When you're choosing between these two listings in industrial pumps flow control, the first fork in the road is function, not budget. One listing is an air-operated double diaphragm pump built to move chemical or petroleum fluids. The other is an air + CO2 flow modulator built around a CKD FCM flow controller, two CKD RB500 pressure regulators, and a Yokogawa control board. The price gap between the two is considerable, but the bigger difference is what each one is designed to do.
Quick verdict
If your task is moving liquids, the double diaphragm pump is the practical pick. If your task is regulating air or CO2 in a process line or lab setup, the CKD/Yokogawa flow modulator is the purpose-built option. Choose by job first, then let the price confirm the direction.
Comparison at a glance
| Dimension | CKD Flow Modulator | Double Diaphragm Pump |
|---|---|---|
| Listed price | USD 899.99 | USD 126.01 |
| Price bar | ||
| Condition | Used | New |
| Primary role | Air + CO2 flow modulation | Fluid-transfer pump |
| Notable specs | CKD FCM controller, 2x RB500 regulators, Yokogawa M3839NE | 1\" inlet/outlet, 35 gpm, 150°F, NPT 1/2\" air inlet, 38 CFM average |
Where each listing stands out
- The flow modulator stands out when the job is air/CO2 flow control. It is a specialized instrument package rather than a liquid pump, which makes it the relevant choice for gas-flow work.
- The double diaphragm pump stands out for fluid-transfer work and is the practical route when your priority is moving fluids without paying for gas-flow control hardware.
Product notes
Air + CO2 Industrial Flow Modulator CKD Flow Controller FCM, RB500 x2 Yokogawa
This used, lab-surplus control package brings together a CKD FCM flow controller, two CKD RB500 compact pressure regulators, and a Yokogawa control board (model M3839NE), all made in Japan. Choose it when your process needs air or CO2 flow modulation and you want the regulators and control electronics in one bundle. Its limitation is that it is a specialized used unit: the seller notes the exact identity was not certain, so it suits someone comfortable with lab-surplus instrumentation rather than someone expecting a documented plug-and-play flow system.
120PSI Industrial Chemical Air-Operated Double Diaphragm Pump 1\" Inlet+Outlet
This is the workhorse liquid-mover of the pair. It's listed as new and built to push up to 35 gallons per minute through a 1-inch inlet and outlet at a rated 120PSI. The aluminum body, acetal ball material, and nitrile diaphragm point toward chemical and petroleum fluid-transfer applications. Choose it when you need a new, relatively low-cost pump for moving fluids. The trade-off is air demand: at an average of 38 CFM, it draws real compressor capacity, and it isn't built for gas-flow modulation like the CKD/Yokogawa unit.
Final choice by use case
If liquid chemical or petroleum transfer is the job, take the 120PSI Industrial Chemical Air-Operated Double Diaphragm Pump. If air or CO2 modulation is the job, take the Air + CO2 Industrial Flow Modulator CKD Flow Controller FCM. Let the task, not the price spread, make the call.
