Rheodyne: Frequently Asked Questions

This section addresses the most commonly asked questions of our Technical Support group. It is updated regularly with the latest customer inquiries.

For more detailed information regarding any of these questions, please refer to the product's operating manual. For other technical questions, try one of the support options shown to the right.

Q: What are the different materials available for the rotor seals?

A: Rheodyne^® offers most rotor seals in three standard materials: Vespel^®, Tefzel^®, and PEEK.

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Q: What are the pH ranges of the Vespel, Tefzel, and PEEK rotor seals?

A: The pH ranges are as follows:

• Vespel 0-10
• Tefzel 0-14
• PEEK 0-14

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Q: What are the advantages and disadvantages of Vespel vs. Tefzel vs. PEEK?

A: The most important issue with these materials is whether the solvents, chemicals, pH, and temperature you are using are compatible with the rotor seal in your valve. For example, Vespel has a pH limitation of 10; Tefzel has a temperature limitation of 50 °C. Chemical compatibility is addressed in the Materials and Tools section. In general, the different types of rotor seals will have the same lifetime and wear at about the same rate. Tefzel and PEEK rotor seals will require a slightly higher torque to turn the valve. For more information see Tech Tip 5: How to Select the Right Rotor Seal.

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Q: What are the chemical compatibility characteristics of Vespel, Tefzel, and PEEK?

A: There is not a simple answer for this question. We have compatibility information on many common solvents; however, since there are thousands of chemicals in use, we do not have information for every one.

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Q: What makes the "scrunching and grinding" sound when I turn the handle of my manual valve?

A: Most likely a corroded thrust bearing is causing the noise. The bearing is located on the valve shaft and is normally well lubricated. If the valve has been mounted with the stator facing up, solvents leaking onto the valve could have leaked down the stator screws and into the thrust bearing. The thrust bearing can be easily replaced. See Question 6 for added information about part numbers.

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Q: My valve is part of a manufacturer's instrument. I need to replace the rotor seal. Do you have the part number?

A: The valves we make for manufacturers (OEMs) are nonstandard products and are manufactured to OEM specifications. As a consequence, these parts are available only through the OEM. Inquiries should be directed to the customer service department of the manufacturer.

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Q: Why does my front-loading valve leak out the injection port only while I am in the LOAD position loading the sample loop?

A: If the needle seal located in the rotor seal is not sealing around the needle, some of the sample will come out of the injection port. The outer diameter and length of the needle must be the correct size for the valve in order for the needle seal to function. If the OD and needle length are correct, the needle seal may have expanded through frequent use. The needle seal can be reformed by pushing down on the needle guide, which in turn pushes on the seal and closes it up. For more information see Tech Tip 3: How to Find and Fix Common Leaks.

Note: Never use a beveled, pointed, or tapered needle. This can permanently damage the rotor seal and stator face assembly.

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Q: Why does my valve leak continually?

A: If your valve is leaking out the injection port, vent line(s), or the stator ring and stator interface, most likely the rotor seal has been scratched. When replacing the rotor seal, l always check the stator face assembly to make sure that it is not damaged. Any chip or crack on the ceramic stator face will damage a new rotor seal in just one turn. If the pressure setting of the valve has been exceeded, this can cause the valve to leak as well. For more information see the Troubleshooting Guide.

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Q: My fluid processor is not responding as outlined in the operating manual.

A: First, confirm that the processor will operate separately from your instrument. To isolate the processor, disconnect the interface cable from your instrument, leave the power supply connected to the processor, and put the processor in the LOCAL mode. Verify the communications mode of your fluid processor module.

To check the communications in the level logic mode (LabPro part number ending in -01):

1. Connect the black and red wires together. In a 2-position processor that is in position 1, the processor will switch to position 2; if the processor is in position 2, it will switch to position 1.
   
2. Disconnecting the black and red wires will switch the processor again.

To check the communications in the BCD mode (LabPRO part number ending in -03):

1. Connect the blue, green, yellow, and black wires. The processor should go to position 1.
   
2. Connect the blue, green, red, and black wires. The processor should go to position 2.

If the processor is responding as described, the problem is with the instrument's communication to the fluidic processor. Contact your instrument manufacturer's technical service department.

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Q: Can any instrument control a fluid processor?

A: Any instrument can be used to control a fluidic processor as long as it has external switches that are a contact closure or a TTL switch.

Regarding the external switches:

• The switches must not send a voltage or a current to the fluidic processor or it will be damaged.
• BCD control requires four external switches.
• Determine whether the instrument's output is level or a pulse logic.
• Both level and pulse logic require only one switch.

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Q: I have a RheBuild Kit. How do I install it?

A: See the RheBuild Kit instructions.

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Q: I think my position sensing switch is broken. How can I test it?

A: See the Testing a Position Sensing Switch instructions.

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Q: The outside ring on my replacement stator face assembly looks different. What happened?

A: The change in color in the outer ring of the stator face assembly is due to a change in material. This material does not contact the fluid flow path, and the change will not affect the function of this part.

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