How to set the alarm and interlock for liquid level and emergency shut-off valves in the tank farm of DCS and SIS systems
How to set up alarms and interlocks for liquid level and emergency shut-off valves in the tank farm of DCS and SIS systems? How do national regulations and documents require this?
Industry expert Fan Yongfeng provides in-depth interpretation of the relevant knowledge on liquid level and emergency shut-off valve alarms and interlocks in the tank farm.
Common issues that instrument technicians face regarding liquid level and emergency shut-off valve alarms and interlocks in the tank farm naturally have answers! We hope you read the article with your questions in mind:
① How many different types of liquid level detection instruments should be equipped in the same storage tank?
② Must key storage tanks, such as those containing liquefied gases and highly toxic liquids that constitute major hazard sources, be equipped with emergency shut-off devices?
③ Must all storage tanks be equipped with high and low liquid level alarms and interlocks?
④ If an emergency shut-off valve is set up, are there any requirements for the installation location?
⑤ Is it necessary to set up an emergency shut-off valve interlock button on site? Are there any requirements for the installation location?
GB50074-2014 "Design Code for Petroleum Storage"
◆ Setting requirements
15.1 Automatic control system and instruments
15.1.1 Storage tanks with a capacity greater than 100m³ shall be equipped with liquid level measurement and remote transmission instruments, and shall comply with the following regulations::
1. The continuous measurement signal of liquid level should be connected to the automatic control system through analog signal or communication method;
2. High and low liquid level alarms should be set up in the automatic control system;
3. The set height for high-level alarm of storage tanks should comply with the relevant provisions of the current industry standard "Design Specification for Tank Areas in Petrochemical Storage and Transportation Systems" SH/T 3007;
4. The set height for low-level alarm of storage tank should meet the requirement of no cavitation of the pump. The set height for low-level alarm of external floating roof and internal floating roof storage tanks (from the bottom plate of the tank) should be 0.2m or more higher than the height of the floating roof falling.
15.1.4 The liquid level measuring instrument used for high high and low low liquid level alarm signals in storage tanks should adopt a separate continuous liquid level measuring instrument or liquid level switch, and should be equipped with alarms and interlocks in the automatic control system.
◆ Interlocking requirements
15.1.2 The following storage tanks should be equipped with high-high liquid level alarms and interlocks, and the high-high liquid level alarms should be able to simultaneously interlock and close the inlet pipeline control valve of the storage tank:
1. Class A, B, and B liquid storage tanks with a turnover of more than 6 times per year and a capacity greater than or equal to 10000m ³;
2. Class A, B, and B liquid storage tanks with a turnover of less than or equal to 6 times in 2 years and a capacity greater than 20000m ³;
3. Storage tanks for Class I and II toxic liquids.
15.1.3 External floating roof and internal floating roof storage tanks with a capacity greater than or equal to 50000m ³ shall be equipped with low-low liquid level alarms. The low-low liquid level alarm setting height (from the bottom of the tank) should not be lower than the height of the floating roof and falling bottom, and the low-low liquid level alarm should be able to interlock and stop the pump at the same time.
15.1.4 The liquid level measuring instrument used for high-high and low-low liquid level alarm signals in storage tanks should adopt a separate continuous liquid level measuring instrument or liquid level switch, and should be equipped with alarms and interlocks in the automatic control system.
[Article Description] 15.1.4 "Separate continuous liquid level measuring instrument or liquid level switch" refers to a set of liquid level measuring instruments specifically designed for high-high and low-low liquid level alarms and interlocks in storage tanks, in addition to "remote liquid level measuring instruments that should be installed".
◆ Setting and interlocking requirements
15.1.2 The following storage tanks should be equipped with high-high liquid level alarms and interlocks. The high-high liquid level alarms should be able to simultaneously interlock and close the inlet pipeline control valve of the storage tank;
15.1.7 The important process machines, pumps, fire pumps, tank mixers, and other electric equipment and control valves of the first-level oil depot should not only be able to be operated on-site, but also controlled and displayed in the control room. The same requirements apply to the second-level oil depot.
15.1.11 The start and stop of the fire pump in the primary oil depot, the switch of the control valve on the fire water pipeline and foam liquid pipeline shall realize remote start and stop control in the fire control room, and the master console shall display the pump operation status and the valve position signal of the control valve.
[Article Description]
15.1.7 This regulation allows for real-time monitoring of the status of electric equipment and timely handling of abnormal situations;
15.1.11 This provision ensure the rapid activation of the fire protection system and timely extinguishing of fires.
GB 50737-2011 "Code for Design of Petroleum Reserve Depots"
◆ Setting requirements
11.1 Automatic control systems and instruments
11.1.2 Each oil tank shall be equipped with a continuous liquid level measurement instrument, a high-high liquid level switch, and a low-low liquid level switch, and shall comply with the following regulations:
1. The accuracy of the liquid level gauge should be better than ±1mm.
2. The continuous liquid level gauge should be equipped with the functions of high liquid level alarm, low liquid level alarm, and high-high liquid level interlock to close the inlet valve of the oil tank. The set height of the low liquid level alarm (measured from the tank bottom plate) should not be less than 2 meters.
