HAPPY PAD

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GOVERNMENT OF INDIA

MINISTRY OF R AILWAYS

SPECIFICATION FOR

THERMOPLASTIC POLYURETHANE SPRING PADS (HAPPY PADS)

FOR LOCOMOTIVES

SPECIFICATION NO. MP- 0.40.99.01

(Revision - 01)

October 2006

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LUCKNOW - 226 011

Cost (Rs).………

R.D.S.O

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Specification for Thermoplastic Polyurethane Spring Pads (Happy Pads) for Locomotives

Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06

CONTENTS

Sl. No. Description Page No.

1. Scope 1

2. Definition 1

3. Instructions for Purchaser 1

4.Minimum Requirements of Infrastructure,Manufacturing, Testing and Quality Control For Approval of Firm

2

5. Material 4

6. Dimensions and Tolerances 4

7. Manufacturing Process and Finish 5

8. Technical Requirements of Spring Pads 5

9. Lot Size, Sampling and Confirmatory Tests 6

10. Marking 7

11. Packing 8

12. Storage 8

ANNEXURES

Sl. No. DescriptionDrawing

No.

I.Spring Pad (Secondary Suspension) for WDP1

(Steel to IS: 2062 Gr ‘C’)SK.VL- 279

II.Spring Pad (Secondary Suspension) for WDP3A &

WDP3AMSK.VL- 280

III. Spring Pad (Primary Suspension) for WDP4 SK.VL- 281

IV. Spring Pad (Primary Suspension) for WAP1 &WAP4 SK.VL- 282

V.Spring Pad (Secondary Suspension) for WAP1 &

WAP4SK.VL- 283

VI.Spring Pad (Secondary Suspension) for WDP1(To be used with Bogie Frame of Corten Steel toIRS: M41)

SK.VL- 284

VII.Spring Pad (Primary Suspension) for WDM3D

(Without Compensating & Equalizer Arrangement)SK.VL- 291

VIII.Spring Pads for Locomotives with Broad Gauge

3-Axle Trimount BogiesSK.VL- 323

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page 2

4. MINIMUM REQUIREMENTS OF INFRASTRUCTURE, MANUFACTURING,TESTING & QUALITY CONTROL FOR APPROVAL OF FIRM

4.1 The firm should have acquired ISO:9000 series certification formanufacturing of Thermoplastic Polyurethane spring pads for locomotives.

4.2 The manufacturer shall have at least the following infrastructure and

manufacturing facilities:

.1 Adequate space and covered area with cemented floor toaccommodate the following:

a. Damp-free space for storage of raw materials

b. Manufacturing Activities

c. Finishing

d. Inspection and Testing

e. Storage and dispatch of finished products

.2 One Injection Moulding Machine of minimum capacity of 500 gms withcontrol panel equipped with the following features:

a. Microprocessor Controlled Machine

b. Minimum clamping force (locking tonnage) of 150 tonnes

c. PLC Controlled Mould Temperature Controller (MTC)

d. Auto Loader/ Hopper Dryer

e. Auto Visual Alarm

f. Mould Height Adjustment Facility

g. Hot Air Oven for Annealing the Finished Product

h. Cooling Water System

i. Desiccant Dryer of Dehumidifier Attached with Dew Point Meter

.3 At least one set of Injection mould.

.4 Suitable material and mould handling facilities like Chain Pulleys,trolleys, Electric Hoists or other suitable equipment.

.5 Suitable tools, cutters, polishing files and Buffing Machine for

deflashing of moulded products.

.6 Electronic Weighing Machine of reputed make of a minimum 2 Kg.capacity with an accuracy of at least ± 0.2%.

.7 The firm shall have facilities for maintenance and polishing of dies andmoulds.

