Problems with pressure control in steam pipeline systems

This post was last edited by “Hasty Passerby” on December 10, 2017, at 13:37. Regarding the design of pressure control in industrial steam pipeline networks, different design institutes have their own practices. One approach is as follows: in medium- and high-pressure pipeline networks—especially those used for supplying power steam (particularly when large-sized equipment accounts for a significant proportion of steam consumption while the overall capacity of the network remains relatively limited)—rapid pressure relief valves (also known as “one-second release valves”) and pipeline pressure regulating valves are installed. These devices serve to counteract any sudden rise in pipeline pressure that may occur when individual large-scale steam-driven units shut down; such a shutdown leads to a rapid decrease in steam consumption, thereby causing a spike in pressure. Waiting for adjustments to be made on the boiler side would take too much time； At this point, releasing it in one second will instantly supply the steam needed to compensate for the decrease in steam consumption by the unit, after which the flow rate will be gradually reduced until it is completely shut off ； At the same time, the pipeline pressure control valve begins to release air for regulation until the pipeline pressure returns to normal. During this period, the plant’s load control system will work in conjunction with the boiler’s load control system to gradually reduce the load, until the pipeline pressure control valve closes and the pipeline pressure stabilizes at the set value. Of course, a safety valve is also installed as a final safeguard. The advantage of this approach is that it allows for rapid adjustment of pressure fluctuations in the steam pipeline network caused by sudden pressure changes, thereby preventing disruptions to the operation of other units and ensuring stable operation of the entire system. The disadvantage is: additional investment is required, and the price of the valve inlet is high ； Under normal conditions, the valve will have some leakage, which causes water to accumulate inside the vent silencer; when the valve releases water rapidly, hot water can spray out, so it is necessary to drain this water promptly and provide a safety margin. Another option is: when the capacity of the pipeline network and the steam demand are high enough, only safety valves are installed, with no regulation system in the pipeline network. In the event of an emergency, since the steam consumption of a single unit constitutes only a small fraction of the total capacity of the pipeline network or the steam consumption of other users on that network, it does not cause significant fluctuations in pipeline pressure. The boiler system can adjust the load to achieve satisfactory results. Third option: In multi-level pipe networks, pressure control valves are installed in the upper-level networks to release pressure to the lower-level networks; however, the capacity of the lower-level networks must be taken into account, and vent valves should be installed as necessary to regulate the pressure in those networks. Safety valves are installed in pipelines at all levels. The advantage is that it saves steam and reduces emissions; the disadvantage is that improper adjustment can affect the pressure stability in the lower-level piping networks, and may even cause fluctuations in the pressure across multiple levels of such networks.

Setting a pressure control valve is used to convert steam with high pressure into steam with low pressure, and a safety valve is installed on the low-pressure side

In multi-level pipe networks, the higher-level network releases pressure to the lower-level networks, but the capacity of the lower-level networks must be taken into account. When the subordinate is too small, a portion needs to be emptied.

It seems I’ve seen quite a few cases where there are no pressure control valves or safety valves installed in the plant’s steam system. Is there something wrong with this setting?

We have used both the configured and unconfigured approaches in our two projects, and no issues were encountered during operation. The setting of the safety valve needs to be confirmed again.

Is safety even more necessary? Is the safety valve placed appropriately at the end of the pipeline network?

It’s a project from a few years ago; I can’t remember the exact location precisely, so I need to clarify the details.

The information is good; it’s worth keeping. Thanks

After implementation, the safety valve was installed on the main pipeline near the upstream side of the main steam-using units. The main consideration is that the pressure at the end of the official pipeline is the lowest; when the safety valve at that end reaches its set pressure, there is greater overpressure in the pipelines upstream, which poses a certain risk. In actual operation, the pipeline network pressure remains about 0.5 MPa below the design pressure.