3. The high-high liquid level switch should have the function of interlocking to close the inlet valve of the oil tank at a high-high liquid level.
4. The low-low liquid level switch should have the function of interlocking to stop the oil transfer pump and close the pump outlet valve at a low-low liquid level. The setting height of the low-low liquid level switch (measured from the tank bottom plate) should not be less than 1.85 meters.
【Explanation of the provisions】 11.1.2 Liquid level is the most important parameter that oil tanks need to monitor, so it is required that "each oil tank should be equipped with a continuous liquid level measurement instrument".The high-high liquid level interlock closing inlet valve can prevent oil overflow when oil enters the oil tank and is a necessary safety protection measure.The setting of the low-low level switch is to prevent the floating top outriggers from descending to the bottom of the tank.The floating roof of a floating roof tank usually floats on the oil surface and comes into direct contact with it. This can effectively suppress the evaporation of oil and gas, and there is no gas phase space except for the sealing ring, greatly eliminating the explosive environment.It should be noted during use that, except for the maintenance of the oil tank, it is necessary to avoid the floating top and falling bottom.Once the floating roof bottoms out, a gas phase space will appear between the oil surface and the floating roof. For crude oil, where there is a gas phase space, there will be explosive gases, which greatly increases the fire hazard.In the fire accident that occurred in a large oil depot in the north in 2010, several 10×104m³ oil tanks were exposed to flames at a close distance of over 10 meters. However, only Tank No. 103 was ignited and eventually burned down. The main reason was that the floating roof of the tank had already fallen to the ground at that time, and there was a small amount of oil remaining inside the tank. Under the roasting of the flames, The oil and gas existing in the gas phase space can be easily detonated and catch fire.The general height of the floating roof support legs is 1.8 meters. Therefore, it is stipulated that "the set height of the low liquid level switch (from the bottom plate of the tank) shall not be less than 1.85 meters". Considering that there should be a processing time of 10 to 15 minutes after the alarm is triggered, it is stipulated that "the set height for low liquid level alarm (from the bottom plate of the tank) should not be less than 2 meters."
11.1.10 The start and stop of fire pumps, as well as the opening and closing of control valves on fire water pipelines and foam liquid pipelines, should be programmed in the fire control room. The main control console should display the operating status of the pumps and the valve position signals of the electric valves.
6.2.23 Storage tanks for flammable liquids shall be equipped with liquid level gauges and high liquid level alarms. If necessary, automatic interlocking facilities for cutting off the feed shall be installed. It is advisable to install an automatic dehydrator.
Interlocking Requirements:
6.3 Above-ground storage tanks for liquefied hydrocarbons, flammable gases, and oxidizing gases.
6.3.11 Liquefied hydrocarbon storage tanks shall be equipped with liquid level gauges, thermometers, pressure gauges, safety valves, as well as measures for high liquid level alarms and automatic interlocking to cut off the feed at high-high liquid levels.
【Explanation of the provisions】 6.3.11 It is stipulated in NFPA 58 "Specification for Liquefied Petroleum Gas" that: "High-level liquid level alarms should be installed on refrigerated liquefied petroleum gas containers."“Refrigerated liquefied petroleum gas containers should be equipped with high-level flow cut-off facilities, and this device should be independent of all instruments.”Even for storage tanks at normal temperature, such regulations are safer.The high-level automatic interlock cut-off feeding device is the last effective means to prevent oil tank overflow. It is currently widely used and a reasonable setting.7.2 Process and public material pipelines
7.2.15 The inlet pipeline of the equipment for liquefied hydrocarbons and flammable liquids with operating temperatures equal to or higher than the autoignition point to the pump should be equipped with a shut-off valve near the root of the equipment. When the equipment volume exceeds 40m³ and the distance from the pump is less than 15m, the shut-off valve should be a remote control valve with manual function, and the distance between the local operation button of the remote control valve and the pump should not be less than 15m.
7.4.7 When the length of the inter-factory pipeline exceeds 5 kilometers, emergency shut-off valves, flow and pressure monitoring facilities should be installed on the pipelines within the fences or land boundaries of the upstream and downstream enterprises.
8.4.5 The above-ground vertical storage tanks for flammable liquids shall be equipped with fixed or mobile fire-fighting cooling water systems. The water supply range, water supply intensity and setting method of such systems shall comply with the following provisions:
5The control valve should be located outside the fire dike and should be no less than 15 meters away from the protected tank wall. The fire-fighting cooling water pipes set after the control valve and on the storage tank should be made of galvanized steel pipes.