4.3 Testing Facilities

.1 The manufacturer shall have atleast the following testing facilities and

other equipment installed in the laboratory with controlled temperatureand humidity for carrying out various tests specified under Para 8:

a. Tensile Testing Machine of adequate capacity

b. Load Compression Testing Machine with a capacity of at least 10tonne

c. Equipment for humidity control of Laboratory

d. Shore ‘A’ Hardness Tester

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e. Melting Point Apparatus

f. Weighing Balance with Specific Gravity determination Kit

g. Muffle Furnace

h. Equipment to test Compression Set as per ASTM D-395

i. Melt Flow Index Tester

.2 The manufacturer shall have facilities for compressive load-deflectioncharacteristics test in accordance to the specification.

.3 Dies / moulds for preparation of various test specimens for therelevant tests shall be available.

.4 All gauges required for checking of dimensions of spring pads shall be

available.

.5 The manufacturer shall have suitable jigs & fixtures for conducting

Load Deflection Test and other tests as per specification.

4.4 Quality Control Requirements.1 The firm should have a system of easy traceability of the product from

raw material stage to finished product stage.

.2 Quality Assurance Plan (QAP) for the product detailing variousaspects and duly approved by RDSO should be available. The QAPshould include the following:

a. Organization chart

b. Process flow chart

c. Stage Inspection details

d. Various parameters to be maintained to ensure controle. Policy of disposal of rejected spring pads

f. Mould repairs

g. Moulding Process Control

h. Identification Marking

The record of implementation of QAP should be maintained fordocumentary evidence.

.3 The firm shall have a system to ensure that moulds are checked atregular intervals. Also, it is ensured that dies/moulds are checked

dimensionally prior to release for production and records of thesechecks are maintained.

.4 The calibration of the Testing/ Measuring Equipments / Weighing

machines should be done at least once in a year unless statedotherwise.

.5 The firm should have a Quality Manual indicating the extent of controlover manufacturing and testing.

.6 The firm should have a system of regular submission of rejections,

detailing rejection rate, cause of rejection, corrective action taken etc.on quarterly basis.

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.7 The firm should have a system of documentation in respect ofrejection at customer end, warranty replacement and failure of spring

pads in service.

.8 The firm should have a system of recording plant, machinery & controlequipments remaining out of service, nature of repairs done etc.

.9 Latest version of relevant specifications and drawings shall beavailable with the firm.

4.5 Qualification and Training

.1 Training needs for all personnel should be identified. Regular trainingshould be organized covering personnel identified for a particular

period.

.2 The Inspection / Quality Control Section should be headed by agraduate Engineer with at least 5 years experience or a Diploma

holder with at least 10 years experience.

.3 Inspection staff conducting non-destructive testing should beadequately trained & qualified by recognized agency and should haveadequate experience.

.4 Laboratory and Shift Engineers shall have a minimum qualification

either a Diploma or a Degree in Engineering (Plastic, Mechanical orElectrical).

4.6 Approval of Firm by RDSO for Supply of Spring Pads for Locomotives

The RDSO guidelines shall be followed for approval of a firm for supply of

spring pads for locomotive bogies to Railways.

5. MATERIAL

5.1 The material used in the manufacture of spring pads shall be“Thermoplastic Polyurethane (TPU)” manufactured by M/s Bayer or any

other world-renowned primary manufacturer of this material.

5.2 Before offering the material for tests, the spring pad manufacturer shall

have a suitable tie-up in the form of a written Memorandum ofUnderstanding (MoU) with the raw material supplier covering supplies andtechnical support.

5.3 The material shall conform to the properties given in Para 8.

5.4 Use of regenerated / re-constituted material is not permitted.

5.5 Unless and otherwise specified in the purchase order, the colour of springpad shall be natural colour of the TPU material.

6. DIMENSIONS AND TOLERANCES

The spring pad shall conform to the dimensions and tolerances as given in the

relevant RDSO drawing.

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7. MANUFACTURING PROCESS AND FINISH

7.1 The pad shall be manufactured by injection moulding only.

7.2 The spring pad shall be smooth, free from air bubbles, surface streaks,

splash marks, pinholes, voids, crazing, blistering etc. All the edges shall beneatly finished and free from flash.

