A Quarterly Newsletter of Parr Instrument Company | September 2016 | Vol. 3 No. 3
Features and Benefits
Liquid Sampling – Valves, Dip Tubes, and Filters
The ability to remove one or more liquid samples during operation of a reactor at elevated temperature and pressure is a basic capability of nearly all Parr reactors. This is commonly done through a head-mounted liquid sampling needle valve via a dip tube connected to the underside of the head and extending below the surface of the liquid.
Though a wide variety of potential sampling situations exist, many fall within manageable categories worth mentioning here, starting with the simplest:
Low viscosity liquid
Though care must be taken whenever withdrawing any contents from a pressurized vessel, removing a sample of thin liquid is typically straightforward. An appropriately sized receptacle capable of withstanding the internal pressure of the vessel can be connected to the sampling valve, and the sampling valve opened and then closed. Following this sequence, the sample container contains any vapor that was in the dip tube as well as any liquid that was forced through the dip tube into the sampling container. One must be careful when dispensing the sample from the sampling container, as the contents are still under pressure.
“Higher” viscosity liquid
A similar approach may be taken, but consideration of the time necessary for the internal pressure to force liquid contents into the sample vessel may be necessary. Similarly, consideration of a larger diameter dip tube and/or larger Cv valve or perhaps a ball valve may be appropriate.
Liquid with solid particles
Two major possibilities exist in this category: collection of both liquid and solid or collection of only liquid. Both present a set of challenges.
For collection of liquid and solid, a primary challenge is the interaction between solids and valves. Powders may be more manageable than larger or abrasive particles, and ball valves are often the valve of choice for liquid/solid handling. Ball valves, though, can be limited in pressure and temperature rating. It has been said around the Parr office many times that “slurries and ball valves do not play nicely together.” Sampling of slurries can scratch ball valve seals so the customer should be aware that they may need to replace the packing and/or the valve with some frequency.
- For collection of only liquid, the solids must be removed. Parr tends to use press-on filters, or less frequently, screw-on filters, at the end of the dip tube to remove solids from the liquid sample. These sintered metal filters are available in a variety of materials, with a variety of nominal pore sizes, often from 0.5 micron to 40 micron. Most of these filters have a relatively small filtration area, so the user should consider how long it will take for a sample of the desired volume, viscosity, and solids content to be collected into a sampling device. If clogging of a press-on filter is a possibility, Parr recommends purchasing a second complete “dip tube with filter,” as the dip tubes are prepared at the factory to accept an individual filter, so filters are not readily field replaceable. However, dip tubes with filters are easily replaced. Screw-on filters are field replaceable and have a larger surface area, but due to their larger size, are usually supplied only for use with 1L and larger vessels.
Liquid Sample Collection Options
Sample collection vessels
Parr offers the 4350 Series Liquid Sampling Vessels as an attractive option for sample collection in any of the above scenarios. The 4350’s can be supplied with volume of 5mL or 10mL, and with isolation, vent, and drain valves, as well as a cooling sleeve. These vessels can be connected to the head-mounted sampling valve mentioned above and are typically rated to 3000psi (200bar), though options are available for higher pressure applications and with custom (larger or smaller) volumes.
Two major benefits of these collection vessels are safety and convenience, as the pressure inside the sample vessel is completely contained, and the user can simply connect the device, open the sampling valve on the head of the main pressure vessel, close the sampling valve, close the isolation valve on the sample vessel, and disconnect the sampling vessel. A disadvantage of this device is that each sample must be manually taken, and that the dip tube must be cleared between samples, or every other sample must be discarded as some of subsequently removed samples will contain the residual material from the interior of the dip tube, which is likely no longer representative of the bulk fluid inside the reactor.
Automated liquid sample collector
Parr is also pleased to announce the introduction of an automated liquid sample collection device – the 4878 Automated Liquid Sampler. This device allows the collection of multiple samples at a user defined interval without requiring the presence of an operator for sample collection. In addition, the contents of the dip tube and sample line can be cleared between each sample to ensure each sample is representative of the fluid inside the reactor at the time of sample collection.
