Regarding steam consumption

Hello, there are mainly a few aspects to pay attention to here: 1. Pressure unit: The unit for steam pressure should usually be kPa or bar, rather than just kPa. 0.4 kPa actually means a very low pressure, equivalent to only 4000 Pa, while the correct value is likely 0.4 MPa, which is 400 kPa. 2. Pressure after pressure reduction: When the steam pressure used by the equipment is reduced from 0.4 MPa to 30 kPa, such a significant drop in pressure can lead to a decrease in steam density and changes in flow velocity, which directly affect the flow rate and the operational efficiency of the equipment. 3. Diameter change issue: Increasing the pipe diameter from DN80 to DN100 is usually done to reduce pressure losses in the pipeline and increase flow rate. However, the specific effects need to be comprehensively evaluated by considering changes in steam pressure and temperature, as well as the total length and layout of the pipes. 4. Flow rate calculation: The original required flow rate of 2 t/h can be reduced to 1.5 t/h after processing, indicating that there is a certain loss in flow rate during the process of pressure reduction and diameter change. It is necessary to determine whether such losses are within acceptable limits, and to consider whether other factors such as pipe leaks or improper valve adjustment are causing additional losses. In summary, it is recommended to check whether the pressure units for the steam are incorrect, and to reevaluate the design of the entire system, particularly the pressure reduction and diameter change sections, to ensure that they meet the requirements of the equipment while taking efficiency and safety into account. If possible, it is best to communicate further with the equipment supplier to confirm the details. .

Thank you very much for your answer. You are absolutely right; the equipment manufacturer requires us to provide steam with a pressure of 0.4 MPa and a diameter of DN80, at a flow rate of around 2 tons per hour, after which it passes through the pressure reducing valve provided by the manufacturer. The steam pressure is reduced to 30 kPa, and then the pipe is resized to DN100. The manufacturer claims that the steam flow rate after pressure reduction can reach 1.5 t/h. But it always seems that the steam flow rate after pressure reduction cannot reach such a high level.

The steam flow rate through a DN80 pipe at 0.4 MPa is insufficient to meet the requirement of 2 T/H; at least a DN100 pipe is needed

The length of the steam pipes before and after the pressure relief valve also needs to be considered

First, you found that the steam pressure value should be 0.4 Mpa before temperature and pressure reduction; so you need to determine what the temperature is Since steam is divided into saturated steam and superheated steam, it is only possible to determine the density of steam once you are aware of both types. The flow rate of 2 t/h mentioned actually refers to the mass flow rate after temperature and pressure compensation (volume flow rate × density = mass flow rate). A DN80 flow meter (using Yokogawa’s vortex flow meter for saturated steam at 0.4 MPa) has a measurement range of 0.13–3.05 t/h; at a flow rate of 2 t/h, the velocity is 54 m/s, which falls within the measurable range. After reducing the temperature and pressure to 30 KPa, switch to a DN100 flow meter (using a Yokogawa vortex flow meter for saturated steam at 30 KPa); its measurement range is 0.12–1.52 t/h, which is already close to 80 m/s, reaching the upper limit of the flow meter’s measurement capacity. This is illogical; it is recommended that you determine the density by observing its volumetric flow rate as well as temperature and pressure, and use various factors as references for making a judgment. Firstly, vortex flowmeters incur pressure loss; after reducing the temperature and pressure, I calculated that the pressure loss was close to 6 KPa, which is a significant amount considering that the initial pressure was 30 KPa.

This post was last edited by pzhmotor on 2025-4-14 at 10:10. Does steam with a pressure of 0.4Mpa become 0.03Mpa after pressure reduction? Similar to air discharge, the back pressure is too low. Is there such a device? With such a low back pressure, the opening degree of the control valve will be very small, and it is highly likely that there will be a loud noise in the steam pipes on site. (The flow rate after the control valve can reach 1.5 t/h; when the pressure difference between the inlet and outlet of the control valve is high, the torque required of the actuator increases, and such control valves are not inexpensive.) Our evaporators operate under similar conditions: saturated steam at around 0.5–0.6 Mpa passes through the control valve and becomes steam at around 0.2 Mpa, which is used as the heat source for the evaporator, with a steam flow rate of 5–8 t/h.

That’s a bit of a waste; it’s already an evaporator. Wasn’t TVR taken into consideration? Is it still the fact that secondary steam is too corrosive and causes severe pollution? If there’s a need, we can discuss the technical aspects. VX 13210220130

It can be a value that’s not actually used; a DN80 pipe might not be sufficient, but a DN80 control valve will definitely do the job