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All you want to know about pneumatic fender

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All you want to know about pneumatic fender
Issue Time:2017-10-02
The Most Complete Technical Information About Pneumatic Fender

1. Background & History

 The "Yokohama  Fender" was developed in 1958. Progress in the development of such floating pneumatic rubber fenders is closely related to the progress and development of ship technology, and has to continuously cope with progressively larger oil tankers such as VLCC's, ULCC's, large gas carriers, bulk carriers and floating structures. Yokohama Fenders are used world wide for ship-to-ship (STS) transfer operations, terminals, and for all kinds of ships.

In 2006, Chinese company invented new manufacturing method of pneumatic fender based on the manufacturing technique of marine rubber ship launching airbag. Jerryborg Marine is one of the earliest manufacturers to produce Yokohama type pneumatic rubber fenders with marine airbag technology.

Since its creation until today, more than millions of fenders have been supplied worldwide both for ship-to-ship and ship-to-dock (STD) operations serving our valuable customers. These fenders play a critical role in the safe operation of ship berthing and mooring.

2. International Standards for floating pneumatic rubber fender

ISO 17357:1/2014 <Ships and marine technology — Floating pneumatic rubber fenders> has been developed to provide guidelines on the quality and performance of all floating pneumatic rubber fenders. Floating pneumatic rubber fenders can play an important role in a ships safe berthing operation and this International Standard is seen as a technical reference to ensure necessary product standards. 

Essentially there are two main types of floating pneumatic rubber fender, defined as either high or low pressure fenders. Although manufactured using different techniques, both high and low pressure fenders work by the same principle. The resistance to berthing vessel momentum is provided by a reaction pressure due to compression of the air inside the fender when deformed by the vessels hull. The 

kinetic energy of the berthing vessel is absorbed during the work done to compress the air inside the fender. Fenders are sized according to the expected duty of the fender in terms of the energy absorption (EA) requirements which will be at the most basic level, a function of the vessel mass and velocity. 

Throughout this International Standard, the minimum essential criteria are identified by the use of the keyword “shall”. Recommended criteria are identified by the use of the keyword “should”, and while not mandatory are considered to be of primary importance in providing serviceable, economical, and practical connectors. Deviation from the recommended criteria should occur only after careful consideration, extensive testing, and thorough service evaluation have shown alternative methods to be satisfactory. 

3.What is the structure of Yokohama type floating pneumatic rubber fender ?

3.1 outer rubber 
rubber layer that covers the outside of the fender to protect the cord layers and the inner liner rubber from abrasion and other external forces 

3.2 inner rubber 
liner of a rubber membrane that seals the pressurized air inside the fender 

3.3 synthetic-tyre-cord layer for reinforcement 
layer made of synthetic-tyre-cord fabric, which maintains the internal air pressure of the fender. As the main fibres of the synthetic-tyre-cord fabric are not braided like synthetic canvas fabric or synthetic belt fabric, there are advantages for its fatigue-resistance performance and pressure-holding performance. 

3.4 Air Valve and Safety Valve
Medium and small sized Floating Yokohama Type Pneumatic Rubber Fenders are equipped with a small air valve, which is the same in size and construction as the air valve of an automobile tire. This valve serves as both air-check, air charge and release valve. On the large size fenders a big valve and a safety valve are equipped, the big valve serves for an air-charging and release, and the safety valve serves for releasing excess internal pressure when the fender is accidentally over compressed. 

3.5 bead ring 
steel ring which is placed at one end (or both ends) of the fender and holds the end of cord layers 

3.6 flange opening 
steel flange which is mounted on the fender, to which an air valve or safety valve can be adapted

3.7 fender cage 
Fender cage covers the outer rubber layer to protect the whole fender body, the fender cage has various versions which also distinguish the fender type. 

3.8 towing ring
Towing ring is connected to opening flange and combine the fender cage for easy lifting and moving. It is often connected with additional end shackle and swivels.

