A Quarterly Newsletter of Parr Instrument Company | March Edition 2015 | Vol. 2 No. 1
Welcome to ParrNotes
Welcome to the first ParrNotes for 2015. We are happy to continue to provide you with tips that we hope you find useful in promoting and servicing your our products. I’m cognizant of the fact that the audience may have varying levels of product knowledge making some topics elementary to the seasoned Parr salesperson. With that in mind, we also try to educate your newer personnel and maybe even stir the memory of the old veterans as well as bring you our latest discoveries of the new things going on in our world, all the while pointing out some applications in industries where we have done business that may not be on your radar in the present. Your input and desires for content are always welcome.
Best of luck for a prosperous 2015!
President & Chief Operating Officer
Features and Benefits
Jacketed Vessels with Two Zones, Custom Request Profiles, and Customized Ports
Parr Instrument Company sells welded-jacketed vessels when the customer either needs to eliminate the electric heater or has special heating requirements for their process. Recently we have had several inquiries for special configurations of cylinders with welded jackets. Three such situations are described below. The customer’s request was to provide a heated zone for the liquid phase of the vessel while providing a cooling zone for the vapor phase of the process. Figures 1 & 2 show a vessel with both an upper and lower welded jacket to help facilitate this customer’s request.
Additionally, the profile of the welded jacket can be adjusted to fit the customer’s needs. The jacket pictured in Figures 3 & 4 was shortened to only heat one part of the cylinder. As long as the cylinder has adequate cylinder wall space to physically accept both of these welded jackets, we are capable of providing custom heating and cooling options.
Traditionally when a welded jacket is added to a vessel, our manufacturing process restricts openings/ports to only the head of the vessel assembly or the cylinder bottom. Some recent special projects challenged our manufacturing and engineering departments to invent new ways to provide access to the sides of the cylinder even in the case where welded jackets were requested by our customers. Figures 5 & 6 show a jacket customized with ports. This feature and others are possible for our welded-jacket assemblies.
We have provided the above images of the different features we can add or incorporate into our welded jacketed assemblies. If you are being asked by your customers for similar features don’t hesitate to request more information or a quote from one of our experienced sales representatives.
Installing or re-taping fittings with Grafoil tape can be a challenge even for skilled reactor technicians. Knowing the correct length of tape to use for the various NPT threads is key to having success.
Another thing to keep in mind is the tape will relax after it has been installed. If you were to tighten two fittings with the same amount of torque with the only difference being the type of tape used, Teflon vs. Grafoil, the fitting with the Grafoil tape will most likely require less torque to remove it. The technician can compensate for this “relaxing” by letting the newly installed fitting sit for an hour or so and then retightening. Below you will find a chart and instructions for installing Grafoil tape.
|Grafoil Tape Lengths|
|1/8” NPT||Cut to Length 1.5” (3.8 cm)|
|1/4” NPT||Cut to Length 2.0” (5.1 cm)|
|3/8” NPT||Cut to Length 2.5” (6.3 cm)|
For the 1/8 and 1/4 NPT’s if you are using Parr part # 1358HC Grafoil Tape, cut the tape in half length wise. Ensure the tape is installed in a clockwise motion as viewed from the bottom (NPT) of the fitting.
Solenoid Valve Modules
Solenoid valve modules are an excellent accessory for Parr stirred reactors. They are a highly cost effective way to utilize the cooling coil on our reactors.
A solenoid valve module plugs into the back of a 4848 or 4875/4876 Controller and will open and close according to the demands of the process, allowing water through the cooling coil. If the temperature exceeds the setpoint, it will open; otherwise it will close.
We find that SVM’s are commonly used for temperature control, for cooling after a reaction, and for exotherm suppression. The effectiveness of a SVM can vary with different applications.
Autotuning is better than an SVM in most cases
In most situations, the SVM is not the right tool for controlling temperature. The tuning of the PID parameters is the best way to control temperature in most cases. Proper tuning involves disabling the SVM and running an auto tune with a blank sample.
Fortunately, auto tuning and usage of an SVM are not mutually exclusive, so it’s perfectly fine to auto tune a system and attach the SVM afterwards. Just try not to depend on the SVM to do the control alone.
