Abstract: A control method and apparatus for startup of turbocompressors to avoid overpowering a driver of the turbocompressor. In a first embodiment, the control system monitors input signals from transmitters of various control inputs. When the input signals exceed threshold values, the control system begins to close the antisurge valve. In a second embodiment, the antisurge valve begins to close after a predetermined time measured from the time startup is initiated. In both embodiments, the antisurge valve continues to ramp closed until the compressor has reached its operating zone, or until the compressor's operating point reaches a surge control line, at which point the antisurge valve is manipulated to keep the compressor from surging.

Abstract: The proposed mechanical method of turbocompressor surge detection uses vibration signals from vibration monitoring equipment mounted on the compressor components to detect a surge event and provide antisurge control thereby. This method utilizes only mechanical information to identify surge, as compared to present day antisurge controllers that use compressor thermodynamic information such as flow, pressure, and temperature to locate a compressor's operating point on a compressor map compared to a surge region.

Abstract: A control method and apparatus for startup of turbocompressors to avoid overpowering a driver of the turbocompressor. In a first embodiment, the control system monitors input signals from transmitters of various control inputs. When the input signals exceed threshold values, the control system begins to close the antisurge valve. In a second embodiment, the antisurge valve begins to close after a predetermined time measured from the time startup is initiated. In both embodiments, the antisurge valve continues to ramp closed until the compressor has reached its operating zone, or until the compressor's operating point reaches a surge control line, at which point the antisurge valve is manipulated to keep the compressor from surging.

Abstract: The proposed mechanical method of turbocompressor surge detection uses vibration signals from vibration monitoring equipment mounted on the compressor components to detect a surge event and provide antisurge control thereby. This method utilizes only mechanical information to identify surge, as compared to present day antisurge controllers that use compressor thermodynamic information such as flow, pressure, and temperature to locate a compressor's operating point on a compressor map compared to a surge region.

Abstract: A control method and apparatus for startup of turbocompressors to avoid overpowering a driver of the turbocompressor. In a first embodiment, the control system monitors input signals from transmitters of various control inputs. When the input signals exceed threshold values, the control system begins to close the antisurge valve. In a second embodiment, the antisurge valve begins to close after a predetermined time measured from the time startup is initiated. In both embodiments, the antisurge valve continues to ramp closed until the compressor has reached its operating zone, or until the compressor's operating point reaches a surge control line, at which point the antisurge valve is manipulated to keep the compressor from surging.

Abstract: A control method and apparatus for critical rotational speed avoidance in a compressor-expander set in a gas refrigeration system. By varying an opening of an antisurge or recycle valve, a shaft power used by the compressor in the compressor-expander set may be varied, thereby varying the rotational speed of the compressor-expander set to move it away from its critical speed zone. Additionally, a feedforward signal may be provided by a compressor-expander set control system to cause an antisurge valve for a recycle compressor to open upon a trip or shutdown of one compressor-expander set.

Abstract: A control method and apparatus for critical rotational speed avoidance in a compressor-expander set in a gas refrigeration system. By varying an opening of an antisurge or recycle valve, a shaft power used by the compressor in the compressor-expander set may be varied, thereby varying the rotational speed of the compressor-expander set to move it away from its critical speed zone. Additionally, a feedforward signal may be provided by a compressor-expander set control system to cause an antisurge valve for a recycle compressor to open upon a trip or shutdown of one compressor-expander set.

Abstract: A control method and apparatus for critical rotational speed avoidance in a compressor-expander set in a gas refrigeration system. By varying an opening of an antisurge or recycle valve, a shaft power used by the compressor in the compressor-expander set may be varied, thereby varying the rotational speed of the compressor-expander set to move it away from its critical speed zone. Additionally, a feedforward signal may be provided by a compressor-expander set control system to cause an antisurge valve for a recycle compressor to open upon a trip or shutdown of one compressor-expander set.

Abstract: Many variables in processes such as those using turbocompressors and turbines must be limited or constrained. Limit control loops are provided for the purpose of limiting these variables. By using a combination of closed loop and open loop limit control schemes, excursions into unfavorable operation can be more effectively avoided. Transition between open loop and closed loop may be enhanced by testing the direction and magnitude of the rate at which the limit variable is changing. If the rate of change indicates recovery is imminent, control is passed back to the closed loop limit control function.

Abstract: A method and apparatus for turbine overspeed protection, useful for steam and gas turbines, is disclosed. The apparatus comprises a spring-loaded rod held by a plurality of energized solenoids in an operating position any time the turbine's shaft rotational speed is less than a trip rotational speed set-point. When the rotational speed reaches the trip rotational speed set-point, both solenoids are de-energized and the spring-loaded rod moves to provide turbine trip. Increased reliability of the solenoids is provided by compressing the spring during the resetting of the rod with an additional electromechanical actuator and by using a plurality of solenoids, each of which is able to provide the force required to hold the spring in its compressed state.

Abstract: Often, an application or process calls for multiple pumps operating within a piping network. Pump load, such as flow rate or pressure, is shared between these multiple pumps. The present disclosure relates to effective means of distributing the pumping load in a manner that satisfies the process requirements while keeping the pumping machinery safe from functioning in damaging operating regions. It also discloses a method of operating pumps in an efficient or optimal fashion. An additional aspect is a method of using an open-loop response to deal with large transients threatening to force a pump into an operating region that might result in damage or destruction.

Abstract: Steam turbine speed-control systems often incorporate pilot valves for controlling the position of hydraulic actuators for steam valves. Operational efficiency of these pilot valves can suffer from imperfections due to manufacturing defects, wear, contaminated oil, and the like, thereby impairing the control system's overall performance. This disclosure relates to a method for improving performance accuracy by incorporating a control system (including additional controllers) dedicated to overcoming the deficiencies of pilot valves or other control system components. With such a system, the lack of adequate control response can be detected by calculating the first time-derivative of a variety of main controlled-parameters. Such parameters can be directly related to steam flow control, such as steam valve position, steam flow rate, and pressure within the steam turbine; or they may be related to the driven equipment: generator power output, flow rate through a compressor, and compressor discharge pressure.

