Red Rubber Flange Gaskets SBR Gaskets Steam Flange Gaskets

author: Qishine Industry

2023-05-16

One-Minute Overview

Red rubber is a rubber sheet grade (usually SBR-based) colored red so it is easy to identify in the field.
It is the standard low-cost seal for low-pressure saturated steam, hot water, and air.
Keep it away from oil, fuel, solvents, and strong acids - rubber swells and fails in those services.
For steam above about 150 deg C or oil service, switch to EPDM or a metallic gasket.

Red Rubber Flange Gaskets at a Glance

Red rubber flange gaskets - often called SBR gaskets or steam gaskets - are rubber sheet gaskets cut for raised-face and flat-face flanges. They seal low-pressure steam, hot and cold water, and air lines in HVAC, building services, and light industrial plants. This guide covers what 'red rubber' is made of, the temperature and pressure limits that matter for steam service, where it fits against EPDM and spiral-wound gaskets, and how to install it so it does not creep or blow out.

What 'Red Rubber' Actually Means

'Red rubber' is a trade name for a flexible rubber sheet, most often based on SBR (styrene-butadiene rubber) with a red pigment. It is not a single compound: hardness, insert (fabric or wire), and filler vary by supplier. What stays constant is the use case - a soft, compressible sheet for low-pressure flange sealing. We stock it in standard ANSI and EN sizes and can cut it to your flange dimensions.

Temperature and Pressure Limits for Steam Service

Use these limits as a starting point, then confirm against the spec sheet of the exact sheet you buy:

Standard red rubber is rated for saturated steam up to about 200 deg F (93 deg C) and 150 psi in class-150 service.
For hot water it runs a little higher, typically to about 120 deg C, depending on the compound.
It stays flexible down to about -20 deg C, so it handles freeze-thaw cycles better than rigid sheet.
It is not rated for oil, gasoline, or hydrocarbon lines - those fluids soften and swell the rubber.

Where Red Rubber Gaskets Fit - and Where They Do Not

Use red rubber where the fluid is water, steam, or air and the pressure is low. It is the default gasket for building heating mains, sterilizers, low-pressure autoclaves, and general utility piping. See our full range of gaskets for other services.

Low-pressure steam and condensate return lines in plants and hospitals.
Hot and cold domestic and process water, including potable water where the compound is certified.
Compressed air and HVAC chilled-water loops.
Do not use it for oils, fuels, solvents, refrigerants, or strong oxidizing acids.

SBR vs EPDM vs Spiral-Wound: Pick by Service

Pick the material by the hottest fluid it will ever see, not by the average:

Parameter	Red Rubber (SBR)	EPDM	Spiral-Wound
Max continuous temp.	~93 deg C (steam) / ~120 deg C (water)	~150 deg C	~550 deg C (with filler)
Oil / fuel resistance	Poor	Poor	Excellent (metal)
Steam suitability	Low-pressure only	Good	Excellent
Compressibility	High (soft sheet)	Medium	Low (needs filler)
Typical cost	$	$$	$$$
Best use	Low-pressure steam, water, air	Hot water, weather, higher temp	High-pressure, high-temp flanges

Practical rule: for steam above 150 deg C or any oil-bearing service, drop sheet rubber in favor of EPDM or a metallic gasket. For mild service, red rubber gives the best return per dollar. Match the gasket to the flange type and pressure class before you bolt it down.

Installation and Torque Notes

Red rubber is soft, so the failure mode is over-compression and extrusion, not bursting. Snug the bolts to the flange-class torque value in three passes (30, 60, and 100 percent of the target) and stop - extra torque does not improve the seal, it crushes the sheet and invites blowout. Replace the gasket every time the flange is opened; the compression set is permanent. Store sheets flat, away from sunlight, ozone (electric motors), and oil.

FAQ

What is a red rubber flange gasket made of?

A rubber sheet based on SBR with a red pigment. It is a soft, compressible seal for low-pressure flanges, not a rigid or metallic gasket.

Can red rubber handle steam?

Yes, low-pressure saturated steam to about 200 deg F (93 deg C) and 150 psi in standard grade. For hotter steam, use EPDM or a spiral-wound gasket.

Is red rubber safe for oil or fuel lines?

No. Oil, gasoline, and hydrocarbons swell and soften SBR. For oil service use a metallic or PTFE gasket; EPDM is also poor with oil.

How tight should I bolt it?

To the flange-class torque value in three passes (30, 60, then 100 percent). Do not over-torque - the soft sheet crushes and can blow out.

Can it be reused?

No. Replace it on every flange opening, because the compression set is permanent and the seal will not recover.

Red rubber or EPDM for outdoor hot water?

EPDM for better heat, ozone, and UV resistance outdoors. Red rubber is the lower-cost choice for low-pressure steam and water indoors.

SAE J518 Flanges: Reliable Connections for Hydraulic Systems

EPDM Gasket Material Properties 60 Durometer Rubber EPDM vs Neoprene

Burr-free bolt edges are the basis of accurate preload: burrs scatter torque, cut gasket surfaces and trap moisture at the thread runout. Compare hand, brush, tumble and CNC deburring, then check the chamfer.

How to Efficiently Remove Burrs from Bolt Edges

2026-07-23

Most insulating gasket purchases fail on material substitution, missing electrical data and weak supplier screening rather than on price. Ask for samples, third-party test reports and case history before the order.

What pitfalls should you watch out for when purchasing insulating gaskets

2026-07-14

Gylon 3500 is Garlock's modified PTFE gasket sheet for acid and solvent service, and counterfeits are common when buying in China. The guide covers supplier screening, three authenticity checks and the pricing levers.

How to Buy Genuine Gylon 3500 Insulating Gaskets at Competitive Prices in China

2026-06-25

Bolt length is defined by head type: under-head for hex and socket heads, full height for countersunk, total length for studs. L = S + H + P turns clamped thickness, nut height and protrusion into one standard length.

Stop Guessing: The 3-Second Rule for Perfect Bolt Length

2026-06-17