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Arrow-white What you need to know about fitting your new coupler and attachments


Apr 19, 2021

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59 mins read

In this Explainer Series article, we'll be answering some common questions that come up about fitting couplers and attachments

So you've got yourself a new excavator, or perhaps you're upgrading your existing machine with a new Tilt Hitch or adding a new Hydraulic Attachment.


Simon Johnston

Mark Gulliard

Robin Stolte

Published 24th March 2021

Question 1:

Where do you start?

It all starts when selecting a new coupler or attachment, particularly with couplers, machine-specific models may be available to cater to a unique hydraulic system (low or high pressure) and for an optimal fit (including space for fittings).

Next is determining your new or existing excavators hydraulic capabilities, and features. Researching what you have to work with will help you decide what you will need to have added (if needed). There are some larges variances here specific to every model and factory specification that we can't cover in just one article; this is where a Hydraulic Specialist can help, more on this later.

Talk to your excavator dealer or coupler supplier for advice on your excavator.

Hitch Circuit

Dedicated Tilt Line

Auxiliary Line 1

Auxiliary Line 2

Question 2:

What are the differences in fitting Couplers and Attachments to an Excavator?

Not all machines come the same from the factory! Some come bare stick (that is no lines and sometimes G.P. bucket). Others may come with a hitch circuit and auxiliaries or even a combination of the latter. The important thing here is the variability in hydraulic systems on excavators.

A Hydraulic Specialist is important here, they can advise and build the best solution for your machine. Let's focus on what will likely be needed to fit a coupler or attachment.

Mini-Tilt or ✓ 
Heli-Tiltor ✓ 
Ram-Tiltor ✓ 
Hydraulic Attachment
(Single Function)
Hydraulic Attachment
(Double function)

The difference in fitting a Coupler (or Tilt Coupler) to an excavator is the use of a Quick Hitch Circuit and either the shared use of an auxiliary or dedicated line for the Tilt function. Discussing with a Hydraulic Specialist is crucial to get the solution that suits the excavators intended role.

A solution from a Hydraulic Expert will involve these things:

  • The installation and design of a Quick Hitch Circuit if not installed or connecting up one that is.
  • Installation and design of Hydraulic piping and hoses from either the boom or dipper if already there, or back to the valve bank.
  • Installation and design of extra valves at the valve bank to support the extra functions.
  • Installation, design or setup of where and how all these different functions are controlled.
  • Setting of flows, testing the system and ensuring correct functionality and speed.

As a basic overview of fitting off standard couplers and attachments, by no means is this exhaustive.

Question 3:

Why don't hose kits come with Couplers and Attachments?

It's reasonable to ask if there are different options for fitting a Coupler or Attachment, but as considered, there are too many variances in OEM factory builds and potential set-ups by an operator that making a 'DIY' kit is not possible.


A reliable and competently built hydraulic system should not be underestimated.

Although hoses may be supplied to specific machines as a 'kit', it is typically limited to standard fitments, of a standard length and type. It's a one-size fit all approach that works as an exception to the rule, not the other way around.

Having a Hose Specialist make and route the hoses will always result in a good fit as lengths are made to suit the attachment. They account for its movement (E.G. on a Tilt Coupler), making sure they're not too short or long, and they'll route them to minimise breakages. A Hose Kit doesn't provide any cost savings when compared to having Hose Specialist make them up for you.

As you can imagine having a Hose Kit for even popular Excavator Models would require extensive research and a lot of stock. Everyone has different preferences; it just couldn't match getting it right the first time.

Hydraulic Expert and Hose Specialist (hosie) what's the difference?

Hydraulic Experts will design, install, build and tune a hydraulic system to fit what's required, this includes adding valves, solenoids, switches, programming the computer that controls the hydraulics and more.

Hose Specialists will makeup and route hoses, add piping, set flows and do general work on a hydraulic system.

Getting the right person for the job saves you cost both ways, as getting it done right increases productivity and reliability. 'Workaround' solutions should be avoided; from our experience, workarounds are the most problematic.

Terminology and Concepts explained:

Hydraulic Flow: in metric this is measured by litres per minute or expressed as LPM, l/min

Rule for working out Hydraulic Flow and Attachment speed:
l/min / 60 x cylinder volume (l) = time in seconds for one full actuation.
(this does not account for any restrictions in the system like fittings, hose diameter or resistive forces)

In this Section:

The Hitch Circuit Explained

Attach2 Sure-Grip Quick Coupler

Hitch Circuit Diagram:

  1. Hydraulic Tank
  2. Safety Switch
  3. Pump
  4. Pressure Relief Valve
  5. Solenoid
  6. Two-Way Valve

What is a Hitch Circuit?

