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Fluid Power Safety Alerts


(Ref. No. SA-007)

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Topic:
There are many people who think that on-the-job training for hydraulics is adequate. Here is a prime example why it simply does not work. In fact, it can leave innocent people vulnerable to severe injury or death.

Hydraulic "flange confusion" -
SAE Code 61, SAE Code 62, or Caterpillar®, 4-bolt flanges? Minute dimensional and physical differences between these connectors can spell the difference between life and death!


Case History -
A diesel mechanic with no formal training in hydraulics, installed a new hydraulic motor on a machine. When he reconnected the hydraulic hoses to the motor, he found that the bolt holes on the 4-bolt, split flanges did not line up with the holes in the motor housing.

Thinking that they had simply not been drilled in the correct position, he promptly took a file to them. In no time at all he had "corrected" the problem.

With nothing more than on-the-job training, he failed to realize that he was modifying an SAE Code 62 (6000 PSI) 4-bolt flange to fit an SAE Code 61 (3000 PSI) motor. The new motor that he installed on the machine was incorrect for the application.

He unknowingly removed the only thing that protected him from making the error of installing a 3000 PSI component in a 6000 PSI system - the bolt-hole dimensions.

In addition to the bolt-hole, center-to-center dimensions, there are also some physical differences between the SAE Code 61 and the SAE Code 62, 4-bolt flanges.
To illustrate how dimensionally similar the SAE Code 61 (3000 PSI) and SAE Code 62 (6000 PSI) 4-bolt flanges are, we have superimposed a Code 61 flange over a Code 62 using a 1" flange in our example.

Code 61 flange superimposed over a Code 62 flange


The "A" dimension of the Code 61 differs from the same dimension of a Code 62 by a meager 0.064" and the "B" dimension by a scant 0.188".

Flange dimensions

Caterpillar® makes a minor change -
Add to this the minor change Caterpillar® makes to their flanges, and the confusion grows proportionately.

Caterpillar® apparently makes their own version of what is almost identical to the SAE Code 62 4-bolt flange. However, they make one departure from the standard SAE Code 62 flange head - the SAE Code 62 dimension "C" (see diagram above) ranges from 0.305" on the 1/2" flange to 0.495" on the 2" flange. Caterpillar® makes their flange head dimension 0.560" for ALL their 4-bolt flanges.

Accordingly, if you are working in a situation where you have SAE Code 61, SAE Code 62, and Caterpillar® 4-bolt flanges, you must be extremely careful not to make errors in determining what fits where - connector identification training is therefore critical!

Avoid 4-bolt "flange confusion" -
To avoid 4-bolt "flange confusion", we have prepared a series of printable illustrations and charts for you. We ask that you share them with others who might be unaware of the differences between hydraulic flanges. In addition, please discuss these critical issues in your safety meetings.
ILLUSTRATION - Captive flange -vs- split flange
There are two types of 4-bolt flanges - captive flange and split flange. A captive flange is a one-piece flange, and a split flange is comprised of two separate flange halves. The bolt-hole dimensions for these flanges are, size-for-size, identical.
CHART - Comparative dimensions for 4-bolt flanges
Nominal
Flange
Size
CODE 61
CODE 62
Caterpillar®
Flange
O.D.
A
B
C
Flange
O.D.
A
B
C
Flange
O.D.
A
B
C
1/2
1.188
0.688
1.500
0.265
1.250
0.718
1.594
0.305
5/8
1.338
0.265
3/4
1.500
0.876
1.875
0.265
1.625
0.938
2.000
0.345
1.625
0.938
2.000
0.560
1
1.750
1.030
2.062
0.315
1.875
1.094
2.250
0.375
1.875
1.094
2.250
0.560
1-1/4
2.000
1.188
2.312
0.315
2.125
1.250
2.625
0.405
2.125
1.250
2.625
0.560
1-1/2
2.375
1.406
2.750
0.315
2.500
1.438
3.125
0.495
2.500
1.438
3.125
0.560
2
2.812
1.688
3.062
0.375
3.125
1.750
3.812
0.495
3.125
1.750
3.812
0.560
2-3/4
3.312
2.000
3.500
0.375
3
4.000
2.438
4.188
0.375
3-1/2
4.500
2.750
4.750
0.442
4
5.000
3.062
5.125
0.442
5
6.000
3.624
6.000
0.442

NOTE:
People who work with Poclain equipment must be aware that the 4-bolt flange connections used on this equipment is completely different to the 4-bolt flanges that are the topic in this safety advisory. See your Poclain literature for information on Poclain 4-bolt flanges.
4-bolt flange identification template -
To further assist you in making the proper 4-bolt flange identification, HYDRA-CHECK®, Inc. (www.hydracheck.com) makes a 4-bolt flange identification template.

This template consists of SAE Code 61, SAE Code 62, and Caterpillar® "slots" that are clearly marked with all pertinent identification. Positive identification can be made by simply matching your connector with the corresponding identification "slot".

The accidents we report are real, and the victims are real. The safety guidelines we provide are to help companies and individuals work safely with hydraulics. All guidelines we provide are general, and are not intended for one specific hydraulic system or machine.

WHEN YOU PURCHASE HYDRAULIC-POWERED MACHINERY AND/OR EQUIPMENT, WE HIGHLY RECOMMEND THAT ONCE YOU DETERMINE THAT IT CAN DO THE WORK YOU WANT IT TO DO, YOU THEN DETERMINE HOW MUCH SAFETY HAS BEEN BUILT INTO IT BY THE MANUFACTURER. IN ADDITION, WE RECOMMEND THAT YOU, WITH THE INPUT FROM YOUR OPERATORS, MECHANICS, ENGINEERS, PRODUCTION PERSONNEL, AND SAFETY DEPARTMENT, FORMULATE A LIST OF MINIMUM SAFETY STANDARDS FOR THE EQUIPMENT YOU PURCHASE. ALTHOUGH WE LIKE TO BELIEVE THAT MOST MANUFACTURERS ARE CONCEREND ABOUT SAFETY, SOME BELIEVE THAT CERTAIN SAFETY MEASURES ARE AN UNNECESSARY EXPENSE. WE FURTHER RECOMMEND THAT ALL THE SAFETY STANDARDS AND RECOMMENDATIONS THAT YOU DEVELOP SHOULD BE REVIEWED BY YOUR SAFETY DEPARTMENT, ENGINEERING DEPARTMENT, AND BY THE RESPECTIVE MACHINE OR EQUIPMENT MANUFACTURER PRIOR TO MAKING THEM POLICY - TOTAL SAFETY CAN ONLY BE ACHIEVED WITH A TEAM EFFORT.

CAUTION!
The Fluid Power Safety Institute™ does everything possible to insure that the information and drawings contained in these documents is accurate, and the procedures are deemed safe and reliable. However, these are general recommendations only and might not be applicable to all situations.

You MUST have your engineering department and service department read these recommendations and make the necessary changes for your specific application.

The Fluid Power Safety Institute™ is not responsible for actions taken by untrained and/or unauthorized persons. ALL hydraulic system service, repair, and troubleshooting should be done by trained, authorized persons ONLY.


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