The KFS is a low volume acrylic rotameter, a variable area flow meter that measures liquid or gas flow using a suspended float in a tapered tube. It delivers accuracy at a low cost in a simple, compact, one-piece acrylic body with removable PVC or stainless steel fittings, and integral needle valves are available. Flow runs vertically from bottom to top, and the float is read at the position indicated on the scale.
Flow ranges and accuracy
The KFS covers water from 0.08–0.8 GPH up to 16–160 GPH and air from 0.08–1 SCFH up to 200–1400 SCFH, with air ranges referenced at 68°F (20°C) and 1 bar absolute. Accuracy is ±2% to ±5% of full scale depending on the model. The pressure limit is 90 PSI (6.2 bar) and the temperature limit is 145°F (62.8°C).
Materials and construction
The KFS uses a durable one-piece acrylic housing. Floats are supplied in glass, stainless steel, or PTFE depending on the model and range, with stainless parts in 304 SS (1.4301) and glass floats in agate. Gaskets are FPM on the KFS-2 and KFS-4 and NBR on the KFS-5. Removable fittings are stainless steel or PVC.
Models and connections
Three model families are offered. The KFS-2 and KFS-4 use an acrylic body with a stainless steel connection at the back, rated ±5% and ±3% of full scale. The KFS-5 uses an acrylic body with PVC connections at the top and bottom, rated ±2% of full scale. Connections are 1/8 inch to 1 inch NPT female.
- KFS-2 and KFS-4: 1/8 inch NPT female at the back for most ranges, stepping up to 1/4 inch NPT female at the back on measuring ranges 69, 70, and 73.
- KFS-5: 1 inch NPT female at the bottom and top.
Needle valves and mounting
Stainless steel needle valves are standard on the KFS-2 and KFS-4, the smaller sizes, providing integral flow control at the meter. The KFS-5 can be supplied with a panel installation kit; when the panel kit is used, the connections are located in the back. Each meter includes #10-32 threaded inserts for mounting.
Installation
The KFS operates on a suspended float principle and is installed vertically with flow entering at the bottom and leaving at the top. Torque the inlet and outlet fittings to no more than 60 in-lb and the mounting screws to no more than 35 in-lb, using thread sealant or PTFE tape for a better seal. On start-up, slowly purge any fluid trapped in the meter.
Applications
The KFS is designed for low volume liquid and gas metering across many settings. Documented sample areas of application include:
- Air sampling equipment
- Aquaculture
- Desalination equipment
- Gas analyzers
- Medical systems
- Photoprocessing equipment
- Water treatment and distribution systems
The KFS is targeted for higher volume OEM applications and has a minimum order quantity. For smaller quantities, see the KFR variable area flow meter.
Common Questions about KFS - Low Volume Rotameter Flow Meter
The KFS works on a proven suspended float system. Metered liquid or gas enters at the bottom and travels upward through a tapered tube, lifting the float to a height that corresponds to the flow rate. The value is read directly on the scale, so no external power is needed to take a reading.
Water measurement spans 0.08–0.8 GPH at the low end to 16–160 GPH at the top. For air, coverage runs from 0.08–1 SCFH to 200–1400 SCFH, measured at reference conditions of 68°F (20°C) and 1 bar absolute. The specific band within these limits is set by the model you order.
Accuracy depends on the model: ±5% of full scale on the KFS-2, ±3% on the KFS-4, and ±2% on the KFS-5. All models share a maximum operating pressure of 90 PSI (6.2 bar) and a maximum temperature of 145°F (62.8°C).
The housing is one-piece acrylic. Floats come in glass, stainless steel, or PTFE according to model and range, with stainless components in 304 SS (1.4301) and agate glass floats. The KFS-2 and KFS-4 use FPM gaskets, while the KFS-5 uses NBR. Fittings are supplied in stainless steel or PVC.
All connections are NPT female, from 1/8 inch up to 1 inch. The KFS-2 and KFS-4 place the connection at the back: 1/8 inch on most ranges and 1/4 inch on ranges 69, 70, and 73. The KFS-5 uses 1 inch NPT female at both the bottom and top.
Yes. The KFS-2 and KFS-4 include a stainless steel needle valve as standard, since they are the smaller sizes, so flow can be set and held right at the meter. The KFS-5 has no standard needle valve but can be ordered with a panel installation kit.
Mount the KFS vertically so flow enters at the bottom and exits at the top. Seal the threads with pipe thread sealant or PTFE tape, then tighten the fittings to a maximum of 60 in-lb and the #10-32 mounting screws to a maximum of 35 in-lb. Purge trapped fluid slowly at start-up.
Each model carries its own order code: KFS-2212 to KFS-2219 for the KFS-2, KFS-4238 to KFS-4273 for the KFS-4, and KFS-5353 for the KFS-5. Option code N0 adds the needle valve and 00 means no option. Ranges 69, 70, and 73 use a 1/4 inch back connection that cannot combine with the KFR-PPHW024 hose set.
Clean the KFS when dirt appears in the tube or float movement becomes restricted. Remove the top plug and float, wash the tapered bore and plug with a mild detergent and soft brush, rinse, and dry with clean air or nitrogen. Do not use solvents, which attack the acrylic. Lubricate the o-rings with halocarbon grease on reassembly.
Product Specifications
Measuring ranges (Water):
0.08 ... 0.8 GPH to 16 ... 160 GPH
Measuring ranges (Air):
0.08 ... 1 SCFH to 200 ... 1400 SCFH
Accuracy
±2 % ... 5 % of full scale
Connection
⅛ ...1" NPT female
Material
acrylic / stainless steel / PVC
Product Features
Needle valve (Standard with smaller sizes)
Sample OEM Applications: Air Sampling, Aquaculture, Desalination, Gas Analysis, Medical Systems, Water Treatment, and Water Distribution.
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