Regarding the filling pipelines for LNG-powered ships and the liquid discharge pipelines for storage tanks

I’ll take the lead for now; I’m hoping that the experts here can give me some advice: handshake

Check online: as close as possible to the LNG storage tank. http://ishare.iask.sina.com.cn/f/jaUbbxHdM4.html p11/27

Typically, a manual shut-off valve and an automatic shut-off valve, both of which are globe valves, should be installed in series on the pipeline at the liquid outlet of the LNG tank. Additionally, the location of the liquid tanks and the arrangement of pipeline penetrations through the hull must also be considered.

This post was last edited by kkkbaa on 2019-10-23 at 10:37; please upvote it again

Thank you very much for your answer. I have another question: are there any requirements regarding the sequence in which automatic and manual stop valves should be installed? Also, I saw in the CCS specifications that there are three types of valves: manual, remote-controlled, and emergency shut-off. Where should these valves that can be operated remotely be installed? Is it okay to install one at each of the filling port and liquid outlet of the LNG tank?

This post was last edited by mg_haichuan on 2019-10-23 at 11:37. In fact, the guidelines you mentioned all contain clear requirements and explanations. Personal understanding: Generally, manual valves are installed at the outlet of the liquid tank, as close to the tank as possible ； The automatic valve may be placed at an appropriate distance from the liquid tank, but it must be outside the machinery space ； Of course, the standard accepts “manual and automatic combined valves”” ； Automatic valves, remote-control valves, ESD valves, etc., can be the same type of valve with a “remote control function” ； Usually, this valve is also called the main gas valve. The main valve can be one or several ； It depends on the number of system devices and how they are arranged.

Thank you for your answer. I have another question: the regulations state that pressure relief valves must be installed on all liquid gas fuel pipelines that could be isolated. Is a pressure relief valve installed on liquid LNG pipelines meant to release liquid, LNG vapor, or both? For example, when the maximum flow rate is reached and the pipeline is almost filled with liquid LNG, the valve releases liquid when the pressure exceeds the set value; it releases vapor to relieve pressure under normal flow conditions. I’ve seen that the safety valves used by many manufacturers are essentially angular spring-type safety valves. As for how such valves are installed in pipelines, is it necessary to run a separate pipeline from the main pipeline for their installation, and then connect it to the venting device?

Yes, the safety valves on gas pipelines are basically the “angular spring safety valves” you mentioned, which are installed after a branch pipe is led off from the main pipeline. In my personal understanding, taking the liquid-phase pipe as an example, during normal operation, if there is overpressure, the liquid medium will naturally be released ； The description just now, “liquid gas fuel pipeline that may be isolated,” should refer to the “closed” section between two valves that can be closed by valves; when liquefied natural gas evaporates and expands, causing overpressure, a liquid-gas mixture is formed.

This post was last edited by kkbbaa on 2019-10-24 09:15. There’s another question. . Can this combined valve of a manual valve and a remote-controlled valve be an automatic valve with a handwheel? Also, to the best of your knowledge, for the control valves on LNG pipelines, should globe valves, ball valves, or butterfly valves be used? My understanding is that ball valves and butterfly valves are suitable for pipelines that come into direct contact with steam, while globe valves are sufficient for pipelines carrying liquid fuel; however, the engineering team requires the use of butterfly valves for all of them. . . Could you give me some advice?

When selecting valves, the requirements of the process system must be taken into account. As stated in the text, it is necessary to have an emergency shut-off device on the LNG pipeline; for such applications, ball valves are commonly used, as they offer rapid shutdown and good sealing properties. Butterfly valves can also be used for shutdown purposes, but their sealing performance usually does not meet the requirements for liquefied hydrocarbons； Globe valves have excellent flow control characteristics and a higher pressure drop, but they are not suitable for emergency shutdown (they are more commonly used as control valves). Therefore, we can reconfirm the process requirements with your process engineering team; unless it is a very large-diameter pipeline (which, based on the information provided, does not seem to be the case here), it is not recommended to use butterfly valves for emergency shutdown. Another suggestion is that the valves on LNG pipelines should, regardless of the type chosen, be connected by welding rather than flanges in order to completely eliminate the possibility of leaks. Regarding the safety relief between two block valves on the LNG pipeline, it relates to TSV valves in the usual sense; when the pipeline is filled with liquid, what is released is the LNG liquid that has expanded due to heat, and this liquid should flow into a closed LNG liquid-phase relief main. I hope this helps!