# Internal Pipe Repair Sleeve Sizes: Reading Bore and Fit Range

Canonical: https://reliancetrenchless.com/en-GB/blog/repair-sleeve-fit-range-and-bore

Published: 2026-08-11 · Updated: 2026-08-11 · By Reliance Trenchless

How to compare measured pipe bore with an internal repair sleeve fit range: measure at the defect, record ovality and offset, and match the installation tool.

An internal pipe repair sleeve is selected from the measured bore at the repair, not from the nominal diameter printed on the line. A DN300 label can describe a pipe that measures differently at the defect, especially after settlement, grouting, lining or an offset joint. The sleeve fit range is a pair of limits, and the measurement has to be taken where the sleeve will actually sit.

Reliance publishes Instant-Lock Small as nine nominal sizes from DN150 to DN600: the DN150–DN500 models use a 400 mm rubber width, and the DN600 model uses 300 mm. Instant-Lock Large covers nine sizes from DN600 to DN2000, all with a 300 mm rubber width. The families overlap at DN600. That overlap is exactly why the measured internal diameter, not the nominal size alone, has to decide the selection.

## What does an internal pipe repair sleeve fit range describe?

A mechanical internal repair sleeve is a stainless steel sleeve with an EPDM jacket, expanded against the host pipe by a locking gear. ASTM F3110 describes the class in its title as a mechanical trenchless point repair sleeve with a locking gear mechanism for pipes of varying inner diameter and offset joints. The title identifies the kind of product; it does not certify a particular sleeve or replace the manufacturer's fit table.

The fit range tells you the minimum and maximum bore between which a model is intended to work. It does not tell you that every bore inside that range is equally suitable. Ovality, a step at a joint, a protruding connection or a rough surface can change the installation. Those conditions belong in the same review as the diameter.

![Conceptual pipe cross-section showing internal diameter measurements at several clock positions and a joint offset, with numbered callouts.](https://reliancetrenchless.com/assets/img/Blog/repair-sleeve-fit-range-and-bore/sleeve-bore-measurement.svg)

**Measure where the sleeve will sit.** 1: internal diameter at the proposed repair; 2: a second clock position; 3: joint offset or step; 4: defect length; 5: sound pipe on each side; 6: access direction. Conceptual diagram; it does not set an allowable ovality or fit limit.

## 1. Measure at the repair, not at the manhole

Take the measurement at the proposed sleeve position. A diameter recorded at the manhole, at the pipe end or on a drawing describes another location. If the defect is a joint with an offset, measure both bores and the step between them.

Record the internal diameter at several clock positions rather than one reading. A single horizontal or vertical measurement can miss an oval section. Keep the instrument, the date and the person who took the reading with the result. If the measurement comes from a CCTV report, distinguish a calibrated measurement from a scaled screen estimate.

NASSCO's assessment guidance is useful for the inspection side: the defect, its location and the observation record have to be identifiable. It does not supply a sleeve fit value. The product table supplies the limits; the inspection supplies the condition.

## 2. Read the minimum and maximum fit columns

Use the model table and compare the measured bore with both limits. Do not compare only with the nominal size in the model name. A model that covers a wide range may be near its upper limit at one end of the repair and near its lower limit at the other if the bore changes.

At DN600, check both families against the measured bore and the available installation equipment. Do not choose Small or Large from the nominal size alone. The correct answer may depend on the actual bore, the sleeve length, the defect geometry and the tool that can be brought to the site.

Record the selected model, the fit range and the measurement that placed it there. If the bore sits close to a limit, say so in the enquiry. A supplier can then confirm whether the standard model is appropriate or whether a different configuration needs review.

## 3. Record ovality, offset and surface condition

Diameter is only one field. Add the following to the repair record:

- the largest and smallest internal measurements at the repair;
- any visible offset or step at a joint;
- the length of the defect and the length of sound pipe on each side;
- the surface condition where the sleeve will expand;
- nearby connections, roots, deposits or previous repairs;
- the access opening and the route to the repair.

