Primeroyal Metering Pump Selection: How to Choose Between PH, PK, PL and PN
PH, PK, PL and PN all belong to the Primeroyal metering pump family. All are designed to API675 and hold ±1% steady-state accuracy from 10% to 100% of rated flow. So what do the four letters actually change? Go through the Milton Roy selection literature and the answer comes down to three numbers: stroke length, thrust and maximum flow.
Below we put the four frames side by side, talk through liquid end choices, and finish with an order for working back from your duty to a frame.
The Four Primeroyal Metering Pump Frames at a Glance
These are the upper limits from the front page of each data sheet (50 Hz):
- PH: 30 mm stroke, 350 daN thrust, up to 948 L/h per head, up to 690 bar;
- PK: 40 mm stroke, 475 daN thrust, up to 2500 L/h per head, up to 930 bar;
- PL: 50 mm stroke, 900 daN thrust, up to 4410 L/h per head, up to 1034 bar;
- PN: 63 mm at 100% stroke, above 9683 L/h per head, maximum pressure depending on liquid end.
The pattern is intuitive: the bigger the frame, the longer the stroke and the more liquid each stroke pushes. Maximum pressure and maximum flow are each the value at an extreme configuration, and they never appear on the same pump. The PN data sheet gives no single pressure limit on its front page, so look up the pressure in the table for the specific liquid end.
What Every Primeroyal Metering Pump Shares
All four frames use the same drive, a variable eccentric mechanism that shifts the eccentric shaft center to change stroke length. Turns 0 to 10 on the adjusting handle correspond to 0–100% stroke, adjustable running or stopped.
A few more points are common across the range:
- Modular liquid ends, with plunger, PTFE diaphragm and metal diaphragm types to choose from;
- Manual or electric stroke adjustment, with pneumatic also available on PK and PL;
- ATEX explosion-proof motors, VFD motors, and double or triple diaphragms with rupture detection.
Once the Primeroyal metering pump frame is chosen, the configuration logic from there on is much the same.
How the Frames Differ
PH: the starting point for low flow at high pressure
The PH is the most compact Primeroyal metering pump in the group, with a single-head unit weighing about 95 kg net. With a 50 Hz motor, stroke rates come in 38, 57, 99, 115, 120, 144 and 180 spm.
In the PH data sheet, the PTFE diaphragm stainless liquid end reaches 250 bar with a 12 mm plunger. Increase the plunger to 70 mm and flow reaches 948 L/h while pressure drops to 9 bar. The M type metal diaphragm reaches 500 bar with an 8 mm plunger.
PK: the middle step
The PK Primeroyal metering pump has a 40 mm stroke and a 2500 L/h flow limit. There is a PKG version with the GSD liquid end, a compact design with triple hydraulic safety protection and an installation monitoring indicator (IMI).
PL: high thrust
The PL has a 50 mm stroke and 900 daN thrust, with flow up to 4410 L/h. Its plunger liquid ends include the NX type, reaching 1000 bar with a 10 mm plunger. The PL also comes in a food-grade design for food and beverage dosing.
PN: high flow
This Primeroyal metering pump has a 63 mm stroke and flow above 9683 L/h. It supports plunger, PTFE diaphragm and metal double-diaphragm liquid ends, and with a fixed-stroke configuration it also complies with API674. Suction capability depends on the liquid end: about 2 m water column for M, H, P and UT types, about 6 m for N and NX.
Using the Primeroyal Metering Pump Tables
Each liquid end has its own table in the data sheet, listing plunger diameter, effective volume, stroke speed, flow at 10 bar, flow at maximum pressure and maximum pressure.
Pick the liquid end type first, then find plunger diameters that meet your target pressure, then check flow. On the same PH frame, for instance, PTFE diaphragm liquid ends run from a 12 mm plunger to 70 mm while maximum pressure falls from 250 bar to 9 bar. Pressure and flow always trade against each other, and every table shows it.
If one head can't deliver enough flow, consider multiple heads. The literature states that multi-head flow equals single-head flow times the number of heads.
Choosing a Liquid End for Your Primeroyal Metering Pump
PTFE diaphragm: broad chemical compatibility, leak-free, with a built-in relief valve. Suits most chemical dosing.
Metal diaphragm: higher pressure, and it handles hot, highly diffusive or radioactive liquids with metal-to-metal sealing.
Plunger: high pressure and low NPSH demand, good for viscous liquids and slurries. The plunger seals with packing, so keep an eye on its condition.
For general chemical dosing, start with the PTFE diaphragm. Once pressure reaches several hundred bar, look at metal diaphragm or plunger.
Larger frames beyond these four
The Primeroyal range doesn't stop at four. PR and PP both exceed 15000 L/h. The newly developed PQ with the HX liquid end reaches 1035 bar. The Primeroyal X series uses a metal double-diaphragm liquid end rated to 1380 bar, aimed mainly at chemical injection on offshore platforms. Routine water treatment and chemical dosing rarely need anything that large.
Working Back From Your Duty to a Primeroyal Metering Pump
With a duty sheet in hand, go through it like this:
- Convert maximum flow to L/h and add adjustment headroom;
- Fix the maximum injection pressure and fluid temperature;
- Compare against each frame's flow limit and circle the frames that cover it;
- In those frames' tables, find the liquid end and plunger diameter by pressure;
- Finally settle adjustment method, motor and explosion protection.
Step 3 often rules out half the options on its own. Most of the time you only need to study one or two Primeroyal metering pump tables closely.
Conclusion
Selecting a Primeroyal metering pump follows a simple order: flow picks the frame, pressure picks the liquid end, and the table picks the plunger. Start with the PH for low flow at high pressure, the PK for medium flow, the PL for high thrust and the PN for high flow. All four share the same drive and adjustment logic and differ mainly in stroke length and thrust. Once the frame is set, choose the liquid end by chemical and pressure.
FAQ
Both PH and PK cover 500 L/h. Which Primeroyal metering pump should I pick?
Look at pressure. A frame with more thrust can usually reach higher pressure at the same flow, though the table has the final word. If pressure is modest, the PH is more compact.
Can every PL reach the 1034 bar in the literature?
No. That's the limit for a specific plunger liquid end with a small plunger. With a PTFE diaphragm liquid end, pressure is much lower.
Can a Primeroyal metering pump run in sub-zero conditions?
The standard ambient range starts at -10 ℃, with an upper limit of +55 ℃ for PH and +50 ℃ for PK and PL. A low-temperature design rated to -40 ℃ is available as an option when ordering.
How fine can flow adjustment go?
Turns 0 to 10 on the handle cover 0–100% stroke, the scale reads in percent, and adjustment can be set to millimeter precision.
Plunger or diaphragm?
For toxic, expensive or leak-intolerant media, choose a diaphragm. For viscous media, media with solids, or very high pressure, consider a plunger.
Send us your chemical, flow and pressure through our contact page and we'll pin down the Primeroyal frame and liquid end against the data sheets with you.