Direct Interchange vs. Like Product: Understanding Pneumatic Component Compatibility

When it’s time to replace a pneumatic cylinder, do you need a direct interchange, or will a like product do? Knowing the difference will ensure ultimate compatibility. 

Form, Fit, Function

Before selecting a replacement cylinder, know what you're comparing. These three factors determine whether you have a true direct interchange or a like product. That distinction matters for how the cylinder installs and performs.

Direct interchange means the replacement cylinder is exactly like the incumbent cylinder in dimension and performance, and should function in the same way.

Like product means the cylinders are not exactly the same, but the new one should work to perform the same task. To spec a like product that will be truly compatible, you need to consider

Form

Form is the starting point. Before considering dimensions or performance, the replacement cylinder needs to be the same type as the original. A double-acting cylinder can't be swapped for a single-acting one without changes to how the system operates. The same goes for rod style, body style, and mounting configuration. If the form doesn't match, fit and function become secondary issues.

Fit

Bore size, stroke length, and overall dimensions all affect fit. The machine may have been designed specifically to accommodate the incumbent cylinder, so a different product could change performance. Dimensional changes can affect performance, though in some cases it can be an improvement.

For dimensions, the key consideration is usually standard (Imperial) vs. metric. ARTEC cylinders, for example, are ISO-certified, which means they follow consistent physical standards. If you have an ISO cylinder already and need to replace it, you can spec the same ISO style and expect it to fit and perform similarly. 

Function

The replacement cylinder must perform the same way as the original. In some cases, that means a direct interchange is the only option. In others, a like product will work, sometimes with minor modifications.

ISO bore sizes are metric, but are often close to standard dimensions. 1 inch and 25mm, for example, are similar enough that a like product can work even if it's not a precise match. That said, if performance requirements are tight, even a slight difference could alter performance.

Porting is typically different. Metric cylinders may have metric or BSPP porting, while standard cylinders are more likely to have NPTP porting. If the incumbent cylinder is already pre-plumbed, you may need an adapter to assure proper fit.

Threading is also different, so if you’re switching between Imperial and metric, the new cylinder may need an adapter to fit. With the right adapter in place, it should work as expected.

Materials

Even if a cylinder checks out on form, fit, and function, there's one more thing to consider: are the materials the same quality?

ISO standards do not cover material quality, so cylinder component materials may vary. This can also affect different brands or styles of standard cylinders. Material differences could affect wear on pistons and seals, which impacts how long the cylinder lasts. Higher quality seals, for example, offer better protection and a longer service life, but a lower quality replacement could mean the opposite.

If you’re upgrading to a higher quality product as a replacement, it likely won’t be a direct interchange. Even if the bore and stroke match, you may still need to adjust the mounting position, swap out fasteners, or add a spacer to get the fit exactly right.

With these details in mind, ask yourself: if I’m doing a direct interchange, will I need to change anything else?

Ask Our Experts

It might sound overwhelming to choose the correct replacement cylinder, especially when you’re looking for a like product. Our engineers are here to help.