8.10.10 The installation of fixed fire-fighting cooling water pipelines for full-pressure and semi-refrigerated liquefied hydrocarbon storage tanks shall comply with the following provisions:
2. The fire protection cooling water system can adopt manual or remote control valves. When the volume of the storage tank is equal to or greater than 1000 cubic meters, remote control valves should be used.
3. The control valve should be located outside the fire dike, and the distance from the protected tank wall should not be less than 15 meters.
According to API standards, adjust the volume of liquefied hydrocarbon equipment to 40m ³. Considering the higher probability of accidents occurring in flammable liquid pumps with operating temperatures equal to or higher than the autoignition point, it is required to install a shut-off valve near the base of the equipment for the inlet pipeline of flammable liquid equipment to the pump with operating temperatures equal to or higher than the autoignition point.
◆ Set requirements
5.5 Liquid storage tanks must be equipped with liquid level detection instruments, and the same tank must be equipped with at least two different types of liquid level detection instruments.
Tanks storing flammable and explosive medium should be equipped with high and low liquid level alarm circuits, and if necessary, an interlocking system between the liquid level and relevant process parameters should also be installed.
AQ 3036-2010"Specification for the Installation of On-site Safety Monitoring Equipment in Tank Farms of Major Hazard Sources of Hazardous Chemicals"
◆ Set requirements5.1 Interlocking automatic control equipment for temperature, liquid level, pressure, and environmental temperature parameters of storage tanks can be set according to actual situations, including automatic cutting or transfer of materials and spray cooling equipment.
5.4.3 The high-high liquid level interlock closing inlet valve can prevent overflow during tank feeding, and stricter safety protection measures need to be taken for the three situations listed in this article.
6.1 Emergency shut-off valves
Emergency shut-off valves shall be installed at the liquid phase inlet and outlet of liquefied petroleum gas (LPG) spherical storage tanks, and their positions shall be in close proximity to the spherical storage tanks.
For large storage tanks, valves with pneumatic, hydraulic, or electric actuators should be used. When the actuator is electric, its power cable, signal cable, and electric actuator should be protected against fire. The shut-off valve should have automatic and manual closing functions, including remote control and on-site manual closing.
（1） Further improve the monitoring facilities in the chemical tank area. Set up high and low liquid level alarms for storage tanks according to regulatory requirements, and adopt measures such as automatic interlocking to close the tank feed valve at ultra-high liquid levels and automatic interlocking to stop material transportation at ultra-low liquid levels. Ensure that the flammable, explosive, toxic and harmful gas leakage alarm system is intact and available. Large, liquefied gas, and highly toxic chemical storage tanks should be equipped with emergency shut-off valves.
（14） The design unit should determine the standard specifications to be adopted for this project based on the characteristics of the hazardous sources in the construction project and the scope of application of the standard specifications. For construction projects involving "two key points and one major", they should at least meet the requirements of the following current standards and specifications, and the strictest safety provisions shall prevail.
（19） Newly built chemical plants must be equipped with automated control systems. It should be determined whether a safety instrumented system needs to be equipped based on the results of the hazard and risk analysis of the process. Large and medium-sized new projects involving key regulated hazardous chemical processes must carry out safety instrumented system design in accordance with relevant standards such as "Functional Safety of Safety Instrumented Systems in Process Industry" (GB/T21109) and "Design Specification for Safety Instrumented Systems in Petrochemical Industry" (GB50770).
（22） Toxic material storage tanks, low-temperature storage tanks, and pressure ball tanks should be equipped with automatic or manually controlled emergency shutdown facilities for incoming and outgoing material pipelines.
Article 13: Hazardous chemical units shall establish and improve safety monitoring and control systems and measures in accordance with the actual situation of the types, quantities, production, use processes (methods), or related equipment and facilities of hazardous chemicals that constitute major hazard sources, in accordance with the following requirements:
（3） Install emergency shutdown devices for key facilities such as toxic gases, highly toxic liquids, and flammable gases in major hazard sources; Facilities for toxic gases shall be equipped with emergency disposal devices for leaked materials. Primary or secondary major hazard sources involving toxic gases, liquefied gases, and highly toxic liquids shall be equipped with independent safety instrumented systems (SIS);
（4） Starting from January 1, 2017, all hazardous chemical tank areas that constitute Level 1 or Level 2 major hazard sources and have not been equipped with emergency stop (emergency shutdown) functions shall be suspended from use;
Notice on Standardizing the Automatic Control Technology Retrofit Work in Chemical Enterprises (No. 109 [2009] of the Jiangsu Provincial Work Safety Supervision Administration).
◆ Set requirements3. Existing storage facilities within the scope of renovation must complete the automatic control technology renovation within the prescribed time limit. Storage areas for highly toxic, flammable, and explosive chemicals must be equipped with liquid level, temperature, and pressure over-limit alarm facilities, gas leak detection and alarm devices, and fire alarm systems. Emergency shut-off devices must be installed on key storage tanks for liquefied gases, highly toxic liquids, and other substances that constitute major hazard sources.
