Understanding Oversized Bore Mechanical Seals
When selecting a mechanical seal, confirming the correct bore size is just as important as choosing the right seal type and face combination. For many pumps, a standard bore will suffice. However, certain pump models and applications require an oversized bore. Misidentifying this detail can lead to incorrect orders, failed installations, and costly downtime.
This article explains what an oversized bore is, when it’s required, and how Paradigm Seals™ makes the selection process simple.
What Is an Oversized Bore?
The bore refers to the inside diameter of the stuffing box where the mechanical seal is installed. In most pumps, this dimension matches standard sizing. However, some pump manufacturers design pumps with oversized stuffing boxes that require a seal with a larger bore dimension to ensure proper fit and operation.
Why Oversized Bores Matter
Installing the wrong bore size can cause:
Improper sealing leading to leaks and equipment damage.
Excessive vibration from a loose fit.
Premature seal failure, increasing maintenance costs and downtime.
Selecting the correct bore size ensures the seal functions as intended, protecting both pump performance and operator safety.
How to Identify an Oversized Bore
Check Pump Model & Manufacturer
Many common ANSI pump models (such as Goulds 3196) may use oversized bores in certain sizes. Always cross-reference with a sizing guide.Measure the Stuffing Box
Using calipers, measure the internal diameter of the stuffing box. Compare this against standard bore specifications.Use Paradigm Resources
Paradigm Seals™ provides:A downloadable Seal Sizing & Manufacturer Cross-Reference Guide
An Oversized Bore Flowchart (PDF)
The online Find Your Seal Form for confirmation
Ordering Oversized Bore Seals from Paradigm Seals™
Paradigm Seals™ offers oversized bore options across our product families, including:
A1 Single Cartridge Seal — Oversized bore available in select sizes
A2 Dual Cartridge Seal — Oversized options for critical pumps
QuickCore™ Seals — Compatible with both standard and oversized bores
When placing an order online, simply choose “Oversized Bore” from the bore size dropdown to ensure the correct seal.
Key Takeaway
An oversized bore isn’t an uncommon complication—it’s a standard variation that pump operators must account for when ordering seals. By confirming manufacturer, model, and bore dimensions, you’ll avoid costly mistakes and downtime.
Paradigm Seals™ simplifies this process with clear sizing resources, an online selector tool, and knowledgeable support—helping you order with confidence.
Next Step:
Watch our full Oversized Bore Video Tutorial (below) for a step-by-step guide to identifying and ordering oversized bore seals.
Download the Stuffing Box Bore Sizing Worksheet (PDF)
