SE500490C2 - Method and apparatus for continuous and automatic monitoring and alignment of the propeller shaft in vessels during operation - Google Patents

Abstract

The invention relates to a method and a device for continuous and automatic monitoring and alignment of a propeller shaft (A), mounted in a plurality of bearings, in a ship upon hull deformations during operation. The inventive method substantially involves: measuring a parameter indicating the state of stresses in the shaft (A); calculating, by means of a special computer program, how the bearings (L) (the offsets) should be changed in view of the measured parameter and the prescribed conditions; adjusting the respective offsets by the calculated change. The inventive device substantially consists of: measuring means (M) which monitor a parameter indicating the state of stresses in the shaft (A); a computer (D) which receives values from the measuring means (M) and calculates, by means of a special program, how the bearings (the offsets) should be changed; control means (S) which receive the offset changes from the computer (D); an actuator which is actuated by the control means (S) and adjusts the respective offsets by the calculated change.

Description

l ') f \ fi nu 493 J C I 2 After installing the propeller shaft, you want to avoid larger hull deformations. It is therefore customary for the stern housing to be mounted on the hull before the axle is installed. However, a mounted stern housing makes installation of the axle more difficult.

Sometimes it is necessary to re-align after a period of sea passage. For example, if the hull sat down or if any other influencing factors deviate significantly from what is assumed in the construction.

However, a new alignment after launching is made more difficult by the fact that certain warehouses are built-in.

Since the bearings are axed in the foundation, a shaft line is affected by hull deformations. In medium-sized and larger vessels, the bearings can be shifted fl your centimeters. Given that a straightening is done with an accuracy of tenths of a millimeter, it will be appreciated that hull deformations cause underloads and overloads in bearings. This worsens wear and noise. In case of underload, 'oil whip' (instability) occurs.

In addition to static forces, the bearings must absorb dynamic forces caused by bending oscillations as the shaft rotates. Such dynamic forces increase seriously if resonance occurs between an oscillation frequency and one of the lower natural frequencies of the shaft. An natural frequency is affected by the stiffness of the lubricating iron in the bearings, which in turn depends on the bearing pressure (alignment).

Some patents relating to the alignment of the propeller shaft in ships are designated SU 1123-937-A, EP-A1-015 654, WÛ87 / Û1439 and EP-A2-405 777. The listed patents relate to various methods or devices for achieving a satisfactory alignment. with fixed bearings in connection with installation or repair. The same applies to other patents concerning alignment as far as is known. The object of the present invention is to provide a method and a device for continuous and automatic maintenance of an optimal shaft line of the propeller shaft in a vessel in the event of hull deformations during operation. An optimal shaft line here refers to a shaft line that is as unbent as possible with respect to the prescribed lower and upper limits for bearing pressure, shaft stresses etc. The spirit is more precise to state: o a way of calculating optimal oífset (an optimal axis); o a method of measuring a parameter of the state of tension in the shaft; o a method of calculating through the measured condition parameter how a previously optimal axis line has changed due to hull deformations; o a way to calculate how the offset should be adjusted so that optimal offset (an optimal axis line) is obtained; o a device which in the engine room of a ship during operation continuously and automatically measures a parameter for the state of tension in the shaft; o a device which, in the engine room of a ship during operation, continuously and automatically adjusts the oifset according to calculated values. (ff I w Cff) For the mentioned calculations, there is a special computer program that differs significantly from other corresponding programs. The current program provides bearing loads and oifset as a result of an optimization with respect to entered limit values for influencing parameters. The optimization takes place with a measurement function: f = | = ß1 | + 1221 II fl I- (2) With function (2) the sum of the offset is minimized with respect to bi- conditions which prescribe lower and upper limits for, for example: o bearing pressure; o stresses and deflections at exposed points on the shaft; o the load on. fl the connection at the motor (specified by the motor manufacturer); o the difference between the load on. the two gear bearings (the gear bearings should be equally loaded with regard to the gear grips).

The minimization of function (2) with respect to the side conditions, results in optimal offset xfpt. It gives as unobstructed a shoulder line as possible, ie an optimal shoulder line e.

