Friday, August 25, 2017

Laboratory Refrigerators Equipped for Specialized Applications

laboratory refrigerator configured for chromatography process glass doors electrical outlets wall ports
Laboratory refrigerators can be specifically configured
to match lab process work.
Image courtesy Powers Scientific
Refrigerated space in a laboratory is not the same as refrigerated food storage space. Yes, of course, both are cold. Laboratory needs, though, can range beyond simple cold storage. Lab cold space work is often an ongoing process that requires a cold environment. There may be application requirements that will not be accommodated by food service or simple cold storage units.

  • Temperature Control - Stored materials and processes in a lab cold space are likely to have a low tolerance for temperature excursions outside a comparatively narrow range. Higher performance controllers, and in some cases modified or specialty refrigeration systems, deliver the performance needed for these applications. 
  • Corrosion - The presence of some chemicals in a lab cold space requires accommodation with a chamber inner liner with adequate resistance to corrosion.
  • Instrumentation and Process Equipment - Lab processes can incorporate the use of equipment and instrumentation within the cold space. Heat generated by the equipment must be removed by the refrigerator cooling system in order to maintain control of temperature. These instruments operate with electric power which must be accessible within the chamber, via installed receptacles, or through capped ports in the cold space wall with an extension cable. The ports can also serve to provide a path for tubing or other instrumentation cables into the cold space from the surrounding lab.
  • Safety - Some chemicals and materials present flammability or explosion hazards when stored or placed in enclosed spaces. Special refrigerators are available that are specifically designed and built to meet the regulatory requirements for storing these hazardous materials.
  • Vibration - Certain processes may require the maintenance of low vibration transmission from the refrigerator cabinet and machinery to the housed process. This requires special attention to the mounting and structure of critical refrigerator machinery and interior supports.
Share your laboratory cold space requirements with a lab equipment expert, combining your own knowledge and experience with their equipment application expertise to develop an effective solution.

Tuesday, August 15, 2017

Keeping the Cool in Your Laboratory Refrigerator

sliding glass door laboratory refrigerator
A small amount of regular maintenance can
assure sustained performance of your lab refrigeration equipment
Image courtesy Powers Scientific
Hardly the highest tech piece of equipment in your lab, that refrigerator or freezer is nonetheless important to much of what goes on in the lab. The supplies or work in process stored in those refrigerated spaces represents precious time and budgeted funds. Knowing and doing a few simple things can keep refrigeration equipment operating smoothly, save energy, and head off costly repairs.

There are a number of different refrigerator configurations, so let me limit this brief explanation to something of a generic lab refrigerator, like that pictured above from Powers Scientific. Here are some basics.

  • Double sliding glass doors
  • Bottom mounted air cooled refrigeration system
  • +4 degree Celsius operating temperature

How does a refrigerator really work?

The refrigerator essentially consists of three things:

  • Insulated Cabinet - The cabinet is what you see, what you refer to as the refrigerator. It contains the stored materials. The cabinet also keeps the cold air from leaking out to the surrounding space and keeps the surrounding air from entering the contained area. The cabinet structure also provides a barrier of thermal resistance to heat transfer, or insulation.
  • Heat Transfer System - Also called the refrigeration system or cooling system, the heat transfer system takes heat from the air within the cabinet and expels, or transfers, it to some medium outside the cabinet. Most often, the medium outside the cabinet is the air in the lab, although it is possible to have a system that employs a liquid, such as water, in place of air. It is important to understand that an air cooled system delivers a net heat gain to the surrounding space. That rejected heat must be removed or otherwise dissipated to keep the space from overheating.
  • Controls - Unbridled operation of the cooling system will not deliver the predictable temperature performance needed for laboratory settings. A controller, in its most basic configuration, must be able to accurately measure the chamber temperature and regulate the operation of the cooling system in response to changes in that temperature.

What are some things to do, or be aware of, with refrigerator operation?

