The installation quality of an evaporator directly determines its service life and production safety. Especially for the 1st, 2nd, and 3rd effect high-concentration evaporators, which come into contact with high-concentration alkaline solutions, even a minor oversight during installation may lead to fatal hazards. Today, we will focus on explaining the core precautions for the installation of high-concentration evaporators, combined with 3 real accident cases, to help everyone avoid those insurmountable "red lines".

For high-concentration evaporators (especially the 1st, 2nd, and 3rd effect ones), the upper and lower sections of the heating chamber as well as the lower section of the separation chamber—all parts directly in contact with high-concentration alkaline solutions—have undergone overall heat treatment before leaving the factory. The purpose is to eliminate equipment stress and prevent the occurrence of caustic embrittlement. This is also the core taboo during the installation phase: it is strictly prohibited to perform any secondary welding-related operations on these parts on-site.

In simple terms, the following operations are absolutely not allowed on the installation site: it is strictly prohibited to open holes in the above-mentioned parts in contact with alkaline solutions, strictly prohibited to gouge out the original welds and re-weld them, strictly prohibited to perform secondary welding after shortening the nozzles, and even insulation nails must not be welded on these parts (insulation shall adopt bundled installation).

Many on-site installation personnel often take chances, thinking that "just opening a small hole" or "welding a short section of the interface" is irrelevant. However, in reality, after secondary welding, even if on-site local heat treatment is performed, it cannot achieve the effect of the overall heat treatment before leaving the factory. Overall heat treatment involves placing the equipment in a special furnace and maintaining a uniform temperature of 630-650℃ throughout the process, ensuring that the inside and outside of the equipment are heated consistently to completely eliminate stress. In contrast, during local heat treatment, even if the temperature measured outside the equipment meets the standard, the temperature inside the equipment will be seriously insufficient, resulting in incomplete stress elimination, which is very likely to cause caustic embrittlement and eventually lead to equipment cracking at the secondary welding position, with unthinkable consequences.

3 Real Cases, Blood-Chilling and Alarming!

Case 1: Unauthorized Hole Drilling, Short-Term Cracking Due to Luck

We once customized a set of evaporator equipment for an enterprise. After the smooth delivery of the equipment, the enterprise put forward an unreasonable request to add an external liquid level gauge opening on the body of the 1st effect evaporator. After learning of this, our technical personnel immediately issued a clear warning: as a key part bearing load and contacting alkaline solution, unauthorized hole drilling on the evaporator body is very likely to cause caustic embrittlement, posing major safety hazards and must not be implemented.

Regrettably, the enterprise ignored our warning, stubbornly believing that a small hole was irrelevant, and insisted on carrying out the hole drilling operation. Little did they know that luck would inevitably bring hidden dangers. Only one to two months after the equipment was put into use, obvious cracking and liquid leakage occurred at the opening.

Case 2: Unauthorized Nozzle Shortening, Illegal Operation Leaving Fatal Hidden Dangers

In another enterprise, during the installation of the evaporator, due to improper adaptation between the equipment size and the installation frame, it could not be lowered smoothly. To facilitate construction and simplify the process, on-site operators arbitrarily decided to cut the short nozzle of the evaporator, and then perform secondary welding after the equipment was lowered in place, attempting to avoid construction difficulties through illegal operations.

After learning of this illegal operation, we stopped it immediately and elaborated on the pros and cons to the relevant person in charge of the enterprise: after cutting the nozzle and performing secondary welding, the welding part will become a high-risk area for caustic embrittlement due to incomplete heat treatment, which is very likely to cause equipment cracking. However, the relevant personnel of the enterprise, on the grounds that "disassembling the gossip beam is difficult and local cutting and welding is efficient", ignored safety and our warning and continued to implement the illegal operation. In the end, as expected, caustic embrittlement and cracking occurred at the secondary welding part during the operation of the equipment.

Case 3: Unauthorized Weld Gouging and Repair, Ignoring Specifications, Hidden Dangers Eventually Leading to Disasters

After the installation of the evaporator in a certain enterprise, a third-party testing agency was entrusted to conduct a comprehensive inspection of the equipment welds. After the inspection, the third-party agency proposed that some welds of the equipment had minor defects and needed to be gouged out for repair welding. After learning of this, our technical personnel immediately raised strong objections and clearly informed the enterprise: the impact of minor weld defects on equipment operation is negligible, while the safety hazards caused by incomplete local heat treatment after gouging out the welds for secondary welding are far more fatal than minor weld defects.

However, the enterprise did not listen to our professional opinions and insisted on gouging out the welds for repair. On the grounds that "the project construction period is tight and time is running out", it refused to transport the equipment back to our factory for professional overall heat treatment, and only performed simple local heat treatment on-site. As we warned, local heat treatment cannot completely eliminate equipment internal stress, and hidden dangers have long been latent. Shortly after the equipment was put into operation, caustic embrittlement and cracking occurred at the secondary welding part.

Core Summary: Adhere to Installation Bottom Lines and Build a Solid Safety Barrier

For evaporators that have undergone overall heat treatment before leaving the factory, the core guideline and taboo on the installation site is only one sentence: it is strictly prohibited to perform any form of secondary welding operations.

The specific requirements must be strictly followed: do not arbitrarily open holes in key parts of the equipment, do not gouge out the original welds of the equipment, do not shorten the equipment nozzles for treatment, do not weld insulation nails on key parts, and insulation operations shall adopt bundled installation; if the equipment really needs welding repair due to special circumstances, it must be transported back to the manufacturer, and professional and technical personnel shall implement standardized overall heat treatment processes to completely eliminate equipment internal stress, eradicate caustic embrittlement hazards from the source, and ensure the safe and stable operation of the equipment.

If you encounter any technical difficulties or questions during the installation and use of the evaporator, please feel free to leave a message for consultation. Our company will arrange a professional technical team to provide you with accurate and efficient solutions as soon as possible, and work with you to build a solid safety line and promote the steady development of the industry.