Supplier-family review · Hydraulic sealing support · No independent pressure or endurance test
QuanSeaL O-ring back-up rings
A back-up ring supports an elastomeric seal against extrusion; it does not replace the seal. QuanSeaL lists five forms, with different installation and motion limits. Start with the existing groove and complete operating conditions.
Support the O-ring. Do not order this as its replacement.
Two components have different jobs.
The supplier describes a back-up ring as a protective support fitted in a groove alongside an elastomeric sealing element, commonly an O-ring in static service. Its extrusion-resistant material helps prevent the pressurised elastomer entering the sealing gap. The back-up ring itself has no intended sealing function. [1]
If the current seal is damaged
Identify the seal, groove, clearance and operating conditions. Ask the responsible engineer to assess the failure and specify the complete seal/support arrangement. A back-up ring alone does not establish the cause or correct every leak.
If you are designing a new groove
Supply the housing drawing and pressure direction. Have the sealing specialist propose the seal, support-ring position and required groove space together. This page supplies no universal groove dimensions.
QuanSeaL explicitly lists excavators and hydraulic-circuit valves among its applications. That establishes the catalogue's industry scope, not compatibility with an excavator model, cylinder, valve cavity or oil specification. The group image is an illustration of multiple forms; it is not a labelled dimensional drawing or evidence of the exact pieces in a shipment.
Choose a form that can be installed in your housing
The supplier's five codes are family names, not complete order codes.
| Family | Form, material and selection boundary |
|---|---|
| BM Solid / rectangular | PTFE; no cut. Listed for static/dynamic service and reciprocating/rotating motion. Confirm how the solid ring will pass into the actual groove without an unapproved installation method. |
| BCM Solid / concave | NBR, FKM or PTFE. The supplier prefers static use and also lists reciprocating motion. Its concave face is described as a larger contact support for the O-ring; no measured life improvement is available here. |
| BG Cut / rectangular | PTFE; listed cut angles 20°, 30° or 45°. Intended as an option for closed grooves where an uncut ring is unsuitable. Static/dynamic and reciprocating/rotating motion are listed; choose an actual approved configuration. |
| BCC Cut / concave | PTFE; listed cut angles 30° or 45°. Closed-groove option, preferably static, with reciprocating motion also listed. Do not infer BG's rotation statement for this family. |
| SP Two-turn spiral | PTFE, rectangular section with angled ends. The supplier limits motion to reciprocation and says its dimensions differ from standard back-up rings. Do not substitute it for a solid ring using only a matching diameter. |
These distinctions come from the supplier's original listing. [1] None of the five entries provides a full size schedule, tolerance stack, installed clearance or item-specific acceptance report. Ask for one controlled drawing that identifies the O-ring and support ring together.
Does a similar ISO form prove the supplier's ring is standard-conforming?
No. ISO 3601-4's public abstract covers five anti-extrusion forms and links them to selected O-ring sizes and housing dimensions in the related standard parts. [3] Similar shape names are not dimension, material or conformity evidence. The supplier separately names AS568, MS27595 and JIS B2407 for BM, and AS568 for BCM. Ask which standard and edition governs the offered drawing; do not treat those references as interchangeable.
Read each operating envelope with its condition
There is no single “250 MPa, 260°C, 2 m/s” rating.
The official family page separates static, reciprocating and oscillating/slow-rotation conditions. Its values are approximate and do not identify a common material, clearance or test configuration. [1]
| Condition | What the catalogue states |
|---|---|
| Reciprocating | Up to approximately 40 MPa. No stroke, cycle rate, temperature or material combination accompanies this value. |
| Oscillating / slowly rotating | Up to approximately 15 MPa. This does not remove SP's separate reciprocating-only restriction. |
| Static | Up to approximately 250 MPa, depending on support-ring material and sealing gap. It is not a rating for every PTFE form. |
| Speed | Up to approximately 2 m/s for reciprocating or rotating motion, depending on material. No guarantee that the pressure and temperature limits apply simultaneously. |
| Temperature | −200°C to +260°C, depending on material. Not a shared operating range for PTFE, NBR, FKM, the O-ring and the fluid. |
Give normal and peak pressure, fluid, temperature range, motion, actual clearance and tolerances. Ask the supplier to identify the proposed material and the permitted combination in writing. The original questionnaire explicitly separates minimum, operating and maximum conditions. [2]
The catalogue provides no pressure-cycle/endurance results, current batch reports or guaranteed leakage figure for a specified assembly. It cannot establish a cylinder's maximum working pressure, a valve's safety function or the life of your O-ring.
