ISO 484-2 SHIP SCREW PROPELLERS - MANUFACTURING TOLERANCES.pdf

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION*MEXAYHAPO~HAR OPTAHMJAIAHR no CTAHAAPTH3AuHM.ORGANISATION INTERNATIONALE DE hORMALISATION

Shipbuilding - Ship screw propellers - Manufacturing tolerances - Part 2 : Propellers of diameter between 0,80 and 2,50 m inclusive Construction navale - Hélices de navires - Tolérances de fabrication - Partie 2 : Hélice de diamètre compris entre 0,sO et 2,5û m inclus

First edition - 1981-08-15 c

UDC 629.12.037.1 : 621.753.1 Ref. No. IS0 4W2-1981 (E)

- w - 6 s Descriptors : shipbuilding, marine propellers, castings, equipment specifications, metal finishing, manufacturing tolerances, dimensional control, dimensional tolerances.

Price based on 6 pages

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Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards institutes (IS0 member bodies). The work of developing Inter-national Standards is carried out through IS0 technical committees. Every member body interested in a subject for which a technical committee has been set up has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the IS0 Council.

International Standard IS0 484/2 was developed by Technical Committee ISO/TC 8, Shlpbuiiding, and was circulated to the member bodies in November 1979.

It has-been approved by the member bodies of the following countries :

Australia France Korea, Rep. of Austria Germany, F.R. Netherlands Belgium India Norway Brazil Ireland Romania Chile Italy Spain China Japan USSR Czechoslovakia Korea, Dem. Rep. of

The member bodies of the following countries expressed disapproval of the document on technical grounds :

Poland

United Kingdom ' Sweden

This International Standard cancels and replaces IS0 Recommendation R 484-1966, of which it constitutes a technical revision.

O International Organization for Standardization, 1981 0

Printed in Switzerland

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INTERNATIONAL STANDARD IS0 484/2-1981 (E)

484 PT 2 - 8 1 4851903 0022546 2

Shipbuilding - Ship screw propellers - Manufacturing tolerances - Part 2 : Propellers of diameter between 0,80 and 2,50 m inclusive

O Introduction

The propeller manufacturer is at liberty to use any equipment and method that enables the tolerances to be verified to the re-quired accuracy.

PQ, corresponding to the desired angle a, and in measuring the difference h in the heights of the points P and Q with respect to a reference plane. (See figure 1 .)

The length PO shall be set out by one of the methods described in 4.1.1 or 4.1.21).

1 Scope

This International Standard defines manufacturing tolerances of ship screw propellers of a diameter between 0,8û and 2,W m.

NOTE - Some deviations for the tolerances should be permitted in certain cases subject to the discretion of the customer or of the designer and the customer.

2 Field of application

This International Standard applies to monobloc, built-up and controllable pitch propellers.

3 References

ISOIR 468, Surface roughness.

I S 0 48411, Shipbuilding - Ship screw propellers - Manufac-turing tolerances - Part 1 : Propellers of diameter greater than 2,W m.

IS0 3715, Shipbuilding - Ship screw propellers - List of equivalent terms.

4 Methods for measuring pitch

4.1 The principle of one method of measurement consists in

setting out along a helicoidal line of radius r a certain length

4.1.1 Use of marking gauges

The length PO shall be set out by means of marking gauges.

4.1.2 Method with a graduated ring

The length PQ shall be set out by means of angle a on a part of a graduated ring of suitable radius (see figure 1).

5 Method for measuring the thickness of the section

5.1 The thickness of a cylindrical section at a point S shall be measured along direction SV (see figure 2) on the plane tangent to the coaxial cylinder and perpendicular to the pitch line of the pressure side of the section (and only along direction SU perpendicular to the pressure side surface or direction ST parallel to the propeller axis when defined in this way on the drawing).

5.2 The maximum thickness at each radius shall be deter-

mined by means of a pair of outside calipers or from the profile obtained by plotting the thickness at various points S, St, S2, S3, etc.

5.3 For checking the leading and trailing edges, use shall be made of section templates. These templates shall be calculated along the straight line or formed to the pitch and radius of the tested section. The length of these templates shall be at least 15 % of the length of the section, with a minimum of 60 mm.

1 I Other methods giving the required accuracy may be used if necessary.

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Small graduated

Figure 1

,- Pressure side

Cylindrical section

Line of maximum thickness the pressure side perpendicular to

Developed cylindrical section

Developed section perpendicular to the pressure side

Pressure side s5

Figure 2

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IS0 484/2-1981 (E) 4 8 5 17 o 3 o ~- o 2 2 5 4 8 -*

S

I

Very high accuracy

High accuracy

II

t 3 % 20 mm f 2 %

15 mm

+ 1 , 5 %

10 mm f 1 %

7,5mm f 5 %

25mm f 4 %

20mm f 3 %

15mm and ' II and 111

A section near the hub - 0,4 R - 0,5 R - 0,6 R - 0,7 R - 0,8 R - 0,9 R - 0,95 R A section near the hub - 0,5 R - 0,7 R - 0,9 R

484 PT 2 - ô 1 -

The leading and trailing edges shall be checked by templates for classes S and I (see table 1). For the other classes, checking may be required by special request at the time or ordering.

