China Petrochemical Corporation Safety Valve Setting Requirements

Sinopec [2001] An Zi No. 30 1.0 General Principle 1.1 Purpose and scope of application 1.1.1 In order to meet the requirements of “Safety valves should generally be checked at least once a year” in the “Pressure Vessel Safety Technical Supervision Regulations” of the State Administration of Quality and Technical Supervision , This regulation is specially formulated. 1.1. 2 This regulation is applicable to the existing and newly built, renovated and expanded production facilities in the enterprises affiliated to China Petrochemical Corporation. 1.1. 3 This regulation is applicable to the nominal pressure range of the safety valve between 0.1~25MPa, and the diameter of the flow channel is greater than or equal to 8mm. 1.1. 4 This regulation does not apply to boiler safety valves, and the setting of boiler safety valves shall comply with the regulations of the former Ministry of Labor’s “Steam Boiler Safety Technical Supervision Regulations”. 1.2 Relevant regulations and standards 1.2.1 “Pressure Vessel Safety Technical Supervision Regulations” (Baofa [1999] No.154 of the Bureau of Quality and Technical Supervision) 1.2.2 GB/T12241-89 General requirements for safety valves 1.2.3 GB/T12242-89 Safety Valve performance test method 1.2.4 GB/T12243-89 Spring direct load safety valve 2.0 Term explanation 2.0.1 Maximum operating pressure P: The highest pressure that may be reached during the operation of the equipment. 2.0.2 Back pressure Pb: The pressure at the outlet of the safety valve, which is the sum of the additional back pressure and the discharge back pressure. 2.0.3 Set pressure (opening pressure) PS: the inlet pressure at which the safety valve disc starts to rise under operating conditions. Under this pressure, a measurable opening height begins, and the medium assumes a continuous discharge state that is perceived by sight or hearing. 2.0.4 Discharge pressure Pd: the inlet pressure at which the valve disc reaches the specified opening height. 2.0.5 Re-seat pressure Pr: After discharge, the valve disc contacts the valve seat again, that is, the inlet pressure when the opening height becomes zero. 2.0.6 Overpressure ΔPO: The difference between the discharge pressure and the set pressure, usually expressed as a percentage of the set pressure. 2.0.7 Opening and closing pressure difference ΔPb1: The difference between the set pressure and the return pressure, usually expressed as a percentage of the set pressure. 2.0.8 Discharge back pressure Pbd (also called “accumulated back pressure” or “dynamic back pressure)”: The pressure formed at the outlet of the valve due to the medium flowing into the discharge system through the safety valve. 2.0.9 Additional back pressure PbS (also called “superimposed back pressure” or “static back pressure)”: The pressure existing at the valve outlet before the safety valve is activated, which is caused by other pressure sources in the exhaust system. 2.0.10 Direct-loaded safety valve: a safety valve that directly uses mechanical loads such as heavy hammers, lever-increased hammers or springs to overcome the force generated by the medium pressure under the disc. 2.0. 11 Pilot-operated safety valve: a safety valve driven or controlled by the discharge of the medium from the pilot valve. The pilot valve itself should be a direct-load safety valve that meets the requirements of the standard. 2.0.12 Balanced bellows safety valve: Balanced bellows safety valve is a kind of balanced safety valve. It reduces the back pressure limit of ordinary safety valves to a minimum by installing a bellows between the valve clack and the relief valve cover. 2.0.13 Full-open safety valve: refers to the opening height of the valve disc. It is generally used under the condition that the discharge medium is gas, and it is fully opened when the discharge pressure is reached. 2.0.14 Micro-opening safety valve: refers to the opening height of the valve flap. It is generally used when the discharge medium is liquid. It starts to open when the set pressure is reached, and continues to open as the pressure increases. 2.0.15 Closed spring type safety valve: refers to the safety valve spring cover is closed, the spring is not in contact with the atmosphere. 2.0.16 Unclosed spring-loaded safety valve: refers to the safety valve spring cover is not closed, the spring can be in contact with the atmosphere. 2.0.17 Additional accessories: In this regulation, it specifically refers to the fixed parts configured on the pipeline for the purpose of safety valve calibration, such as rupture discs, valves, pipes, pipe fittings and pressure gauges. 2.0.18 On-line verification: refers to the use of additional accessories on the safety valve pipeline, the verification personnel use appropriate special appliances, and the safety valve verification and pressure are carried out in the original place without disassembling the safety valve and the production device is not shut down. Tuning. 2.0.19 Offline verification: refers to dismantling the safety valve and transporting it to a place specializing in safety valve verification for safety valve verification and pressure setting. 