7.3 The machining on spring pads after moulding is permitted, if required.However, the finished dimensions must conform to relevant RDSOdrawing.

8. TECHNICAL REQUIREMENTS OF SPRING PADS

8.1 Physical Properties

The physical properties of material of spring pad shall be checked from the

finished product wherever practicable and the remaining checks shall becarried out from the test specimen prepared under the identical conditionsof moulding of spring pad using the same raw material. The checks shallbe conducted as per methods given in ASTM Standards mentioned below

and their values shall conform to the following limits:

Sl. Property Test Method Units Permissible Limit

1. Specific Gravity ASTM D792 - 1.12 to 1.25

2. Tensile Strength ASTM D412 kg/cm2 250 (Minimum)

3. Elongation atBreak

ASTM D412 % 300 (Minimum)

4. Hardness ASTM D2240 Shore ‘A’ 85 – 95

5.Compression Set

at 800 ± 10C for 24(+0/-2) hours

ASTM D395 % 45 (Maximum)

8.2 Oil Resistance Test

The swelling as determined by the method given in IS: 3400 (Part VI) using

an immersion period of 72 (+0 / -2) hours at 100 ± 10 C shall not be more

than the limits given below:

Sl. Volume Swelling Medium Permissible Limit

1. In Lubrex -150 20 % (Maximum)

2. In Grease (Servogem 2 or 3) 15 % (Maximum)

8.3 Resistance to Hydrolysis

After Hydrolysis on boiling in distilled water at atmospheric pressure for 72(+0 / -2) hours, the tensile strength, elongation at break and hardness shallnot vary from the value obtained before boiling by more than the followinglimits:

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8.4 Compressive Load-Deflection Test

The spring pad shall be subjected to three successive loadings up to 5tonnes. During the fourth cycle, the spring pad shall be compressed with a

load of 50 kg and deflection taken as ‘zero’ at this point. The deflection at

load of 5 tonnes shall then be recorded with the help of dial gauge(s) /digital display. The deflection value shall not be less than 0.50 mm.

9. LOT SIZE, SAMPLING AND CONFIRMATORY TESTS

9.1 The Inspecting Agency for the purpose of inspection of the product in

reference to a Purchase Order shall carry out the checks as given below:

.1 The Inspecting Agency shall verify the following aspects beforecarrying out inspection of spring pads:

i. The delivery period of the Purchase Order is valid.

ii. Check the Internal inspection record carried out at various stagesof manufacture of the product by the firm’s quality controldepartment for the product being offered and confirm that theresults of the internal inspection records are in order.

ii i. The measuring instruments, gauges, testing facilities, etc are inworking order and they are calibrated.

iv. The latest copies of all reference specifications mentioned in thisspecification are available with the firm.

.2 The lot size of spring pads to be offered in one inspection shall be 500

nos. or full quantity if the order is for less than 500 nos.

.3 The sample size, which shall be randomly drawn by the Inspecting

Agency from each lot of spring pads offered for inspection forverification of various properties is detailed below. The following tests

shall be carried out on the finished product wherever practicable andthe remaining checks shall be carried out from the test specimen

prepared under the identical conditions of moulding of spring pad usingthe same raw material. The samples shall be tested as per the testmethod specified in Para-8 and the values shall conform to the

corresponding permissible values.

Sl. Property Permissible Limit

1. Tensile Strength ± 20 %

2. Elongation at break ± 20%

3. Hardness (Shore ‘A’) ± 5

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11. PACKING

The spring pads shall be suitably packed in cardboard boxes to protect them

against damage during transit and storage.

12. STORAGE

The spring pads shall be stored in a cool and dry place.

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page i

ANNEXURE- I

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page ii

ANNEXURE- II

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page iii

ANNEXURE- III

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page v

ANNEXURE- V

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page vi

ANNEXURE- VI

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Motive Power Directorate (Vehicle Dynamics Group), RDSO, Lucknow Specification No. MP-0.40.99.01, Rev.01 Oct.’06 Page vii

ANNEXURE- VII

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HAPPY PAD

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