(Daily Question) Coal-to-oil and olefins forum, 2018.2.21
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3.jpg Participation: Prize of 5 Wealth； Correct answer: Reward of 10 wealth points ； Note: This post is valid for 48 hours. Question: (DMTO) Olefin separation unit: Why is an overspeed protection device required for the turbine? A turbine is a high-speed rotating machine, and the centrifugal stress on its rotating components is proportional to the square of the speed; in other words, as the speed increases, the centrifugal stress rises rapidly. When the turbine speed exceeds the rated speed by 10%, the centrifugal stress increases by 21% compared to the stress at the rated speed ； When the turbine speed exceeds 20% of the rated speed, the centrifugal stress increases by 44% compared to the stress at the rated speed. Excessively high rotational speeds can also cause the impeller, which is in an interference fit, to loosen on the rotor, leading to damage such as frictional collisions between moving and stationary parts, thereby posing a serious threat to the safe operation of the steam turbine. Therefore, steam turbines are equipped with overspeed protection devices. When the turbine control system fails and the speed exceeds the rated speed by 10%-12%, the overspeed protection device activates, quickly closing the main steam valve and the control valves to cut off the steam supply to the turbine, thereby causing it to stop operating urgently! Note: The answers will be announced automatically in two days!
A steam turbine is a high-speed rotating device, and the centrifugal force on its rotating components is proportional to the square of the speed; in other words, as the speed increases, the centrifugal stress rises rapidly. When the turbine speed exceeds the rated speed by 20%, the centrifugal stress is approximately 1.5 times that at the rated speed; at this point, not only do the components that are fitted together by tight fits in the rotating parts become loose, but the centrifugal stress also exceeds the strength limit of the materials, leading to damage to those components. For this reason, superspeed protection devices are installed in all turbines; these devices activate when the rotational speed exceeds the rated speed by 8%~12%, quickly shutting off the steam supply and causing the turbine to stop operating.
A steam turbine is a high-speed rotating device, and the centrifugal force on its rotating components is proportional to the square of the speed; in other words, as the speed increases, the centrifugal stress rises rapidly. When the turbine speed exceeds the rated speed by 20%, the centrifugal stress is approximately 1.5 times that at the rated speed; at this point, not only do the components that are fitted together by tight fits in the rotating parts become loose, but the centrifugal stress also exceeds the strength limit of the materials, leading to damage to those components. For this reason, superspeed protection devices are installed in all turbines; these devices activate when the rotational speed exceeds the rated speed by 8%~12%, quickly shutting off the steam supply and causing the turbine to stop operating.
A steam turbine is a high-speed rotating device, and the centrifugal force on its rotating components is proportional to the square of the speed; in other words, as the speed increases, the centrifugal stress rises rapidly. When the turbine speed exceeds the rated speed by 20%, the centrifugal stress is approximately 1.5 times that at the rated speed; at this point, not only do the components that are fitted together by tight fits in the rotating parts become loose, but the centrifugal stress also exceeds the strength limit of the materials, leading to damage to those components. For this reason, superspeed protection devices are installed in all turbines; these devices activate when the rotational speed exceeds the rated speed by 8%~12%, quickly shutting off the steam supply and causing the turbine to stop operating.
When a turbine suddenly loses all of its load or when the control system fails, the speed of the turbine can rise to levels that exceed the limits allowed by the rotor’s strength, leading to serious damage to the equipment. The overspeed protection device is designed to activate when the speed exceeds 110–112% of the rated speed; it then automatically shuts down the main steam valve and the control valves, thereby bringing the turbine to a stop urgently and protecting the equipment from damage.
Question: (DMTO) Olefin separation unit: Why is an overspeed protection device required for the turbine? Answer ① At high speeds, the increase in steam inflow leads to an increase in the bending stress on the blades; simultaneously, the stress and resulting deflection on the diaphragms and stationary blades also increase ； ②When operating at excessive speeds, the increased steam intake leads to an increase in axial thrust, which raises the temperature of the tungsten carbide bearings; in severe cases, this can result in the destruction of these bearings ； ③When operating at high speeds, the opening degree of the speed control valve reaches near its limit, and the hydraulic actuator also reaches near its maximum travel distance; this leads to a deterioration in the performance of the speed control system. Both the rate of speed variation and latency increase, resulting in poorer stability of operation.
When a turbine suddenly loses all of its load or when the control system fails, the speed of the turbine can rise to levels that exceed the limits allowed by the rotor’s strength, leading to serious damage to the equipment. The overspeed protection device is designed to activate when the speed exceeds 110–112% of the rated speed; it then automatically shuts down the main steam valve and the control valves, thereby bringing the turbine to a stop urgently and protecting the equipment from damage.
Is the centrifugal stress on rotating components proportional to the square? When the turbine speed exceeds the rated speed by 10%, the centrifugal stress increases by 21% compared to the stress at the rated speed ； When the turbine speed exceeds 20% of the rated speed, the centrifugal stress increases by 44% compared to the stress at the rated speed. This isn’t a quadratic relationship, right?
Why is an overspeed protection device installed in turbines? Answer: Turbines are devices that operate at high speeds, and the centrifugal force on their rotating parts is proportional to the square of the speed. In other words, as the speed increases, the centrifugal force rises rapidly. When the turbine’s speed exceeds 1.5 times the stress level corresponding to its rated speed, the parts that are fitted together by tight fits within the rotating components will loosen, and the centrifugal force will exceed the strength limit of the materials, resulting in damage to those components. Therefore, the turbine is equipped with an overspeed protection mechanism that activates to shut it down when the speed exceeds the rated speed by 10-12%, thereby protecting the safety of the equipment.
Turbines are devices that operate at high speeds. The centrifugal force on their rotating parts is proportional to the square of the speed; in other words, as the speed increases, the centrifugal force rises rapidly. When the turbine’s speed exceeds 1.5 times the stress level corresponding to its rated speed, not only do the components that are fitted together under tight fit loosen, but the centrifugal force also exceeds the strength limit of the materials, leading to damage to those components. Therefore, turbines are equipped with overspeed protection devices that activate and shut down the turbine when the speed exceeds 10–12% of the rated speed, thereby preventing further operation