These fields explain why two pipes with the same nominal size can need different sleeves. They also show what the supplier has not been told. A statement that the pipe is "DN300" is not a measurement record.

Do not invent an allowable ovality or offset limit. ASTM F3110 addresses pipes of varying inner diameter and offset joints as a class, but the project still needs the manufacturer's configuration guidance for the selected sleeve. If the condition falls outside the published table, ask for a review rather than forcing the nearest model.

## 4. Match the sleeve, the installation tool and the access

The sleeve is installed from inside the pipe, so access is part of the selection. Confirm the entry opening, the route, the tool envelope and the working length. A sleeve that fits the bore but cannot be delivered to the repair is not a usable selection.

The Small and Large families use different installation equipment. Do not carry an inflation procedure from one family to the other. Ask for the procedure that matches the selected model, and keep the tool identification with the installation record.

| Record | What to write | What it does not prove |
| --- | --- | --- |
| Bore | Measured internal diameter at several clock positions | That the bore is round along the whole repair |
| Fit range | Model minimum and maximum from the current table | That the selected model is approved for the site |
| Defect | Type, length, offset and surface condition | That the sleeve will restore structural capacity |
| Access | Entry, route, tool envelope and working length | That the site can be entered safely |
| Installation | Tool model and procedure revision | That the installed sleeve passed a project test |

For the installation sequence and tool set, the [trenchless installation guide](https://reliancetrenchless.com/en-GB/resources/trenchless-installation-guide) and the [sleeve installation-set article](https://reliancetrenchless.com/en-GB/blog/instant-lock-sleeve-installation-set) provide the next level of detail. The [small sleeve product page](https://reliancetrenchless.com/en-GB/products/instant-lock-sleeves-small) carries the current model table. The project measurement still decides which row applies.

![Conceptual table map linking measured bore, sleeve fit range, defect record, access and installation tool.](https://reliancetrenchless.com/assets/img/Blog/repair-sleeve-fit-range-and-bore/sleeve-fit-fields.svg)

**Five fields, one selection.** The measured bore is compared with the current model table; the defect, access and tool records decide whether that model can be installed. A nominal pipe size does not replace any of the five.

## FAQ: Internal pipe repair sleeve sizes

### Can I choose a sleeve from the nominal pipe size?

No. The nominal size identifies the line, but the fit range is based on the measured internal diameter at the repair. At DN600 the Small and Large families overlap, so the measured bore and the installation equipment have to decide.

### Is one diameter measurement enough?

It is a start, not a complete record. Measure at several clock positions and note ovality, offset and surface condition. A single reading can miss a shape change that affects the installation.

### Does ASTM F3110 approve a particular sleeve?

No. ASTM F3110 is a practice for the class of mechanical trenchless point repair sleeves with a locking gear mechanism. Its title does not certify a product, and this article does not claim that an Instant-Lock sleeve is listed or approved under it.

### What if the bore is outside the published fit range?

Ask for a configuration review. Do not force the nearest model or assume that a wider range covers the condition. Send the measurements, defect record, access information and the installation tool available so the supplier can confirm whether a standard or custom arrangement applies.

## References and source documents

- [Reliance — Instant-Lock Small and Large internal pipe repair sleeves: model ranges, materials and installation tools](https://reliancetrenchless.com/assets/doc/brochures/Reliance%20Instant-Lock%20Small&Big.pdf)
- [ASTM F3110-14(2024) — Practice for Proper Use of Mechanical Trenchless Point Repair Sleeve with Locking Gear Mechanism for Pipes of Varying Inner Diameter and Offset Joints](https://doi.org/10.1520/F3110-14R24)
- [NASSCO — Pipeline assessment: condition observation and defect records](https://www.nassco.org/trenchless-technology/assessment)
- [Reliance — Trenchless installation guide for Instant-Lock point repair](https://reliancetrenchless.com/en-GB/resources/trenchless-installation-guide)