GB2132971A

GB2132971A - Winch control systems

Info

Publication number: GB2132971A
Application number: GB08233792A
Authority: GB
Inventors: Stephen Leofric Rhodes; David Charles Hawkins
Original assignee: Decca Ltd
Current assignee: Decca Ltd
Priority date: 1982-11-26
Filing date: 1982-11-26
Publication date: 1984-07-18

Abstract

A winch system comprises a drum 8 which is rotatable about an axis perpendicular to the winding axis of the drum so that the layering of cable on the drum can be automatically controlled. <IMAGE>

Description

SPECIFICATION Winch control systems This invention relates to the control of winches and in particular winches which are used forwinding cable which is used for lowering equipment, such as measuring equipment, into bore hoies. In general the invention relates to winches which may be used both on on-shore and off-shore installations but some aspects of the invention are particularly concerned with off-shore operations.

One aspect of the present invention concerns the amelioration of the difficulty of winding by means of a winch, a very long length of cable. A cable which is used in the circumstances indicated above may be particularly long, for example, of the order of six miles (ten kilometers). It is customary to employ, for raising and lowering equipment by means of the cable, a winch having a large aspect ratio, that is to say of long length compared with its diameter. A particular difficulty is providing appropriate layering of the cable on the winch, that is to say ensuring so far as is possible that successive coils of the cable on the winch are progressively displaced to and fro along the length of the winding drum so that the cable is wound on the drum in a multiplicity of layers of coils in as uniform a manner as is feasible.Such layering is important for utilising efficiently the capacity of the winding drum and avoiding unneces saryvariations in the tension of the cable. It is known to provide an auxiliary guide which acts on the cable to vary its angle of approach relative to the drum but the usual arrangements are not particularly satisfactory. In general, varying the direction of movement of the cable is inconvenient. Moreover, particularly in land based operations, the disposition of the winch on a winching truck may require very precise placement of the truck relative to the derrick for proper operation of the guiding mechanism and such placement may not be reasonably feasible.

Furthermore, it is found in practice that the proper guiding of the cable requires the attention of a skilled operator, usually called the winch man.

Another aspect of the invention concerns the control of a winch in off-shore operations. If the winch, as is usual, is disposed on a floating platform, then although the vertical movement of the platform in response to the wave motion of the sea is slow, there is nevertheless a significant movement of the tool relative to the earth and for a variety of purposes it is desirable to provide compensation for the movement of the supporting platform so as, for example, to maintain the tool at a more constant depth or at a more constant speed of movement, depending on circumstances.

A particular winching system which will be described hereinafter is intended to be versatile enough to be of improved performance according to both the aforementioned aspects of the invention and generally but different sub-combinations of the system are particularly relevant to particular aspects of the invention.

One important combination of features in the system according to the invention includes the provision of a turntable or an equivalent mounting of the winch so that the winch itself can be pivoted, usually about an upright axis, so as to alter the angle between cable being wound on to or payed off the winch. The combination preferably includes a means for metering the winding of the cable by the winch.

This metering may be performed by means cooperating with and responsive to the rotational winding movement of the winding drum of the winch but could comprise means adapted to respond to lengthwise movement of the cable. The combination further preferably comprises a control means, preferably including a control for a motor drive for the turntable, for driving the turntable automatically so as to control the layering of the cable on the drum.

One important function that the control means preferably performs is the automatic change in the position of the turntable or the automatic reversal of the movement of the turntable as the coiling of the cable approaches one end of the winch so as to provide a reversal in the sense in which the cable is coiled on the winch.

The control means may be constituted by hardware but it may include a microprocessor as described.

A further aspect of the invention concerns the control of a winch motor in response to variation in winching speed or the position of the cable or tool thereon relative to the surface of the earth. In particular, the system preferably comprises a variable speed drive (preferably including a hydraulic motor) for the drum of the winch means for monitoring the position or speed of the cable relative to the bore hole in which it is lowered and control means for controlling the motor to compensate for the said variation. In one particular form of such a control system, the winch motor may be operated to provide, in accordance with an absolute determination of the position of the tool, automatic payout or windup of the cable in compensation for the effect of wave motion on a platform supporting the winch.

The accompanying drawings illustrate by way of example the mechanical parts of a winch according to the invention. In the drawings: Figure lisa plan view from above of the winch; Figure 2 is a view of one end of the winch; and Figure 3 is a partial view of the other end of the winch, viewed from the right-hand side of Figure 1.

The winch shown in the drawings comprises a housing 1 which is pivotally mounted by means of a main shaft 2 to which is keyed a collar 3 which extends laterally and is pivotally connected with the piston 4 of a double acting hydraulic ram 5 of which the other end is pivotally connected to a support 6.

The ram and the shaft are disposed below the winch housing 1 in a base 7. The winch includes a drum 8 of which the ends are delimited by flanges 8 and 10.

The drum 8 is driven by means of a hydraulic motor 11. At that end of the drum remote from the motor 11 are slip-rings in a housing 12, the slip-rings having an external connection 13.

By means of the ram 5 the drum can be rotated about an axis perpendicular to the winding axis of the drum. Control signals for operation of the ram may be obtained from a drum revolution sensor 14.

Claims

CLAIMS (Filed on 24.11.83)

1. A winching system comprising a winch including a cable-carrying drum, means for driving the drum so as to wind cable on to or pay off cable from the drum, a pivotable mounting for the winch so that the winch can be pivoted about an axis so as to alter the angle between the winch and the cable which is being wound on to or payed off from the winch, and control means for driving the turntable automatically so as to control the layering of the cable on the drum.

2. Awinching system according to claim 1, including means for metering the winding of cable by the winch.

3. A winching system according to claim 1 or claim 2 in which the control means provides an automatic change in the position of a turntable or the automatic reversal of the movement of the turntable as the coiling of the cable approaches one end of the drum so as to provide a reversal in the sense in which the cable is coiled on the drum.

4. A winching system according to any foregoing claim, in which the drive for the drum is a variable speed drive and the system further comprises means for monitoring the position or speed of the cable and control means for controlling the variable speed drive to compensate for variation in the effective winching speed.