The issue regarding Class A materials and the construction of cofferdams around liquid ammonia pumps in SH3014

The question you raised is very important; many newcomers might have the same confusion. I understand what you mean: the specification states that \"a retaining wall should be installed around pumps other than those of Category A A and liquid ammonia.\" Does that mean that for pumps of Category A A and liquid ammonia, no retaining wall is required? In fact, I personally think that the phrase “except for…” here is mainly used to emphasize that embankments are not required in these two types of situations, but it does not mean that their installation is prohibited. There are several possible reasons: Class A media (such as liquefied hydrocarbons) tend to vaporize and spread easily after a leak, and bunds may instead lead to the accumulation of vapor clouds, increasing the risk of explosion. Therefore, regulations do not recommend the use of ordinary bunds; instead, explosion-proof drainage ditches or other measures for directed flow are required. Liquid ammonia is highly corrosive and toxic, and in the event of a leak it can form pools of liquid at low temperatures; ordinary barriers may be corroded or frozen apart, thereby losing their protective function. Therefore, special materials for impermeable flooring or barriers are usually required. It depends specifically on the explanatory text of the standards or design examples; it is recommended that you consult the explanatory notes for SH/T3014 or the accompanying design manuals. If you still have doubts, it is best to seek advice from the standards drafting organization or colleagues in chemical engineering design firms, as such details are related to safety assessments. In short, for what the standards specify as \"should be installed\", it must be done as required; while something that is not mandatory does not mean it is prohibited. In actual engineering projects, a comprehensive assessment based on the properties of the medium, the surrounding environment, and fire safety requirements is necessary. Hope this is a little helpful to you~

According to Article 4.3.1 of the \"Design Code for Pump Areas in Storage and Transportation Systems of Petrochemical Enterprises\" (SH/T 3014-2012), enclosures shall not be installed around pumps for Class A liquids and liquid ammonia pumps. Note: SH/T 3014-2012 is a recommended industry standard; in actual design work, it is necessary to strictly comply with the mandatory standard \"Code for Fire Protection Design of Petrochemical Enterprises\" (GB 50160). In the event of any conflicts between the two, GB 50160 shall prevail. Currently, GB 50160 also emphasizes that liquefied hydrocarbon pumps should not be installed within fire dikes, and it imposes strict fire separation distances and ventilation requirements for the layout of pump areas handling volatile media.