The "Guidelines for Safety Risk Investigation of Liquefied Hydrocarbon Storage Tank Areas in Chemical Enterprises (Trial)," issued by the Ministry of Emergency Management on March 31, stipulate in the second overall requirement for process control that emergency shut-off valves should be installed in the lower inlet and outlet pipelines of liquefied hydrocarbon storage tanks. These valves must be located close to the tank, equipped with remote operation capabilities, and fitted with handwheels. Additionally, measures should be in place to prevent misoperation of the handwheels.

One stone stirred up a thousand waves, and experts were also confused when executing it, especially for major hazard source liquefied hydrocarbon storage tank areas. When the liquid level is high and the automatic interlock closes the emergency shut-off valve, the presence of a handwheel in local manual mode can render the interlock ineffective. In scenarios where a high liquid level causes significant leakage or a fire, the emergency stop button would also be ineffective. It is highly unlikely that anyone would risk their life to operate the handwheel manually under such hazardous conditions.

There has always been controversy over whether companies or designers need to install a handwheel mechanism for shut-off valves. Design institutes and companies have their own reasons due to their different focuses. Is it necessary to equip emergency shut-off valves with a handwheel device?

Firstly, we should clarify which type of valve the handwheel device is installed on. Standards provide different requirements for different scenarios and valve configurations. For example:

SH/T3005-2016, "Design Specification for Selection of Automation Instruments in Petrochemical Industry," and HG/T20507-2014, "Design Specification for Selection of Automation Instruments," stipulate that a handwheel mechanism should be installed on control valves without bypasses.

SH/T3184-2017, "Design Specification for Automation System of Petrochemical Tank Farm," stipulates that electric actuators should be equipped with handwheels.

GB/T50892-2013, "Design Specification for Instrument Control System of Oil and Gas Field and Pipeline Engineering," stipulates that emergency shut-off valves used for process safety production interlocking or control valves installed in prohibited hazardous areas should not be equipped with handwheel mechanisms. Control valves used for other functions and without bypasses should be equipped with handwheel mechanisms.

The requirements for setting the handwheel on control valves are essentially consistent across different standards.

However, for emergency shut-off valves with safety interlocks, the requirements differ among various standards. For example:

HG/T20507-2014, "Specification for Selection and Design of Automation Instruments," stipulates that control valves used for process production safety interlocking of emergency shut-off valves should not be equipped with handwheel mechanisms.

SH/T3005-2016, "Design Specification for Selection of Automation Instruments in Petrochemical Industry," stipulates that the handwheel should have clear markings for manual and automatic positions, with a locking mechanism for the automatic position.

From the above, it can be seen that the setting of the handwheel has always been a controversial issue. Different standards and specifications (domestic and foreign), as well as different engineering companies (domestic and foreign), have different regulations. Even within the same company, there may be different regulations at different times.

Overall, setting and not setting a handwheel each have their own advantages and disadvantages.

HG/T20507-2014 "Design Specification for Selection of Automation Instruments" focuses on the advantages of not setting up, sacrificing some functions. It stipulates that control valves used for process production safety interlocking of emergency shut-off valves should not be equipped with a handwheel mechanism. This is to prevent small and medium-sized units from falling behind in management and posing safety hazards.

SH/T3005-2016 "Specification for Selection and Design of Automation Instruments in Petrochemical Industry" was released slightly later. When preparing it, a horizontal comparison was made with foreign situations, and there was no prohibition. It can be set up, but corresponding management measures need to be added to suppress the shortcomings. Management measures may vary among different enterprises.

If the emergency shut-off valve belongs to the safety instrumented emergency shut-off valve, which is used for safety instrumented functions (SIF) of SIL1 and above, if a handwheel is installed, its supporting compensatory measures, that is, the management of the handwheel, should comply with the standards of functional safety and meet the management requirements of the SIS safety lifecycle.

In engineering, specific analysis can be conducted, and each configuration has its advantages and disadvantages. Different scenarios also have different characteristics. In some cases, there are definite main contradictions and concerns, while in other cases, there is no unique safety state. In this case, more detailed and comprehensive analysis is needed.

Engineering solutions are usually not unique, and sometimes there can be multiple reasonable solutions. It is important to note that if exemption is granted for a certain aspect, compensatory measures that meet the requirements should be provided. The main contradictions and safety status, product situation, standards, and document requirements are factors that should be considered.

Reprinted from official account: instrument circle

Mega-tek Instrument Classroom