Usage:
All Caterpillar Products
Rollover Protective Structures (ROPS) are overhead structures that provide operators some degree of protection if a rollover occurs. Falling Object Protective Structures (FOPS) are overhead structures that provide operators with reasonable protection from falling objects, such as trees and rocks.
Any modifications to these structures such as welding, drilling, cutting, or addition of attachments, can change the metallurgy or structural strength. Such changes can reduce the effectiveness of the structures and must be avoided. Despite Warnings on a plate attached to the ROPS and Warnings published in the Operation and Maintenance Guides and other literature, some people continue to void or impair the capability of the structure to protect the operator by making modifications or alterations to the structure. Because many countries require the manufacturers to certify ROPS and FOPS, the unauthorized alteration or modification of these structures voids the certification. As a result, government inspectors can and do shut down a machine for such unauthorized use.
For example, a customer welded fire extinguisher mounting brackets on ROPS legs in the wrong place. He replaced the ROPS at his expense because the welds were in a critical area and these ROPS could not be certified. Other examples of actual illegal modifications are shown in Illustrations 1 and 2.
Illustration 1. Major faulty alteration made to legs to carry pipe.
These problems probably result from the mistaken belief that the ROPS structure system has very strong components and it can not be weakened by a few small holes or welds. An expression often heard is, "If this ROPS is strong enough to support this big machine in a rollover, surely the ROPS is strong enough to carry the item that has been mounted on it". The ROPS will probably support the items, but the real question is: Will it meet the regulatory requirements with these alterations? Destructive testing would be necessary to verify the newly created design. Obviously, this is unacceptable for each alteration or modification.
Why Modifications To ROPS Often Void Their Certification
Every design for a ROPS/FOPS structure has to meet or exceed demanding tests to be certified. The minimum performance criteria for these structures is based on the weight of the machine, and was developed under the sponsorship of the Society of Automotive Engineers (SAE) which has been incorporated into government regulations. The performance criteria require a destructive test of a representative ROPS system which includes the ROPS structure and the machine frame member to which it is attached. The test consists of bending the ROPS laterally until it deflects sufficiently to absorb a specified amount of energy with a minimum specified bending force based on the type of machine and its weight. The deformed ROPS then must withstand a vertical load of at least twice the machine's weight.
Illustration 2. Canopy legs cracked by addition of water containers on the ROPS canopy to fight fires.
Every new ROPS/FOPS has a certification plate that lists the SAE and ISO (International Standards Organization) practices that must be complied with to pass the preceding tests. See Illustration 3.
As stated on the plate, structural damage, an overturn, modification, alteration, or incorrect repair can void the certification. Now, you may wonder if the ROPS can ever be used if something happens to it. Yes, the ROPS can be used if the repairs or installation of attachments are within limits specified by the manufacturer. Beyond these limits, no amount of reinforcements will prove or disprove the question of certification. Recertification can not be done by calculations. The only way to prove its capability is to subject the ROPS system to all the tests required by SAE and ISO. Obviously, this is not practical since the ROPS would be destroyed. This simply means that the ROPS may not only be unsafe, but also illegal in some countries.
The previous paragraph mentions that limited repairs or installation of attachments in certain designated areas can be done without voiding the certification. This is covered in detail in the following Special Instruction Forms prepared by Caterpillar Tractor Co.:
- English SEHS6929-02
- French SFHS6929-02
- German SGHS6929-02
- Spanish SSHS6929-02
- French SFHS6929-02
These instructions are for use by Caterpillar dealers as a guide for ROPS service without voiding ROPS certification. They cover inspection, permitted repairs, replacement criteria, and permitted modifications and installation of attachments.
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Do not make any repairs, modifications, or installation of any attachments to the ROPS/FOPS structure that is not authorized in the applicable Special Instruction. Such action will not only void the certification but will reduce, if not eliminate, the ability of the structure to provide crush protection for the operator in a rollover or from a falling object.
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Illustration 3. Example of certification plate attached to all new ROPS/FOPS structures.
Users should not make any repairs or modifications to a ROPS/FOPS structure without concurrence of a Caterpillar dealer. Failure to do so may result in a ROPS that is uncertified and must be replaced to comply with the government regulations.
