The KOBOLD VKM is an all-metal, viscosity-compensated variable area flow meter, commonly referred to as a rotameter, rated up to 5000 PSIG in stainless steel construction. Designed for oil measurement in demanding industrial applications, it addresses the pressure limitations inherent to glass-tube rotameters, which are generally restricted to below 300 PSI. The all-metal design suits environments involving high pressure, mechanical shock, vibration, or temperature variation where traditional rotameter materials would be impractical.
The VKM transmits flow data through the meter body via a magnetic float, coupling its position to an external scale, reed switch, or electronic transmitter. This fully enclosed design makes it a reliable choice for mobile hydraulic and industrial applications where robustness and integrity are critical.
Viscosity and Density Compensation Without Recalibration
The VKM utilizes a cylindrical flow tube with a spring acting against the float to provide the counteracting force to the fluid flow. The float is designed with an integral orifice that enables it to compensate for changing viscosity and density of the fluid without a significant loss of accuracy.
The integral orifice float eliminates recalibration or scale replacement needs for viscosity variations due to temperature fluctuations or media changes, a significant advantage over standard rotameters. The VKM is able to compensate for changes in viscosity between 1-540 cSt and handle varying density with up to a 30 lb/ft3 difference from the calibration media.
Install the VKM in Any Orientation
The design does not rely on gravity for proper function, so the VKM is not restricted to the vertically upward flow required for traditional rotameters and can be installed in any orientation. Mounting is universal without recalibration, and units are ordered to match the line's flow direction, according to specifications.
Pressure Ratings, Flow Ranges, and Accuracy
The VKM is available in two pressure ratings: 3600 PSIG in brass and 5000 PSIG in stainless steel, exceeding requirements for the large majority of industrial oil systems. Eleven flow ranges from 0.03-0.4 GPM to 2.1-21 GPM provide precise measurement for oil service, with accuracy of ±5% of full scale according to specifications.
Operating temperatures reach up to 212°F (100°C), accommodating the high temperature systems typically seen with hydraulic oils and lubricating fluids. The VKM-8 compact-electronics version carries a 176°F maximum media temperature according to specifications.
Made in the USA and BABA Compliant
As a Build America, Buy America (BABA) compliant flow meter manufactured in the United States, the VKM meets federal requirements for public infrastructure projects. This compliance ensures eligibility for federally funded programs while supporting domestic manufacturing capabilities. Government facilities and public utilities specify the VKM knowing it satisfies both performance requirements and procurement mandates.
Flow Transmitter, Switch, and Display Options
Optional compact electronic displays with 4-20 mA outputs allow the VKM to function as a flow transmitter within automated systems. The LED display provides local flow indication, while the analog output integrates with PLCs and SCADA systems. Reed switch options support discrete flow monitoring for set point indication or high/low flow alarms. The VKM carries cCSAus certification.
Common Questions about VKM - All-Metal Viscosity Compensating Flow Meter and Switch
A hollow float with a sharp-edged orifice travels inside a cylindrical bored metal housing, rising against spring force as the medium flows. Float position corresponds to a particular flow rate, read from the needle indicator. Permanent magnets fitted around the float operate reed contact switches that remain hermetically sealed from the fluid.
According to specifications, flow media include clean mineral oil, water, and other compatible liquids, with viscosities from 1 to 540 cSt. It is recommended for clean, homogeneous fluids: large dirt particles can impede float movement, and ferritic particles deposited on the magnetic float may produce the same false switching effects.
No. The float's built-in orifice keeps the same direct-reading scale as viscosity shifts by as much as 540 cSt, with ±5% additional variation according to specifications. Density may differ from the calibration medium by up to 30 lb/ft3 on the same scale, so temperature swings do not force rescaling.
Nickel-plated brass models (VKM-x1) are rated to 3600 PSIG, and 304 stainless steel models (VKM-x2) to 5000 PSIG, per the datasheet. Maximum media temperature is 212°F (100°C), except VKM-8 versions with compact electronics, which top out at 176°F.
Yes. Spring loading, rather than gravity, provides the counterforce against flow, so mounting position does not affect function. Ordering options cover flow entering from bottom, top, left, or right, letting the meter fit horizontal runs, vertical downflow, or vertical upflow lines.
Switching choices include a normally open reed contact as standard or an SPDT changeover option, both cCSAus approved per the datasheet. VKM-8 compact electronics add a 3-digit LED display, a linear three-wire 4-20 mA output into loads up to 500 Ω, PNP or NPN switching, and a 5-pin M-12 connection powered by 24 VDC ±20%.
Wetted parts on brass models (VKM-x1) are nickel-plated brass with NBR seals, while stainless versions (VKM-x2) use 304 stainless steel with FKM seals. Every model pairs a 301 stainless steel orifice and spring with an oxide ceramic magnet, and the pointer indicator is rated IP54.
Process connections are inline threaded fittings from ¼" to 1" NPT, with G-thread equivalents (G¼ through G1) listed in the ordering tables. An optional special connection provides an outlet female thread inlet BVB manifold. Connection size is selected through the ordering code.
Yes. The product page lists the VKM as made in the USA, with BABA (Build America, Buy America) compliant models available. That status supports specifying the meter on federally funded infrastructure work where domestic content rules apply. It also carries cCSAus approval for North American installations.
Product Specifications
Measuring/Switching Range
0.03...0.4 to 2.1...21 GPM
Fittings
¼"...1" NPT Threads
Material
Ni-Plated Brass, SS
Max. Pressure
3600 PSIG (Brass) / 5000 PSIG (SS)
Max. Media Temperature
212 °F (100 °C) (176 °F for VKM-8xxx)
Options
Reed Contact, Analog Output, Compact Electronics
Product Features
Viscosity Compensation to 540 cSt (No Scale Recalibration Necessary)
Density Compensation to 30 lb/ft3 (0.48 SG)
Installation In Any Position
Max. Pressure - 3600 PSIG (Brass) / 5000 PSIG (SS)
Certifications/Approvals: cCSAus
BABA (Build America, Buy America) compliant models available
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