Abstract: A method and apparatus for estimating the instantaneous rotational speed of a bottom hole assembly at the lower end of a drill string. In one embodiment, a method includes driving the drill string by a drilling mechanism at the upper end of the drill string. A fundamental frequency of stick-slip oscillations suffered by the drill string is estimated. Variations in a drive torque of the drilling mechanism are determined. Known torsional compliance of the drill string is combined with the variations in the drive torque. An output signal representing the instantaneous rotational speed is provided.

Abstract: A method and apparatus for estimating the instantaneous rotational speed of a bottom hole assembly at the lower end of a drill string. In one embodiment, a method includes driving the drill string by a drilling mechanism at the upper end of the drill string. A fundamental frequency of stick-slip oscillations suffered by the drill string is estimated. Variations in a drive torque of the drilling mechanism are determined. Known torsional compliance of the drill string is combined with the variations in the drive torque. An output signal representing the instantaneous rotational speed is provided.

Abstract: A device for preventing a primary relief valve in a mud system from opening at a pressure lower than a nominal opening pressure includes a flow restrictor between a mud pump of the mud system and the primary relief valve. In addition, the device includes a cavity between the flow restrictor and the primary relief valve.

Abstract: A method for detection of a leak in a fluid affected component of a piston machine includes obtaining a vibration signal from a vibration sensor disposed proximate to at least one valve block of the piston machine. The vibration signal includes vibration generated by valves in the valve block. The method further includes presenting the obtained vibration signal for analysis by at least one of a human or a computer, analyzing the obtained vibration signal with respect to revealing a malfunction related to a fluid affected component of the piston machine, and selecting the obtained vibration signal emitted from the valve block during the closed periods of the valves for presentation.

Abstract: A method for detecting and localizing a valve leak in a piston machine having a shaft includes: attaching one or more vibration sensor to a valve block of the piston machine; measuring the vibrations from at least one of the vibration sensors; attaching a sensor to the piston machine where the sensor is designed to produce, directly or indirectly, an angular shaft position signal for the shaft; determining, directly or indirectly, an angular shaft position signal for the shaft; transforming vibration signals from the one or more vibration sensors into one envelope signal representing an instant vibration level; using the angular position signal for constructing window functions that pick the envelope signal in selected angular shaft sectors; using the window functions to find sector based averages of the vibration level; and comparing said averages with a critical ambient vibration level to detect and localize leaks in one or two valves.

Abstract: A method for reducing resonant vibrations and dynamic loads of cranes, whose horizontal and vertical motion of the pay load are controlled by a boom winch controlling the luffing motion of a pivoting boom and a hoist winch controlling the vertical distance between a boom tip and the load. Where the method includes determining the resonance frequencies of the coupled crane boom and load system, either experimentally or theoretically at least from data on inertia of the boom and stiffness of at least a boom rope, a hoist rope, a pedestal and an A-frame. The method further includes automatically generating a damping motion in at least one of said winches, that counteracts dynamic oscillations in the crane, and adding this damping motion to the motion determined by a crane operator.

Abstract: A machine includes at least one piston and a pump shaft. A method for detecting a leak in the machine includes receiving a vibration signal from a vibration sensor disposed on at least one of an upstream pipe and a downstream pipe of the machine, receiving a rotational speed signal and an angular shaft position signal from a speed and position sensor disposed on the machine, calculating a rotational speed and an angular shaft position of the pump shaft, calculating at least one complex harmonic Fourier amplitude of the received vibration signal, low pass filtering the at least one complex harmonic Fourier amplitude, calculating a deviation amplitude as a magnitude of a complex difference between the filtered amplitude and a base amplitude, and monitoring the deviation amplitude to detect a leakage.

Abstract: A method for detection of a fluid leak related to at least one piston machine (1), where the method includes: —attaching a pressure sensor (18, 24) to at least a pressure side of the at least one piston machine (1); —measuring the pressure on the pressure side of the at least one piston machine (1); —attaching a transmitter (28) to the at least one piston machine (1), said transmitter (28) rendering a signal for calculating the rotational speed of the at least one piston machine (1); —calculating the speed of the at least one piston machine (1); —calculating the sum of nominal flow rates from all piston machines (1); —calculating a flow rate compensation factor; —calculating a normalized pressure (42) to be equal to the discharge pressure multiplied by the said compensation factor for the flow rate; and —monitoring the normalized pressure (42) to detect a leakage.

Abstract: A method and apparatus for estimating the instantaneous rotational speed of a bottom hole assembly at the lower end of a drill string. In one embodiment, a method includes driving the drill string by a drilling mechanism at the upper end of the drill string. A fundamental frequency of stick-slip oscillations suffered by the drill string is estimated. Variations in a drive torque of the drilling mechanism are determined. Known torsional compliance of the drill string is combined with the variations in the drive torque. An output signal representing the instantaneous rotational speed is provided.

Abstract: A method and apparatus for damping stick-slip oscillations in a drill string. In one embodiment a method includes damping the stick-slip oscillations using a drilling mechanism at the top of said drill string. The speed of rotation of the drilling mechanism is controlled using a PI controller. The control is characterised by tuning the PI controller so that the drilling mechanism absorbs most torsional energy from the drill string at a frequency that is at or near a frequency of the stick-slip oscillations.

Abstract: A machine includes at least one piston and a pump shaft. A method for detecting a leak in the machine includes receiving a vibration signal from a vibration sensor disposed on at least one of an upstream pipe and a downstream pipe of the machine, receiving a rotational speed signal and an angular shaft position signal from a speed and position sensor disposed on the machine, calculating a rotational speed and an angular shaft position of the pump shaft, calculating at least one complex harmonic Fourier amplitude of the received vibration signal, low pass filtering the at least one complex harmonic Fourier amplitude, calculating a deviation amplitude as a magnitude of a complex difference between the filtered amplitude and a base amplitude, and monitoring the deviation amplitude to detect a leakage.

Abstract: A method for reducing cogging torque effects of an electrical permanent magnet machine includes running an “a” test and a “b” test with different cogging compensation signals. A first value is calculated by multiplying a complex cogging amplitude of the compensation signal applied for the “a” test with a complex amplitude of a vibration signal resulting from cogging torque of the “b” test. A second value is calculated by multiplying a complex cogging amplitude of the compensation signal applied for the “b” test with a complex amplitude of the vibration signal resulting from cogging torque of the “a” test. A desired complex cogging compensation amplitude is calculated by dividing the difference between the first and second values by a difference between the complex amplitudes of the vibration signals resulting from the “b” test and the “a” test. A cogging compensation torque is applied to the machine based on the desired complex cogging compensation amplitude.

Abstract: A method for detection of a fluid leak related to at least one piston machine (1), where the method includes: —attaching a pressure sensor (18, 24) to at least a pressure side of the at least one piston machine (1); —measuring the pressure on the pressure side of the at least one piston machine (1); —attaching a transmitter (28) to the at least one piston machine (1), said transmitter (28) rendering a signal for calculating the rotational speed of the at least one piston machine (1); —calculating the speed of the at least one piston machine (1); —calculating the sum of nominal flow rates from all piston machines (1); —calculating a flow rate compensation factor; —calculating a normalized pressure (42) to be equal to the discharge pressure multiplied by the said compensation factor for the flow rate; and —monitoring the normalized pressure (42) to detect a leakage.

Abstract: A method for detection of a leak in a fluid affected component of a piston machine includes obtaining a vibration signal from a vibration sensor disposed proximate to at least one valve block of the piston machine. The vibration signal includes vibration generated by valves in the valve block. The method further includes presenting the obtained vibration signal for analysis by at least one of a human or a computer, analyzing the obtained vibration signal with respect to revealing a malfunction related to a fluid affected component of the piston machine, and selecting the obtained vibration signal emitted from the valve block during the closed periods of the valves for presentation.

Abstract: A drawworks (10) comprising a permanent magnet motor (60) mounted inside a drum(40), said permanent magnet motor arranged to drive said drum via a gear system(50), characterised in that said gear system is located at least partially within said drum.

Abstract: A method of determining a leakage in a piston machine comprising at least two pistons is provided. The rotational velocity of the piston machine, and therefore the volume flow through the piston machine, is varied periodically as part of a time-limited active test while measuring the differential pressure and the angular position. An angular position-based Fourier analysis of the measured values from differential pressure and rotational velocity measurements performed during the test are used to experimentally determine the amplitude ratio and phase angle difference between volume flow variations and pressure variations. The amplitude ratio and phase angle difference are used, together with an angular position-based Fourier analysis of the measurements of differential pressure and rotational speed made after the active test, to determine the amplitude and phase of the leakage flow.

Abstract: A method of filtering out pressure noise generated by one or more piston pumps, where each pump is connected to a common downstream piping system, and where the discharge pressure is measured by a pressure sensitive gauge, wherein the instantaneous angular position(s) of the pump(s)' crankshaft or actuating cam is/are measured simultaneously with the discharge pressure and used as fundamental variables in an adaptive mathematical noise model.

Abstract: A valve arrangement for reciprocating machine, where the arrangement (1) comprises an in-valve (18) and an out-valve (19), each valve (18), (19) being a springloaded one-way valve designed to open for flow when the pressure differential in the direction of flow provides a force that exceeds the spring tension, wherein the valves (18, 19) are mounted in a casing (8) that forms or is connected to the cylinder head of the reciprocating engine (2). The in-valve (18) and the out-valve (19) are mounted in a sleeve (16) designed to be fitted in a bore (9) in the casing (8), and where fluid may flow to the sleeve (16) from an inlet (11) in the casing (8) and into the sleeve (16) via the in-valve (18), and where the sleeve (16) is provided with at least one perforated area where fluid may flow radially out of or into the sleeve (16) via holes (50, 51), thereby flowing to or from a passage (14, 15) that forms a perpendicular or near perpendicular connection with the bore (9).

Abstract: A method of and device for detecting a leak in reciprocating machinery (1), comprising at least two pistons (2, 2?), by the volume flow at least out of the reciprocating machinery (1) being monitored and analysed, e.g. by means of Fourier analysis, in order to make it possible to detect a flow component, where the flow component has a frequency that differs from the fundamental frequency of the reciprocating machinery, the fundamental frequency of the reciprocating machinery being constituted by the rotational frequency of the reciprocating machinery multiplied by the number of pistons (2, 2?) in the reciprocating machinery.

Abstract: An apparatus and method for protecting against the problems associated with heave of a floating drilling rig are disclosed. The disclosed invention is a unique inline compensator in which a plurality of cylinders housed within a tubular housing and a plurality of low pressure and high pressure accumulators function together to provide a system for compensating for heave in the event a primary heave compensation system fails or becomes inoperative. The typical inline compensator of the present invention utilizes a plurality of hydraulic cylinders that act in opposite directions and that have different piston areas such that the piston rods of the cylinders are extended or retracted at different pressure levels to account for heave. The typical inline compensator of the present invention is self-contained and compact enough to fit in the limited space available on a floating drilling structure. Further, a pair of inline compensators of the present invention can be utilized with coiled tubing operations.