GB2493946A

GB2493946A - Crane monitoring system

Info

Publication number: GB2493946A
Application number: GB1114641.2A
Authority: GB
Inventors: James Fraser Dunphy
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-08-24
Filing date: 2011-08-24
Publication date: 2013-02-27
Anticipated expiration: 2031-08-24
Also published as: GB2493946B; GB201114641D0

Abstract

A monitoring system comprises means 1 for measuring acceleration at the end 8 of a crane jib 2, sensors 1, 3 and 4, CPU and display unit. It provides information on the display or human machine interface regarding the safe working load of the crane mounted on board a ship by taking into account the measured acceleration and derating from the maximum static safe working load. Acceleration information may also be displayed. The means for measuring acceleration may be at least one single axis accelerometer 1 attached to the jib by being loosely attached to the crane line 6 or a hoist upper limit switch of the crane or a gimbal assembly mounted on the jib end 8. The accelerometer 1 may be maintained in a vertical plane by a stabilising mechanism 7. Alternatively a multi axis accelerometer may be used. The safe working load may be calculated in a CPU of a PC based system by calculating the vertical acceleration at the end of the jib and then calculating the safe working load based on the maximum static safe working load of the crane derated by the measured acceleration and a calculated derating factor. Other sensors 3, 4 may be provided to sense the angle of the jib from the horizontal, the extension of a crane boom, the angle of the crane relative to the ship centreline and heave, pitch and/or roll of the ship. Acceleration data may be logged and used to predict acceleration of the jib end and hence safe working load.

Description

Description Title

Crane Monitoring System

2 Background

This invention relates to ship mounted cranes which do not have heave compensation.

When a ship is lifting a load the Safe Working Load of the crane is affected by the heave of the ship. This limit is reduced in relation to the amount of acceleration at the end of the jib. This reduced capacity in lifting loads must be accounted for by the experience of crane operators assessing sea state conditions and making a judgement on what the Safe Working Load will be.

3 Statement of invention

This invention proposes to measure the rate of acceleration and to calculate a derating factor to the Safe Working Load (SWL) of the crane. Then calculate the "actual" SWL from the "static" SWL value the operator has entered into the system.

It further proposes to predict the derating factor for other crane positions based on the logged measurement of the acceleration and the planned angle and extension of the jib relative to the centre line of the ship.

4 Advantages This system will enable the operator to make a more informed decision on whether or not the proposed lift can be safely carried out. At present lifting operations can be delayed because of marginal sea state and the operator being over cautious with what can be lifted in the conditions. This results in additional costs and delays.

Whereas under estimating the severity of the sea conditions could lead to damage and danger.

Figure 1 shows the crane with the position of the other sensors in the system. Item 1 is the accelerometer measuring in the vertical axis. 2 is the crane jib, 3 are sensors used to measure the angle of the boom, 4 is a reference sensor measuring the heave, pitch and roll of the ship, 5 is the operator cabin where the Processor and Display are iocated In figure 2, a stabilising mechanism 7 includes an accelerometer sensor 1 which is attached to the end of the crane jib 8 and around the lifting rope 6. This stabilising mechanism will hold the sensor in the vertical plane. The acceleration sensor will measure the acceleration in g at the end of the jib.

Other mounting mechanisms are not shown in this figure but are mounted in similar positions. These are dependent on the installation requirements of the individual crane to which this invention is applied. The accelerometer, item 1, may be mounted directly on the hoist upper travel limit switch and may not need a stabilising mechanism attached to the jib end and around the rope. If a three axis sensor was used then this could be mounted directly on the jib end of the crane.

The signals from the sensors will be routed back to a Programmable Logic Controller (PLC), or other Central Processing Unit (CPU) and then displayed on a Human Machine Interface (HMI) or other Display.

The HMI display will be designed to give a simple readout which is easy to interpret, for derated current SWL as well as maximum and average boom tip acceleration (mis2) over a period of time. These values will be constantly re-calculated and refreshed. The averaging time will be selected to avoid confusing flicker as each wave passes, but updated often enough to give valuable real time information.

Operational features the display may also show Heave (mis), Pitch & Roll (deg/s) from a 2nd motion sensor mounted at the base of the crane. Jib angle is a useful parameter to display for cranes that have angled jibs. For boom type cranes the extension length is a useful parameter to display and measured load if not already on crane instrumentation.

The operator will be able to display a trend of the above data logged over a period of up to one hour.

The Data logger will be equipped with Ethernet connectivity so that real time data can be viewed remotely and logged data can be down loaded without needing to access the crane operator's cabin.

The calculations and display of the parameters are controlled by the software in the Processor and HMI.

Further development of this invention is to include the capability of predicting the maximum boom acceleration based on the logged data and weather forecast data made available over an internet connection.

Claims

<claim-text>Claims 1. A crane monitoring system measuring acceleration at the end of the crane jib, comprising of sensors, CPU and display unit.</claim-text> <claim-text>2. A crane monitoring system according to claim 1 using at least one single axis accelerometer mechanically attached to the jib, said mechanical fixture loosely attached to the crane line in the vertical axis.</claim-text> <claim-text>3. A crane monitoring system according to claim 1 with at least one single axis accelerometer attached to the hoist upper limit switch of the crane.</claim-text> <claim-text>4. A crane monitoring system according to claim 1 with at least one single axis accelerometer mounted on a gimbal assembly, mounted on the jib end.</claim-text> <claim-text>5. A crane monitoring system according to claim 1 using at least one multi axis accelerometer measuring acceleration in earth axis coordinates, mounted on the jib end.</claim-text> <claim-text>6. A crane monitoring system according to claim 1 using at least one multi axis accelerometer measuring acceleration in X, Y and Z axis, the said measurements being resolved mathematically into equivalent earth axis within software by the said control system.</claim-text> <claim-text>7. A crane monitoring system according to claim 1, the calculations being done in the said control system comprising of a CPU and displayed on an HMI.</claim-text> <claim-text>8. A crane monitoring system according to claim 1, the calculations being in the said control system comprising of a PC based system and displayed on a monitor.</claim-text> <claim-text>9. A crane monitoring system according to previous claims 1 through 8; the said sensors providing information that allow the following to be calculated in the said control system and displayed on the said display unit; calculation of vertical acceleration at the end of the jib; the calculation of the Safe Working Load (SWL) based on the maximum static SWL of the crane then derated by the measured acceleration and a calculated derating factor.</claim-text> <claim-text>10. A crane monitoring system according to previous claims 1 through 8 the said sensors providing information that allows the following to be calculated in the said control system and displayed on the said display unit; calculation of the vertical acceleration at the end of the jib; the calculation of the Safe Working Load (SWL) with the crane jib moved to different positions relative to the ship, based on the maximum static SWL of the crane then derated by the measured acceleration and calculated derating factor; the average acceleration over a time period; the average derated safe working load over a period of time; additional sensors providing the following information -the current angle of the crane jib relative to the horizontal axis; the length of extension on boom type cranes; the angle of the crane relative to the centre line of the ship; heave of the ship; pitch of the ship; roll of the ship.</claim-text> <claim-text>11. A crane monitoring system according to claim 9 and 10 the data calculated being logged in the said control system logging module.</claim-text> <claim-text>12. A crane monitoring system according to claim 9 and 10 further calculations in the said control system which predict the acceleration at the jib end based on the logged data over a period of time; and or the said control system retrieving from an Ethernet connection weather forecast data from other information systems and using this data to predict the acceleration at the end of the jib and hence derating of Safe Working Load.</claim-text>