SPECIFICATION OF NEOPRENE RUBBER SEALS

Transcription

1 SPECIFICATION OF NEOPRENE RUBBER SEALS 1.0 SCOPE This specification establishes the requirements for the manufacture, inspection, testing, packing, guarantee & supply of Neoprene Rubber Seals for Fuelling System Sealing Doors. 2.0 APPLICABLE SPECIFICATIONS AND DRAWINGS Latest issues of the following specifications and standards in effect at the time of manufacture shall constitute a part of this specification to the extent indicated herein. 2.1 Specifications ASTM D-395 ASTM D-573 Description Method B (Test for compression set) (Test for heat aging) ASTM D-2000-SAE 1200 (Elastomeric Materials Classification) Refer Annexure I for Salient Test Requirements of above ASTM Specification. 2.2 Drawings Sr. No. Drawing No. Description 1. NAPP-1/21321/2138/DD Seal for F/M Vault Access Door Flapper-I 2. NAPP-1/21321/2139/DD Seal for F/M Vault Access Door Flapper-II 3. NAPP-1/21325/2114/DD Seals for F/M Service Area Access Door Flapper-I 4. NAPP-1/21325/2115/DD Seals for F/M Service Area Access Door Flapper-II 5. NAPP-1/21321/2163/DD Seal for Built-in Personnel Access Door ENDLESS SEAL (Item No. 10 of drawing.) NOTE:- Quantity is one no. for one door (Quantity indicated in drawing as 3 nos. to read as 1 no. only.) Total quantity required in the indent is 10 Nos. only and supplied has to quote for 10 Nos. as per the requirement. 6. NAPP-1/21324/2123/DD Seals for West Accessible Area & F/T Auxiliary Room Sealing Doors. Seal for Door Flapper-I. 7. NAPP-1/21324/2124/DD Seals for West Accessible Area & F/T Auxiliary Room Sealing Doors. Seal for Door Flapper-II. Note:- CS profile & dimensions of the seals should be as per the enclosed Annexure- 2 of the specification. However length & other dimensions shall be as per respective drawings. Page 1 of 7

2 3.0 MATERIALS AND WORKMANSHIP Materials which are not specifically designated herein and which are necessary for the fulfillment of this specification shall be of good quality. Workmanship shall be consistent with high grade industrial practice and shall be adequate to achieve the accuracies and dimensional requirements called up in the drawings and this Specification and to ensure satisfactory operation and service life of the equipment. 4.0 GENERAL FUNCTION AND DESCRIPTION The seal assemblies as shown in the drawings when mounted on the door flappers of various sealing doors shall provide a leak tight barrier between F/M Vault / F/M Service Area / West Accessible Area / F/T Auxiliary Room and Accessible Areas in the closed (locked) position of the sealing doors. 5.0 REQUIREMENTS 5.1 Material of Seals The seals shall be made of Neoprene Rubber. No other type of rubber shall be mixed with it. The rubber compound used shall be non-corrosive to steel, resistant to air, ordinary water and heavy water (PH 9.5) and shall be suitable for continuous operation at a temperature of 55 deg. C. and 50% relative humidity and shall not become sticky. The mechanical properties of the material shall be as follows: Shore Hardness : 38 to 42 Durometer A Tensile Strength : 105 Kg/cm 2 (min.) Ultimate Elongation : 350% (min.) Supplier shall manufacture the rubber seal with shore hardness 38 to 45 in place of shore hardness mentioned in the drawing. 5.2 Quality of the Seals and Dimensional Tolerances All the seals shall be free from voids, cracks, depressions or improper blending. All seals shall be moulded to the shapes as shown on respective drawings. They may be moulded in parts and joined together to form the specified shapes. The joints shall be made in the factory and shall satisfy all requirements regarding strength and dimensional tolerance. The seals shall have the following dimensional tolerances: Radius : 1.0 mm Height and other dimensions : + 0 mm - 1 mm Page 2 of 7

3 5.3 Compression Characteristics The cross section of seals shall be such that the compression stiffness (load per unit compression) shall be about 6 kg/mm checked on a 200 mm length of the seal. Minor changes in seal configuration may be required to achieve the above stiffness. The above value is applicable for seal as per serial no. 1, 2, 4 & 5 as mentioned in para 2.2. For seal at serial no. 3 of para 2.2 supplier shall check the stiffness of the seal. The value shall be less than 6 kg/mm. Manufacture of seals shall be taken up only after establishing the stiffness as mentioned and clearance by NPCIL in writing. 5.4 Compression Set The seals shall not have more than 25 % compression set when tested as per ASTM D-395 Method B for 22 hours at 100 deg. C. 5.5 Heat Aging Samples shall be heat aged at 100 deg. C. for 70 hours and tested as per ASTM D-573. Changes in properties shall not exceed the following limits: Tensile Strength : 30% Ultimate Elongation : 50% (max.) Durometer Hardness : 15 points 5.6 Operating life The seals shall be manufactured for an estimated life of 3 years and 5000 cycles of 8 mm compression. The fatigue test as described in Section 7.3 of this specification shall be carried out on the test seal for 5000 cycles. There shall be no physical damage or failure of the seal. The permanent set after 5000 cycles shall not be more than 1 mm. 6.0 MANUFACTURE OF SEALS FOR TESTING & SUPPLY 6.1 The supplier shall manufacture first, three samples of test seal for compression test and test them for determining compression stiffness and fatigue life. The supplier may make suitable changes in the suggested shape, if necessary, in consultation with the Purchaser to get the properties specified herein. Three samples each of test seals with modified shape shall be similarly subjected to compression test and fatigue test to ensure that they meet the requirements. 6.2 Bulk manufacture of the seals shall be taken up only after the test seals have been tested and results are approved by the Purchaser. The bulk seals shall be manufactured by following the same manufacturing procedures as the test seals. All dimensional requirements specified in the drawing shall be met. Representative samples shall be prepared for each batch of bulk supply seals and tested as per ASTM Specification D-395, D-573 to establish the requirements of compression set and heat aging. Page 3 of 7

