How to select your quick couplings? Guidelines to make the right choice in quick coupling types.

Which is the right type of quick release coupling for my installation?

Depending on the requirements, quick couplings can be divided into 2 different connection types: single connection couplings and multi-connection couplings. A single connector coupling manually connects both sides of the same fluid line. The multi-connection coupling allows for manual or automated connection of several fluid and/or electrical lines.

When choosing the connection type, assessing the compatibility between the quick coupler end, and the connecting end of the system is crucial for a seamless integration. We have identified eight factors that should be considered when deciding on quick coupling solutions.

By considering these factors, you can select the most suitable quick couplings that guarantee optimum flow of fluids, and flawless environmental and circuit integrity, while meeting safety, functionality, and efficiency requirements for your systems.

Factors to consider

The key criterias and aspects for our quick couplings are: safety, antipollution, fluid and environmental compatibility, customer installation, fluid flow passage, shutoff types and locking mechanism.

Safety is incorporated within our product ranges, from the earliest stages of design. It guides all our developments, for people’s health, respect for the environment and the integrity of industrial equipment. Accidents represent significant direct or indirect costs for industries. A significant focus for Stäubli is compliance with industry standards, and the increasingly stringent regulations.

Preventing connection errors: for example, color-coding or clear labeling minimizes the risk of mechanical misalignments.
Safety locking: Bayonet, double operation, Safety pin
High temperature: double shutoff technology
Breathing air supply: Stäubli's couplings comply with EN safety standards.
Compressed air: "anti-hose whip" system

Learn more about safety by reading our dedicated Safety whitepaper on this matter

There are 3 shut-off types:

Full flow: the line remains open after disconnection. Used for high gas flow rates that are non-hazardous, for an economical solution in simple low-pressure water circuits, or when using very viscous liquids.
Simple shutoff: only one side of the line closes upon disconnection. Used when there is no particular risk for the user or the environment.
Double shutoff: both sides close after disconnection. Prevents the loss of fluid in the pipes and contains potential pressure.

It is essential to ensure that the chosen coupler can handle the system's operational pressure effectively, without encountering any flow-related issues. The maximum allowable pressure during connection under pressure should be verified.

The nominal pressure refers to the pressure level designated for continuous operation, aligning with the quick connector's design. Pressure drop, measured in bars, signifies the pressure reduction within the quick connector. Controlling this drop is crucial to uphold optimal fluid flow and maintain adequate pressure levels.

Diameter and size

The size of the quick connector is determined by its length and outer diameter. The passage diameter, usually ranging from 2 to 50 mm, influences the flow efficiency of the quick connector. It is critical to match the coupler's size and diameter with the system's requirements to avoid flow restrictions or leakage.

Sealing guarantees that fluids remain contained when connecting or disconnecting. The sealing is ensured by elastomeric O-rings.

There are two main types of seals:

Piston-cylinder sealing: Piston seals maintain sealing contact between a piston and cylinder bore. There is no fluid loss upon disconnection.
Front sealing: suitable for a wide range of applications

An elastomeric seal is characterized by its dimensions, its material, and its hardness. Even with this type of seal, there is always a minimal risk of leakage. The leakage rate is commonly measured in Ncm3/s.

Parameters to consider for selecting and specifying the sealing material:

The nature of the fluid
Service pressure
Temperature range

Stäubli’s sealing rings for quick connectors are mostly made of Nitrile (NBR), Fluorocarbon or Ethylene-propylene.

Stäubli's research and development teams are dedicated to designing connection solutions that enhance the user experience of Fluid Connectors (FCS) quick connectors. What sets Stäubli quick couplings ahead and makes them the preferred choice?

1. Efficiency:

Automatic connection
Connector orientability
Connection of large diameters
Connection under residual pressure
Multi-connection and high connection cycles

2. Safety:

Key-lock fittings
Safety locking
Flat face non spill coupling technology
Filling handle for alternative fuels

3. Comfort:

Locking connectors
Color-coding
Locking sockets
Orientation of the control lever in multi-connection

Especially for transferring hazardous fluids, the anti-pollution function is important for preventing fluid loss, end air insertion during connection and disconnection.

The main application areas where the antipollution function is essential are:

Brake circuit in motorsports
Transfer of chemicals and pharmaceuticals
Liquid fuel supply
E-cooling and temperature regulation of electronic equipment
Hydraulic applications

What are the main criteria governing the choice of materials when designing a fluid connector? The material selection is related to the expected mechanical and chemical resistances and potential weight/volume constraints for onboard applications.

Mechanical resistance (pressure resistance, fatigue, number of connections...)
Chemical compatibility with conveyed fluids
Resistance to corrosion and external environment
Weight
Cost

Main materials are:

Brass
Stainless steel
Aluminum
Titanium alloy

The locking mechanism ensures the connection of a socket and a plug, holding both parts and then disconnecting them. There are 3 different types of locking connections:

1. Automatic locking connections which requires only one action to connect one part to another

2. Semi-automatic locking connections which requires a double action

3. Manual locking such as thread locking.

Various types of locking mechanisms exist for quick connectors:

Push-Button: intuitive and ergonomic
Ball: Common, versatile, economical
Needle or steel torus: Economical, cons: low pressure and bulky
Bayonet: Visual control of connection, compact and intuitive
Thread or screw: Pressure pulsation, high pressure
Claw: Compact, low pressure
Finger or gripper: Compact, high pressure
Pin: Ergonomic and economical, low pressure

Fast, easy and compact, ball locking is the most common in the market because of the high mechanical resistance, the residual pressure, the good resistance to vibrations, and minimizing the effort required for connection.

Factors to consider when selecting a locking type:

Service pressure, Usage and environmental conditions, Ergonomics, Safety, Cost, Shutoff

The benefits of Stäubli quick couplings

Stäubli offers a wide range of standard dry disconnected and quick couplings as well as highly specialized connectors compatible for all types of circuits and applications, meeting the needs of all industries. Stäubli’s connection solutions provide the following advantages: