Overhead Stirrer

Why does my compact stirrer operate slower than expected at low viscosities?

Over-tightening the compact overhead stirrer can generate additional resistance and compromise the stirring speed. Therefore, we do not recommend over-tightening the red cap seen in the image below. New systems may be more sensitive to overtightening. The sensitivity will reduce after the first few hours of operation, reducing the resistance and improving the stirring performance.

Can you supply overhead stirrer motors for ATEX areas?

None of our standard overhead stirrers are ATEX (Ex) compliant.  Even if you sourced an ATEX-certified stirrer motor, it would not mean that the rest of the system is suitable for ATEX environments. The best option is for the overhead stirrer (and overall system) to be situated in a non-ATEX area if possible, e.g. inside a fume hood and operating below the lower explosive limits of any flammable materials, if your site safety experts determine this is acceptable.

What hardware do I need to purchase to use AVA?

If you only want to use AVA in demonstration mode, then all you need is a laptop/computer to download AVA Software onto. If you want to use AVA to control real devices, you will also need one or more Data Hubs, correct RS232 cables to connect the Data Hub(s) to the devices, an Ethernet Switch if you are using multiple Data Hubs and of course the devices themselves if you do not currently have them.
  • RR20200 Data Hub 4 Port and RR20202 Data Hub 2 Port
Available with different plug options. Includes the Ethernet cables needed to connect the Data Hub to the PC or the Ethernet Switch.
  • RR20454 Ethernet Switch
Required if you want to connect multiple Data Hubs to the PC. (You would use multiple Data Hubs if you have more devices than RS232 ports on the Data Hub.) You will need the correct RS232 cable to connect each device to the Data Hub. If the device is not one supplied by Radleys, the manufacturer should be able to advise you on the correct RS232 cable.
  • Automation modules
For example, RR20500 Gravimetric Additions Module, contain devices compatible with AVA plus accessories such as the correct RS232 cables. Please see our website or the AVA brochure for more details.

I have seen pictures of the VISCO JET rotors. Do I need to buy a shaft separately?

Each VISCO JET rotor is supplied with a shaft that you attach (by screwing the two parts together). The shaft is 10 mm in diameter and 500 mm in length.

Can you tell me the Hei-TORQUE equivalent to my old RZR (or RS) overhead stirrer?

There are not 1:1 Hei-TORQUE equivalents for the previous models of overhead stirrers. There are many differences between the ranges. Therefore, you need to consider your requirements (your application etc.), and from that determine the most appropriate Hei-TORQUE model for you.  Please see the separate FAQ entry for help with choosing a Hei-TORQUE model.  Please feel free to contact us if you require any further guidance.

How can I determine the best Hei-TORQUE model for me?

With a few simple questions, you can identify which of the new Heidolph Hei-TORQUE overhead stirrer motors would be appropriate for you.
  • Do you want to accurately measure torque in Ncm, or is a general indication (bars like phone signal) acceptable?
→ If a Ncm reading is required, you need a Hei-TORQUE Ultimate (Hei-TORQUE Precision).  Otherwise, a Value would be fine.
  • Do you want to connect the overhead stirrer to a computer software system for automated monitoring or control?
→ If yes, you need a Hei-TORQUE Ultimate (Hei-TORQUE Precision), for an RS232 (or USB) interface.
  • What level of torque (turning force) do you require – low, medium or high?  This is related to the viscosity of your application – e.g. if you are stirring viscous materials, you need an overhead stirrer with high torque.  If you are currently using an overhead stirrer, you can consider the torque of that (at your stirrer speed).
→ Low torque (low viscosity) – you can use a 100 model. Please note, however, that we do not typically recommend a 100 unit for use with Reactor-Ready – a 200 or 400 would be preferred. → Medium torque (medium viscosity) – a 200 model should be acceptable. → High torque (high viscosity) and low speeds – you need a 400 model. Please note, if you want to work at medium to high speeds, a 200 model would provide more torque than a 400, because the 400s have 2 different gears – different speed ranges with different maximum torques.  Please refer to the graphs below: Graph of Ncp and speed rpm
If you require any further guidance, please feel free to contact us – we’ll be happy to help.

In AVA, when a pause step is occurring, what does the equipment do?

An experiment can be paused in AVA either when you press the pause button, or the experiment reaches a pause command you have added to a step in the Schedule. When an experiment is paused, the effect on devices is as follows:
  • Peristaltic pump (either standalone or as part of an addition/pH step) or syringe pump: the pump stops during the pause.
  • All other controlled devices hold the current setpoint during the pause.  If the device is in the process of ramping the setpoint when the pause occurs, then during the pause it maintains the setpoint it had got to at that point.  For example, if a stirrer is being ramped from 60 rpm to 120 rpm and the step is paused whilst stirring at 85 rpm, it continues to stir at 85 rpm for the duration of the pause, before resuming the ramping again after the pause.

In AVA, what does ‘range’ mean for an overhead stirrer motor?

‘Range’ refers to the speed range (gear) of the overhead stirrer.  Please refer to your overhead stirrer instruction manual for further details about gearing and speed ranges. When you add an overhead stirrer in the Apparatus window in AVA, its properties box will appear and at the bottom of the ‘Device Limits and Settings’ section is the range. In AVA, the range is set to 1 as default, but you can change it to 0.  ‘0’ selects stirring speed range 1 and entering ‘1’ selects stirrer range 2. AVA tells the stirrer which gear to use, and thus alters its stirring speed range accordingly. You should manually configure the maximum and minimum speed limit values according to which range setting you select for your stirrer.