7.4 Should the propeller manufacturer wish to compensate

for an error on the pitch (inside or outside the tabulated tolerances) by means of an alteration in the propeller diameter, he may do so only with the customer's agreement.

6 Accuracy classes

The accuracy class shall be selected by the customer, the in-dications in table 1 serve as guide in this choice.

7.5 The design pitch is the pitch of the reference line as

defined below.

The design pitch line of a section is a helical reference line for the section in question for which the section ordinates for the face and the back are given.

Table 1

Class Manufacturing accuracy I It could be a line joining the nose and tail of the section but may be any other conveniently placed helical line.

7.6 The local pitch at a point B (figure 1) is determined by

measuring the difference in height between two points P and Q situated at equal distances from point B and on either side of the latter (BP = BQ) and by multiplying the difference in height by ~. This shall be compared with the local pitch as calculated from the face offsets for the same points.

ff

I I I I Medium accuracy I I 111 I Wide tolerances I

7 Tolerances on the pitch

Table 2

There shall be four pitch measurements for class S, three for class I, and two for class II. These measurements shall be con-secutive (the initial point of each measurement coinciding with the final point of the adjacent measurement). Each measure-ment span shall be sufficiently long to maintain adequate accuracy in the pitch measurement in compliance with clause 16. Where necessary the number of measurements may be reduced in order to comply with the latter requirement.

Class I v I Designation of pitch I f 1,5% 10 mm

' -2% 15 mm ai Local pitch With a minimum of

b) Mean pitch of each radius of each blade With a minimum of

c) Mean pitch per blade With a minimum of f l %

7,5 mrn t 1,5%

10 rnm

7.7 The pitch per radius and per blade is determined for each radius by multiplying the difference in height between the extreme measuring points by - . 360 ff f 0,75 %

5 mm t l %

7,5 mm

& 0,5 % I di Mean pitch for I propeller k 0,75 %

5 mm 7.8 mean of the pitches per radius for the blade in question.

The mean pitch per blade is defined as the arithmetic With a minimum of 4 mm

NOTE - The tolerances of table 2 are expressed as percentages with minimum tolerance of the design pitch corresponding to the radius for designations a) and b) and the mean design pitch for designations c) and d).

7.9 The mean pitch for the screw propeller is defined as the

arithmetic mean of the mean pitches per blade.

7.1 Pitch shall be measured at least at the radii indicated in table 3. By agreement between the interested parties, different radii may be measured.

8 Tolerances on the extreme radius of the screw propeller

Table 3 8.1 screw propeller radius.

The tolerances in table 4 are expressed as percentages of

Table 4 I Class I Radii 1

I f 0,2 % 1 & 0,3 % I f 0,4 % I f 0,5 % I Tolerance 7.2 The measurement of local pitches for classes S and I is further controlled as described in clause 10. With a minimum of I 1,5 mm I 1,5 mm I 2 mm I 2,5 mm I

7.3 The tolerances on the local pitch and on the mean pitch

of each radius of each blade given in table 2 a) and b) are increased by 50 % for sections at 0,4 R , or less.

8.2 need to be reduced.

In the case of a ducted propeller, these tolerances may

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IS0 484/2-1981 (E)

9 Tolerances on the thickness of the blade Table 5 section

Class

S I II 111 Specification

Flus tolerances + 2 % +2,5% + 4 % + 6 % With a minimum of 0,5 mm 1 mm 2 mm 3 mm

Minus tolerances I With a minimum of I - , I % I - 1.5% 1 - 2 ” I - 4 % I

- O 5mm - 1 mm - 1 5mm - 2 mm

9.1 those at which the pitch is measured.

The thickness shall be measured at the same radii as

9.2 the local thickness.

The tolerances in table 5 are expressed as percentage of

9.3 The maximum thicknessses indicated on the drawing

shall not be less, after deduction of the minus tolerance, than the thicknesses required by the Classification Society con-cerned.

I O Checking and tolerances of the form of blade sections

These apply only to propellers of class S and I and to the same radii as those at which the pitch is measured.

To avoid discontinuity of form, the deviations resulting from consecutive measurements of local pitch and thickness shall

Propeller class I : i

I On the figure the deviations 1 are multiplied by 20

The values which are too 1 high are underlined

A

O

Deviation in local pitch

Difference

- - _ _ I

484 PT 2-81 -1 4853703 0022547 8 I-

not differ from each other by more than half the tolerance envelope (for example if the tolerance is + 2 % 1 - 2 %, the permitted difference of consecutive deviations is 2 %.)

