The centrifugal compressor features four stages of compression; will reducing the pressure at the outlet of the high-pressure cylinder affect the pressure at the inlet of the low-pressure cylinder?
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As the title indicates, our plant uses centrifugal compressors with four stages of compression. The drive unit is a water-cooled, fully condensed steam turbine, and dry gas seal discs are used for sealing. There are three anti-surge valves at the outlets of the four stages, leading back to stages one, two, and three. In the past, the requirement for the outlet pressure at stage 4 was to be no less than 0.8 MPa. A few days ago, in order to reduce steam consumption, it was decided that there was no need to control the flow rate of water in the accompanying condenser (previously, we would reduce the water flow in the condenser when the pressure dropped). For the ice machine, the outlet pressure at stage 4 only needs to be no less than 0.6 MPa, while the inlet pressure at stage 3 is 0.3 MPa. I would like to ask whether, under winter conditions, the pressures at stages 1 and 2 might become particularly low
Previously, when the pressure at stage 2 was below 0.08 MPa, the outlet temperature of the ammonia cooler we used reached -24°C; according to the equipment’s nameplate, the lowest possible temperature is -25°C. I am concerned that reducing the pressure at stage 4 could affect the pressure at stage 2, thereby causing the temperature to exceed the requirements specified for the equipment
If there are operating procedures, they still need to be followed, as this issue involves many different factors. If it is necessary to change the relevant conditions, a feasibility study report must first be prepared, and approval must be sought from the higher-level department in charge of equipment. Afterwards, the equipment department will participate in organizing the evaluation and conducting on-site tests. Due to the many factors involved, it is recommended to break down this issue by considering the function of system devices as that of individual devices, to determine whether it falls within the allowable parameters of those devices. For reference.