65~350 ≤10
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e) The selected emergency shut-off valve should be of the fail safe type.
4.4.4 Liquefied hydrocarbon spherical tanks shall be equipped with high and low liquid level alarms and high-high liquid level interlock measures to shut-off feed. The detection components for high-high liquid level interlocking shall be independently set and may use ultrasonic waves, tuning forks, floating balls, capacitive level switches, etc.
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Sinopec [2011] Jian 518 "Design Regulations for Selection of Emergency Shut-Off Valves for Liquefied Hydrocarbon Spherical Tanks"
◆ Set requirements
3.1 Emergency Shut-Off Valve
Specially designed for installation on the inlet and outlet pipelines of liquefied hydrocarbon spherical tanks, it can quickly and tightly shut-off (TSO) and isolate flammable and toxic materials in case of fire, leakage, or other accidents in the tank area. When the liquid level of the ball tank reaches or exceeds the high-high liquid level limit, the emergency shut-off valve can be used to prevent material overflow from the tank. No other fittings or valves shall be installed between the emergency shut-off valve and the spherical tank mouth except for the connecting pipe, and the distance between them shall meet the requirements of piping installation, valve maintenance, and process. The emergency shut-off valve should have automatic and manual closing functions, and the manual closing function should include remote control in the control room and on-site manual closing.
4.5.11 An on-site operation switch for emergency shut-off valves should be installed outside the fire hazard zone of the liquefied hydrocarbon spherical tank area. The contact signal should be directly sent to the electromagnetic valve of the pneumatic actuator or the ESD action terminal of the electro-hydraulic or electric actuator for manual closure of the emergency shut-off valve in case of emergency.
(November 20, 2018) Sinopec Anfei [2018] No. 477 "Guiding Opinions on the Rectification of Atmospheric Storage Tank Areas for Flammable and Combustible Liquids in Sinopec"
◆ Interlocking requirements
4.1.4 The emergency shut-off valve on the tank feed pipeline should be interlocked with the high-high liquid level alarm instrument of the tank.
◆ Setting and interlocking requirements：
4.1 Emergency shut-off valve setting
4.1.1 Emergency shut-off valves should be installed on the inlet and outlet pipelines of tanks storing extremely hazardous liquids (Class I) and highly hazardous liquids (Class II), Class A and Class B flammable liquid tanks with a capacity greater than or equal to 3000m ³, other flammable liquid tanks with a capacity greater than or equal to 10000m ³, and tank farms that constitute Class I and Class II major hazard sources. The emergency shut-off valve should be able to be remotely controlled to shut-off from the control room.
4.1.2 The emergency shut-off valves for storage tanks in refineries, petrochemical plants, and petrochemical plants should be pneumatic valves and should have a fault shut-off function; The emergency shut-off valves for crude oil depots, finished oil depots, and storage tanks in oil pipeline ancillary stations can use electric valves.
4.1.3 The emergency shut-off valve on the storage tank inlet and outlet pipelines can be shared with the process control valve.
4.1.4 The emergency shut-off valve on the tank feed pipeline should be interlocked with the high-high liquid level alarm instrument of the tank.
4.1.8 The time for the emergency shut-off valve to be fully opened or fully closed by pneumatic or electric actuators should not exceed 180 seconds.
4.2.1 Storage tanks for benzene, liquefied hydrocarbons, and liquid ammonia should be equipped with independent Safety Instrumented Systems (SIS).
2. For storage tanks belonging to first or second level major hazard sources, in addition to setting high and low liquid level alarms, corresponding alarms and linkage protection measures should also be set for low-low and high-high liquid levels. An independent SIS system is required for storage tanks, and the root valves on the inlet and outlet pipelines should be equipped with fire prevention measures (emergency shut-off valves should have manual operation function and fire prevention measures should be taken). In case of high liquid level or fire accidents in the storage tank, the SIS system interlock should be used to cut off the feeding.
g) The selection of emergency shut-off valves at the root of liquefied hydrocarbon spherical tanks should comply with the "Design Regulations for Selection of Emergency Shut off Valves for Liquefied Hydrocarbon Spherical Tanks" (Sinopec Jian [2011] No. 518); The fireproof cover of the emergency shut-off valve at the root of the spherical tank should be a rigid fireproof protective cover suitable for outdoor environments. The fireproof protective cover should be able to ensure that its internal temperature is below 80 ℃ within 30 minutes under a hydrocarbon fire at 1093 ℃.
Guan San Han [2018] No. 27, General Office of the State Administration of Work Safety (February 7, 2018)
◆ Setting and interlocking requirements：
（1） Jiangsu Tianjia Yi Chemical Co., Ltd. (13 items)
5. The DCS and SIS pressure transmitters of some of the two nitration reactors share a pressure tapping point.
6. The benzene tank area and methanol tank area, which constitute a second level major hazard source, have not been equipped with emergency shut-off valves at the root of the tanks.
