Laboratory Refrigerator

Prof. Asma Shaukat

I am sure you all think that you know what a refrigerator is?

Do you?Really?

A refrigerator isa) An apparatusb) An equipmentc) An Instrumentd) A Machinee) A tool e) an equipment

Introduction

The most important piece of equipment

in laboratories

Principle of operation

It is an insulated cabinet with a door and

a refrigeration unit that generates and

maintains the required low temperatures.

Conservation refrigerators in the range of

2 to 8 °C.

Low temperature freezers in the range of –15 to –35 °C.

Ultralow temperature freezers in the range of

–60 to –86 °C

WHAT IS THE PURPOSE OF THESE REFRIGERATED STORAGE UNITS?

PURPOSE OF REFRIGERATED STORAGE UNITS

These units are used for storage of:

Reagents

Stock cultures

Media

Patient specimens

Blood and its derivatives

Biological fluids

In general, the higher the temperature the more chemical and biological activity is present.

By reducing temperature, one can control the effects on the composition and structure of substances to be preserved.

In the laboratory, systems of refrigeration are

used for conserving substances such as reagents and biological elements which would otherwise decompose or lose their properties.

What Physical concerns should be addressed while installing refrigerators?

Physical concernsLocated in a well ventilated area allowing

2-4 inches at the top, back, and sides for proper air circulation.

Avoid placing these units in areas with hot drafts and direct sunlight.

Proper leveling of the units will ensure the most efficient operation.

Place a carpenter’s level on top of the unit and adjust the leveling screws until the bubble is centered in the level.

If a carpenter’s level is not available, adequate leveling can be obtained using the door as a guide. When the unit is level, an open door will not swing further open or closed until it is moved manually.

Biohazard signsWhen patient samples or cultures are

stored in these units, a biohazard sign should be in plain sight.

Never store food or drink for human consumption in a laboratory refrigerator.

How often should we make various quality control checks?

Performed routinely

Daily, weekly, monthly, annually

After adjustment or repair

DailyEnsure internal blower fans are

operating.

Check unit temperatures when they are first opened each morning and record results on the temperature chart.

The internal temperature of a laboratory refrigerator should be 2 to 8°C ± 1°C.

Temperature log

AnnuallyEnsure the unit is still level.

Check power cords for signs of wear. Frayed or cracked cords must be repaired by cutting them down or replacing them. Never use electrical tape to cover cracks or frays.

Check door gaskets for obvious deterioration and replace them if they are cracked, torn or warped.

Equipment maintenanceQuarterly

Six monthly

Annually

QuarterlyClean the interior:

Remove refrigerator contents, unplug the unit and leave the door open allowing it to reach room temperature.

Clean the internal walls, removable parts and the exterior with an approved disinfectant and thoroughly rinse with water to remove residual disinfectant.

Plug the unit in, close the door and wait one hour before checking the internal temperature.

Once within range, return contents to the unit.

Warning: Avoid using steel wool or other abrasive materials for cleaning

the shelves and drawers. Avoid using gasoline, naphtha or thinners,

as these damage the plastic, the packing or the paint on the surfaces.

Door gasket can be verified by

usinga) Level bubblesb) paperc) Plastic d) special toolse) suction cups b) paper

Door gasket verification:Open the door.Insert a strip of paper of about 5 cm in width

between the door gasket and the edge of the refrigerator’s body where the gasket is housed.

Close the door.Pull the paper gently from the exterior. The

paper must put up resistance when being moved outwards. If the paper can be moved without resistance, the gasket must be substituted.

Warning: A door gasket in bad condition produces various problems in the functioning of cooling units:1. It allows humidity to enter which condenses and freezes inside the evaporator.2. It increases the time needed by the compressor for maintaining the selected temperature.3. It affects the storage temperature.4. It increases the operational costs.

How often should we defrost a

laboratory refrigerator and what is the proper procedure to defrost it?

Six monthlyDefrosting:

Verify that the thickness of the frost is more than 8 mm.

Remove the contents of the compartments.Disconnect the freezer.Leave the door open allowing the unit to reach

room temperatureRemove the water while it is accumulating in the

compartments. Use a sponge or a piece of absorbent cloth.

Place a towel to avoid the melting ice from wetting the front and interior part of the refrigerator.

Once defrosted and warm, clean the interior and exterior with an approved disinfectant and thoroughly rinse with water to remove residual disinfectant.

Plug the unit in, close the door and wait one hour before checking the internal temperature.

Once within range, return contents to the unit.

Warning: Never use sharp elements to remove ice or frost from the evaporator. Such an

action can perforate the wall of the evaporator and allow the

refrigerant gas to escape causing a serious defect which can only

be repaired by a specialist.

