RTD, RTX and SHP are the three AR industrial series, and people mix them up constantly. The short version: they are not three grades of the same pump. They sit at three different points on the flow-versus-pressure curve, and picking between them is mostly a matter of which end of that curve your job lives on.

Here is what we actually stock, so you can see the shape of it.

The AR industrial series at a glance

Read the flow column and the pressure column together and the whole thing resolves. RTD moves water. SHP makes pressure. RTX covers the middle and is the one that fits in a smaller space.

RTD: when you need volume

The RTD series starts at 21 GPM and tops out at 52.8. Nothing else in AR’s catalog moves that much water. It runs slow, 800 to 1000 RPM, on a 35 mm shaft, which tells you it is a belt-driven or gear-reduced pump and always will be.

Slow speed is the reason it lasts. Plunger seal life is largely a function of how many strokes the pump makes, and a 1000 RPM pump makes a third as many as a 3400 RPM one for the same hours on the clock.

A few specific models:

Note the trade. As flow climbs, pressure falls. That is not a limitation of the design, it is the power budget. Every one of those pumps is drawing somewhere in the 50 to 63 BHP range at full output.

One correction worth making. You will read that RTD pumps are suited to “mud and debris-laden environments.” They are not, and no triplex plunger pump is. These pumps need clean, filtered water. Grit destroys plungers and holds check valves open. The confusion comes from hydro-excavation, where an RTD is a common choice, but on a hydrovac the pump handles clean water going out and the vacuum system handles the slurry coming back. Two separate paths. Feed a plunger pump dirty water and you will be buying seals every week.

SHP: when you need pressure

The SHP series runs 7,250 PSI, which is 500 bar. Flow is 4 to 5.8 GPM. That combination is the definition of the pressure end of the curve.

The design change that gets talked about is the head, with the intake valves sitting directly above the plungers. That geometry lets the chamber fill more completely at high speed, which is what makes the pressure achievable without cavitation.

SHP is for surface preparation, coating removal, hydro-demolition and scale that will not come off any other way. It is a bad choice for general washdown. At 4 GPM you will be there all day, and 7,250 PSI will wreck most of what you point it at.

The SHPA series is the related line. The SHPA4G70HN runs 4 GPM at 7,000 PSI on an 18 mm shaft.

RTX: the middle, in a smaller box

The RTX series spans the widest range of the three, 7.9 to 39.6 GPM at 1,450 to 4,350 PSI, on a 30 mm shaft at 1450 to 1800 RPM. Smaller shaft, faster speed, smaller footprint than an RTD at comparable output.

RTX is also the line with the most variants, which matters when your build has a constraint:

• RTX85-SX and RTX100-SX are left-hand shaft, for when the drive has to come in from the other side.
• RTX-HW85.150N is rated to 185°F for hot water systems.
• RTX-SS100.100N has a stainless head for chloride and caustic exposure.
• The DD versions come as hydraulic direct-drive assemblies.

How to actually choose

Work in this order.

1. Pressure first. Above 4,350 PSI there is one answer and it is SHP. Below that, pressure rarely decides it.
2. Then flow. Above about 40 GPM, only RTD gets there. Under 20 GPM, RTX is usually the smaller and cheaper install.
3. Then check your power. GPM × PSI ÷ 1460 gives brake horsepower at the shaft. Size the motor 10 to 20 percent above it. An RTD200-100 wants roughly 52 BHP; an RTX30 wants about 24. That number often decides the whole thing before the pump does.
4. Then the mechanical fit. Shaft size, rotation direction, mounting, and whether you have room for a slow-speed pump and its drive.

One last thing about speed. RTD at 800 to 1000 RPM and RTX at 1450 to 1800 both require a reduction from a standard motor or engine. None of these are direct-drive pumps for a 3400 RPM gas engine. If someone is trying to sell you one for that, the pump will not last a season.

More detail on each line: RTD series, RTX series, SHP series.

Tell us your flow, pressure, drive and space and we will narrow it to a part number. Contact us or email sales@wshpwr.com.