discharge. Discharging condensate at low pressure results in less energy loss.
Saturation temperature and pressure correspond to each other for saturated steam. Pressure control is necessary for temperature control in sterilization processes and surface temperature control in paper drying machines. Pressure reduction valves are installed to control the pressure and, in turn, control the temperature of process equipment.
Process equipment has its own design pressure. When the supplied steam pressure exceeds the requirements of the process system, pressure reduction is needed. Some systems use high-pressure condensate to generate low-pressure flash steam for energy-saving purposes. When there is insufficient flash steam production, pressure reduction valves are used to supplement with low-pressure steam.
Pressure reduction can reduce the steam load on the boiler because steam at low pressure has higher enthalpy. The enthalpy values are 1839 kJ/kg at 2.5 MPa and 2014 kJ/kg at 1.0 MPa. Therefore, low-pressure steam is more suitable for equipment use.
Regarding the use of back pressure valve., users are particularly concerned about how to use them effectively and meet the actual needs of application equipment. First, it is important to understand the basic types of pressure reducing valves and their respective advantages and disadvantages.
In conclusion, pressure reducing valves are necessary in steam pipelines to ensure equipment safety, achieve fluid control, enhance system safety, and conserve energy. The selection and installation of pressure reducing valves should be based on specific application requirements and pipeline design parameters, following relevant standards and specifications.