Quick Answer
For a -8 ORB adapter, use the O-ring that comes with the fitting for a reliable seal; only use a crush washer as a backup when the O-ring is damaged or missing.
Why O-Ring Sealing Is the Default for ORB Fittings
O-Ring Boss (ORB) fittings are designed to seal with an O-ring seated in a groove on the fitting's face. When tightened against a flat port, the O-ring compresses to create a positive seal that resists vibration and thermal cycling better than a crush washer.
A crush washer, by contrast, relies on deformation to fill gaps. It can work, but it is not the intended sealing method for ORB ports. Using one may void warranty or lead to leaks if the washer is over-tightened.
When a Crush Washer Might Be Acceptable
If you lose the O-ring or have a port that is scratched or pitted, a crush washer can provide a temporary seal. Choose a washer that matches the port size (e.g., -8 ORB uses a 5/8-inch washer) and replace it every time you disassemble the fitting.
Keep in mind that a crush washer is a one-time-use component. Reusing it increases the risk of leaks.
Why the Adapter Material Matters
The 5/16" Quick-Connect to -8 ORB Adapter from ACUITY is machined from 7075-T6 aluminum, which is stronger than typical 6061-T6. This reduces the chance of stripping threads or cracking the hex when you torque it, which helps maintain a proper O-ring seal.
The anodized finish also resists corrosion, keeping the sealing surface clean and preventing leaks over time.
How to Seal a -8 ORB Adapter: Step-by-Step
- Inspect the O-ring and port: Check that the O-ring is seated in the groove and free of cuts. Clean the port face with a lint-free cloth to remove debris. Never install a damaged O-ring; replace it before proceeding.
- Apply a light lubricant: Coat the O-ring with a thin layer of engine oil or assembly lube to help it seat without rolling. Do not use thread sealant on the O-ring; it can cause the O-ring to slip.
- Hand-tighten the adapter: Thread the adapter into the ORB port by hand until the O-ring contacts the sealing surface. Stop hand-tightening as soon as you feel resistance; do not force it.
- Torque to spec: Use a torque wrench to tighten to the manufacturer's recommended value (typically 18-25 ft-lb for -8 ORB). Do not exceed the spec. Over-tightening can crush the O-ring or damage the port.
- Pressure test and check for leaks: After installation, pressurize the system and inspect the joint for leaks. If a leak appears, re-torque slightly or replace the O-ring. A leak after re-torquing means the O-ring is damaged; replace it rather than tightening further.
Product Facts
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5/16" Quick-Connect to -8 O-Ring Boss (ORB) Adapter, 62mm flange to tip: This adapter uses 7075-T6 aluminum and is anodized for durability, with a flanged hex to avoid wrench damage. The stronger material and protective finish help you achieve and maintain a leak-free O-ring seal without damaging the fitting during installation.
5/16" Quick-Connect to -8 O-Ring Boss (ORB) Adapter, 62mm flange to tip