Dash numbers (often written as -4, -6, -8, etc.) are a standardised way to specify the size of hydraulic hoses and fittings. This system of numbers is crucial for ensuring proper component matching in hydraulic systems.

How to Read Dash Numbers

In flexible hoses, the dash number represents the hose’s nominal INNER diameter in sixteenths of an inch. For example:

Dash Size	Inner Diameter (inches)	Common Applications
-4	4/16″ = 1/4″	Small hydraulic systems, pilot lines
-6	6/16″ = 3/8″	Medium-duty equipment
-8	8/16″ = 1/2″	General industrial equipment
-12	12/16″ = 3/4″	Heavy construction equipment
-16	16/16″ = 1″	Large industrial machinery

In a hardline or tubes, the dash number represents the tube’s nominal OUTER diameter in sixteenths of an inch.

Selection Tips

When selecting a hydraulic hose size, consider:

• Required flow rate of the system
• Maximum operating pressure
• Pressure drop limitations
• Space constraints in the application

Important Considerations

• Pressure Ratings: Larger dash numbers typically handle higher flow rates but pressure ratings depend on hose construction
• Flow Velocity: Proper sizing ensures optimal flow velocity
• Compatibility: Always match dash numbers between hoses and fittings to ensure proper sealing

⚠️ Always consult manufacturer specifications and pressure ratings when selecting hydraulic hoses. Incorrect sizing can lead to system inefficiency or failure.