8. The cabinet room and monitoring room were illegally set up in the nitrification plant.
（2） Xiangshui Kunpeng Chemical Co., Ltd. (15 items)
6. The fractionation system has not achieved automatic control.
11. The doors and windows of the control room and cabinet room face devices with fire and explosion hazards.
12. The ESD system does not have dual circuit power supply.
（3） Jiangsu Dahua Chemical Industry Co., Ltd. (11 items)
4. The DCS control room of the device is a non explosion proof structure, with doors and windows facing the 1 # production workshop that poses a fire and explosion hazard.
8. The tank area that constitutes a Level 1 major hazard source is not equipped with an emergency shut-off valve at the root of the tank.
9. The removal of the instrument interlock has not gone through the relevant procedures.
（4） Jiangsu Yongtai Technology Co., Ltd. (9 items)
3. There are many safety hazards in the tank area that constitutes a Level 1 major hazard source, such as the emergency shut-off valve not being set at the root of the tank; The storage tanks are not equipped with on-site liquid level indicators, and some tanks only have one static grounding point.
（2） Jiangsu Sierbang Petrochemical Co., Ltd. (9 items)
4. The on-site interlocking pump of the device did not indicate interlocking in a prominent position on the coupling protection cover.
7. The gland ports of some instrument junction boxes are not sealed and not explosion-proof; Some static jumper wires of the instrument body and junction box have fallen off.
（3） Jiangsu Helirui Technology Development Co., Ltd. (17 projects)
8. There is no emergency shutdown system for devices involving key regulated hazardous chemical processes.
17. The control room is located inside the production facility.
（4） Jiangsu Xincheng Chemical Co., Ltd. (13 items)
6. The equipment involving key regulated hazardous chemical processes has not achieved automated control and emergency shutdown.
（1） Jiangsu Zhongneng Silicon Industry Development Co., Ltd. (12 items)
3. The control measures for major hazard sources are not perfect. For example, if the enterprise constitutes a first level major hazard source, the evaluation in the current situation evaluation report may allow the social risk curve to fall within the lowest possible reduction zone, and the potential risks that exist have not been analyzed and relevant risk management measures have not been formulated and implemented as required.
7. The safety instrumented system is incomplete, such as the emergency shutdown system that is not set up independently of the process control system for devices involving hazardous chemical processes according to regulations.
19. The newly developed hazardous chemical production process is directly industrialized without undergoing small-scale, pilot, or industrial trials; The chemical process used for the first time domestically has not undergone safety and reliability verification organized by relevant departments of the provincial people's government; The new device has not developed a trial production plan for feeding and start-up; Fine chemical enterprises have not conducted reaction safety risk assessments in accordance with regulatory requirements.
Notice on Further Strengthening the Safety Management of Chemical Tank Areas (No. 68, 2014) issued by the General Administration of Work Safety
◆ Setting and interlocking requirements
（1） Further improve the monitoring facilities in the chemical tank area. Set up high and low liquid level alarms for storage tanks according to regulatory requirements, and adopt measures such as automatic interlocking to close the tank feed valve at ultra-high liquid levels and automatic interlocking to stop material transportation at ultra-low liquid levels. Ensure that the flammable, explosive, toxic and harmful gas leakage alarm system is intact and available. Large, liquefied gas, and highly toxic chemical storage tanks should be equipped with emergency shut-off valves.
（2） Strengthen the production and operation management of chemical tank areas. During normal operation, it is strictly prohibited to create a space between the floating roof of the inner floating roof tank and the material. In special circumstances where ultra-low liquid level operation is necessary, when restoring the feed, it is necessary to ensure that the feed flow rate is less than the limit flow rate to prevent static electricity from causing accidents. When there is an alarm for high or low liquid level, immediate measures must be taken.
（6） Tank areas involving key regulated hazardous chemicals should undergo regular hazard and operability analysis.
Guiding Opinions on Strengthening Leakage Management in Chemical Enterprises (No. [2014] 94) issued by the General Administration of Work Safety
◆ Setting and interlocking requirements：
（8） Improve the automation control system. Production facilities involving key regulated hazardous chemical processes and hazardous chemicals must be equipped with automated control systems, safety interlocks or emergency shutdown systems, and combustible and toxic gas leak detection and alarm systems in accordance with safety control requirements. The emergency stop system and safety interlock protection system must meet the functional safety level requirements. Corresponding safety technical measures should be taken for hazardous chemical storage devices, such as high and low liquid level alarms, high-high and low-low liquid level interlocks, and emergency shut-off devices.