4 Supplier shall make the suitable simple template to check the proper fitment of the seal. This will ensure the correct fitment of seal in door flappers. 7.0 SHOP TESTS The supplier shall conduct the following tests in a manner satisfactory to the Purchaser or his authorised representative. Prior to commencement to shop test the supplier shall prepare detailed procedure for tests specified herein and furnished these for approval by the purchaser. 7.1 Determination of Compression Set The compression set for the seals shall be determined by ASTM D-395 Method B except that the test specimen shall be compressed to 50% of its original thickness. The test temperature shall be 100 deg. C. and period of test shall be 22 hours. 7.2 Compression Stiffness Test This test shall be carried out using a suitable testing fixture where compression load and deflection can be measured. The seal shall be loaded without impact, in steps of 5 kg. The loading of seal shall be uniform along the length of seal. The loading shall continue till a minimum of 8 mm compression of seal is achieved. A graph of load versus compression shall be plotted and furnished to the Purchaser. 7.3 Fatigue Test The test set up shall be capable of applying cyclic load on the seal. An eccentric on a rotating shaft or by a hydraulic cylinder with suitable stroke may be used. The sample of test seal, suitably held by the retainer plates shall be subjected to 5000 cycles of 8 mm compression. All samples shall be checked visually and dimensionally immediately after the test and the compression set shall be determined. The dimensions of samples shall be again recorded 15 days after the test to determine any delayed recovery. 7.4 Heat Aging Test Standard specimens shall be made and tested as per the requirements of ASTM D TEST CERTIFICATION Following certificates and test reports, signed by a responsible technical representative of the supplier shall be sent to the purchaser along with the material: a) Test report pertaining to all the tests carried out by the supplier for the material of seals. b) Test report pertaining to all tests as per the specification. c) Dimensional inspection report for each seal. d) Certificate of compliance that the seals conform to requirements of this specification. Page 4 of 7

5 9.0 QUALITY SURVAILLANCE The seals shall be subject to Quality Surveillance by the purchaser or his authorised representative at all stages of manufacture, for which purpose the Supplier shall : a) Allow access at all reasonable times during manufacture, inspection and testing. i) To premises in which work is being carried out, ii) iii) Drawings and all tooling involved, Gauges, instruments testing equipment etc. required for inspecting the work. b) Obtain acceptance of material in the form of Shipping Release before delivery PACKING Prior to packing, each set of seal shall be mounted on suitable wooden frame work to retain its shape and prevent twisting. The wooden frame work containing a set of seal shall be covered with weatherproof barrier in the form of a polyethylene cover. All such wooden frame works shall be clearly marked with their identities such as name of sealing door, door flapper number etc. All the wooden frame works containing seals shall be further packed in sturdy wooden boxes to provide protection against deterioration, deformation or damage during transport and storage in a tropical climate. Page 5 of 7

6 SALIENT TEST REQUIREMENTS AS PER ASTM STANDARDS ASTM D-395 METHOD B (TEST FOR COMPRESSION SET) A1.1 Test Specimen ANNEXURE-I The test specimen shall be a cylindrical disc of dia mm and mm thick. The specimen may be prepared by direct moulding or cutting with dye. A1.2 Compression Device The compression device shall consist of two flat plates spaced apart and bolted. The specimen will be compressed between parallel faces of the plates. The plates shall be made of steel of sufficient thickness to withstand the compressive loading without bending. The surface against which the specimen is held shall have a highly polished chromium plated finish and shall be thoroughly cleaned and wiped dry before test. To maintain the constant deflection required, spacer bars having thickness of mm shall be used. A1.3 Procedure Measure the original thickness of the specimen to the nearest 0.02 mm using dial micrometer. Place the specimen between the plates of compression device with the spacers on each side. Tighten the bolts uniformly until plates compress the specimen upto the spacer thickness. Place the assembled specimen in the oven for 2 hours and allow it to remain at 100 deg. C. for 22 hours. After 30 min. cooling, measure final thickness at centre of test specimen. ASTM D-573 (Test for Heat Aging) A2.1 Test Specimen Dumbbell shaped test specimens of 2 mm thickness will be used for this test. Their forms shall be such that no mechanical, chemical or heat treatment will be required after aging. At least 3 test specimens to determine the original physical properties of each sample and also three specimens of the same material for each exposure period of the test and after aging properties shall be used for this test. At least 24 hours must elapse between vulcanisation of specimen and start of the test. A2.2 Heating Device The heating device shall be air oven with provision for suspending the specimens vertically without touching each other or sides of the oven. A thermometer located in upper central portion of the oven shall record the actual aging temperature. Page 6 of 7

7 A2.3 Procedure Determine the hardness, tensile strength and ultimate elongation of the original 3 un-aged specimens within 96 hours of the start of the aging test. Place the other 3 test specimens in oven after operating temperature of 100 deg. C. has been attained. Age the specimens for 70 hours. Determine the hardness, tensile strength, ultimate elongation of aged specimen after cooling to room temperature for not less than 16 hours nor more than 96 hours. Page 7 of 7