Do you need an engineer to clean the

condensor? What would be the next best option?

YOU

Cleaning of condenser:Disconnect the electrical feed cable.Verify the position of the condenser. Remove the

condenser’s protective grids and the protective filterRemove the dust and grime deposited on the surface

of the condenser. Use an aspirator equipped with a suction brush. Run it over the entire surface of the condenser to remove grime or accumulated dust. Verify that the tubes’ surfaces as well as those of the heat conducting wings are clean. Vacuum the filter as well

Replace the cover.Connect the refrigerator to the electrical connection.

Warning: If the condenser is not clean, this will interfere with the

heat transference process and the refrigerator could “heat” or

function at temperatures different than selected.

vaseline and bleach are well known

beauty products. But these beauty products have other

uses too. Can you use these products for the maintenance of your refrigerator?

yes

AnnuallyInspect door gasket for mould. When present, clean the gasket with a

10% bleach solution. Rinse thoroughly to remove all residual

bleach and dry completely. Apply a thin layer of Vaseline or

ArmorAll to maintain flexibility.

Temperatures of laboratory refrigerators must be monitored with National Institute of Standards and Technology (NIST) traceable thermometers.

Thermometers for refrigerator are in range of (-5 to 15ºC)

What is the proper method of using an

electronic thermometer?

PrincipleThe thermometer uses a separate probe attached

to the device by a 3 meter long cable.

It is advisory to fix this probe in a glycerol tube.

Because when you buy the thermometers made for monitoring the fridge temperature it comes in glycerol. It is a liquid that doesn't evaporate and stays stable when the temp fluxes when the door is opened and shut. Also its nontoxic and innocuous.

Digital thermometers

Glycerol

Stopper

Drop counter

Plastic tube

Procedure:Installation of thermometer

Pull down the battery cover. Install the battery with correct polarity positioningCheck if thermometer works

Thermometer will have a full segment display for about 3 seconds

After 3 seconds normal fridge sensor temperature will be displayed

Peel off the adhesive tape cover sheet on the sensor holder.

Put the sensor inside a glycerol tube to limit temperature fluctuations when opening the fridge door

Firmly attach the tube with the sensor inside the fridge. The best place to attach the tube is in the middle of the fridge.

Use strong tape to attach the tube in an upwards position.

Pull the cable and the thermometer through the opening of the rubber sealing of the fridge door.

Attach thermometer outside the fridge by using the magnets on the back of the device.

Press [°C/°F] button to select temperature unit [Celsius or Fahrenheit].

Print the registration form. Fill in the correct information in the

header of the registration form.Paste the registration form on the fridge.

Make sure the form is clearly visible.

Glycerol tube:Use the knife to make an incision in the

stopper. The incision has to be big enough so the cable of the thermometer can go through it.

Pull the sensor and the cable through this incision in the stopper.

Take the scissors and cut off the tip of the drop counter

Take the needle and make a small hole in the reservoir of the drop counter so air bubbles can escape

Pull the sensor and the cable through the drop counter. Tweezers can be used to facilitate this job.

Fill the plastic tube with glycerol. Fill it so the stopper can be put on without spilling too much glycerol. Place the tube in a rack in upwards position.

Fill up the stopper with silicones. This is necessary to prevent leakage of the glycerol when the tube is not in the upwards position in the fridge.

Push the sensor with the drop counter and the stopper in the plastic tube until it fits.

While pushing the stopper, make sure air bubbles disappear through the hole in the reservoir of the drop counter

Place this construction in an upwards position and let it dry for 24 hours.

After 24 hours, check if the silicones have dried overnight by holding the tube upside down.

Use tape to firmly attach the stopper on the plastic tube.

Every six months thermometers will be calibrated against a certified thermometer, which meets NIST standards.

Records of each calibration will be kept.

Validation

Utensils

Instruments

Equipments

Validation: overall term used for establishing documented evidence through defined testing that a system or piece of equipment meets designed criteria and the adequate provisions have been established

Qualification: is used to determine whether equipment operates as it was designed and in a reproducible manner.

Qualification procedures are determined by written protocol and testing of the equipment.

Global Harmonization Task Force (GHTF) structure

IQ – Installation Qualification Demonstrates that the key aspects of the process

equipment and ancillary system installation meet the plan.

OQ – Operational Qualification Demonstrates that process control limits and

action levels are set that result in product meeting specification.

PQ – Performance Qualification Demonstrates that the process, under anticipated

conditions, consistently produces a conforming product

What does this mean?We determined the optimum process

parameters

We conducted challenge tests to demonstrate robustness

We now run the process under normal conditions over time

Process validation is defined a discipline

Established methods define the approach

Following these methods will help ensure that processes operate effectively, i.e., do not produce nonconforming material.