A Quarterly Newsletter of Parr Instrument Company | September Edition 2014 | Vol. 1 No. 3
Welcome to the third issue of ParrNotes
Where has the year gone? We lay out plans for a new year, projects come in and go out, new people come on board and some retire, and in between it all life happens. Now here we are wrapping up the third quarter of what’s been a very busy year. With a healthy order book and high level of current business, it’s looking to be an exceedingly active fourth quarter. As always, we will do our best to meet the end of year customer requests. Let us know how we are doing. Good luck selling!
President & Chief Operating Officer
Features and Benefits
Pressure Control on Batch Reactors
Parr Instrument Company’s stirred reactor systems have PID programmable temperature control as a standard feature unless the user requests a welded jacketed system which would require temperature control from a customer supplied circulator. However, these same reactors come standard with a manual pressure gage to measure the pressure inside the vessel. The pressure is dependent on the introduced pressure from an external source (i.e. N2 or H2 gas cylinder), the temperature of the system, and the contents of the reactor.
For users who want to data log their pressure, we offer the Pressure Display Module (PDM) as an optional upgrade. This allows the pressure to be displayed electronically and recorded with the purchase of a PC communication cable. This feature does not offer pressure control for the system.
When a customer wants to add pressure control to their batch reactor we offer an optional manual Back Pressure Regulator (BPR). The BPR allows the customer to adjust the release pressure of the reactor during operation. These manual back pressure regulators are temperature sensitive which sometimes requires the system to be configured with either a Reflux Condenser (RC) or Reflux Take-off Condenser (RTC) to protect the temperature sensitive seals in the BPR.
Since our stirred batch reactors are normally configured with a 4848 Controller, the manual BPR would be the most economical way to add this pressure control upgrade. For automated pressure control of a batch reactor system, the controller would have to be upgraded to our 4871 Process Controller. The automated BPR is normally only configured with a continuous flow through system which typically needs other automated features that are controlled by the PLC.
Figure 1 shows the manual BPR feature configured to a 5103 600 mL Low Pressure Glass Reactor System (Project 914435). This feature could also be added to a non-stirred reactor system if needed. Figure 2 shows a non-stirred system with a reflux condenser for a 4683 1.8 L Reactor (Project 913529).
If you are interested in a system with pressure control please contact one of our Technical Sales Representatives and we would be glad to assist you.
Parr Magnetic Drives – Smooth Operator
Maintaining your magnetic drive is essential to trouble free operation. Our repair technicians are often presented with troublesome issues that could have been avoided through regular cleaning and maintenance. It is important to note that reactants can make their way into the rotor housing. Solids, and especially polymers, build up over time and will fill the voids inside the rotor housing. This creates a situation where more force is required to rotate the magnetic drive which can result in premature wear of the bushings and thrust washers contained inside the magnetic drive.
In order to keep your magnetic drive running smoothly, Parr recommends that you service it annually unless operating conditions or poor performance warrant it sooner due to the wide spectrum of operating conditions encountered. Instructions on how to service magnetic drives are available in our new Magnetic Drive Maintenance Guide Video (featured below) and in our Magnetic Drives Operating Instruction Manual (234M).
Parr offers a complete line of magnetic drive replacement parts, most of which are in stock and available within two days of your order. Our Repair Department is here to assist in a complete rebuild or contact anyone in our Technical Sales Department to help you in choosing the proper parts for your magnetic drive.
Magnetic Drive Maintenance Guide Video
This video is a visual supplement to aid in performing routine maintenance on Parr Magnetic Drives. The video is found on
We hope the video will be a useful tool for our mutual customers.
Please subscribe to our YouTube page to stay current with Parr Instrument Company videos.
Motor Fuses in 4848, 4843, and 4875 Controllers
Parr controllers use a variety of fuses and resets to protect our DC variable speed motors. These work together to protect the motor and associated hardware, but not all of the components are accessible from the outside.
The most visible motor component is on the outside of the chassis. In controllers with 180VDC motors, this is a lit motor fuse holder which will illuminate if the fuse pops. In controllers with 90VDC motors, there is a black and white motor reset button which will pop out if the maximum current is breached.
In the case of the 180VDC motor, there are also two fuses inside the chassis, mounted right on the motor board itself. These are fast acting and very fast acting fuses. These should be checked if the external fuse is good, but the motor is still not functioning. These fuses are not present on the 90VDC motor configuration.
The fast acting and very fast acting fuses are there to provide protection in the event of a quick power spike in the motor current. Common culprits for this are:
- Switching on the motor at full power suddenly by turning on the motor switch with the knob at full power
- Switching from Local to Remote control while the Remote control is calling for full power
- Having the impeller hit something, freezing up the stirring
This is more of an issue in motors ½ hp and greater. Smaller motors don’t spike as high, and tend to not pop the fast and very fast acting fuses.
More information about Parr’s controller fuses may be found in our 4848 Reactor Controller Instruction Manual (548M).
Continuous-flow reactions have long been practiced in commercial operations such as petroleum refining and many other chemical production facilities. More recently it has become common to see tubular reactors replacing or augmenting batch, stirred-tank operations being performed in laboratories and within commercial operations in the pharmaceutical industry. There are a number of reasons for this shift; among them are:
- Flow reactors are easier to automate and permit sequential changes
- Parametric changes can be performed at will, leading to possibility of real-time analysis
- Residence time becomes a function of flow rates and is, therefore, easy to change
- Amount of product becomes a function of time, not larger equipment
- Multi-step reactions and reactors are possible
- Increased safety occurs when smaller amount of reactants and products are present at any given time
- With increased surface-to-volume ratios, heat transfer and temperature control in tubular, continuous-flow reactors are also increased
- Since mixing occurs in a smaller space, it can occur more rapidly
- Improved control of mixing, temperature, and residence time leads to improved selectivity
- Scale up of laboratory tubular reactors may be simpler than scaling stirred tanks
- Higher operating pressures are more easily attainable in reactors of smaller diameter
To discuss your next project and how to best equip your lab for investigations of continuous-flow reactions, contact the Technical Sales Team at Parr Instrument Company.
Let us build one for you.
Working with volatile solvents in non-stirred reactors sometimes causes a process where the pressure gage shows a reading significantly less than the vapor pressure of the solvent at the operating temperature. This is caused from the temperature in the vessel not being uniform.
The pressure in a single species system is dependent on the vapor pressure of the material. In our reactors, this is typically the vapor pressure of the solvent. As you heat the vessel, the temperature around the edges becomes hot, but the temperature near the center is cooler. Although the heat will eventually come to steady state, there is a constant heat loss through the vessel (most notably the head fittings), so at steady state the center temperature will be appreciably cooler than the temperature at the wall. It is somewhat like a big dart board where the bull’s-eye is the coldest part.
We tend to locate the thermocouple closer to the wall than the center, so the measured temperature is greater than the average temperature in the vessel, and it is the average temperature of the solvent which dictates the overall vapor pressure.
One of the benefits of a stirred reactor is that the mixing evens out this temperature distribution. With turbulent mixing, it is generally a good assumption that temperature in the liquid phase is uniform.
2014 International Organically Bound Tritium (OBT) Workshop
September 15-18, 2014
6th Symposium on Continuous Flow Reactor Technology for Industrial Applications Workshop
September 23-26, 2014
AIChE Annual Meeting
November 16-21, 2014