Seeking instructions for heating steam pipes

The key is to thoroughly warm the pipes and drain a large amount of steam by backwashing.

The so-called warm-up of pipes involves slowly heating components such as pipes, valves, and flanges using steam, allowing their temperature to rise gradually. This is done to avoid introducing steam suddenly into pipes that are at low temperatures, thereby preventing excessive thermal stress that could damage these components. At the same time, it drives out the condensate water in the pipeline to prevent water hammer during steam supply. The heating time for cold steam pipes is generally no less than 2 hours ； The heating up time of hot steam pipes is generally 0.5 to 1 hour. When warming up the pipes, it is necessary to check whether the steam pipes expand properly and whether the supports and hangers are in good condition. If any abnormality occurs, the pipe warming should be stopped to identify the cause and resolve the fault.

By the way, what do cold steam pipes and hot steam pipes mean respectively?

Are there standard requirements for the heating rate of steam pipes? Are there standard requirements for the pressure increase rate of steam pipes?

Before heating the steam pipes, the entire system pipeline network should be inspected first. Heating process: It is carried out in sections, with the low-point vent being opened gradually section by section, all the way to the user end. Based on the pressure and temperature readings of the pipeline network, gradually reduce and eventually shut off the vent of the preheated pipeline, thereby slowly increasing the pressure and temperature inside the pipeline. Basically, keep the heating rate at no more than 50°C per half hour. When heating 10 kilograms of steam to 160–200°C, it is also necessary to do so slowly. This range is the process of transition from saturation to superheating, during which water hammer and leaks are most likely to occur. When warming the pipes, pay close attention to the valves at the pipe connections; tighten them promptly if any leaks are detected

(Forwarded) Steam pipe heating: 1) Follow the inspection procedure – first close all valves and open all drain valves along the pipeline. 2) Slowly open the steam inlet valve; pause when steam starts flowing, and open it a little more if there is no severe water hammer. 3) Check in the direction of steam flow: close one drain as soon as steam is detected there, then proceed to the next drain and close it once steam is detected there, continuing until steam is detected at the end. 4) Once steam is present in all the pipelines, open the steam introduction valves to increase the parameters to the desired pressure. 5) Check again along the process. There is another way of starting up the plant: it involves a sliding-parameter start-up method. As soon as the boiler starts, steam is sent to the pipeline network, and the steam-using equipment is also supplied with steam. The parameters of the steam system match the rate at which the boiler heats up and increases pressure, which allows **the startup time of the steam system to be reduced. There is no risk of water hammer or vibration (of course, the drain valves still need to be opened). I have used this method to start up medium-pressure and low-pressure steam systems on many occasions, and there has never been any pipeline vibration or water hammer; moreover, the startup time is reduced and steam consumption is minimized.

May I ask whether the large vent valve should be opened before steam is introduced into the pipe for heating? ? How much to open?