Durlon® 9000 Step Ring Gaskets
The innovative one piece Durlon® Step Gasket design prevents the possibility of gasket separation common in "glued" Step Gaskets

Durlon® Step Ring Gaskets are used extensively in Sulfuric Acid plants often found in Phosphate refineries. Applications include 150# RF (Floating) Lap Joint Flanges and Mondi™ Ductile Iron Sulfuric Acid Piping.

The Durlon® Step Ring Gasket is an improved Step Ring Gasket design which has been used in MONDI™ piping since 1985. Durlon’s Step Ring Gaskets have provided excellent service for many acid producers in a variety of demanding applications.

The Challenges

Acid piping systems are subject to thermal cycling through years of operation and aggressive chemical corrosion. It is important to use the proper gasket. GRI’s Durlon® Step Ring Gaskets are fabricated from Durlon® 9000. Durlon® 9000 filled PTFE gasket is compatible with sulfuric acid in all concentrations and has excellent physical properties such as sealability and recovery that maintain the seal even with extreme thermal cycling and vibration and with proper installation normally does not need to be retorqued. Durlon® Step Ring Gaskets will not cold flow into the pipe ID or outside the flange OD like other materials.

The Step Gasket Problem

Gasket Resources has improved upon the original design of the “glued” Step Ring Gasket that was specified and used for years. The old design Step Gasket consisted of a 1/16″ thick standard ring section plus a 1/16″ thick inner ring section. Both sections are bonded (glued) together. The standard ring section is for locating and centering within the bolt circle. The inner ring section is for sealing. Total thickness at the inside diameter is 1/8″ (3mm) in the critical sealing area.

What periodically happens is that the bond weakens and the gasket sections separate during disassembly, the separated gasket often travels down the pipe and ends up in a pump or valve. The pump or valve has to be disassembled, the separated gasket removed, and the pump or valve re-assembled, losing operating time and unnecessary maintenance costs and frustration.

The Solution

Gasket Resources has improved upon the original design of the Step Ring Gasket by maintaining the same dimensional design, but the gasket is CNC machined out of one piece of Durlon® 9000 gasket material. The one solid piece design prevents the possibility of gasket separation and the unneeded maintenance cost of ending up in your pumps and valves. Our Durlon® Step Gaskets are easy to install, they seal well and they remove with the peace of mind that gasket separation will not occur.

Please see our Durlon® Step Ring Gasket Literature for additional installation information.


  • Class 150 RF Floating (Lap Joint) Flanges
  • Mondi™ Ductile Iron Sulfuric Acid Piping
Warning: Durlon®gasket materials should never be recommended when both the temperature and the pressure are at the maximums listed. Properties and applications shown are typical. No application should be undertaken by anyone without independent study and evaluation for suitability. Never use more than one gasket in one flange joint, and never reuse a gasket. Improper use or gasket selection could cause property damage and/or serious personal injury. The data reported is a compilation of field testing, field service reports and/or in-house testing. While the utmost care has gone into publishing the information contained herein, we assume no responsibility for errors. The information and specifications contained in this website are subject to change without notice. This revision cancels and obsoletes all previous editions.