SVM is good at low temperatures
However, in cases where the temperature is low (under perhaps 100 °C in most vessels) the solenoid is an excellent tool. At low temperatures there isn’t enough driving force to remove heat quickly, so it takes a long time for temperature to drop once the heater is turned off, making control difficult.
The SVM can be used to allow a slow flow of water through the coil, so when the heater turns off the water removes heat instead of depending solely on heat loss to the environment. It is often advantageous to allow water to flow before the temperature reaches setpoint, making the heater fight the cooling as it approaches setpoint.
Cooling down after a reaction
Parr reactors have a lot of thermal mass, so it takes a long time to cool down after a reaction; commonly all afternoon. This makes it nearly impossible to do more than one run in a day with a reactor. With an SVM the operator can simply drop the setpoint after the reaction is through, and the SVM will run cooling water through the coil, cooling it to a handling temperature in far less time.
The SVM is probably the best tool for suppressing temperature overshoot due to exothermic reactions. Since the cooling coil is immersed in the liquid it offers the most direct way to remove heat from the system. External jackets and external coils are an alternative but don’t act on the bulk fluid as directly and so are generally less effective.
Adjust the regulating valve for good control
The SVM module includes a regulating valve in series with the on-off solenoid valve. The controller can actuate the on-off solenoid valve, but the regulating valve must also be adjusted so it doesn’t overpower the system.
The SVM can remove a lot of heat from a system quickly, and so it can overpower a heater. This is not an issue if the only goal is to bring down the temperature quickly after a run or an alarm, but it creates problems if the goal is to maintain temperature around a setpoint.
A regulating valve that is too far open will result in significant temperature oscillations as the cooling water overpowers the heater, turns off, and then the heater catches up.
A regulating valve that is too far closed will not do its job effectively and the temperature will creep above setpoint and stay there for long periods of time.
Calorimetry Applications Other than Fuels
It’s well known that Oxygen Combustion Calorimeters can be used for coal, coke, and other fuels. Did you know that calorimeters can also be used for virtually any solid or liquid sample?
One use that does not get a lot of attention is testing food for human or animal use.
In the U.S. there is a pet food manufacturer that tests their product before it is fed to the animals and then they test the urine and feces after the animal has processed it. This tells them how much of the nutrients are being absorbed by the animal. They can then modify their processes in order to optimize absorption.
The San Diego Zoo uses a Parr calorimeter to test the food fed to their Giant Pandas to ensure that proper nutrients are being provided. The Smithsonian National Zoo uses a calorimeter to test the energy content of animal milk and observe changes in that energy content over the course of nursing the young animals.
There can be some challenges to testing food:
- The sample should be as homogeneous as possible. If you are going to test a hamburger – blend it together so that all components are represented.
- Samples with high water content may have to be dried or spiked to get successful combustion.
One thing to remember – the calorimeters report the results in International Table (IT) calories.
1 food calorie = 1000 IT calories.
Please contact us if you would like more information on this or other applications for calorimetry.
Parr Team Member Focus
Cathy Senatra, Shipping & Inventory Control Supervisor
Cathy is originally from Port Byron, Illinois but now resides in Moline, Illinois where she moved to start her family.
Cathy has been with Parr Instrument Company for 35 years. She is our Shipping & Inventory Control Supervisor where she helps make sure we have the items needed to fulfill our customers orders.
Some of the things that Cathy likes most about working for Parr is watching the growth of the company over her time here and all of the unique equipment designs that we build.
Cathy is very thankful to everyone who has taught her so much and for the opportunity to be a Parr employee.
ChemBio Finland 2015
March 18 – 19, 2015
Look for: Oy G.W. Berg & Co Ab
Middle East Coatings Show 2015
March 19 & 20, 2015
Look for: Venktron Electronics Ltd
March 19 & 20, 2015
Look for: Analis sa/nv
249th ACS Spring National Meeting and Exposition
Come visit us and check out the debut of our brand new booth!
March 22 – 24, 2015
Look for: Parr U.S.A.