Proper scale-up is a matter of maintaining the same number of revolutions between the pilot and production vessels.

Scale up of one process to a larger size (or smaller size in reverse) unit has been shown by Rutgers University to be essentially a matter of maintaining the same number of vessel rotations. The larger unit will typically turn more slowly so that it will take longer to achieve the same number of rotations but the number of rotations is the key.

A few caveats are in order:

1. The units should be geometrically similar which basically means the same shape vessel.

2. The units should be filled to the same percent of total volume fill level.

3. With V-shape vessels, the units should be filled symmetrically with minor ingredients loaded equally in both legs of the Vee (if loading is not done through the main vessel valve).

According to the conclusions in chapter 5, Batch Size Increase in Dry Blending and Mixing by Dr. Albert W. Alexander and Dr. Fernando J. Muzzio
published in Drugs and the Pharmaceutical Sciences, Volume 118, Pharmaceutical Process Scale-Up, the above conclusions are correct.

The authors reached these five specific conclusions::

1. Make sure that the units are loaded consistently in the larger unit as they were in the smaller unit. (Item #3 above.)

2. The number of revolutions is key whereas rotational rates are largely unimportant.

3. Ensure that the sampling regimen used is adequate including a sufficient number of samples that are correctly analyzed to provide an accurate description of the blend that is achieved.

4. One way to decrease the time frame required to achieve a blend is to reduce the fill level in the blender.

5. Addition of asymmetry to the vessel can greatly reduce the amount of time necessary to produce a proper blend- for instance, by using a Gemco slant cone blender.

The authors go on to comment that the above guidelines are cautionary rules to be applied in general but may require additional work and refinement for
any specific powder system.

Questions or comments regarding this article can be addressed to sales@okgemco.com

It is our understanding that the OSHA regulation of using light beams as personnel exclusion safety devices requires that the light beam be sufficiently far from the machine to ensure that the machine is fully stopped before anyone could be hit by the rotating vessel. Specifically we have been told that the separation has to allow for a distance of 66" per second from when the beam is first interrupted to when the blender is fully stopped. The time must include the response time of the light beam which can vary with manufacturers from 0.025 seconds upward.

As Gemco units use pneumatic brakes to provide a soft stop and not impact the gears, our actual stopping times vary from machine to machine based upon vessel RPM, capacity, shape, unit fill level, certain options such as a Gemcomatic drum loader and material density. We therefore can not provide the actual stopping time for our units.

The time for large units can however be a full second or more. This means that the light curtain would have to be positioned more than 66" back from the extreme limit of rotation to be compliant. Often such distances are not available within the blending rooms so actual physical barriers are used instead. The typical installation uses an interlock on the room door to accomplish this goal. Some installations then go beyond the door interlock and use a light curtain installed parallel to the floor, perhaps an inch off the floor, to ensure that no personnel stayed in the room once the door was closed.

Air System PMC            continued

The most common inspections are daily PMCs, and these are simple visual and mechanical checks that take no more than few minutes to perform. A PMC vital to your Gemco equipment's continued good heath is the Air System Check.

To ensure proper operation of your GEMCO pressurized air is required. This air usually is piped to the unit and connected to a filter, regulator and lubricator, mounted on the equipment frame. The lubricator outlet is connected to the remainder of the air system and the Main Air Pressure Switch.

You must ensure that there is at least 85psi air supplied to the unit at all times through a half-inch minimum pipe or hose to allow for the volume of air required to operate the unit.

Inspect the lubricator and make sure it is at least half full of lightweight 10 wt oil.

check the o-ring seal for cuts or wear.

inspect the bowl itself look for any small cracks or chips replace as required.

Inspect the regulator looking for leaks or wear, broken parts. Inspect the gauge face lens for clearness and replace parts as required.

Inspect the filter assembly, remove the bowl and clean it as needed.

check to see if the drain device is operating; look for cracking of the bowl or o-ring problems on the drain valve, replace parts as required.

Check the rest of the air system for leaks, both while the unit is stationary and rotating.

This simple check should take no more than 15 minutes. It should be done at the start of every shift if you run more than one shift, but it should be done at least once a day.

Gemco Introduces New Lab Blender

The new Gemco cantilever solids type lab blender design includes many new features. The motor and controls are enclosed in a NEMA 4X stainless steel electrical cabinet. The safety gates are built in and internally interlocked. Due to the wide range of vessel sizes the unit is designed to accommodate, including small vessels for 100 grams of powder or less, the
design includes a variable speed drive to enable the smallest vessels to be run at the proper (higher) speeds required for a proper blend as well as scale-up calculations when the quantities increase.