Technical Information

U.S. and Canadian Coast Guard, American Bureau of Shipping, and Lloyds Register accept the Flexible Reach Rod concept for marine use.

How To Measure Flexible Reach Rods:

Click here to view the manual on "How To Measure Flexible Reach Rods".

Performance:

Flexible Reach Rod systems performance depends on four basic considerations:
1) Size and type of valve
2) Product which flows thru valve
3) The length of the run
4) The amount of effort that one person is able to exert on a hand wheel

Preliminary Considerations:

Torque loads required to operate valves vary widely between different manufactorers. To specify a given operating torque for all valves of one size and type would not indicate with sufficient accuracy the actual torque to be considered when designing a flexible reach rod control system for a particular valve.
However, it is possible by assuming that a valve hand wheel is large enough for one man to operate, to base the design of a remote system on the size of the valve hand wheel and the "normal" effort which the average person is able to exert on a hand wheel rim. This information will follow in table #1 and is self-explanatory. One man can apply a "normal" effort to the hand wheel of a valve provided the hand wheel is located lower than the person's head so that they can apply both hands, without difficulty, to the hand wheel rim. Under these conditions it has been found that his effort will vary from 35lbs. of pull per hand on a 4" hand wheel to 66lbs. of pull per hand on a 24" hand wheel.
It is an approved practice to support the flexible reach rod using various types of brackets every 36 to 48 inches. It is realized that this is not practical in every instance but it should be the installer's objective at all times. However, it is important that the flexible reach rod be supported at both ends of each bend.
Formulas are available to allow the engineer to designate a particular flexible reach rod based on valve size, types,its working pressure and the distance from the operator to the valve. This information is available on request. However, the technical information furnished in this bulletin should be sufficient for normal decision making regarding which reach rod is necessary for a particular application.

Torsional Defection:

Remember that the torsional deflection or the angular difference in twist is between input and output ends of a flexible reach rod system are directly proportional to its overall length. It is recommended that the total deflection caused by using a maximum input load be maintained at no greater than an accumulative 180 degrees (see table 2). By using this as a guide, it will assist the engineer to correctly recommend the flexible reach rod to be used for a particular valve.

Minimum Operating Radius:

Always keep in mind that the bends in a flexible reach rod should be as generous and should not be fetched up tighter than those indicated below:

The flexible reach rod as assembled is lubricated, and under normal circumstances, should not require re-lubrication for up to three years. However, there are grease-fitting plugs in the lower and upper ferrules that can be removed and replaced with a zerk fitting. In cases of extreme temperature conditions, special lubricants are recommended that would insure efficient operation.
Lubrication of the flexible reach rod is accomplished by first removing both grease fitting plugs and installing a zerk fitting at the upper station. Manually pump the lubricant into the reach rod until grease flows from bottom plug hole. Reinsert grease plugs at both ends and test the system. It is advisable to rotate the core at the same time that pressure is applied. This will insure uniform distribution of the lubricant throughout the entire system.

Mounting Support:

The flexible reach rod must be supported every 3-4 feet. This is necessary to prevent curling and kinking when a high torque is applied and to insure that the ferrules do not support all the weight of the reach rod.

Maintenance:

Flexible Reach Rods are often used in instances where they are only operated after long intervals of time. It is recommended that the flexible reach rod systems be operated at least once a month.
In many instances where valves have not been operated for long periods of time, foreign material may collect on the valve disc and it will require higher than normal torque to operate the valve. Application of forces greater than one man's effort at the remote station can cause failure in the flexible shaft system or valve thus requiring repair of replacement of one or both.
It is recommended that periodic inspection covering the entire length of the flexible reach rod should be performed. This includes a visual inspection for damage to casing, ferrules or the adapter. Once again, common sense is the criteria for this product.

TABLE #1

*Valve operating torques per Mil-S-16059 B (Ships) and Navsea 9048-LP-022-7010 (formerly Navships250)

TABLE #2

WARNING: Failure to follow guidelines could cause serious damage to the Flexible Reach Rod