Water hammer phenomenon in steam heaters

This post was last edited by wanlirn on 2023-10-31 09:52. The steam pipe has too small a diameter or is too long, resulting in high resistance. In your case, the diameter is already fixed; the solution is to add more parallel tube bundles. The one-way length of the steam coil should not exceed 200 times the pipe diameter; otherwise, it will be difficult to drain the condensate water, leading to water hammer

The water hammer phenomenon occurs when steam cools down and suddenly liquefies in the pipes, resulting in a rapid reduction in volume; as steam is quickly replenished, water hammer is generated. If all the condensate water generated by heat exchange can be removed, water hammer can be avoided. But this comes at the cost of a loss in steam volume, for reference.

Water vapor should enter from above and exit from below; if it enters from below and exits from above, water hammer phenomenon will occur.

This post was last edited by cust008 on 2023-11-2 09:09. The problem description is not very clear; it should be explained how it is put into use and under what circumstances water hammer occurs. In my opinion, before introducing steam, the drain valve should be preceded by a drain line (it is advisable to have such a drain line); steam should be introduced slowly until no water more flows out of the drain line, after which the drain line can be closed and the drain valve activated. If water hammer still occurs, consider blockage or failure of the steam trap, as well as an incorrect selection of the steam trap.

I agree with the view from the fifth floor: if the condensate is not drained in time, water hammer can occur when steam and water mix. It is recommended that the poster observe the operating condition of the steam trap, in order to rule out issues related to its selection and any malfunctions first. If the drainage capacity is insufficient, it is possible to consider adding a condensate collector with level control (one that drains only liquid and not vapor), to collect the condensate first before allowing it to be drained! We also use graphite heat exchangers heated by steam (which require a significant amount of steam). With a drainage system like the one described by the original poster, where a check valve is used to connect to the bottom drainage outlet, water hammer and surge effects will definitely occur, causing fluctuations in the system. Since the steam trap operates intermittently, it is not possible to ensure that no water accumulates in the pipes at the bottom. With a condensate collector in place, using a steam trap is also unreliable (the system may contain acid, and steam traps have a high failure rate); the only options are multiple exhaust vents (which result in high energy consumption) or automatic level control!

1. Is the selection of the steam trap correct? Does its flow rate meet the amount of condensate generated, with a sufficient margin? If the pipe is too thin, it cannot be enlarged as required. 2. Does the steam trap come with a front filter? If not, a front filter needs to be installed. 3. Does the steam trap have back pressure? 4. Is the steam trap of the immediate-drain type? Condensate accumulated at its front end should be drained promptly. 5. Add a longer distance between the steam trap and the tube bundle, although this seems non-standard. 6. Is the steam trap broken?

We have encountered this situation in finned heat exchangers; we took measures such as selecting the appropriate drain valve, adjusting the steam pressure, and making changes to the piping. As mentioned on the second floor earlier, trying to reduce the length of the piping and increasing the number of steam inlets and outlets can help improve the situation. In the end, the direction of the heat exchanger was adjusted during maintenance, which prevented this phenomenon from occurring. It is an engineering example, but it may not be suitable for your specific conditions; please use it as a reference.

Water hammer occurs in such situations, usually due to the design of the heat exchanger or an excessive temperature difference between the steam and the medium being heated, which results in a two-phase flow of vapor and liquid inside the coil. Since the drainage from the steam trap is not continuous and the liquid storage space within the coil is limited, pressure fluctuations occur within the coil during the drainage process, which may lead to water hammer effects. During the initial design phase, it is possible to consider having the process medium flow in the tube side and steam flow in the shell side; in this way, the shell side functions like a drum, and any condensate will accumulate at the bottom, preventing water hammer from occurring. Given that this heat exchanger is already in use, the difficulty of carrying out modifications is high. It is recommended to consider installing a collection tank at the condensate outlet of the heat exchanger, using this tank for water drainage. The advantage of this approach is that it increases the storage space for condensate, ensuring its timely removal. Moreover, when the drain valve discharges water, it does not cause significant changes in the vapor-liquid volume within the coils, which should help reduce the effects of water hammer. This is provided for reference only.

Study*study*~! ! The statement is by no means filler! ! !

Steam enters the pipe, and condensation is generated continuously; whether drainage is provided or not makes no difference at all