Product Overview
PTFE Spiral Backup Ring for LMI Milton Roy Check Valve Rebuilds - New, Bagged and Labeled
Condition
New and unused. The ring is a milky white translucent PTFE spiral of roughly two turns, with clean square-cut ends and the faint surface lines you expect from machined or molded fluoropolymer. No cracks, chips, discoloration or flat spots are visible, and the material has the soft matte look of PTFE that has never been compressed in a gland. It arrives in a resealable zip-top poly bag carrying a printed order label that reads ORDER ITEM PART NUMBER, K07829 F, 0408-0073-221, plus a handwritten shelf code. Sold each: one ring per order. Four are on hand, and the photographed piece is representative of the group rather than a promise about every bag.
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Product Overview
This is LMI Milton Roy part number 0408-0073-221, a spiral backup ring in PTFE, also cataloged under NSN 5330-00-341-9914. A backup ring is the unglamorous half of a seal: it sits behind the o-ring and blocks the elastomer from extruding into the clearance gap when pressure spikes, which is what turns a good seal into a weeping one. The spiral form is the reason this style exists - the ring can be wound on over a shoulder or into a groove without stretching a solid ring past its limit, so a technician can service a valve body without pulling it further apart than necessary. PTFE is chosen here for chemical inertness and a low friction face, which is why it shows up in chemical feed and metering service where the fluid is unfriendly to ordinary polymers. The original listing states the practical rule plainly: new o-rings and new spiral backup rings should go in every time the check valves come apart. Dimensions are not confirmed here, so match the part number or NSN against your pump's parts list before ordering.
Key Features
- Part number: LMI Milton Roy 0408-0073-221
- NSN: 5330-00-341-9914
- Type: spiral backup ring, o-ring anti-extrusion support
- Material: PTFE, white and translucent
- Form: continuous spiral of approximately two turns with square-cut ends
- Condition: new, unused, never compressed in a gland
- Packaging: resealable poly bag with printed part-number order label
- Sold each: one ring per order
- Dimensions: not confirmed - verify against your pump parts list before ordering
Applications
- Water treatment technician rebuilding the suction and discharge check valves on a chemical metering pump during scheduled service
- Plant maintenance mechanic assembling a small parts kit so the next teardown does not stall waiting on a seal
- Municipal operator chasing a slow weep at a check valve and replacing every soft part rather than guessing which one failed
- Depot or MRO buyer sourcing against NSN 5330-00-341-9914 for a stocked spares bin
Frequently Asked Questions
What exactly arrives in the package?
One PTFE spiral backup ring in its labeled poly bag, as photographed. O-rings, valve balls, seats and any other kit hardware are not included - this listing is the backup ring only.
Why replace the backup ring every time the check valve comes apart?
Because it has already taken a set. Once a backup ring has been squeezed into a gland it carries the shape of that gland, and reusing it hands the o-ring a worn support surface at the exact spot extrusion starts. The guidance in this listing is the standard one: fresh o-rings and fresh spiral backup rings go in at every check valve disassembly.
How do I confirm this is the right ring for my pump?
Match the number, not the picture. The bag label and the listing both carry 0408-0073-221, and the item is also cataloged as NSN 5330-00-341-9914. Cross-reference either one against your pump's parts breakdown. We have not measured the ring, so do not size it from the photos.
Is PTFE the right material for my chemical?
PTFE is one of the more chemically inert seal materials in common industrial use, which is why it is specified for feed pump service. That said, we cannot confirm compatibility with your specific fluid, concentration or temperature - check the material against your chemical compatibility chart before you put it in service.
I only need two or three. Why order them here instead of a bulk seal lot?
Because a backup ring is counted out, not bought by the pound. You need one per valve, maybe a spare for the shelf, and nobody wants a bag of fifty PTFE rings for a pump that gets serviced twice a year. Order the exact count your rebuild calls for and stop there. Shipping is a flat $8, free once your order passes $28, so a few small parts added to a larger order ride along at no extra cost, and orders leave our Idaho warehouse the same or next business day.
PTFE does its best work where nobody is looking, holding a seal steady against chemistry that eats everything softer. Put a fresh one behind the o-ring, close the valve up, and go back to forgetting the pump exists.