2.0.20 Quick-switching device: refers to a device that is installed under the double safety valve and can quickly change the relationship between in-use and standby of the safety valve. 2.0.21 Opening height h: the actual lift of the valve clack from the closed position. 2.0.22 Frequency jump: The safety valve disc moves back and forth quickly and abnormally, and the disc contacts the valve seat during the movement. 2.0.23 Flutter: The safety valve disc moves back and forth quickly and abnormally, and the disc does not touch the valve seat during movement. 2.0.24 Lead seal: a complete activity in which the bonnet of the safety valve is locked by a designated professional with a special tool, or the handwheel of the cut-off valve is locked according to the design requirements, and the seal cannot be opened without permission. 3.0 Selection and Ordering of Safety Valves 3.1 Selection of Safety Valves 3.1.1 For the expansion and pressure relief of incompressible liquids, a low-open safety valve or a full-open safety valve should be used. When the medium is a liquid, a full-lift safety valve is selected, its action performance becomes a micro-lift type, and the inner diameter of the nozzle should be calculated according to the micro-lift type. 3.1.2 Generally, only spring-type safety valves or pilot-type safety valves are used in petroleum and petrochemical production equipment. 3.1. 3 The balanced bellows safety valve should be selected in the following situations: 1. The back pressure of the safety valve is greater than 10% of its set pressure and less than 30%; 2. When the medium is corrosive, easy to scale, and easy to coke, it will affect When the safety valve spring is working normally; however, the balanced bellows safety valve is not suitable for phenol, wax liquid, heavy petroleum distillate, coke powder, etc. media, nor is it suitable for reciprocating compressors. 3.1.4 Pilot safety valves should be selected in the following situations: 1. When the back pressure of the safety valve is greater than 30% of its set pressure; 2. For occasions requiring particularly good sealing performance of the safety valve; 3. Toxic and harmful to the medium When using a non-flowing pilot valve (that is, when the pilot valve is opened, it does not discharge the medium). 3.1.5 Except for the safety valves for water, steam, air, and nitrogen, all safety valves should be of closed spring type structure. 3.2 Safety valve manufacturing standards and selection 3.2.1 Safety valve manufacturing standards There are currently two safety valve manufacturing standards adopted in China: National standards (spring direct load safety valve GB12243-89) API (American Petroleum Institute) standards (Flanged Steel Safety—Relief Valves API Standard 526 fourth Edition, 1995) 3.2.2 Safety valves installed on equipment and pipelines that handle flammable, explosive, hazardous, and toxic media should use safety valves manufactured by API standards. 3.2.3 When it meets one of the following places, safety valves manufactured by national standards should be used. 1. Install in places with low emission requirements such as water, steam, air, and nitrogen. 2. The continuous operation time of the equipment protected by the safety valve is less than one year, or other places with lower requirements. 3.3 Ordering requirements 3.3.1 Strictly place an order according to the parameters in the designed safety valve specification sheet, and carefully conduct various inspections in accordance with relevant standards. The manufacturer must provide a product quality certificate and install a firm metal nameplate on the product. The content should comply with According to the relevant regulations of the State Bureau of Technical Supervision, the imported safety valve shall be inspected in accordance with the requirements of the contract. 3.3.2 Manufacturers should be required to do a good job of packaging products so that the safety valve always maintains a vertical state during transportation. 3.4 Cut-off valve of the safety valve 3.4.1 The cut-off valve upstream and downstream of the safety valve shall meet the following conditions: 1. The pressure level of the upstream and downstream cut-off valve shall be consistent with the pressure level of the inlet and outlet pipes of the safety valve; 2. The nominal diameter of the inlet and outlet of the shut-off valve shall not be less than the nominal diameter of the inlet and outlet flanges of the safety valve; 3. Generally, the shut-off valve should be a rising stem gate valve or a shut-off valve. If a gate valve is selected, the valve stem should be installed horizontally. 4.0 Safety valve setting and selection principles 4.1 Typical safety valve setting 4.1.1 Method 1: Only one safety valve is installed, and there is no cut-off valve before and after the safety valve (see Figure 1). 4.1.2 Method 2: Only one safety valve should be installed, and a cut-off valve should be added before and after the safety valve (see Figure 2). 4.1.3 Method 3: Only one safety valve is installed, and a cut-off valve and auxiliary line valve should be added before and after the safety valve (see Figure 3). 