Standard vs. Oversized Bore Seals: What’s the Difference?
When it comes to replacing or upgrading a mechanical seal, understanding bore size is one of the most important steps in selecting the right product. At Paradigm Seals®, customers often ask: What’s the difference between a standard bore and an oversized bore seal? This guide breaks it down so you can confidently choose the correct option for your pump.
What Is Bore Size?
The bore size refers to the inside diameter of the seal chamber (stuffing box) in which the seal is installed. Simply put, it’s the opening where the seal sits inside your pump. Bore size affects not only the fit of the seal but also its long-term performance.
Standard Bore: The typical opening size specified by the pump manufacturer. This is typically designed for braided mechanical packing.
Oversized Bore: A larger-than-standard opening, designed to give more room for the mechanical seal for cooling or to prevent clogging for solids.
Non-Standard Bore Sizes: Be aware or pump variations due to repair or wear-and-tear.
Why Oversized Bore Options Exist
Over time, pumps can undergo modifications, repairs, or wear that alter the stuffing box dimensions. Manufacturers also design some pumps with slightly larger bores to accommodate specific operating conditions. Oversized bore seals provide the flexibility to maintain reliable sealing even when the pump cavity isn’t standard.
How to Tell If You Need Oversized
Check Pump Documentation: Manufacturer specs often note when oversized options are available.
Measure Carefully: Use calipers or micrometers to measure the stuffing box bore. Compare to standard dimensions in the sizing guide.
Seal Selector Tool: Paradigm Seals® makes it easy to cross-reference your pump model against available seal sizes and bore options.
What Happens If You Choose the Wrong Bore
Bore Too Small: The seal may not fit into the seal chamber or may interfere with the pump components, preventing proper installation.
Bore Too Large: The gland bolting and gland gasket may not properly fit or locate to the seal chamber, which can prevent correct installation or result in leakage.
Non-Standard Bore: If the pump has been modified or the bore dimensions are uncertain, contact Paradigm to confirm the correct seal fit before ordering.
Paradigm’s Approach
Every Paradigm seal — from the 8610/8610S Single seals to the 8620 Dual seal — is available in standard and oversized bore options. This ensures you can order the right fit for your pump without worrying about compatibility.
Key Takeaway
Always confirm your bore size before ordering a replacement seal. If you’re unsure, download the Seal Sizing & Manufacturer Guide or submit the Find Your Seal Form with your pump details. Paradigm’s experts will help you get it right the first time.
Download the Stuffing Box Bore Sizing Worksheet (PDF)