Guiding Opinions on Strengthening Chemical Process Safety Management (2013) No. 88 issued by the General Administration of Work Safety on July 29, 2013
◆ Setting and interlocking requirements
（5） Establish a risk management system. Enterprises should establish a risk management system for chemical processes, clarify the scope, methods, frequency, and responsible persons of risk identification, specify the requirements for the application of risk analysis results and the implementation of improvement measures, and conduct risk identification analysis on the entire production process.
Risk identification and analysis of production and storage facilities involving key regulated hazardous chemicals, key regulated hazardous chemical processes, and major hazardous sources of hazardous chemicals (hereinafter referred to as "two key and one major") shall be carried out using Hazard and Operability Analysis (HAZOP) technology, generally conducted every three years. For risk identification and analysis of other production and storage facilities, methods such as safety checklists, job hazard analysis, pre hazard analysis, failure type and effect analysis (FMEA), HAZOP technology, or a combination of multiple methods can be selected based on the complexity of the facility, and can be conducted every 5 years. When there are significant changes in the management structure, personnel composition, production equipment, or production safety accidents of enterprises, risk identification and analysis should be carried out in a timely manner. Enterprises should organize all personnel to participate in risk identification and analysis, striving for full coverage of risk identification and analysis.
（7） Develop acceptable risk standards. Enterprises shall determine their acceptable risk standards in accordance with the requirements of the Interim Provisions on the Supervision and Management of Major Hazardous Sources of Hazardous Chemicals (Order No. 40 of the State Administration of Work Safety), based on relevant national regulations or international standards. Enterprises should promptly develop and implement measures to eliminate, reduce, or control unacceptable risks identified through identification and analysis, in order to keep the risks within an acceptable range.
Notice on Issuing the Basic Requirements for Intrinsic Safety Diagnosis and Governance by the Provincial Emergency Management Department (Su Emergency [2019] No. 53)
Printed by the Office of Jiangsu Province Emergency Management Department on June 6, 2019
◆ Setting and interlocking requirements
1. Major hazard diagnosis
According to the "Criteria for Determining Hidden Hazards of Major Production Safety Accidents in Chemical and Hazardous Chemical Production and Operation Units (Trial)" (Safety Supervision Administration General Manager [2017] No. 121), major hidden dangers should be strictly judged without omission or misjudgment.
5. According to the "Notice of the State Administration of Work Safety on Publishing the First Batch of Key Supervised Hazardous Chemical Processes Catalogue" (Safety Supervision Administration General Manager [2009] No. 116), the "Notice of the State Administration of Work Safety on Publishing the Second Batch of Key Supervised Hazardous Chemical Processes Catalogue and Adjusting Some Typical Processes in the First Batch of Key Supervised Hazardous Chemical Processes" (Safety Supervision Administration General Manager [2013] No. 3), GB/T50770, GB/T20438, GB/T21109 and other regulations, and based on the HAZOP analysis recommendations, list and diagnose the compliance of automatic control (including DCS, PLC, Emergency Shutdown System, SIS) safety functions of production equipment involved in key supervised hazardous chemical processes, and list non conformities item by item.
6. According to the requirements of documents such as the "Interim Provisions on the Supervision and Management of Major Hazardous Sources of Hazardous Chemicals" (Order No. 40 of the former State Administration of Work Safety) and the "Guiding Opinions of the State Administration of Work Safety on Strengthening the Management of Chemical Safety Instrumented Systems" (General Administration of Work Safety [2014] No. 116), list and diagnose the compliance of safety functions such as automation control, safety instrumented systems, emergency shutdown systems, or emergency shutdown facilities of production equipment (storage facilities) that constitute major hazardous sources, and list non conformities item by item.
（1） Automatic control of raw material, product storage tanks, and equipment storage tanks
1. Flammable liquid storage tanks, toxic liquid storage tanks, low-temperature storage tanks, and pressure tanks with a volume greater than or equal to 100m ³ should be equipped with liquid level continuous measurement remote transmission instrument components and local liquid level indicators, and equipped with high liquid level alarms. Floating roof storage tanks and storage tanks with extraction pumps should also be equipped with low liquid level alarms; The pressure tank for flammable and toxic media is equipped with a high-high liquid level or high-high pressure interlock to stop feeding. If the design plan or HAZOP analysis report proposes the need to set up low low liquid level automatic interlocking pump shutdown and shut-off discharge valve, its requirements should be met.
2. Liquid raw material and finished product storage tanks with a volume of less than 100m ³ involving 16 types of self-explosive hazardous chemicals should be equipped with a high liquid level alarm. If the design plan or HAZOP analysis report proposes the need to set high-high liquid level alarms and interlock to shut off the feed valve, or low-low liquid level alarms and interlock to stop the pump, their requirements should be met.
3. Storage tanks for Class I and II toxic liquids, storage tanks for Class AB and Class AB flammable liquids with a capacity greater than or equal to 1000m ³, and other flammable liquid storage tanks with a capacity greater than or equal to 3000m ³ should be equipped with high-high liquid level alarms and interlock closure of tank inlet pipeline control valves.
