Thread Content
Liquefied hydrocarbons refer to hydrocarbon liquids and other similar liquids that, at 15°C, have a vapor pressure greater than 0.1 MPa; they possess hazardous properties such as flammability and explosiveness. The storage tank area for liquefied ethylene is classified as a area containing major hazard sources. It is a key target for routine inspections, as well as a focal point in the special safety rectification efforts concerning liquefied hydrocarbons. In the actual production process, when facing various inspections and abnormal operating conditions, the professionalism, systematic approach, and targeted strategies of production technicians in the ethylene tank area help to reduce various risks and ensure safety and reliability in areas with major hazards. A collection of Q&A answers has been prepared regarding the various issues encountered in the design, construction, commissioning, operation, maintenance, and inspection of ethylene storage areas, in the hope of providing some assistance to professionals in similar industries. This article will be published in 3 installments. Public account release: Petrochemical Engineering Notes Table of Contents 29. What is the function of the liquid stabilizing pipes in ethylene spheres? 30. What is the inspection cycle for ethylene spheres? 31. Why cannot water be used directly to spray at the leak or source when ethylene leaks? 32. How to handle ethylene leaks effectively and quickly? 33. What is the critical amount for ethylene storage? 34. How to prevent low temperatures during the emptying of ethylene spheres? 35. How to test the ethylene transfer pump at the start of operation? 36. What are the characteristics of vertical ethylene transfer pumps that take in liquid from the top? 37. Is it necessary to install a water injection line for the ethylene tank? 38. Is it necessary to add a protective cover to the emergency stop button on the auxiliary operating console in the control room? 39. What are the functions of the instrument interlock reset button and the reset logic? 40. What should be the state of the instrument maintenance bypass switch during normal operation? 41. What is the joint debugging of instruments? 42. What is the firework operation level within the fire dike of the ethylene tank farm? 43. How to conduct a hydrostatic test after the tank installation is completed? What should be noted? 44. What common characteristics do brittle failure accidents of spherical tanks have? 45. What are the failure risks of ethylene tanks throughout the entire lifecycle? 46. What are the consequences of the failure of ethylene spheres? 47. What are the main failure modes and preventive measures for ethylene tanks throughout their entire lifecycle? 48. What are the fire and heat insulation measures for ethylene spheres? 49. What is the purpose of an emergency shut-off valve in an ethylene tank? 50. What are the classification levels for hot work conducted outside the fire dike in the ethylene tank area? 29. What is the function of the stabilizing tube in an ethylene spherical tank? The liquid-stabilizing pipes inside ethylene spherical tanks are primarily used to stabilize the flow of liquid within the tank, thereby reducing fluctuations and pressure surges. Their specific functions are as follows: ① Suppress liquid fluctuations and maintain stable pressure; ② Prevent the formation of vortices and gas entrainment; ③ Reduce the risk of static electricity accumulation; ④ Protect the level gauge. 30. What is the inspection interval for ethylene spherical tanks? According to TSG21-2016 “Safety Technical Supervision Regulations for Stationary Pressure Vessels”, a first inspection involving opening the tank must be conducted one year after an ethylene spherical tank is put into service. The subsequent inspection cycle is determined based on the safety status level of the initial inspection: for safety status levels 1 and 2, inspections are generally carried out every 6 years. The safety status level is 3: the cycle is shortened to 3–6 years. The safety status level is 4: It requires monitored use, with a cumulative monitoring period not exceeding 3 years, and monitoring measures must be established. The safety status level is 5: The defect must be addressed; otherwise, use should not continue. Periodic adjustments under special circumstances: The inspection interval must be shortened in the following cases: when the medium is highly corrosive or there is a risk of stress corrosion ； Harsh operating conditions or defects detected ； When using the Risk-Based Inspection (RBI) technique, the maximum period does not exceed 9 years. 31. Why cannot water be used directly to spray at the leak or source when ethylene leaks? When ethylene leaks, using water to directly spray the leak or its source is highly dangerous and ineffective. The impact of water flow cannot dilute it effectively, which may accelerate the spread of ethylene and expand the area at risk of explosion; fast-moving water can generate static electricity, which may ignite ethylene vapor. Secondly, the jetted water flow may carry ethylene into the drainage system, triggering an explosion. After an ethylene leak, it vaporizes rapidly, causing the temperature to drop to -104°C. Direct exposure to water can lead to brittle fracturing of equipment or pipes due to the low temperatures, thereby exacerbating the leak. Using water directly to flush out ethylene leaks is a typical mistake; it can trigger explosions, exacerbate the disaster, or delay effective response.