To avoid undue deviation in overall camber, the algebraic sum of the percentage deviations resulting from any two consecutive measurements of local pitch shall not be in ex-cess of 1,5 times the allowable tolerance (for example if the tolerance is f 2 %, the sum of consecutive deviations shall lie between f 3 %. See figure 3.)

Alternatively, the satisfactory continuity of the cylindrical sections may be verified by the use of suitable flexible templates.

The leading and trailing edges shall be checked by templates, or equivalent devices, to demonstrate their ac-curacy to the drawing to within the following tolerances of the face and the back :

class S : f 0,5 mm class I : f 0,75 mm

Alternatively by agreement between the manufacturer and the user, the edges shall be checked by templates made in three parts for each edge (see figure41 a short nose template controlling the final edge detail, and two fairing templates from the nose, one to the face and one to the back, each covering about 20 % of the blade length. These templates shall fit with a tolerance of 0,25 mm for class S and O,% mrn for class I.

- O 0,5 5ó - 3,5 % -

I O

Sum

- 4% - - 4 % 3.5 % - 0,5 %

Figure 3

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484 PT 2 - 8 1 I 4 8 5 1 7 0 3 0022550 4 I

Tolerance I f 1 , 5 % I f z %

Short nose template made to size + max tolerance

+ 3 % l f 5 %

L F o r m templates for pressure and suction sides separated by 6 mm for independent application

Figure 4 sections

Tolerances on the length of the blade

Table 6

I

S I I I II I 111

I Specification

I With a minimum of I 4 mm I 7 mm I 10 mm I 12 mm 1

11.1 The tolerances in table 6 are expressed as percentages

of the values of the ratio : diameter divided by the number of blades (DIZ) .

11.2 The lengths of the sections of each blade shall be

measured at five radii at least for class S (example : 0,3 R - 0,5 R - 0,7 R - 0,8 R - 0,95 R ) and four radii for classes I, II and III.

12 Tolerances on the location of blades, reference lines, and blade contours

12.1

The reference line is positioned as a straight line on the drawing by location of the point M on the pressure side of the bladeand a point O on the axis of the propeller.

This point M shall be marked on a cylindrical section at a radius outside 0,5 R and, if possible, near 0,7 R.

It is in principle selected in such a way that the line OM cuts the largest possible number of blade sections.

The ratio between the angles pE (leading edge) and ps (trailing edge) is indicated on the drawings (see figure 5).

Point M' on the manufactured propeller shall be determined in such a way that a ratio pE./p~ equal to the ratio &pS as found on the drawings can be obtained at the considered radius (see figure 6).

Marking of lines of reference

E

/ I

OM > 0,5 R

= is indicated by dimensions on the drawings 9s

Figure 5

Figure 6

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484 P T 2 - 8 1

The reference planes through points M' are used to check the shape of the leading edge and skew back, as well as the blade angular deviationl).

12.2 Tolerances on the contour of the leading

edge

The tolerances shall be calculated on the radii according to table 3 on the corresponding arcs and are valid for the arc lengths E"M" (see figure 6). They are given in percentages of DIZ in table 6 (D = diameter, 2 = number of blades).

The tolerances for the distance E"M" shall be double the values given in table 6, provided that the contours of the blade edges are fair.

12.3 Tolerances on the angular deviation between

two consecutive blades

The tolerances shall be :

- for class S and I : f lo

- for class II and III : f 2 O

13 Tolerances on rake, axial position and relative axial position of consecutive blades

The rake is characterized by the position of the reference line PP' (see figure 7). This is measured by the distance to a plane W perpendicular to the axis of rotation of the screw propeller at three points (at least) A, B and C situated at 0,3 R or 0,4 R , 0,6 R or 0,7 R , 0,9 R or 035 R .

Table 7 gives the tolerances on these distances d (A), d (BI and d (C) expressed as a percentage of the propeller diameter D to control the axial position of the blades. The same tolerances (and not double tolerances) are applicable to differences such as d (BI - d (Cl, for the same blade, to control the rake; and to differences such as dl(C) - d2 (C), for two consecutive bla-des, to control the relative axial position.

Table 7

Specification

Deviation of plottings on each blade at points A, B and C (situated at 0,3 R - 0,6 R and 0,95 R 1 with respect to plane W perpendicular to the axis

S f 0,5 %

Plane W i I R c

Figure 7

14 Surface finish

The surface texture of the blades, expressed as an arithmetic mean deviation, Ra, in micrometres, in accordance with ISO/R 468, shall have a roughness not greater than :

- 3 from the hub for propellers of class S;

- 6 from the radius 0,3 R for propellers of class I;

- 12 from the radius 0,4 R for propellers of class I I ;

- 25 from the radius 0,5 R for the propellers of class III.

15 Static balancing Class I

When finished, all propellers shall be statically balanced.

16 Measuring equipment

The maximum permissible inaccuracy of the measuring equip-ment shall not exceed half the tolerance on the dimension or quantity to be measured or, in the case of geometric measurements, 0,25 mm, whichever is the greater.

1) For skew back definition see IS0 3715.

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