4. Liquid storage tanks that constitute a first or second level major hazard source hazardous chemical tank area should be equipped with high and low level alarms and high-high and low-low level interlock emergency shut-off inlet and outlet pipeline control valves.
5. Storage tanks for flammable or toxic liquids should be equipped with high-level alarms and high-level interlocks to shut off the feeding. The high-level tank of the device should be equipped with a high liquid level alarm and a high-high liquid level interlock to cut off the feed or overflow pipeline. It is recommended to install a low-low liquid level interlock to stop the extraction pump or shut off the discharge facilities.
7. For hazardous chemical tank areas involving toxic gases, liquefied gases, and highly toxic liquids, independent safety instrument systems should be installed for first and second level major hazard sources. The detection and execution components of each circuit should be independently set, and the safety instrument level (SIL) should not be lower than level 2.
9. Flammable and highly toxic liquid storage tanks with high-level interlocking function should be equipped with two different principle level gauges or level switches. High level interlocking measuring instruments and basic control circuit level gauges should be set separately. The liquid level measurement of pressure storage tanks should be equipped with a set of remote transmission instruments and local indication instruments, and another set of liquid level measurement instruments or switches dedicated to high-high liquid level or low-low liquid level alarms and interlocking shut-off of tank feed (discharge) valves should be installed.
14. Emergency shutdown systems should be equipped for major hazard sources of first and second level hazardous chemicals, and emergency shut-off devices should be installed for key facilities such as toxic gases, highly toxic liquids, and flammable gases in major hazard sources. The safety function of the emergency stop (emergency shutdown) system can be achieved through either the basic process control (DCS or SCADA) system or the safety instrumented system (SIS). For safety integrity (SIL) level 1, the safety function of the emergency stop (emergency shutdown) system can be achieved through the basic process control (DCS or SCADA) system, or through the safety instrument system (SIS). For safety integrity (SIL) level 2 or above, the emergency stop function must be achieved through the safety instrument system (SIS).
Notice of the General Office of the State Council on Issuing the Comprehensive Safety Governance Plan for Hazardous Chemicals (State Council Document [2016] No. 88)
◆ Setting and Interlocking Requirements
（1） Safety Instrumented Systems (SIS) include safety interlock systems, emergency shutdown systems, and detection and protection systems for toxic and hazardous gases, flammable gases, and fire. The SIS is independent of the process control system (e.g., Distributed Control System [DCS]) and remains dormant or idle during normal production. It can instantly and accurately activate to safely stop the production process or automatically transition to a predefined safe state when a situation that may lead to a safety accident occurs in the production facility. The SIS must have high reliability (i.e., functional safety) and standardized maintenance management. Based on the consequences and risks associated with the failure of safety instrument functions, these functions are categorized into different Safety Integrity Levels (SIL 1-4, with Level 4 being the highest). Safety instrument loops of different levels have varying technical requirements in terms of design, manufacturing, installation, commissioning, and operation and maintenance.
（11） Toxic and Flammable Gas Detection and Protection Systems: The design and implementation of toxic and flammable gas detection and protection systems must strictly comply with relevant standards to ensure their reliability. These systems should be independent of the basic process control system.
（12） Starting from January 1, 2016, new chemical plants involving "two key points and one major" (key regulated hazardous chemicals, key regulated hazardous chemical processes, and major hazard sources) in large-scale and foreign-funded chemical enterprises should be designed with safety instrumented systems that meet the requirements of this guidance document.
（13） Starting from January 1, 2018, all new chemical plants and hazardous chemical storage facilities involving "two key points and one major" must be designed with safety instrumented systems that meet the required standards. Starting from January 1, 2020, all other new chemical plants and hazardous chemical storage facilities must comply with functional safety standards and be designed with safety instrumented systems that meet the required standards.
（14） Existing Production Facilities and Storage Units Involving "Two Key Points and One Major": Chemical enterprises and hazardous chemical storage units with existing production facilities or facilities involving "two key points and one major" should conduct a comprehensive process hazard analysis (e.g., Hazard and Operability Study [HAZOP]) and determine the safety instrument functions and risk reduction requirements through risk analysis. They should promptly assess whether the existing safety instrument functions meet the risk reduction requirements.
（15） Based on the assessment, enterprises should develop management plans and regular inspection and testing programs for safety instrumented systems. For safety instrument functions that do not meet the requirements, relevant maintenance and rectification plans should be developed. The assessment and improvement of safety instrumented systems should be completed by the end of 2019. Other chemical plants and hazardous chemical storage facilities should implement the requirements of this guidance document accordingly.
