Please share good suggestions and experiences to help make our pipe and valve division more successful
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In today’s era of rapid advancement in science and technology, all of you colleagues will have fleeting good ideas, practices, and experiences at your respective work places (excluding trade secrets, of course). I’d like to share this with everyone to pool our ideas – maybe there will be some unexpected surprises! I’ll take the lead on this topic first. An example is as follows: In the fine chemical coatings industry, a process that involves the use of a highly precise and expensive grinder is required. After grinding, there is a buffer tank; since the product is in the form of very fine powder, powder explosions can occur. To protect the grinder, a special anti-explosion valve is installed in the pipeline between the grinder and the buffer tank (I really can’t remember its exact English name anymore, as only a few manufacturers abroad are capable of producing it). The purpose of this valve is to close itself when a shock wave is generated by a powder explosion, thereby allowing pressure to be released through a blast door in the buffer tank, thus protecting the grinder. Due to the high cost of the product, a foreign company made the following improvement: based on their experimental data, the explosion pressure was found to be below 1.0 MPa; therefore, instead of relying on pressure relief, they opted for pressure resistance in the buffer tank (by increasing the design pressure of the tank to 1.0 MPa). Special anti-explosion valves were installed on the inlet and outlet pipes of this buffer tank. When an explosion occurs in the tank, these valves close completely, thereby protecting the grinding equipment and preventing loss of the expensive product. Feel free to leave comments!
Let me add another point: in cases where a burst disc is installed in front of a safety valve, due to the limitations in domestic burst disc manufacturing capabilities (the burst area could not reach 100%), it was common practice to use a burst disc that was one or two sizes larger than the safety valve, followed by the use of an adapter tube before connecting the safety valve. In fact, many manufacturers abroad have recommended that the burst disc and the safety valve have the same diameter and be connected directly, that is, the inlet flange of the safety valve should be firmly connected to the holder on the burst disc. The pressure gauge and check valve lead directly from the upper clamp. This way, 1. it reduces the pressure drop at the inlet of the safety valve for the equipment being protected (it is now required that this pressure drop not exceed 3% of the set pressure of the safety valve), and 2. it eliminates the need for a reducing tee, two flanges, etc. Therefore, it is recommended that for imported safety valves and rupture discs, direct connection should be used whenever possible. If domestic products are used, the possibility of direct connection can be discussed with the manufacturer (as domestic products should also continue to reduce the gap with foreign products)
I would like to add that safety valves are extremely important safety devices; they are crucial for protecting equipment and pipelines in the event of an accident. To ensure smooth discharge, many regulations require that the pressure drop from the protected equipment to the inlet of the safety valve not exceed 3% of the set pressure. This implies that the pipeline should be as short as possible. However, in some cases, due to the lack of appropriate space for piping during the initial design phase, as well as considerations related to the support structures needed to handle the backpressure generated by the safety valve’s discharge and stress calculations, the pipeline leading to the safety valve inlet may have multiple bends and a long length. This results in excessive inlet resistance that does not meet the requirements, necessitating an increase in the diameter of the inlet pipeline. But this, in turn, leads to new stress issues. It’s a vicious cycle. I suggest that when designing the piping system, attention should be paid to the location of the pipeline leading to the safety valve inlet (after all, the number of safety valves is not very large). The stress in this pipeline should be calculated, and it’s not necessary to use fire temperatures – operational temperatures are sufficient (this point can be discussed, as safety valve discharge occurs suddenly in the event of an accident)
One more push: Please share with everyone the mature or immature ideas you have at work; there might be unexpected gains as a result! Let me give another example of changing the approach. In an import facility, two pumps (one in operation and one as a backup) use dual mechanical seals, with the material being transported as the sealing fluid. Due to the corrosive nature of the medium and the toxicity of the catalysts present, the entire sealing system is made of zirconium material. There are three shared pieces of equipment (2 filters and 1 jacketed cooler), 20 valves, 4 instruments, and 20 meters of special-material piping. Not only is the investment very high, but the additional valves and equipment also increase safety risks. Later, I thought of our original company, which specialized in designing acrylonitrile plants – the by-products of these plants contain the highly toxic substance hydrogen cyanide. Initially, shielded pumps were used; once magnetic pumps became fully developed, they were widely adopted. With this in mind, it was obvious that our plant could also use magnetic pumps, and indeed, similar plants in China already use them. By changing our approach, we were able to save a significant amount of money, reduce the amount of piping work required, and eliminate many safety hazards – so why not do it? Sometimes it seems like there is no way out, but by changing one’s approach, things can take a turn for the better
The examples given by the senior experts are quite specialized; most of those involved in HaiChuan have just started working, so they may not reach the same level of expertise as you (including me). At the same time, since many people who come to Haichuan are there to ask questions, aside from the moderators, there aren’t many who actually come to Haichuan just for fun like we do. So I also suggest that experienced experts could create a special session to share, in the form of stories, interesting incidents they encountered during their design work or issues that hold some instructive value; I think this way, more people might be willing to participate.