After inserting the optimal offsets zfpt in the equation system (1), the load FT ”is obtained in stock at an optimal axis line. The corresponding pressure pg "= Fl-" t / Ah where A, - is the bearing bearing surface. It is assumed that the pressures of n - 2 bearings are available.

The possibilities of maintaining an optimal shaft line in the event of hull deformations depend on how many bearings are adjustable. If n - 2 bearings are adjustable, the same shaft line can be constantly maintained.

If fewer than n -2 bearings are adjustable, a new shaft line is calculated if the foundation changes so that the old shaft line can not be maintained or is no longer optimal. The new axis line gives a new value to. function (2) depending on the side conditions and the number of adjustable layers.

The method and device specified by the present invention are achieved according to claim 1 and 4, respectively. Special embodiments are specified in the subclaims.

Figure 1 shows an axis line.

Figure 2 shows spacer plates (H) between bearings (L) and foundation (F Figure 3 shows a propeller shaft (A) supported by a number of bearings. The aft bearing is fixed in the foundation in the usual way. Other bearings outside the engine (LI - L4) is mounted on piston-cylinder assemblies (K1 - K4) which are part of hydraulic pressure circuits with control means (S1 - S4), pumps (P1 - P4) and measuring means (M1 - M4) The control and measuring means are connected to a common computer bearings (L) and piston-cylinder assembly (K) with pressure circuit.

C) xffs CD (H GQ ß Lf. 1 ") Û i U 4 An exemplary embodiment of the present invention will now be described with reference to Figure 3. The application essentially means: 1.

Measurement of the bearing pressures pf "with the measuring means and feeding of the values to the computer. Calculation with the computer (D) of: op! = P; _ Pimš o offset changes Aag- by inserting Ap; in the equation system (1) where Ap, -A , - = aüAscl + anArcg - - - amAazn; o volume changes AV, - which in the pressure circuit give carbon changes Aag-_ o pressure deviations Ap;. Feed from the computer (D) of AV, - to the respective control means (SQ).

. Commissioning with the control means (S, -) of the pumps so that the pistons (K¿) are adjusted Aag.

Advantages: o the preparation of the alignment of the propeller shaft is simplified; o limits are determined instead of specific values; o Hypothetical inputs are unnecessary; o the installation of the shaft is simplified; o The stern housing can be mounted on the hull after the axle installation; o The bearing pressures remain within the prescribed limits; o press. the gear or motor bearings are almost constant; o new alignment after launch is not required; o extreme bending stresses are avoided; o fatigue decreases; o bearing wear decreases; o the noise decreases; o bend oscillations are damped; o oil whip in stock is avoided; o Dangerous natural frequencies can be shifted.

Claims (5)

ÛÛÛ - * -: i; - \ J \ J '~ J Patentkrav Method of continuously and automatically monitoring and aligning a fl stored propeller shaft (A) in a ship during hull deformations during operation, characterized by the eating measures: o measuring a parameter indicating the state of tension in the shaft (A); o with a special computer program calculate how the bearings (offset) are to be changed with regard to the measured parameter and prescribed conditions; o adjust the respective offset with the calculated change. Method according to claim 1, characterized by the measure: o measure the pressures acting on the bearings. 3. A method according to claim 1 or 2, characterized by the eating measures: o feeding the measured pressures to a computer (D) which calculates offset changes with a special program; o feed each olfset change to the respective control means (S); o with each control member (S) operate a switchgear that adjusts or otherwise with the calculated change. Device for continuous and automatic monitoring and alignment of a fl stored propeller shaft (A) in a ship in operation, characterized by: o measuring means (M) which monitor a parameter indicating the state of tension in the shaft (A); o a computer (D) which receives values from the measuring means (M) and with a special program calculates how the bearings (o fi set) are to be changed; o control means (S) which receive the offset changes from the computer (D); o switchgear which is operated by the control means (S) and adjusts the respective offset with the calculated change. Device according to claim 4, characterized in that: o that the measuring means (M) consists of a pressure gauge; o that the switchgear consists of a hydraulic circuit which includes a pump (P) and a piston-cylinder unit (K) which is arranged between the foundation (F) and the bearing (_13 cr »