Notice of the State Administration of Work Safety on Issuing the Key Guidance Catalogue for Safety Inspections of Chemical (Hazardous Chemical) Enterprises ([2015] No. 113)
◆ Setting and interlocking requirements
◆ Equipment and facility management
19. Oil and gas storage tanks that fail to meet the following requirements as required:
(1) Liquefied hydrocarbon storage tanks should be equipped with level gauges, thermometers, pressure gauges, safety valves, as well as high-level alarms and high-high level automatic interlock to cut off the feed. Fully frozen liquefied hydrocarbon storage tanks should also be equipped with vacuum relief facilities and high and low-temperature detection, and should be connected to the automatic control system.
(2) Gas cabinets should be equipped with upper and lower limit alarm devices, and automatic interlocking shut-off devices for inlet and outlet pipelines should be installed;
(3) Emergency shut-off valves should be installed at the liquid phase inlet and outlet of liquefied petroleum gas spherical storage tanks, and their positions should be close to the spherical storage tanks;
(4) Spherical storage tanks for propylene, propane, mixed C4, residual C4, and liquefied petroleum gas should be equipped with water injection measures.
Article 33 of the Safety Production Law; Article 6.3.11 and 6.3.12 of the Fire Protection Design Code for Petrochemical Enterprises (GB50160); Article 6.1 and Article 7.4 of the Safety Design Specification for Liquefied Hydrocarbon Spherical Storage Tanks (SH3136);
20. Devices involving hazardous chemical processes and key regulated hazardous chemicals are not equipped with automated control systems; Or large-scale chemical plants involving hazardous chemical processes that are not equipped with emergency shutdown systems.
Article 9 of the Implementation Measures for Safety Production License of Hazardous Chemical Production Enterprises (Order No. 41 of the State Administration of Work Safety).
25. Hazardous chemical process production equipment involving exothermic reactions that are not equipped with dual power supply or control systems that are not equipped with uninterruptible power supply (UPS).
Article 38 of the Work Safety Law, Technical Specification for Electrical Design of Production Equipment in Petrochemical Enterprises (SH3038), and Design Specification for Power Supply and Distribution Systems (GB50052).
◆ Safety management
28. There are doors and windows on the side of the control room or cabinet facing devices with fire or explosion hazards. (Rectification must be completed before 2017);
Article 38 of the Safety Production Law and Article 5.2.18 of the Fire Prevention Design Code for Petrochemical Enterprises (GB50160).
API STD 2510-2011 Design and Construction of LPG Installations
◆ Setting and interlocking requirements：
9.3.4 Emergency Shutoff Valves
9.3.4.1 Emergency shutoff valves shall be provided in the loading-unloading system for tank cars, trucks, and marine facilities and shall incorporate the following means of closing:
a. Manual shutoff at the installed location.
b. Manual activation from a location accessible during an emergency.
A safety analysis shall be the basis for determining the need for the following:
a. Automatic shutoff in the event of an LPG release.
b. Automatic shutoff through thermal (Þre) actuation.
9.3.4.2 Installation practices for emergency shutoff valves shall include those speciÞed in 9.3.4.2.1 and 9.3.4.2.2.
9.3.4.2.1 When hose or swivel piping is used for liquid or vapor transfer, an emergency shutoff valve shall be installed in the Þxed piping of the transfer system within 20 linear ft of pipe from the end to which the hose or swivel piping is connected. Where the ßow is in one direction only, a check-valve may be used in place of an emergency shutoff valve if the
check valve is installed in a dedicated storage vessel Þll line or vapor return line. When two or more hoses or swivel piping arrangements are used, either an emergency shutoff valve
or a check-valve (for unloading lines only) shall be installed in each leg of the piping.
Note: If check valves are used in place of emergency shutoff valves, the owner/operator should have a program to assure the reliability of these devices.
9.3.4.2.2 The emergency shutoff valves or backßow check valves shall be installed in the Þxed piping so that any break resulting from a pull will occur on the hose or swivel piping
side of the connection while the valves and piping on the plant side of the connection remain intact. This may be accomplished by the use of concrete bulkheads or equivalent
anchorage or by the use of a weakness or shear Þtting. Refer to NPGA Bulletin 128.
Where a review establishes a need, remotely operated shutoff valves (ROSOV) [sometimes used as and called emergency isolation valves (EIV)] should be considered during the PHA and FHA processes. Use of these and other isolation valves should be included in emergency procedures. However, use of automatic (fire or heat actuated) self-closing valves should be used only after a hazard analysis or MOC review to determine whether inadvertent activation may cause undesired consequences. This review should confirm the automatic valve system is inherently safe by a rigorous process safety review since closure of the valve in a nonfire situation or at the wrong time in a fire event may have undesirable consequences, such as causing excessive pressure in a process system or preventing the orderly shutdown sequence of equipment or transfer of product from tanks or vessels during an emergency. The review should include a determination of the safest alternative (“open” or “closed”) on loss of power if ROSOV are used. Discussion of emergency valves (ROEIV, EIV, EBV, ROSOV) can be found in API 553 and UK HES Information Sheet CHIS2.
Reprinted from official account: process equipment, instrumentation and electrical appliances
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