How Caterpillar Certifies ROPS/FOPS Structure Systems
The ROPS/FOPS structure system includes the basic structure, mounting components and frame. See Illustration 4. All these parts together form a system, which must pass regulated test requirements in certain SAE and ISO Recommended Practices. See Illustration 3.
Illustration 4. These components of a ROPS/FOPS system are all tested together.
The specimen tested is a representative sample of the structure used in production. After completion of the test, material samples are taken from the specimen and evaluated for compliance with material properties. All ROPS must be tested. Normally, two representative specimens are required for a complete evaluation.
The most important requirement is the limitation on deflection (bending) of the structural members. No part of the structure during testing is allowed to penetrate a specified volume of space inside each ROPS/FOPS. See Illustration 5. This volume of space is called deflection limiting volume (DLV). The DLV assures that, within the limits of the ROPS structure, there is adequate space to prevent crushing the operator.
A FOPS (Falling Object Protective Structure) test is normally conducted first on a ROPS if it also provides FOPS protection. Tractors with a roll bar-type ROPS, such as a D8L, D9L, or D10 Tractor have FOPS protection in the cab roof, so this test is done on the cab only. The test consists of dropping a cylinder-like casting 5.19 m (17 ft) on a certain impact point on the FOPS. The falling object weighs 227 kg (500 lb). Again, the top of the FOPS must not be damaged enough to contact the DLV.
Specific rollover requirements are derived from investigations of ROPS that have performed the intended function in a variety of actual rollovers, as well as analytical considerations based on the ROPS and the machine frame. The structure must be able to resist certain side and longitudinal loads (forces) to absorb energy, and pass a vertical load test after the side and longitudinal loads are removed. At no time during any of the testing is the structure allowed to enter the DLV. The forces and energy requirements vary according to the type and weight of the machine.
Illustration 5. Location of deflection limiting volume inside the ROPS.
The test ROPS is mounted to its machine frame in the same manner as in production. The frame is rigidly bolted to a large bedplate. The DLV is installed in the same location as the operator. See Illustration 6. A horizontal load cylinder is mounted to a large fixture bolted to the bedplate. See Illustration 6. The machine frame can be bolted to the bedplate in different positions to permit applying the horizontal force to the sides, front, or rear of the ROPS.
Illustration 6. Overall view of a ROPS being tested by applying a side load.
The vertical load (not a falling object test) is applied by a cross beam over the ROPS with a cylinder fastened to each end of the beam. See illustrations 6 and 7. This is done on a ROPS after removing the side or longitudinal load. The vertical load is "2W" (twice the weight of a fully equipped machine).
Illustration 7. The vertical load test is applied after the side and longitudinal load tests.
During the various tests, the force applied and the amount of ROPS deflection are monitored continuously to determine when the force and energy absorption criteria are satisfied. This is done by a computer and data acquisition unit in a remote control room. The control room also contains the remote hydraulic controls and provides protection for observers. See Illustration 8.
Illustration 8. Inside view of the control room looking into the test laboratory.
Most test specimens are loaded to destruction (Illustration 9) even though they pass the various tests at lower loads. Caterpillar does this to determine the maximum loads required for an actual failure.
How To Obtain A New Rops/Fops Certification Plate
Any ROPS/FOPS certification plate (Illustration 3), that is knocked off or damaged to the extent it cannot be read, should be replaced as soon as possible. There have been instances where the government inspector has shut down the machine because it did not have the certification plate.
Almost every machine has a certification plate with a different part number because the machine model and weight must be stamped on the plate. Dealers should do one of the following to obtain a new plate:
Illustration 9. A ROPS specimen pushed to destruction after passing the criteria needed for certification.
... If you know the plate part number in the lower right corner, order this number on a Class 2 or 3 order in the usual manner.
... If you do not know the part number, an MAO (Made As Ordered) procedure is required. Give the following information to your dealer service contact at your assigned parts facility: Machine Model, Machine Serial No. (or Product Identification No.), and specify language if other than English is wanted.
When the new plate is received, be sure it is installed on the same machine for which the plate was ordered.
Do not install a certification plate on any ROPS/FOPS that has been modified or damaged because this particular structure may no longer be capable of furnishing the certified protection stated on the plate.