More information about this device can be found elsewhere in this newsletter, here.
For more information about manual or automated liquid sample collection options, please contact Parr Customer Service.
Parr Heater Serviceability
Not all of Parr’s heaters are considered serviceable. This article is meant to help describe which of Parr’s heaters are serviceable and why some are not.
First, it’s important to note that when servicing Parr heaters that it’s advised to wear dust masks to prevent insulation fibers from being inhaled as any airborne particles may be considered a health hazard. Ensure that dust masks are appropriately rated for any such fibers and that the masks are fitted properly.
Tubular Rod Heating Elements
Parr’s heaters that utilize tubular rod heating elements, often referred to as calrod heating elements, are fully serviceable. Preformed replacement heating elements are readily available along with any electrical, insulating, or enclosure related parts.
Ceramic Fiber Heating Elements
Parr’s heaters that utilize ceramic fiber heating elements are fully serviceable. The ceramic fiber type heaters are typically used with reactors that are rated above 350°C. It is common for the refractory type insulating components to also need to be replaced as they become brittle from long term exposure to high temperatures.
Enclosed band heaters that are used on some 25/50 mL Micro reactors can be serviced by replacing the band heating element and integral cord. However, be advised that this can be quite a cumbersome task.
Flexible Mantle Heaters and Glass Fabric Mantles
Parr’s flexible mantle heaters and glass fabric heaters are not serviceable. They do have a long life when well maintained, but due to the construction are impractical to service. Most complete heater assemblies are readily available for replacement.
Aluminum Block Heaters
The heating elements used in Parr’s aluminum block heaters can be replaced, but are often oxidized to the point where they must be removed by carefully drilling out the cartridge sleeves. It’s also recommended that all of the cartridge heaters be replaced at once as the fiberglass wire insulation can become damaged during servicing. Tapered plumbed fittings are often oxidized to the point that if they are loosened, they will no longer be able to be resealed. When this occurs, the entire block must be replaced.
If you have any questions regarding the servicing of Parr’s electric heaters, please contact our customer service staff.
New Product Announcement
4878 Automated Liquid Sampler
We are excited to announce our new Automated Liquid Sampler which will be released for sale in October of 2016.
The new Model 4878 Automated Liquid Sampler provides a safe and reliable method for collecting multiple liquid samples from heated and pressurized reactors.
- Ability to extract up to six liquid samples without the need for continued operator presence
- Operates up to the maximum working pressure of all standard Parr reactors and pressure vessels
- Touch screen controller with easy-to-navigate graphical displays
- Compact footprint
- Stand alone design compatible with any new or existing Parr reactors and pressure vessels
- User-definable parameters including time between samples, number of samples, and number of loop sequences
- Capability to connect with mobile devices on both iOS and Android platforms
- Customizable design
Visit the Parr Dealer Extranet to download dealer specific information with further details to help you and your team prepare to promote this new instrument.
Please contact us with any further questions regarding the new Automated Liquid Sampler.
Mass Flow Controllers
Mass Flow Controllers are becoming more common in Parr reactor systems. They are a possibility in any application where there is a gas feed, but are mostly used in continuous flow systems or in very large reactors where a high pressure gas burette is not feasible.
Selection of a suitable MFC should be done with the assistance of a Parr sales representative, but this article will attempt to detail the basic required information and illuminate some of the guiding principles while working with an MFC.
In Parr systems, a Mass Flow Controller is used to deliver gas to a reactor at a desired flow rate. They are typically utilized with a back pressure regulator at reactor exit to maintain a constant pressure in the reactor.
Do you need an MFC?
MFCs are not common on lab scale batch reactors. While many of our batch reactors require a gas feed, this is typically done by charging the reactor with sufficient gas to carry out the batch reaction, or by utilizing a high pressure gas burette for semi-batch reactions. Both of these measures are significantly less expensive than an MFC.
On continuous flow systems where a constant flow of gas will be required, MFCs are required. Tubular reactor systems typically have them, and sometimes larger reactors (perhaps 2-gal or larger) use them too, where getting a high pressure gas burette with sufficient volume is not as cost-effective as an MFC. Finally, some applications require precise mixtures of gases in real time, a function that’s difficult to do without MFCs.
