Waukesha Tru-Fit Gearcase vs. ISR- What are they and which should I use?

At Triplex Sales, we specialize in providing novel solutions to our customer’s complex process challenges. We have a number of tools to help us do this, and in today’s post, we’ll be taking a look two of them- the Tru-Fit and Integral Speed Reduction gear case options for Waukesha pumps. Specifically, we’ll be looking at what they do and when you should consider them.

To start, what do the Tru-Fit Gearcase and ISR options do? In short, both do essentially the same thing- they allow us to eliminate a jaw type coupling between the pump drive shaft and the gear reducer shaft, creating a direct drive and saving significant space. In eliminating the coupling, we also eliminate the need to align shafts or have a coupling guard that could create a potential hazard.

Next, let’s take a closer look at the history of each. The ISR was originally developed about 30 years ago in house by Waukesha Cherry Burrell. Originally developed to eliminate the need for a jaw or long coupling, the ISR comes in three sizes- the model 49 for the 30 series pumps, model 79 for the 60 and 130 pump sizes, and the model 239 for the 220 series of Universal Pumps. The model 49 is suitable for 1.5-7.5 HP, which the 79 and 239 are suitable for 3-10 HP and 7.5- 30 HP, respectively. Available only in cast iron, each model has ~4 or 5 different gear ratios (i.e. output speeds).

While the Tru-Fit gear case option accomplishes the same thing, it’s quite a bit different than an ISR. The Tru-Fit is a hollow bore Nord reduction unit that SPX creates a special adapter for to match with a Universal pump. It’s “newer” than the ISR and features a large range of sizes- with about 10-20 gear ratios available per horsepower size. Available for both horizontal and vertical porting applications and in both carbon steel and stainless steel, the Tru-Fit gearcase allows us to save a huge amount of footprint and avoid having to align pump and motor shafts.

So if you want to eliminate a coupling and save space, which one should you use? Unless you have a large install base of existing ISRs, we suggest you go Tru-Fit. The Tru-Fit gives us all the advantages of coupling elimination- smaller footprint, no shaft alignment, no coupling guard, and is available in a number of different sizes and horse powers. It is well supported by Nord and readily available. The ISR is only available in very certain frame sizes (for instance, you couldn’t use a 15 HP 250TC frame motor with a U1 Model 130) and there are only four gear ratios per size. It also is not available in stainless and isn’t great for higher speeds.

For that reason, in applications where we are looking to eliminate a jaw type coupling, we’ll push our partners towards a Tru-Fit. Being the latest and greatest, it’s available in stainless steel and a number of horsepower and reduction ratios that you can tailor to your application. In fact, our new “standard” pump setup at Triplex is an all-stainless steel Universal pump paired with a stainless Tru-Fit gear case and stainless motor on a stainless steel round tube base. Absolutely stunning.

But if you have a facility full of ISRs, don’t worry, Triplex is  still here to help and support you with your new units, maintenance, and parts. Just don’t be surprised if we try to steer you in another direction for your next application.

If you have any questions about either Tru-Fit, ISR, or any sanitary PD pump option, please contact a Triplex Sales Engineer today.