Frequently Asked Questions (Faq)

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HI-TECH Capabilities

Q: Can Hi-Tech supply OEM parts?

A: Yes. We can supply most OEM parts.

Q: Does Hi-Tech have the means to pick up large compressor cylinders from our plant?

A: Yes. Our fleet of trucks have the ability to pick up and deliver most parts.

Q: Does Hi-Tech manufacture and stock PTFE rings and riders?

A: Yes. We have an inventory of the most popular sizes of PTFE bushings and can manufacture at a moment’s notice.

Packing Cases / Pressure Packing / Wipers

Q: Are the garter springs on the packing supposed to force the packing against the rod for sealing?

A: No, not on pressure packing. The garter springs are for assembly purposes only. The packing rings function from being gas loaded. Garter springs on oil wiper packing do provide all of the loading on the rings as they are not exposed to the process gas pressure.

Q: How do I install my pressure packing?

A: Match marks on the side of the rings will face towards the pressure or cylinder.

Q: Is it better to install packing rings around the piston rod or should I plunge the rod through the packing case?

A: It is preferable to plunge the rod through the packing case, providing you use a thread protector preferably with the same OD as the rod. Plunging a rod with unprotected threads will damage the packing and cause leakage. Hi-Tech custom manufactures many styles of thread protectors.

Q: What are the purpose of the tie rods on a packing case?

A: The tie rods are for alignment purposes. The packing cups have to have correct angular alignment for the vent, purge, coolant and lube lines to operate effectively.

Q: Why are packing cups lapped?

A: We recommend always lapping packing cups to create an effective sealing surface.

Piston Rings / Rider Bands

Q: Does PEEK material have the same side clearance as PTFE?

A: No. PEEK based materials have a lower coefficient of expansion so the side clearance is less than PTFE based materials at ambient temperature, almost half. Side clearances are calculated so that at operating temperature there remains ample side clearance so that the
rings can still “ float” in the groove with rod movement.

Q: What particulars do I need to be concerned with about my solid PTFE rider rings?

A: Be sure that after installation the rings are gripping the piston tightly and that if heat is used in the installation process that it does not exceed 400 degrees F.

Q: Why do I have to use solid rider rings versus a cut rider?

A: The use of cut rider rings is always preferable over the use of solid band style rider rings, but if the rider ring over travels any valve ports and/or counter bores in the cylinder, solid band style rings should be used, particularly if more than half of the ring width over travels a port or counter bore. The reasoning is that a cut ring could expand and get “clipped“ or damaged.

Q: Why do some rider bands have grooves in them?

A: The side and face relief grooves are to prevent the rider bands from acting like a piston ring and allowing the gas to bypass the rider band. They also have a lubricating benefit in helping
to distribute oil around the cylinder in a lubricated environment. Typically you will see the grooves angled in opposite directions to help prevent the rider band from spinning.

Piston Rods

Q: Why is the RMS on a piston rod important?

A: Surface finish is important, especially in non-lubricated applications, as it has a direct effect on the wear of the rings, frictional heat concerns, and efficiency of the seal.

Thermal Spraying

Q: When thermal spraying a product, how do you determine the base material?

A: Our state of the art Niton XRF material analyzer allows us to determine the exact material composition of the base material which allows us to choose the best coating for the application. When a new product is needed, it allows us to match the material of the product
identically.

Valves

Q: Does Hi-Tech lap the valve seats when reconditioning our valves?

A: Yes, this more readily facilitates an effective seal between the valve seat and sealing elements and a good seal between the seat and guard surfaces, rather than simply machining or grinding.

Q: Why should I have Hi-Tech do a complete recondition of my valves instead of just replacing the internals in our own shop?

A: A complete reconditioning is recommended due to the wear that can occur on sealing surfaces and spring wells. A worn or deepened spring well can change the pre-load of the springs causing your valve to run inefficiently and/or spring breakage. Hi-Tech inspects and verifies that all OEM tolerances are within optimum operating limits. Hi-Tech also pressure tests all valves after reconditioning to ensure proper sealing.