4. What is the performance testing of pneumatic rubber fender ?

Manufacturer shall provide the certificate which confirms successful results of the tests which are evaluated by a major classification society and the performance confirmation of prototype fender test shall be done every ten years.

4.1 parallel compression test
To determine the performance of the fenders given in Clause 7, a performance test shall be performed. Applying a compressive force perpendicularly to the fender, the fender shall be compressed until its energy absorption reaches the GEA value. The compression speed shall not exceed 80 mm/min. 

The reaction force and internal pressure shall be recorded at least every 5 % percentage deflection. The test shall be repeated twice with an interval of 5 min between the two tests. The energy absorption and the reaction force shall be obtained from the mean value of the two test records. 

A fender meets the required GEA performance if it achieves 100 % of its GEA energy absorption without exceeding 65 % deflection and 110 % of its GEA reaction.

4.2 Angular compression test
An angular compression test shall be performed to determine the fender deformation property. If the fender is too large to be mounted on the testing machine, the test can be performed on a miniature-size fender. The reduction scale shall be such that it will ensure that the tests will be representative. 

It has been shown that 1/30 or larger scale sizes are acceptable if relative performances at parallel and several angular conditions are to be compared at the same fender. 

4.3 Durability test 
A durability test shall be performed to verify that the products are suitable for use as fenders, and that they have sufficient durability to withstand the berthing energy. 

The test shall comprise at least 3000 repetitive cycles of parallel compression from the original diameter to the maximum deflection. After 3 000 repetitive cycles, there shall be no cracks and other harmful defects on any part of the fender. No reduction of the GEA shall be accepted. 

If the fender is too large to be mounted on the testing machine, the test can be performed on a miniature-size fender.

4.4 Compression-recovery test 
Fenders are compressed and released repeatedly over a very short period of time. Therefore, a compression-recovery test shall be performed to confirm that the fenders have sufficient compression recoverability. 

After compression of the fender to the guaranteed energy-absorption deflection, the fender shall be kept in this compressed state for 1 min, then the load shall be released instantaneously. The fender diameter shall recover more than 97 % of its original diameter within 5 min after the load to the fender is released. 

The test shall be performed using an actual-size fender or a miniature-size fender larger than one-fifth the size of the actual diameter. 

4.5 Puncture-resistance test 
puncture-resistance test shall be performed to confirm that the products have sufficient puncture-resistance strength. The test shall be conducted in accordance with the static puncture test (CBR test) in ISO12236:2006.

The specimen shall be made using the same materials, construction, and production method, except for the number of ply of the reinforcement cord layer which shall be the number applied for the smallest size fender, i.e. normally two plies. 

The force applied to break through the specimen shall be larger than 15 kN.

5.What is the test and inspection for commercial fenders

Acceptance testing and inspection for purchased fenders shall be based on the tests and inspections indicated in this clause. 

5.1  Material test of rubber 
The material test of the outer rubber and the inner rubber shall be conducted in accordance with the specifications and the results shall satisfy the requirements. 

5.2 Dimensional inspection 
The dimensions of all the fenders shall be inspected at the initial internal pressure and the results shall be within the following tolerances: 
a) length: +10 %, −5 % ; 
b) diameter: +10 %, −5 %. 

The diameter shall be obtained from the average of at least two different measurements taken at the middle of the cylindrical section of the fender. The diameters of bead ring or other steel material around the flange opening shall be inspected, and the results shall be less than 0,20 D (D: fender diameter). 

5.3 Air-leakage test 
The air-leakage test shall be conducted on all fenders at initial pressure for more than 30 min, and the test results shall confirm that there is no air leakage. 

5.4 Hydrostatic-pressure test 
The hydrostatic-pressure test shall be performed for 10 min at the hydrostatic pressure shown as “Test pressure at 0 % deflection” and there shall be no leakage of water and no defects during the test. The frequency of the test shall be one per 20 fenders of each size and pressure. If the customer so requests, one per order of each size and pressure if the quantity is less than 20. Circumferential and longitudinal lengths shall be measured at 10 kPa pressure and at the test pressure.