4.1.4 Method 4: Install only one safety valve, and install a group of rupture discs before the safety valve; between the rupture disc and the safety valve, install a four-way component interface for online verification (see Figure 4). ). 4.1.5 Method 5: Only one safety valve is installed, and a set of rupture discs are installed in front of the safety valve; between the rupture disc and the safety valve, a four-way component interface for online verification is installed, and the rupture disc is installed A cut-off valve is installed at the front and after the safety valve (see Figure 5). 4.1.6 Method 6: Refers to the situation where two safety valves are installed at the same time, and a cut-off valve is installed before and after each safety valve, so that the safety valves can be used as backup for each other (see Figure 6). In the figure: LC——Lead seal closed; LO——Lead seal open: In Figure 2, Figure 3, Figure 6, the four-way component joints before and after the safety valve are shown. Install it only when online verification is required, otherwise it can be cancelled. 4.2 Selection principle of setting method 4.2.1 When one of the following conditions is met, the safety valve can be set according to method 1: 1. In the operation unit of intermittent or mass production, it can meet the requirement of one school a year. 2. In order to meet the requirement of a safety valve school once a year, the materials in the equipment can be emptied. 4.2.2 For equipment that needs to operate continuously for more than one year, and during the safety valve calibration time, other measures can be used to ensure that the system does not overpressure, and safety valves can be set according to method 2. 4.2.3 When one of the following conditions is met, the safety valve can be set according to the third method: 1. During the safety valve calibration time, other measures cannot be used to ensure that the system does not overpressure; When the auxiliary line valve is used to discharge materials. 4.2.4 When one of the following conditions is met, set the safety valve according to method 4: 1. When the medium is one of the following conditions: a. Viscous medium; b. Corrosive medium; c. The medium will self-converge; d. The medium contains solid particles. 2. When a safety valve is installed and only rupture discs are added to meet the requirements of online verification. 4.2.5 In the case of 4.2.4, and when the rupture disc needs to be replaced online during the operation period of the equipment, the safety valve shall be set according to the fifth method. 4.2.6 Where none of the above methods can meet the requirement of “generally at least once a year”, parallel backup safety valves can be set up according to Method 6, and lead seals are used to keep them in one open and one closed state. 4.2.7 According to the needs of the system, when two or more safety valves are installed in one release source, in order to meet the requirement of “generally at least once a year”, one of the above six methods should be selected according to the requirements. It can not only meet the requirements of use, but also configure it in a more economical way. 4.2.8 The setting of safety valves with special requirements for the process can be implemented in accordance with relevant regulations. 5.0 Installation and transportation requirements 5.1 Safety valve installation requirements 5.1.1 The safety valve must be verified and pressure-qualified before installation, and the lead seal can be installed. The lead seal should be marked with the verification date; 5.2 The lead seal of the cut-off valve must be before and after the safety valve When it is necessary to install a shut-off valve, it must be confirmed that the shut-off valve is flexible and easy to use, and is equipped with an obvious switch mark, and the lead seal should meet the design requirements. 5.3 Transportation and storage During transportation and storage, the safety valve should always be kept in a vertical state in order to keep the position of the guiding parts and springs unchanged. 6.0 Calibration and maintenance 6.1 Safety valve calibration 6.1.1 Safety valves should generally be checked at least once a year. 6.1.2 The safety valve is out during use< 3 Transportation and storage During transportation and storage, in order to keep the position of the guiding parts and springs unchanged, the safety valve should always be kept in a vertical state, and it is strictly forbidden to pull it down and carry it. 6.0 Calibration and maintenance 6.1 Safety valve calibration 6.1.1 Safety valves should generally be checked at least once a year. 6.1.2 The safety valve is out during use< 3 Transportation and storage During transportation and storage, in order to keep the position of the guiding parts and springs unchanged, the safety valve should always be kept in a vertical state, and it is strictly forbidden to pull it down and carry it. 6.0 Calibration and maintenance 6.1 Safety valve calibration 6.1.1 Safety valves should generally be checked at least once a year. 6.1.2 The safety valve is out during use<