Is there already a safety valve on the main steam pipe? Is it necessary to install separate safety valves on the towers as well?

The safety valve on the equipment is used to protect it

Petroleum and Chemical Industry Regulation 5.5.1: Pressure vessels with a maximum operating pressure of 0.1 MPa or higher shall be equipped with safety valves； According to Petrochemical Regulation 5.5.3, in the same system, if there is already a safety valve at the pressure source, then safety valves are not required for other equipment. If both conditions are met simultaneously, isn’t that contradictory?

I think this should be understood in this way: there is a safety valve at the source of pressure within the same system, and the entire system can be regarded as having such a safety valve; moreover, the activation pressure of this safety valve is less than or equal to the activation pressure of the safety valve that should be installed on the equipment itself. In this case, once the safety valve on the main pipe activates, the safety valve installed on the equipment will not activate either； In another scenario, there is a safety valve at the source of the pressure, and its operating pressure is higher than that of the safety valve that should be installed on the equipment itself. In such a case, even though the safety valve on the main pipe activates, the equipment may still experience overpressure; therefore, it is necessary to install another safety valve on the equipment to provide protection. In general, if a safety valve is installed at the source of the pressure and it prevents the equipment from experiencing overpressure after it activates, there is no need to install another one on the equipment ； If no safety valve is installed at the source, or if one is installed but it still causes overpressure in the equipment, a separate safety valve must be installed on the equipment side as well.

The analysis is reasonable and in line with the actual conditions on site! Liking for you!