Type D Isolation Gaskets
Type D isolation gaskets provide cathodic protection and sealing in high-pressure, high-temperature piping.
Description
Type D isolation gaskets are specifically designed to fit into the ring groove of ring-type joint flanges. They are manufactured to ANSI specifications and available in basic oval as well as octagonal shapes. Also available are BX gaskets with pressure ratings to 15,000 PSI.
The materials used for those gaskets are often phenolic, G10, or G11.
Components of a Complete Type D Isolation Gaskets
The gaskets are rarely used alone; they are often used with insulation sleeves, insulation washers and steel washers.
Central Gasket Retainer
The materials for the isolation gasket retainer in D types are often phenolic, G10, or G11. They fit tightly within the RTJ groove to handle fluid containment and joint isolation.
Insulating Sleeves
The sleeves are often G10, G11, Mylar, Nomex, or phenolic.
Isolating Washers
The isolating washers are often G10, G11, Mylar, Nomex, or phenolic.
Steel Backup Washers
The steel backup washers are usually zinc-plated carbon steel, as it is cheap. But SS304 or SS316 are also options. Each bolt hole has 2 steel backing washers.
Physical Properties of Isolation Gasket Materials
| Gasket Materials | Dielectric Strength | Compressive Strength | Water Absorption | Tensile Strength | Operating Temp (°C) |
|---|---|---|---|---|---|
| Plain Phenolic | 500 vpm | 25 ksi | 1.6% | 20 ksi | -54 - 104 |
| Neoprene Faced Phenolic | 500 vpm | 25 ksi | 1.6% | 20 ksi | -54 - 79 |
| G7 | 350 vpm | 40 ksi | 0.07% | 25 ksi | -196 - 232 |
| G10 | 550 vpm | 55 ksi | 0.1% | 45 ksi | -128 - 130 |
| G11 | 550 vpm | 57 ksi | 0.1% | 43 ksi | -45 - 176 |
| G10+SS316 | 550 vpm | 65 ksi | 0.1% | 50 ksi | -128 - 130 |
| Reinforced PTFE | 350 vpm | 2.3 ksi | 0.01% | 1450 psi | -196 - 260 |
