about pre-insulated steel pipes, involving multiple standards such as EN 253, TRONG 448, TRONG 488, TRONG 489, as well as material standards such as API 5L, ASTM A53, vân vân. First of all, I need to sort out the specific content and application scope of these standards. According to the information I have searched, TRONG 253 mainly targets steel pipe components of direct buried hot water pipe networks, trong khi EN 488 involves steel valve components.