Overview
A flange spacer is a component inserted between flanges to maintain a defined gap, replace a removed item, or form part of a line-blank assembly. Depending on the project, the term can refer to a paddle spacer, spacer ring, spectacle-blind open side, or a custom flanged spool spacer. The phrase “flanged spacer” is therefore ambiguous and should be supported by a drawing.
ASME B16.48 covers defined line blanks within its scope. Custom spacers and spool pieces may follow different design and documentation requirements.
Why It Matters for Pipe Components
A spacer changes the joint stack, stud length, gasket arrangement, alignment, and sometimes the pressure boundary. A thin ring used only for spacing is not automatically suitable as a pressure-containing line blank.
Operational isolation components need clear open/closed identification, handling features, corrosion protection, and safe changeover procedures. Their weight can be significant.
Installing an unengineered spacer to correct pipe misalignment or an excessive gap can overload flanges and create leakage.
Methods, Parameters, or Process
Identify the function first, then select the correct component type and pressure design.
| Component | Function | Key controls |
|---|---|---|
| Paddle spacer | Open position in a line-blank pair | Thickness, bore, handle, rating, identification |
| Paddle blank | Solid isolation position | Pressure design, handle, facing, weight |
| Spectacle blind | Connected blank and spacer | Rotation clearance and identification |
| Spacer ring | Maintains a defined gap or replaces thickness | Design purpose and pressure suitability |
| Flanged spool spacer | Adds pipe length with flanged ends | Pipe design, welds, flange alignment |
| Shim/temporary spacer | Installation aid only where approved | Not a substitute for engineered component |
Supplier and Inspection Checklist
- Ask for a drawing when the term flanged spacer is used.
- Define whether the item is pressure retaining or only dimensional.
- State flange standard, size, class, facing, and material.
- Confirm bore, thickness, handle, and identification.
- Calculate stud length for the complete stack.
- Provide gaskets on both sides where the design requires them.
- Inspect flatness, facing, edges, and corrosion.
- Plan lifting and changeover access.
- Use lockout, depressurisation, and isolation procedures for operational blanks.
Application to Pipe Fittings, Valves, and Flanges
Line blanks are used for positive isolation during maintenance, commissioning, and process changes. Spacer rings can maintain the same joint thickness when the blank is removed. Flanged spool spacers serve a different function by adding a short pressure-containing pipe section.
Valves, strainers, and equipment may require removal spools or spacers for maintenance access. These should be designed rather than assembled from loose washers or unapproved rings.
FAQ
Is a flange spacer the same as a blind flange?
No. A blind flange closes one flange end. A spacer is inserted between two flanges and may be open or part of a blanking system.
What is a paddle spacer?
It is the open component paired with a paddle blank in a line-isolation arrangement.
Does a spacer need two gaskets?
An inserted pressure-joint component commonly has sealing interfaces on both sides, but follow the approved design.
Can washers be used as a flange spacer?
Not as an improvised pressure-joint solution. Use an engineered component and approved assembly.
Why does stud length change?
The inserted thickness adds to the joint stack and must be included in bolting selection.
Next Steps
Clarify the function and request a drawing. Specify standard, size, class, material, thickness, facing, bore, handle, gaskets, bolting, marking, and operating procedure.
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