This article is intended for engineers, procurement managers, and plant operators evaluating materials for lined pipe systems. It is important to note upfront: SG&P manufactures exclusively thermoplastic flange spacers. We do not supply metal spacers of any kind. If your application requires metal, we are not the right supplier — but if you are open to understanding why thermoplastic may be the better solution for your system, read on.

What Is a Flange Spacer and Where Is It Used?

A flange spacer is a precision-machined ring or disc installed between two pipe flanges. Its primary functions are to maintain a fixed gap between flanges, allow for the installation of measurement instruments such as flow meters or orifice plates, accommodate pipe misalignment, and provide a sealing surface in certain configurations.

Flange spacers are used across a wide range of industries including chemical processing, water and wastewater treatment, oil and gas, pharmaceutical manufacturing, food processing, and semiconductor fabrication. In all of these environments, the choice of spacer material has a direct impact on system performance, maintenance frequency, and total cost of ownership.

The Case for Thermoplastic Over Metal

1. Superior Chemical Resistance

This is the single most important reason to choose thermoplastic in corrosive service. Metals — including stainless steel, carbon steel, and even exotic alloys — are vulnerable to corrosion when exposed to acids, caustics, halogens, and other aggressive chemicals. Corrosion leads to degradation of the spacer, contamination of the process fluid, and eventual flange joint failure.

Thermoplastic materials such as PVDF, PTFE, and Polypropylene are inherently resistant to a broad spectrum of corrosive chemicals. They do not rust, oxidize, or pit. In environments where metal would require costly alloy upgrades or frequent replacement, a thermoplastic spacer provides long-term, maintenance-free performance.

2. Ideal for Lined Pipe Systems

Thermoplastic flange spacers are specifically engineered for lined pipe systems — piping where a thermoplastic liner (PVDF, PTFE, or PP) is bonded to the inside of a steel pipe to protect against corrosion. In these systems, the flange face dimensions are different from standard steel pipe flanges because the liner extends to the face of the flange.

SG&P manufactures all spacers to lined pipe flange dimensions as standard. A metal spacer designed for standard steel flanges will not fit correctly in a lined pipe system without costly modification. Thermoplastic spacers eliminate this compatibility issue entirely.

3. No Galvanic Corrosion Risk

When dissimilar metals come into contact in the presence of an electrolyte, galvanic corrosion occurs — one metal corrodes at an accelerated rate. This is a well-known problem in piping systems where flanges, bolts, and spacers are made from different metals.

Thermoplastic spacers are electrically non-conductive and completely immune to galvanic corrosion. They can be installed between flanges of any metal without risk of accelerating corrosion in adjacent components.

4. Significantly Lower Weight

Thermoplastics are dramatically lighter than metals. PVDF, for example, has a density of approximately 1.78 g/cm³ compared to 7.9 g/cm³ for stainless steel — less than a quarter of the weight. For large-diameter spacers or installations where multiple spacers are used, this weight reduction simplifies handling, reduces installation labor, and lowers shipping costs.

5. Lower Total Cost of Ownership

While exotic metal alloys can be extremely expensive, thermoplastic spacers — even high-performance fluoropolymers like PVDF and PTFE — are generally more cost-effective over the life of the system. Thermoplastics do not corrode, do not require protective coatings, and typically outlast metal spacers in chemically aggressive environments, resulting in fewer replacements and lower maintenance costs.

6. Electrical Non-Conductivity

In applications where electrical isolation between pipe sections is required — common in cathodic protection systems and certain chemical processing environments — thermoplastic spacers provide inherent electrical isolation. Metal spacers require additional isolation kits or gaskets to achieve the same result, adding complexity and cost.

When Metal Spacers Are Used — And Why SG&P Does Not Supply Them

Metal flange spacers are used in applications involving very high temperatures, extreme mechanical loads, or environments where chemical resistance is not a concern and structural strength is the primary requirement — such as high-pressure steam lines or structural piping systems in non-corrosive service.

SG&P specializes exclusively in thermoplastic fabrication. We do not manufacture, stock, or supply metal flange spacers of any type. Our expertise, equipment, and manufacturing processes are focused entirely on precision thermoplastic machining. If your application genuinely requires a metal spacer, we recommend consulting a metal fabrication specialist. However, if you are currently using metal in a corrosive or lined pipe application and are experiencing corrosion, premature failure, or fit issues, we encourage you to contact us — thermoplastic may be the solution you have been looking for.

Which Thermoplastic Material Is Right for Your Application?

SG&P manufactures flange spacers in three primary thermoplastic materials:

• PVDF (Polyvinylidene Fluoride) — Best all-around performer; excellent chemical resistance, high mechanical strength, UV resistant, operating temperature up to 280°F
• PTFE (Polytetrafluoroethylene) — Maximum chemical and thermal resistance; suitable for the most aggressive environments and highest-purity applications; operating temperature up to 500°F
• Polypropylene (PP) — Cost-effective option for general-purpose corrosive service; excellent resistance to dilute acids, caustics, and aqueous solutions; operating temperature up to 225°F

For a detailed comparison of these materials, see our article: PVDF vs PTFE vs Polypropylene: Which Material for Your Flange Spacer?

SG&P Thermoplastic Flange Spacer Product Line

SG&P manufactures 11 types of thermoplastic flange spacers, all available in PVDF, PTFE, and Polypropylene, machined to lined pipe flange dimensions:

• Blind Ring Spacer
• Standard Ring Spacer
• Blind Full Face Spacer
• Standard Full Face Spacer
• Tapered Bore Ring Spacer
• Tapered Bore Full Face Spacer
• Orifice Ring Spacer
• Orifice Full Face Spacer
• Reducing Ring Spacer
• Reducing Full Face Spacer
• Compensation Ring Spacer

All spacers are custom-machined to your exact dimensions and specifications at our Freeport, Texas facility.