This guide explains what each spacer type is, how it differs from the others, and when to specify it. All spacers are available in PVDF, PTFE, and Polypropylene, machined to lined pipe flange dimensions at SG&P's Freeport, Texas facility.

Why Spacer Type Selection Matters

The type of flange spacer you specify determines how it interfaces with your flanges, whether it provides a full sealing surface or a ring contact, whether it blanks off flow or maintains it, and how it handles bore size transitions. Specifying the correct type from the start avoids costly field modifications, rework, and system downtime.

The 11 spacer types SG&P manufactures fall into four functional categories: standard gap spacers, blind (blanking) spacers, bore transition spacers, and flow measurement spacers.

Quick Reference: All 11 Spacer Types

Standard Gap Spacers

Standard Ring Spacer

The Standard Ring Spacer is the most commonly specified thermoplastic flange spacer. It is a ring-shaped component with a full bore opening that maintains a precise gap between two flanges. It is used when a fixed standoff distance is needed between flanges — for example, to accommodate a valve, instrument, or other inline component — without restricting flow.

Specify a Standard Ring Spacer when:

• You need to maintain a consistent gap between flanges in a lined pipe system
• Full, unrestricted flow through the bore is required
• The flange connection uses a raised face or ring-type joint configuration

Standard Full Face Spacer

The Standard Full Face Spacer performs the same gap-maintaining function as the Standard Ring Spacer but covers the entire flange face rather than just the bolt circle area. The full face configuration provides gasket contact across the full face of the flange, which is required for certain flange types — particularly flat face flanges — to distribute bolt load evenly and prevent flange distortion.

Specify a Standard Full Face Spacer when:

• Your flange connection uses a flat face configuration
• Full face gasket contact is required by your piping specification or engineering standard
• You need uniform bolt load distribution across the full flange face

Blind (Blanking) Spacers

Blind Ring Spacer

A Blind Ring Spacer is a solid ring — it has no bore opening. It is used to isolate or blank off a section of piping, effectively blocking flow at the flange connection. Unlike a blind flange (which replaces an entire flange), a Blind Ring Spacer is inserted between two existing flanges and is far easier to install and remove.

Blind Ring Spacers are commonly used for hydrostatic pressure testing, temporary isolation of pipe sections during maintenance, and permanent isolation of unused branch lines.

Specify a Blind Ring Spacer when:

• You need to isolate a section of lined pipe without removing flanges
• Temporary or permanent flow isolation is required at a flange connection
• Pressure testing of an upstream section is needed

Blind Full Face Spacer

The Blind Full Face Spacer is a solid disc that covers the entire flange face with no bore opening. It combines the blanking function of the Blind Ring with the full face coverage of the Full Face configuration. It is used in applications requiring complete flow isolation with full face gasket sealing on both sides.

Specify a Blind Full Face Spacer when:

• Full flow isolation is required on a flat face flange connection
• Both faces of the flange require full gasket contact during isolation
• Your piping specification requires full face blanking for pressure containment

Bore Transition Spacers

Tapered Bore Ring Spacer

The Tapered Bore Ring Spacer features an internal bore that transitions from one diameter to another through a tapered profile. It is used when the bore size of two mating pipes or components differs and a smooth, gradual transition is required at the flange connection. The tapered profile minimizes turbulence and pressure drop at the transition point.

Specify a Tapered Bore Ring Spacer when:

• Two pipes of different bore sizes are being connected at a flange joint
• A smooth bore transition is needed to minimize flow disturbance
• The flange connection uses a raised face configuration

Tapered Bore Full Face Spacer

The Tapered Bore Full Face Spacer provides the same bore transition function as the Tapered Bore Ring but with full face coverage. It is used on flat face flange connections where a bore transition and full face gasket contact are both required.

Reducing Ring Spacer

The Reducing Ring Spacer connects two pipes of different diameters at a flange joint. Unlike the Tapered Bore which provides a gradual transition, the Reducing Ring steps directly from one bore size to another. It is used when connecting a larger pipe or component to a smaller one at a flanged connection.

Specify a Reducing Ring Spacer when:

• You are connecting two pipes of different diameters at a flanged joint
• A direct bore step-down (rather than a taper) is acceptable for the application
• The flange connection uses a raised face configuration

Reducing Full Face Spacer

The Reducing Full Face Spacer performs the same diameter reduction function as the Reducing Ring but covers the full flange face. Specified for flat face flange connections where a bore reduction and full face sealing are both required.

Flow Measurement Spacers

Orifice Ring Spacer

The Orifice Ring Spacer contains a precision-machined orifice opening — a calibrated restriction in the bore — used for flow measurement. When installed between flanges, it creates a measurable pressure differential across the orifice that can be used to calculate flow rate. Thermoplastic orifice spacers are ideal for corrosive fluids where metal orifice plates would be subject to chemical attack.

Specify an Orifice Ring Spacer when:

• Flow measurement is required in a corrosive or lined pipe system
• A differential pressure flow measurement method is being used
• The process fluid would corrode a metal orifice plate

Orifice Full Face Spacer

The Orifice Full Face Spacer provides the same precision flow measurement function as the Orifice Ring but with full face coverage for flat face flange connections.

Flange Spacer Types

Compensation Ring Spacer

The Compensation Ring Spacer is designed to accommodate dimensional variations in lined pipe systems. Lined pipe systems can have slight variations in liner flange face dimensions due to manufacturing tolerances, thermal expansion, or installation conditions. The Compensation Ring Spacer bridges these dimensional gaps, ensuring a proper fit and sealing interface at the flange connection without requiring modification to the pipe or flange.

Specify a Compensation Ring Spacer when:

• Dimensional variation exists between mating flange faces in a lined pipe system
• Thermal expansion or contraction has created a gap that needs to be taken up at the flange joint
• Standard spacer dimensions do not achieve a proper fit due to liner manufacturing tolerances

Ring vs. Full Face: How to Choose

All 11 spacer types come in either a ring configuration or a full face configuration. Here is a simple rule:

• Ring spacers are used with raised face flanges — the gasket and sealing contact occurs only within the bolt circle area
• Full face spacers are used with flat face flanges — the gasket and sealing contact extends across the entire flange face

When in doubt, check your flange facing specification. Raised face (RF) flanges are the most common in industrial piping systems; flat face (FF) flanges are typically found on equipment with cast iron or non-metallic flanges where full face contact prevents flange distortion under bolt load.

All Spacers Are Custom-Machined to Your Specification

Every spacer we manufacture is machined to your exact dimensions — pipe size, flange class (150, 300, 600, etc.), bore diameter, thickness, and material. This ensures a precise fit in your lined pipe system without field modification.

We manufacture in PVDF, PTFE, and Polypropylene as well as other plastics. For help selecting the right material for your chemical service conditions, see our Chemical Resistance Guide: Plastic Flange Spacers in Corrosive Environments .