More excavators are now coming with a hitch circuit as standard and as a rule, have these common components: Hitch Control Valve, Solenoid, Pressure Relief and Control Switch.

The Hitch Control Valve explained: The Control Valve is a 2-way valve that operates the lock and unlock (also referred to as clamp and unclamp) function of the Coupler.

The Solenoid Explained:

The Solenoid is an electronic on/off actuator that alters the diverter valve state in the Control Valve, this is controlled from the cab by the Coupler Control Switch.

The Pressure Relief Explained:

A Pressure Relief prevents over-pressurisation of the system and damage, once the pressure goes beyond a pre-set limit flow is bypassed back to the tank. This can happen at the end of the cylinder stroke.

The Control Switch Explained:

The Control Switch is a crucial safety element and is what the operator uses to control a Quick Couplers function. Since a switch is open to error, it must contain some safeguards to prevent this and ensure reliable, straightforward operation of a Quick Coupler. A Control Switch's procedure can vary by excavator as some models now come with one built-in. Still, generally, all Control Switches should follow the ISO standard of basic operation.

Dedicated Tilt Line explained

Attach2 Heli-Tilt Quick Coupler

Dedicated Tilt Line Circuit Diagram:

  1. Hydraulic Tank
  2. Toggle Switch
  3. Pump
  4. Pressure Relief Valve (Excavator)
  5. Solenoid
  6. Four-Way Valve
  7. Pressure Relief Valve (Heli-Tilt Actuator)


More excavators are coming with two auxiliary lines these days, so generally a dedicated tilt line may not required. You will require a dedicated tilt line if your machine comes with no auxiliary lines or it comes with one auxiliary line, and you need to use that auxiliary line to power another attachment whilst using the tilt function.

A lot of these parts function similar to the hitch circuit but is tuned to suit the tilt function.

The Four-Way Control Valve Explained:

The Control Valve is a 4-way valve that operates the tilt function of the Coupler.

The Solenoid Explained:

The Solenoid is an electronic on/off actuator that alters the diverter valve state in the Control Valve, this is controlled from the cab by the toggle switch.

The Pressure Relief Explained:

A Pressure Relief prevents overpressurisation of the system and damage, once the pressure goes beyond a pre-set limit flow is bypassed back to the tank. This can happen at the end of the tilt action, or if there is too much pressure applied to the tilt coupler. This can be adjusted by a Hydraulic Expert.

Auxiliaries explained

Auxiliaries what are they?

In this instance, Auxilliary lines are hydraulic lines that provide power to hydraulic attachments; they are routed using lines from the Valve Bank to the dipper arm and terminate with some type of QRC. An operator can then connect a hydraulic attachment and use the appropriate control to actuate it. Where variances in set-up occur is their valve set-up on multiple lines.

E.G. A Tilt Coupler can 'T' off an Auxilliary using a tap, this saves the cost of adding in extra Valves for another auxiliary/dedicated Tilt line. However, this means a hydraulic attachment cannot be used simultaneously with a Tilt Coupler.

A Quick Hitch Circuit must be dedicated.

Common Complaints Answered

These are some of the common questions and complaints we get that can be traced back to how something is fitted or programmed; in most instances, some simple adjustment by a skilled technician fixes it.

My Tilt Coupler moves too slowly

(See rule for working our Hydraulic Flow) Having the Hydraulic Flow set to the preferred LPM will help speed up or slow down the actuation of the piston (cylinder or motor).

My Tilt Coupler relieves without much force applied

Excavators have a built-in relief valve in the hydraulic pump and sometimes the individual valves, the relief prevents over pressurisation, a hose burst from occurring, or worse. Some equipment allows these to be adjusted and can come from the factory set too low for a Tilt Coupler. (See section: Dedicated Tilt Lines, diagram point 4)

My Coupler starts locking or unlocking as soon as I hit the switch

Any number of different scenarios can cause this. The key is the circuit is getting enough pressure without operator input to start actuating, a Hydraulic Expert can find out where and why this is happening and configure the machine so the Coupler only starts activating during crowding or curling.

Product Explainer Couplers

Simon joined the Attach2 team in 2018 and is well known for pointing a big camera around in addition to typing, lots of typing. He has a varied background in construction and management and is passionate about using his experiences to see businesses succeed through excellent visual and text-based communications. And yes Simon wrote this in 3rd person about himself."

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