Specify the extrusion gap and material before price
“PTFE ring” leaves important choices unresolved.
QuanSeaL describes virgin PTFE as its standard option for low-to-medium loads because of cold-flow behaviour. It names glass, bronze and carbon filled PTFE for higher load requirements, and modified thermoplastics for high-pressure sealing support. It also offers moulded material options for larger quantities on request. [1] No particular filler percentage, compound designation or fluid compatibility is confirmed for an offered ring.
Hardware information
Provide rod/bore and gland diameters, groove width/depth, tolerances, extrusion gap, surface condition and housing access. State inch or metric units. The supplier's form also asks for runout and hardware material/finish where relevant. [2]
Operating information
Name the fluid and other contacting media, contamination, pressure direction and pulsation, motion, stroke/cycle rate or rotation conditions. Separate measured normal conditions from transient or unknown values. Ask for a defined compound rather than assuming all filled PTFE performs alike.
For an existing groove, disclose whether dimensions may change. The questionnaire has explicit nominal/tolerance and “change OK” inputs, and a back-up width field. [2] A replacement must not quietly consume space needed by the existing sealing element. Have the responsible specialist approve the arrangement, installation route and any housing change.
Do not order a back-up ring from the worn part's apparent diameter alone. Retain the original seal designation and obtain the housing drawing. If these are unavailable, request an identification/measurement procedure from the supplier before authorising manufacture.
Approve the ring and seal as one documented configuration
Keep procurement approval separate from operating validation.
- Freeze the proposed drawing. Identify BM/BCM/BG/BCC/SP, dimensions and tolerances, cut/spiral form, compound, companion seal and installation arrangement.
- Agree sample evidence. Set dimensional checks, material identification and handling/packing requirements for the offered parts. Request any relevant test evidence with its actual configuration and conditions.
- Define your validation. Specify leakage, operating cycle and acceptance criteria with qualified engineering responsibility. A supplier's blank form asking for expected life does not mean it guarantees that life.
- Control repeat orders. Keep the approved revision and material designation with your spare-parts record. Require approval for changes to compound, geometry, seal pairing or manufacturing source.
MOQ, stock, price, lead time and warranty are not established by the reviewed family page. Request them against the approved configuration and quantity. CivilEquip has not visited the factory or independently tested these rings. See the separate QuanSeaL factory review for identity and certification-evidence boundaries.
Send the supplier an application they can assess
Edit this brief; unknown inputs should remain marked unknown.
Sources & review
- QuanSeaL original back-up ring catalogue ↗
Five supplier forms, materials, motion restrictions and conditional operating envelopes. No item-specific tolerance or combined operating rating.
2026-10-11 - QuanSeaL original application questionnaire ↗
Four pages viewed: application/operating conditions on page 2, hardware and performance inputs on page 3; page 4 contains no technical fields. A blank enquiry form, not a test certificate.
2026-10-11 - ISO 3601-4 original public abstract ↗
Dimension/tolerance scope for five anti-extrusion ring forms and relationship to selected O-ring and housing dimensions. Public abstract only; full paid dimensional tables not reviewed. No supplier conformity inferred.
2026-10-11
Specifications come from the manufacturer’s published information and the sources above; buying advice is written by CivilEquip with AI assistance. Ask the manufacturer to confirm the data for your configuration. Editorial policy · Report a correction.