Dielectric Insulated Unions

Fail Safe Leakproof Reliability
At any pressure, HART O-Rings actually strengthen the seal rather than loosen it.STANDARD O-RINGS | |
V | Viton® Florocarbon A (FKM-A) |
E | Ethylene Propylene (EPDM) |
ES | High-Temp Steam EPDM [up to 550*F max] (EPDM E0962) |
T | Teflon® Tetrafluoroethylene (PTFE) |
B | Nitrile / Buna N (NBR) |
SPECIALTY O-RINGS / SEALS | |
N | Neoprene® Polycloroprene (CR) |
K | Kalrez® 4079 Perfluoroelastomer (FFKM) |
HN | Hydrogenated Nitrile (HNBR) |
EP | NSF-61 Approved EPDM (Ethylene Propylene) |
G | Metallic Graphite Spiral Wound Seal |
I | No O-Ring (Integral Seat "Ball to Cone") |
Teflon®, Viton®, Kalrez® are Registered Trademarks from DuPont |

Static
The O-ring is fitted into a machined groove between the two halves of the union. When the halves are drawn together the O-ring compresses to an ovalized cross-section, forming a positive, resilient seal which serves to block the fluid, thus sealing even at low or no pressure.
Under Load
As pressure is increased the O-ring is forced to flow and is "squeezed" into the downstream side causing the O-ring to conform to the shape of the end, blocking the groove gap. The more the system pressure increases, the more effective the seal.Straight-Away Breakout
The flat faced construction allows for slipping the component in and out without disturbing the surrounding tube or pipe sections. Pipe alignment is much easier with Hart Unions since it is unnecessary to spring the line during make-up or disassembly.
Specialty Orders
Specialty O-Rings also available. Inquire within.Ordering
The charts below contain all the information necessary to place an order. Use the appropriate codes in the manner shown below.Example: a Class 3000 Female Threaded 1" Union with Viton O-ring and 316 Stainless Steel Ends is coded as follows:

When a size reduction or change in material is needed, simply enter the Tailpiece code and then the Threadpiece code separated by a slash as shown below.
Example: A Dielectric Class 3000 Union with a Dielectric Coated A105 Carbon Steel Tailpiece that is 3/4" Female NPT, with a 304 Stainless 1/2" Male NPT Threadpiece, Teflon O-Ring, is coded as follows:

For more information, a quote, or to order, call 1-800-769-0503 or contact us at sales@hartindustries.com
DESCRIPTION | TAIL | THREAD PIECE | SIZE | O-RING | ||||||||||||||||||||||||||
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Female NPT (FNPT) Class 3000 Pipe | 31 | 31 | 0 (1/8") 1 (1/4") 2 (3/8") 3 (1/2") 4 (3/4") 5 (1") 6 (1 1/4") 7 (1 1/2") 8 (2") 9 (2 1/2") 10 (3") 11 (3 1/2") 12 (4") |
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Male NPT (MNPT) Class 3000 Pipe | 32 | 32 | ||||||||||||||||||||||||||||
Socket Weld (SW) Class 3000 Pipe | 33 | 33 | ||||||||||||||||||||||||||||
Socket Weld (SW) Class 3000 Tube | 34 | 34 | ||||||||||||||||||||||||||||
Butt Weld (BW) Class 3000 Pipe | 35 | 35 | ||||||||||||||||||||||||||||
Sweat Copper Tube | 36 | 36 | ||||||||||||||||||||||||||||
Female NPT (FNPT) Class 6000 Pipe | 61 | 61 | ||||||||||||||||||||||||||||
Male NPT (MNPT) Class 6000 Pipe | 62 | 62 | ||||||||||||||||||||||||||||
Socket Weld (SW) Class 6000 Pipe | 63 | 63 | ||||||||||||||||||||||||||||
Socket Weld (SW) Class 6000 Tube | 64 | 64 | ||||||||||||||||||||||||||||
Butt Weld (BW) Class 6000 Pipe | 65 | 65 |
MATERIAL | OPTIONS (PREFIX) | ||||||||||||||||||||||||||||||||||
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CUSTOM OPTIONS AVAILABLE | ||||||||
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Call to Order: 800-769-0503
Dielectric (Insulated) Series
Class 3000 and 6000 Unions