Types of MFCs
There are many types of MFCs on the market, but Parr typically uses thermal mass flow units manufactured by Brooks in the United States and Bronkhorst in Europe. The same type of technology is used on Mass Flow Meters, which use the same thermal mass flow measurement mechanism, but do not have an automated valve to adjust the flow rate.
Specifications Needed to Purchase a Mass Flow Controller
Maximum pressure – This tells us what type of MFC to use. Significant cost savings are available for units operating below 1500 psi.
Outlet pressure – This is the operating pressure of the reactor or an average pressure of typically expected operating range.
Inlet pressure – This is the pressure of your gas tank. Best practice is to use a forward pressure regulator on the gas tank to maintain a constant inlet pressure to the MFC. We find that we get a great deal of repeatability and accuracy if the MFC is calibrated for an inlet pressure that is 300 psi greater than the outlet pressure.
Process gas – The MFC operates by splicing off a small stream of gas going through it and heating it up to see how much the temperature rises. The amount of temperature rise, and therefore the flow accuracy, is dependent on knowing the gas is being used. The MFC electronics are calibrated to the heat capacity of the expected gas.
Flow rate – The MFC has a 50:1 turn down ratio, which means that it will control within a flow range that matches this ratio. That is, the maximum flow rate will be 50 times greater than the minimum flow rate. Some example max/min ranges include: 2-100 sccm, 10-500 sccm, 50-2500 sccm, etc.
Control method – The MFC requires a control box to send it a set point, read back the flow rate, and supply it with power. Most commonly it is powered with a 4871 Process Controller or an A2200E Flow Control Box.
Mounting – The orientation of an MFC is important. MFCs are very high precision devices which will not read accurately if they are not calibrated in the correct orientation. At Parr, we prefer mounting them horizontally, with the base down. In most cases this specification is Parr’s to deal with, though, since we typically take care of mounting the MFC and routing the process piping to the reactor.
Please contact us for further information about configuring a Parr reactor system with Mass Flow Controllers.
Tubular Vessel Assembly with Removable 4” Viewing Diameter Windows
We recently built and delivered a tubular vessel for a customer who needed sight glasses with a viewing diameter larger than any of Parr’s standard offerings.
The custom manufactured vessel had the following salient features:
Double ended with sight glasses and inlet/outlet connections on both heads
- Removable sight glass housings with a 4” viewing diameter
- Rated for use up to 1400 psi @ 470°C
- Horizontal vessel with cart sub-assemblies for convenience of installation and removal of heads on either end permitting user to independently service each sight glass housing unit outside of the vessel assembly
- Non-welded construction
A horizontal split tube furnace was used to provide uniform heating.
Please contact us if you would like more information on this custom system and reference order number 916109.
Information about Parr’s standard window/sight glass assembly options are described in Technical Note No. 227.
Parr Team Member Focus
Kevin Johnson, Purchasing Manager
Kevin was born and still lives in Davenport, Iowa. He received his degree in Operations and Supply Chain Management from Iowa State University in 2006.
Mr. Johnson joined Parr Instrument Company in 2008 and has worked in our purchasing department for over six years. He handles all things purchasing related where he purchases everything from mundane staple removers to exotic metals. Kevin partners with our suppliers to solve complex problems with win-win solutions.
When asked what he likes best about his job, Kevin said “The people at Parr are great and in my role I get to work with so many different departments within the company. Our production schedule is always changing with new orders or special customer requests. I enjoy working with others, inside and outside of our company, to do our best to meet our customer’s needs.”
When not at work, Kevin enjoys spending time with his family, leading a bible study at his church, and playing and organizing a disc golf league.
Kevin is a valuable asset to Parr and we are happy to have him on our team!
The Korean Institute of Chemical Engineers
October 19-21, 2016
Look for our representatives from MK Science Co., Ltd.
8th Symposium on Continuous Flow Reactors
November 8 – 10, 2016
2016 AIChE Annual Meeting
November 13 – 18, 2016
San Francisco, California
View our complete 2016 Trade Show schedule.