Push-Lock Hose Assembly Fitting Installation

Push-lock hose and fittings offer a reliable, clamp-free solution for pneumatic systems up to 350 psi. Specialized barbs ensure a secure, leak-free connection, and proper tools simplify installation while maintaining safety and integrity.

Push-lock is the generic name for a system of hose and fittings, AKA; Push-Lok®, Push-On, Insta-Grip, Field Attachable, etc. depending on manufacturer. It is a great product that allows quick on-site assembly of hose assemblies used for hydraulic, pneumatic, and fluid power systems that operate at maximum pressures up to 350 psi. The hose is available in inside diameter trade sizes of #4 (¼”), #6 (⅜”), #8 (½”), #10 (⅝”), #12 (¾”), and #16 (1”),

A partial list of markets where it is used in the fluid power industry:

Transportation
RV & Bus
Military
Construction
Agriculture
Grounds & Building Maintenance
Forestry
Railroad
Utility Equipment
Personnel Lift Equipment
Machine Tool
Oil Field Service
Waste & Refuse
Material Handling
Marine
Paving & Road Maintenance
Aviation Ground Support Equipment
Industrial Automation
Mining
Automotive Manufacturing
Plastics Forming

One major advantage to the push-lock system is clamps or crimp sleeves are not used nor recommended to secure the fitting into the hose. This makes for a physically smooth connection that is safe to handle, saves assembly time, and will not loosen. Connections that require clamps or crimp sleeves can loosen with time and use as the hose material ages, resulting in leaks. Additionally the clamps themselves can have unsafe sharp edges to work around or handle, (See Photo Upper Right).

The push-lock system is not perfect though. Installing fittings can be physically challenging and must be done correctly to avoid potentially dangerous blow-off situations. Often modifications are made to the hose by heating the end with a heat gun and/or using grease on the fitting barbs, though it does make the assembly easier, the practice has likely compromised the hose fitting connection and should not be put into service.

Understanding the design of the hose and fittings is the best way to make sure the hose / fitting connection is leak free and can meet the design pressure.

Push-lock Fittings are designed and manufactured to make the connection between hose and a large number of common industry standard connections such as National Pipe Thread, JIC, SAE 37° Flared Fittings, Nut and Ferrule, to name a few. Fittings are available in brass, plated steel or stainless steel. The unique feature is the specially designed barbed section on which the hose will be installed. It contains three distinct barbs that have a taller profile from root to peak than standard barb fittings and lock into the inside liner of the hose, (See Photo Upper Right). The space in between barbs allows the hose to fully conform to the barb and creates a very effective connection. The two outer barbs actually grip the inside diameter of the hose. The third barb creates a shoulder for holding the tell tail plastic yellow cap that covers the end of the hose when installed.

The Hose for push-lock fittings has inner and outer rubber layers laminated together with a high tensile fiber braid or mesh laminated in between them that is designed to work like a Chinese finger trap. The rubber materials can include Nitrile (Buna N), EPDM, Neoprene and can be used in combination. When pressing a fitting into the hose, the hose must grow in size to get over the larger diameter of the barbs on the fitting. Once the hose is completely pushed onto the fitting up into the yellow cap, the internal liner material conforms to the 3 barbs on the fitting. As pressure is applied, the braid and rubber laminations shrink around the barb creating a pressure tight seal.

Hose designed for push-lock fittings is available to meet many temperature, pressure and chemical requirements. It is also available in multiple colors to aid in color coding applications where multiple hoses perform different functions.

Installing the hose onto the push-lok fitting may seem like a simple task but it is more like trying to push a rope up a hill. There are several factors that further complicate the process:

Hose temperature: The colder the hose, the less it will want to expand to get over the barbs on the fitting.
Hose diameter: #6 (3/8”) through #12 (¾”) diameters have lower insertion forces so are easiest to assemble. #4 (¼“) hose is typically the toughest to install because it doesn’t have as much material to expand to get over the barbs on the fitting. The barbs on the fittings are the same height from root to peak regardless of overall diameter so the smaller hose needs to stretch a larger percentage to get over the barbs. Additionally, the small overall diameter hose is much harder to grip and create enough force with your hands to push over the barbs. At the other end of the spectrum, the insertion force on #16 (1”) or hose increases because of the larger surface area and it has a tendency to collapse then being pushed onto the fitting due to a relatively thin wall.
Fitting Style: 90° and 45° elbow fittings (See Photo Lower Left), that incorporate a small piece of bent tubing between the barbs and the adjacent port connection don’t have a surface perpendicular to the axis of the barbs. Pushing a hose on them can be a real challenge. Stabilizing the fitting by putting it in a vice to push the hose on by hand can mare the finish and compromise the fitting. Banjo fittings (See Photo Lower Right), have a spherical surface to push against so they can be tough to assemble without a special fixture to stabilize them while pushing them into hose. It may appear they can be clamped in a vise by the flat sides of the ball shaped end but those are actually sealing surfaces on which there will be sealing washers and should not be compromised. Tube stub fittings, (See Photo Upper Left), that connect push-lock hose to a metal tubing connection should not be vice held as it will damage the ferrule sealing surface. Pushing the hose onto the fitting with the tube end against a flat surface typically just causes a slide-out with hand injury and can also deform the end so that the nut and ferrule may not fit. Performing on-site or in the field installations without a way to hold the fitting is nearly impossible.

Creating a constant pressure and feed rate once fitting insertion has started is the key to successfully complete an installation. The hose quickly conforms to the shape of the barbs. With hand installation the hose can generally be pushed over the first 2 barbs. However, in the time it takes to reposition your hands for the last push, the hose liner conforms to the shape of the first two barbs. Good luck getting it moving by hand again. We hear a lot about getting the hose halfway onto the fitting and it won’t go any further. Without the aid of an operation specific tool that can create enough force to finish the insertion, there is not much choice other than to cut the hose off and start over.

Assembly Tools can simplify the hose-fitting assembly process and there several different ones to choose from. The tools that are available are generally hand operated and in one way or another multiply hand or arm force to press the fitting into the hose. Portability is a consideration. Most of the assembly tools are designed to be mounted on a bench. Most of the time an assembler has to take the hose to the tool. Taking the tool to the application saves time and ultimately money. If you are working with the specialized fittings that we mentioned earlier, it is important to select an assembly tool that can easily adapt to those fittings to hold it stable while pushing the hose on. Many bench mounted tools do not easily adapt to elbows, banjo or tube stub fittings.

Hose Safety is very important. Heating the end of push-lock style hose and/or using oil or grease to ease assembly SHOULD NOT be done. There are approved water soluble lubes for assembly of stubborn fittings. One such products is P-80 Emulsion, it provides a thin film of lubrication to significantly reduce friction when assembling rubber or soft plastic parts and it dries without compromising the connection.

When making or repairing hoses for any purpose, DO NOT mix fitting and hose styles. Hose that is not designed with the appropriate internal braid pattern will not create a satisfactory connection to push-lock fittings. It is also true standard barb fittings will not hold in push-lock hose without clamps or crimp sleeves. If not sure, replace the complete hose assembly using known components.

Push-lock hose and fittings can save time and money in applications where cut to length is important. Easing the installation process for the installer with a point of use tool ensures the barb hose connection is fully and safely installed. Barb-Tech Push-Lock Tools meets the needs for these applications.