M.K. Plastics

M.K. Plastics Axijet Compared to Greenheck Vektor MS (or HS)

Today’s blog post comes directly from one of our manufacturers, M.K. Plastics. In this technical article, they compare their Axijet with Greenheck’s Vektor MS.


Axijet-S High Plume Dilution Fan

The M. K. Plastics Axijet is an induced flow fan tested in accordance with AMCA Standards 260 and 300, and licensed to bear the AMCA certified ratings seal. It dilutes the exhaust effluent with entrained air. By design, it delivers high nozzle velocity at low BHP. As such, when used with a VFD, the Axijet offers a broad turndown range while maintaining high nozzle velocity, without the need for additional mechanical or electrical accessories.


Vektor MS High Plume Fan

The Greenheck Vektor-MS, on the other hand, is not an induced flow fan, and offers no dilution of the exhaust effluent. It is a mixed flow fan with an exhaust transition sized to maintain a minimum discharge velocity of 3000 FPM.

This product has two motor actuated damper blades at the discharge, each  one  on  its  own  actuator. That’s  two  additional control points in the system. This is referred to as a variable geometry nozzle. The premise is that as you turn the fan down with a VFD, the twin motor operated damper blades on the discharge modulate closed to restrict the area and maintain a 3000 FPM discharge velocity. That’s two additional control points in the system.


Variable Geometry Nozzle

As the fan RPM  decreases, normally fan BHP would be reduced by the cube of the decrease in fan RPM (the fan laws). But, as the damper blades close, they present greater resistance to the fan, which, in turn, drives the fan BHP up. The variable geometry nozzle actually pushes the system curve to the left. So the HP reduction does not follow the fan laws.

With the Axijet, which has a high nozzle velocity by design, the fan can be turned down (typically at least 40%) and still maintain a nozzle velocity above 3000 FPM, without additional moving parts or extra controls.


Consider this case example…

Variable volume critical exhaust system. Maximum performance 24,000 CFM at 3.5” SP. The Client wishes to maintain 3,000 FPM discharge velocity through at least a 40% turndown.


The M.K. Plastics Axijet-S 4025


Vektor-MS 40

And compare…


Clearly, the M. K. Plastics Axijet offers the following advantages:

  1. Competitive HP/energy (operating) cost
    1. Competitive turndown range
    2. Lower noise
    3. Lower installation and wiring cost
  2. Lower equipment first cost
  3. No discharge parts to seize or become inoperable due to failure or weather
    1. Higher nozzle velocity
    2. Higher effective plume height
    3. The added benefit of dilution air
  4. Less complicated controls

And regarding controls, the Greenheck Saave system simply reacts to a master sequence signal from the BMS to the VFD, and adjusts the discharge damper to maintain discharge velocity. Each fan operates independently. And in multiple fan systems, each fan needs its own reactive control for the discharge damper only.

In contrast, the M. K. Plastics Patented LeadLag system actively controls fan motors, VFDs, isolation dampers, and bypass dampers (when required) to maintain pressure of volume in the system, whichever is the dependant variable. LeadLag also cycles operation of the redundant ran while maintaining full system control. LeadLag reports control activity to the BMS.

The M. K. Plastics Axijet with Leadlag control, is a simpler more reliable, and more complete critical exhaust solution!

For more on M.K. Plastics visit www.mkplastics.com today, or contact us.

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