  • Doors - Doors are part of the cabinet containment that keeps cold air from escaping and warm air from entering. They should operate smoothly, without requiring undo force to open or close. When closed, the doors should set firmly against their sealing surfaces and any gaskets should be kept clean and free of dirt and grit that can inhibit sealing and lead to premature deterioration. A simple periodic inspection and wipe down with a wet cloth will go a long way toward maintaining good performance. Doors that creak or squeak when operated should be further examined for excessive hinge or bearing wear, possibly in need of lubrication.
  • Condenser - This is the device that ejects heat to the surrounding space on the example air cooled unit. On most refrigerators, the condenser will be located either on the top of the cabinet or in a compartment below the cabinet. To locate the condenser, look for louvers or a grille that permits air to flow to the condenser. It is important that air be able to flow freely across and through the condenser. If the fins on the condenser become clogged or blocked with dust, pieces of paper, tape, bags, plastic, or anything else that inhibits free air flow, the cooling capacity of the system will be reduced. Excessive blockage can cause the equipment to fail. A simple cleaning can be accomplished with a vacuum cleaner or a flow of compressed air. Even if you are not the person who will ultimately clean the condenser, it is important to know when to schedule the maintenance to be done.
  • Evaporator - Inside the refrigerator there will be a fan unit that also houses a finned evaporator. The chamber air flows across the evaporator surface and is cooled by evaporating refrigerant. Keep the air flow passage free of accumulated dust and debris that may block air movement through the fan housing and across the evaporator. Sometimes pieces of plastic film or paper can get loose in the refrigerator and be drawn into the inlet side of the evaporator, blocking some of the air flow. In most cases, it is just useful to inspect and recognize when service might be needed. 
  • Temperature - Over time, you will grow accustomed to normal refrigerator performance. Any long term excursion of chamber temperature outside of the expected performance range is cause for a service call. There is only one way that operation will be right, but a vast number of ways that it can go wrong. A short term, probably no more than one hour, temperature excursion out of range likely is the result of excessive heat load. The most common causes of this are large additions of warm mass to the chamber or excessive door opening time or frequency. Any temperature anomaly that lasts longer than about one hour is cause for diagnosis by a qualified technician.
A lab refrigerator is not a piece of equipment that garners close scrutiny by lab occupants. The best plan may be to have a qualified technician inspect the equipment on a regular basis. Inspections are generally inexpensive and can often be scheduled along with regular maintenance of other equipment in the lab. Share your questions and concerns about laboratory refrigeration applications for all temperatures and sizes with application experts. Combining your own on site knowledge and experience with their product application expertise will result in an effective solution.

Wednesday, August 9, 2017

Refrigerators for Laboratory Applications

laboratory refrigerators
Several different types of laboratory refrigerators
Image courtesy Powers Scientific
Many laboratories have a need for refrigerated space. The requirements for that space vary widely enough to support a very broad range of refrigerated cabinets, providing variants and optional features that meet every need. Refrigerators tend to last for a long time, so it's practical to make a considered decision when procuring one for the lab. Here are some items to include when selecting a new lab refrigerator.

  • Materials to be Stored: Certain flammable materials requiring cold storage must be kept in a refrigerator specifically designed and rated for the storage of those materials. Less hazardous materials can be accommodated by a wider variety of choices. 
  • Storage Temperature: Determine the most sensitive content for the proposed refrigerator. What are the highest and lowest temperatures providing suitable storage conditions? Lab refrigerators are generally not precision control chambers. Know the requirements of your contents and the capabilities of the refrigerator. Make sure they are compatible.
  • Controls and Monitoring: What are your needs for control, display, and monitoring of cabinet temperature? Is a dial thermometer a sufficient temperature indicator, or is a digital display more appropriate? There are many options available. Think about how temperature should be monitored and out of range occurrences handled. Keep in mind that electronic controls will not function during a power failure without a backup power source. Maintaining documentation of chamber temperature under all conditions may require inclusion of battery backup for data logging and alarm devices.
  • Cabinet Size: Lab refrigerators are available in sizes ranging from a few cubic feet to units as large as a grocery store display line. Take the time to make a layout of your storage needs, everything that will go in the refrigerator. This will help in determining the best size for your application. 
  • Doors: The refrigerator doors are the user interface for the unit. They are what you touch every time the refrigerator is accessed. Make sure the selected doors meet the application needs for interior visibility, security, and ease of access. Also take into account the space where the refrigerator will be installed. Sliding doors do not encroach on the surrounding space, as a hinged door would.
  • Heat Rejection: An often overlooked aspect of lab refrigerator operation is where the heat removed from the chamber interior will go. A refrigeration system is a heat transfer machine, taking heat from the chamber air and rejecting it from the condenser. The condenser is usually air cooled, resulting in that heat being released into the space where the refrigerator is installed. There must be an identified path for that rejected heat to be further transferred out of the installation space, otherwise the space will increase in temperature until the refrigeration unit fails. If an assessment of the proposed installation space for the refrigerator fails to identify sufficient ventilation, there are several refrigeration system schemes that can be substituted for the self-contained condenser most often seen on lab refrigerators.
  • Accessories: There are more available options and accessories for laboratory refrigerators than could be included here. Users should describe to potential vendors the manner in which the refrigerator will be used. Refrigerators employed as simple cold storage units will have a simple set of requirements. Those used as part of a process may have very special configuration requirements. 
  • Transit: Some lab refrigerators are quite large. Of course, you should measure the space where the unit is to be installed, making sure there is a fit. Do not forget to verify that the equipment must pass through all the doors, hallways, elevators, and other spaces that make up the path from delivery point to installation point.
There is much more detail that may be involved in making the best selection. Enlisting the assistance of a laboratory equipment specialist will help speed you through the selection process and create a successful purchase, delivery, and installation plan.