Unions can be provided with any connection type on the threadpiece side (welded, sweat, threaded, etc) and can be made to transition between different piping sizes!
HART Industrial O-Ring Unions are engineered to provide Class 3000 and 6000 Service and are the most popular union in the industry for general purpose applications. The flat face design provides turbulence-free fit across seats. This design is ideal where piping requirements dictate the necessity of having a flat face seal to make and break the pipe line. All HART Unions are made in the USA!
Standard O-Ring Union Features:
- Turbulence Free: All unions provide a turbulence-free fit across the seats
- O-Ring Isolation: The O-Ring seal is strategically located in the thread piece face reducing O-Ring media contact and added protection against abrasives and erosion.
- Precision Machined components: All unions are precision machined to provide high quality and fail-safe leak proof reliability.
- Interchangeable End Connections: Threaded, socket weld, and butt-weld ends are interchangeable. This feature reduces overall costs by eliminating unnecessary nipples, bushings, couplings and inserts.
- Material Versatility: Unions can be provided in all standard metals or combination of metals. This includes 304 Stainless, 316 Stainless, A 105 Carbon Steel, Brass, Monel 400, Hastalloy, and Titanium.
- Excellent vibration resistance: Seals will not loosen, even under extreme pressure and pressure surges.
3D Animations

Specifications
Standard O-Ring Union Features:
• Turbulence Free: All unions provide a turbulence-free fit across the seats• O-Ring Isolation: The O-Ring seal is strategically located in the thread piece face eliminating O-Ring media contact and added protection against abrasives and erosion.
• Precision Machined components: All unions are precision machined to provide high quality and fail-safe leak proof reliability.
• Interchangeable End Connections: Threaded, socket weld, and butt-weld ends are interchangeable. This feature reduces overall costs by eliminating unnecessary nipples, bushings, couplings and inserts.
• Material Versatility: Unions can be provided in all standard metals or combination of metals.
• Excellent vibration resistance: Seals will not loosen, even under extreme pressure and pressure surges.
• No maintenance: Once initial seal is made, no further tightening required
HART Dielectric Polymer Composite Coating
Hart Industrial Dielectric O-ring Unions are engineered to provide the most effective and efficient method of preventing electrolytic deterioration. The union design provides insulation against galvanic corrosion and also breaks current flow eliminating any stray corrosion.Coating Features (ASSE Standard #1079-2005):
• Excellent resistance to wear, abrasion, and shipping• Provides resistance to rust/corrosion per ASTM B-117 Salt Fog Tests.
• Operating temperatures from -100F to greater than +400F
• Excellent resistance to ultraviolet light
• Superior adhesion to a variety of substrates including Steel, Brass, Copper, Stainless Steel, Monel, and Titanium.
Fluid/Solvent Resistance (ASTM D1308-79):
• HCI (pH2) Hydrochloric Acid (room temp) No Effect• NaOH (50%) Sodium Hydroxide (room temp) No Effect
• MEK Methyl Ethyl Ketone at room temp No Effect
• Salt Spray (ASTM B-117)
• >500 hours- No Blistering
• Castrol Hydraulic Fluid at 200F Gloss decrease, no loss of coating integrity
• Ethylene Glycol at room temperature No Effect
Physical Properties:
• Typical Coating Thickness: 3-6 MIL• Pencil Hardness: H (ASTM B3363)
• Breakdown Voltage: >20000 volts at 650μm (ASTM D149)
• Volume Resistivity : 1.26 x 1016 ohm-cm (ASTM D257)
• Gloss Finish: High