Abstract: Steam turbine speed-control systems often incorporate pilot valves for the purpose of controlling the position of hydraulic actuators for steam valves. However, the operational efficiency of these pilot valves can suffer from imperfections due to manufacturing defects, wear, and the like, thereby impairing the control system's overall performance. For these reasons, this disclosure relates to a method for overcoming a faulty pilot valve by incorporating a control system (including additional controllers) dedicated to the pilot valve. In this type setup, not only can the position of the pilot valve be a control variable, but the velocity of actuation of this valve can also be used as another control variable. Therefore, the results of separate controllers, using these two control variables, can be combined to improve the dynamic response of the steam turbine speed-control system.

Abstract: Accurate and effective antisurge control for turbocompressor stages is augmented by measuring the flow rate of fluid entering or leaving the stage of compression. On the other hand, turbocompressors with sidestreams, such as ethylene, propylene, and propane refrigeration compressors, pose unique antisurge control challenges; in particular, measurements for the flow rate entering (or leaving) the compressors' middle stages are not available in most cases. Furthermore, the methods used to cope with this lack of flow measurements are prone to introducing errors and producing false transients, as well as being cumbersome and difficult to implement. For these reasons, this disclosure relates to a method for protecting turbocompressors with sidestreams from the damaging effects of surge.

Abstract: Compensating for the complex changing shape and location of a turbocompressor's surge limit line can be difficult and imprecise when using antisurge controllers that do not incorporate sufficient capability. Based upon various operating conditions, surge limit line changes can be attributed to a number of process variables. These effects are particularly relevant to multistage centrifgal and axial turbocompressors operating with variable rotational speed and equipped with adjustable inlet or diffuser guide vanes, or both. This invention relates to an innovative method of antisurge control in which the function of those process variables (comprising the turbocompressor operating condition parameters) is used to calculate distances to the surge reference line. The function is formed as a superposition of the functions of lesser numbers of variables.

Abstract: An objective in a natural gas liquids (NGL) plant is that of achieving and maintaining maximum productivity. If this plant is equipped with a turboexpander that drives a gas compressor (recompressor), maximum turboexpander productivity provides maximum plant productivity attained by maximum compressor power. This is accomplished by manipulating the compressor operating point location (by adjusting the opening of the antisurge valve) and by controlling rotational speed. The subjects of the proposed invention are the method and apparatus (comprising a turboexpander/recompressor rotational speed controller and a recompressor antisurge controller) providing maximum turboexpander/recompressor rotational speed and recompressor operating point location (corresponding to maximum power) by opening the turboexpander's adjustable nozzles and the recompressor antisurge valve.

Abstract: The exactness of surge-limit information facilitates the determination of how safely a turbocompressor can operate as well as determining the size of the operational envelope in which a compressor can function with a closed antisurge valve. Furthermore, in order to accurately describe the complete interface between stable and unstable operation, a sufficient number of test points must be found. Consequently, if a turbocompressor operates within the broad ranges of rotational speed or guide vane position or both of them, the unit must be repeatedly tested using different values of process variables; as a result, each test leads the turbocompressor into surge which can be detrimental because of strong dynamic loading. For that reason, this invention describes a technique employed during turbocompressor testing (either without generating surge or with a minimum number of surges) for defining both the shape and the location of a turbocompressor's surge limit.

Abstract: This invention discloses a method for limiting a critical variable (such as, discharge pressure or suction pressure or pressure ratio) of either a compressor station or an individual compressor when these machines are subjected to large, fast disturbances. Each configuration, whether a station or an individual compressor, is equipped with two PID controllers: (1) a main controller for compressor critical variables and (2) a limiting controller that participates in modulating recycle valves. At the onset of sudden, large changes of mass flow at a compressor's or station's discharge, the effectiveness of the two controllers (acting independently) may be insufficient to prevent discharge pressure from reaching the shutdown set point which, in turn, disrupts the process supported by the compressors, and the longevity of the drivers is diminished. For these reasons, this disclosure relates specifically to a technique that combines the functions of the main and limiting controllers.

Abstract: Pilot valves used in electrohydraulic control systems are driven by either an electromagnetic electromechanical actuator or an electromotor electromechanical actuator. A drawback of electromagnetic actuation is that on brief interruptions of electrical power the actuator causes a trip response to the pilot valve, whereas a drawback of electromotor actuation is that on complete interruptions of electrical power the actuator cannot independently cause a trip response of the pilot valve on demand. The proposed modification, involving the pilot valve, provides a means to effect a trip response regardless of the electromechanical actuator type used, together with overcoming the drawback of electromotor actuation. To realize the trip response, an additional piston (connected to the electromotor actuator's stem) is positioned between the actuator stem and the pilot valve.

Abstract: The operation of quickly taking a turbocompressor off-line from a parallel configuration, of a gas pipeline compressor station, may encounter increased mechanical action (in particular, vibration) upon recycle piping and the additional risk of compressor surge. For these reasons, this invention relates to a method and apparatus for decreasing vibratory loads and for increasing surge prevention effectiveness, while initiating an off-line operation, by (1) altering the surge control line's location, at a preset rate, from its initial location to a predetermined new location; and (2) decreasing the turbocompressor's deceleration rate when the operating point intercepts the surge control line before the control line reaches its new location. Upon completion of the off-line activity, the control line returns to its initial location; and the reduction of compressor speed will cease on reaching a preset value.