Milton Roy Metering Pump Selection Guide: Reading G Series Model Codes and Flow Tables

People often ask us for the Milton Roy metering pump selection guide as if it were one big book. In practice Milton Roy literature comes as separate series brochures: the G series GM/GB mechanical diaphragm pumps, MAXROY B, the Milroyal B and D hydraulic diaphragm pumps, and the Primeroyal API 675 range each have their own data sheets. What you really need to learn is two skills: breaking a model code into its segments, and reading the flow table together with pressure. This article uses the G series brochure as the worked example, for engineers, buyers and maintenance staff who need to specify or replace a pump.

Step one in any Milton Roy metering pump selection guide: pick the series

Before opening a brochure, use flow and pressure to choose the series. Otherwise you will search the wrong document for a size that is not there.

From the published ranges, the G series mechanical diaphragm pump reaches 1800 L/h per head and 12 bar maximum discharge pressure. MAXROY B is a mechanical diaphragm pump with a built-in relief valve, rated up to 1100 L/h and 10 bar. For higher pressure you move to hydraulic diaphragm designs such as Milroyal B, listed at up to 250 bar per head. Primeroyal is the API 675 family for process duties with strict specification requirements. For a side-by-side overview, see our guide to Milton Roy metering pump models. Most low-pressure water treatment dosing lands in the G series.

How the Milton Roy model code is built in the Milton Roy metering pump selection guide

The G series brochure has a product code and flow/pressure table. Reading left to right, the code segments are: series, flow, liquid end, connection, motor, adjustment, base, options. Each segment has its own code list, and selection simply means filling them in one by one.

Series and flow

The Milton Roy metering pump selection guide lists two series codes, GM and GB, each followed by a four-digit flow code such as GM0050 or GB0080. The number roughly equals the flow at maximum pressure: GM0050 is 50 L/h, GB0080 is 82 L/h and GB1800 is 1800 L/h. So GM0005 is a few liters per hour, not a large pump.

Liquid end, connection and motor

The liquid end is a single letter: P for PVC, T for PVDF, S for 316, and B for black PP on GM pumps. Application-specific codes include V for high viscosity, K for slurry, M for mixtures and F for sodium hypochlorite, while Z means special materials to be confirmed with the factory. If you dose hypochlorite, the Milton Roy metering pump selection guide points you to the F option rather than plain PVC.

Connection codes cover NPT threads, rigid tube and hose fittings, and availability depends on size and head material; a dash in the table means not offered. Motor codes cover power, voltage and phase, with explosion-proof versions and options supplied without a motor.

Adjustment, base and options

Adjustment sets how flow is controlled: M is manual stroke adjustment, and there are electric stroke actuators (E-STROKE on 4-20 mA), variable frequency control and motor on/off controllers, some limited to GM or GB only. Base code N means no base. Option N is standard; A adds a stroke counter; B, C and D are double diaphragm rupture detection combinations.

Reading the flow table in this Milton Roy metering pump selection guide

Each row has four columns: code, LPH@P max, SPM and P max. LPH@P max is flow at the maximum pressure of that size, SPM is strokes per minute, and P max is the highest allowed discharge pressure.

Two points matter when you read a Milton Roy metering pump selection guide. Pressure is stepped: larger sizes have lower pressure ratings, and the 12 bar series maximum is far from what the biggest sizes can do. So find the band that covers your back pressure first, then pick flow inside it. Second, sizes with similar flow can run at different SPM. Higher SPM means shorter, more frequent strokes; lower SPM means bigger strokes and more pulsation, which matters on long discharge lines that may need a dampener.

The footnotes under the table also count. Some SPM values cannot use 60 Hz motors, and some pressure ratings require a larger motor. Skip those notes and the code you quote may not be buildable. Every Milton Roy metering pump selection guide we have used carries notes like these.

Our order for quoting with a Milton Roy metering pump selection guide

When we check a code, we work in this order:

1. Use maximum dose and back pressure to fix the series.
2. Pick a flow size with enough pressure and some flow margin.
3. Choose the liquid end letter for the chemical.
4. Confirm the connection available for that size and material.
5. Set motor voltage and whether it must be explosion-proof.
6. Choose adjustment for your control method, then decide on stroke counting or rupture detection.

The accessories section states that a safety (relief) valve is mandatory, so make sure it is on the quote. For help choosing the G series size itself, read Milton Roy G series GM/GB selection.

Conclusion

The Milton Roy metering pump selection guide is really a set of series brochures. Choose the series by flow and pressure, decode the model in the order series, flow, liquid end, connection, motor, adjustment, base and options, and always read the flow table with its pressure column and footnotes. The same approach works for the API 675 models covered in our Primeroyal PH, PK, PL and PN guide. To see available models, visit our Milton Roy brand page or the mechanical diaphragm metering pump range. Send your chemical, maximum dose, back pressure and power supply, and contact our engineers to check the full code.

FAQ

Can I order straight from a code built with the Milton Roy metering pump selection guide?

Use it for the inquiry, but have the factory confirm it. The brochure notes that this code applies to G series pumps built by Milton Roy's Shanghai plant, and other plants or series may follow different rules.

GM or GB?

The Milton Roy metering pump selection guide answers this with flow. GM covers small to medium sizes, GB covers larger ones. Where they overlap, compare pressure and head design.

At what pressure is the table flow measured?

The column heading says LPH@P max, so it is flow at the size's maximum pressure. At lower back pressure the flow will differ a little; verify with a calibration column after installation.

What if I cannot decode one segment?

Look it up in that segment's code list. If it is not listed, write "consult factory." Never guess, because one wrong character changes what arrives on site.

My old nameplate does not match the current brochure. What now?

Older models may use naming that is not in the current Milton Roy metering pump selection guide. Send a nameplate photo with flow, pressure and head material, and match a replacement in the current code.