Reply to 5# zero229: Let’s talk about something light-hearted. We have a project in Daqing, where the steam trap assemblies are depicted vertically in the process diagrams. One of the contractors, lacking experience in the chemical industry, failed to follow the piping diagram’s layout (which is horizontal) and instead arranged them vertically, just as shown in the process diagrams. Let’s take a break from work for a moment
Many construction companies do this these days; some of our factory’s projects are affected by it as well. The contractors don’t even look at the piping diagrams and simply install things according to the flowcharts, which forces us to make corrections later on – it’s very troublesome. Moreover, many construction companies these days are not professional enough; they can’t even understand piping diagrams, it’s frustrating.
There are those who install equipment without checking the layout drawings
You mentioned the steam trap assemblies, and I think we could discuss the layout of such assemblies. The layout of steam trap assemblies is often related to the type of steam trap chosen. Currently, bimetallic steam traps are commonly used, and the installation guidelines for these traps specify that they should be installed horizontally. Together with the valves located before and after the steam traps, this results in a large amount of space being required. For devices that need extensive heating, this layout poses significant challenges. Nowadays, there is a growing tendency to install steam traps vertically (and we have indeed done this), but few steam traps can be installed in this manner. This presents a contradiction; I’m curious to know how others address this issue in their designs, or if they have any good suggestions.
This post was last edited by zero229 on 2011-9-19 21:36. I think it’s a serious problem not to check the layout diagram when setting up equipment; I’ve encountered this situation myself as well. A reforming unit at a factory had its design already completed and construction was in progress when the client suddenly requested the addition of another reactor, which was to be connected either in series or in parallel with the existing reactor. It is well known that the temperatures and pressures in reactor pipelines are quite high; considerable effort was put into finalizing the design. Yet, the client demanded that the existing reactor be rotated 90° (since the equipment was installed on the ground). After making the necessary adjustments, a change order was sent to the construction site. However, the construction team ignored both the new requirement and the change order, and simply lifted the existing reactor into place. It was only after the new reactor arrived that it was discovered that the existing reactor had been installed in the wrong orientation, forcing the design firm to revise the installation drawings again – it was truly a hassle.
Reply to 5# zero229: I agree with your view; it is possible to organize “Lectures on Pipe and Valve Knowledge” events. Carrying it out on a short term basis seems to have little meaning; after all, this is a very broad topic, and if explored in depth, few people will participate ； Saying it simply is uninteresting. But pursuing it over the long term is of great significance; such a long-term approach not only covers all aspects related to pipes and valves but also provides depth in the learning process. Over time, quantitative changes will surely lead to qualitative changes: 1. On one hand, it enables systematic study of knowledge related to pipes and valves, allowing beginners to learn happily and sustain their efforts, making progress little by little every day ； 2. On the other hand, experienced senior experts can share their knowledge; by giving to others, they benefit themselves as well, experiencing joy in doing so ； Moreover, everyone can discuss together; it is through communication that progress is achieved. A diversity of opinions and ideas is beneficial, both for the forum and for every member.