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LABORATORY FITMENTS

LABORATORY FITMENTS

Laboratory fitments include

1. Benches
2. Water taps
3. Gas taps
4. Sinks
5. Electric gadgets
6. Fume chambers
7. Fire extinguishers
8. Shelves

1. Laboratory benches

Laboratory benches provide surfaces upon which laboratory experiments and test are done. There are two main patterns of laboratory benches i.e.

1. Permanent assembly benches
2. Unit assembly benches

Permanent assembly benches

Permanent assembly benches are permanently fixed hence do not allow future modification or else they must be destroyed incase necessary changes are to be made.  They are   designed for specific purposes. These are benches on which laboratory services e.g. water, electricity and gas taps should not be placed on them.

Unit assembly benches

They are temporarily fixed, flexible and movable and therefore can allow   future modification.

Laboratory benches can also be classified into the following three categories based on the positioning in the lab.

1. Wall benches

They run along the side walls of the laboratory. Heavy equipment’s, water, taps and gas taps are usually placed on these benches

1. Island benches

They occupy the center space of the laboratory. In majority of labs, they do not have water, gas and electricity taps

1.   Demonstration or lecture benches.

These benches are usually found at the front of the lab near the board and are used by the teacher when demonstrating an experiment to students

Benches should have enough working surface area and good working height. For student benches, it is recommended that they have a working surface area of ≥0.36m2 per pupil.  The height should be 900mm with good clearance for legs when the pupil is seated at the bench. A measurement of 240-270mm from the top of the stool to the underside of the worktop allows sufficient upper leg clearance for one to sit comfortably at the work surface.

All laboratory  services e.g. water, electricity, gas  should be on the  demonstration benches,  be within the reach of  persons sitting  next to the bench( i.e. within 600mm) and be of the same height as the pupil benches.  The perimeter benches should be on two walls and with adequate structures to support it.

The materials for constructing laboratory benches should be;

1. Suitable for the intended purpose of the laboratory e.g. for  medical , biological or chemistry lab
2. Cheap, durable  easily available  and easy to clean
3. Poor conductor of electricity
4. High mechanical strength and Free from vibrations
5. Resistant to chemical  and water attack
6. Free from shrinkage and distortion
7. Don’t burn easily

Materials used for making laboratory benches

1. Wood

Advantages

1. Cheap and easily available
2. Poor conductor of electricity
3. High mechanical strength

Disadvantages

1. Easily attacked by fungi, pest and bacteria
2. Easily distorted if not well treated
3. Easy to burn
4. Easy to be cut

              Application:  Physics and chemistry Laboratories

2. Metal e.g. stainless steel, aluminum.

Advantages

1. High mechanical strength

1. Water resistant
2. Free from shrinkage and distortion
3. Don’t burn easily

Disadvantages

1. Conduct heat and electricity

1. Expensive

Application: Food, medical, biology and radiology laboratories

3. Concrete

Advantages

1. Free from vibrations ,

1. Have high mechanical strength
2. Heat resistant

Disadvantages

1. Easily attacked by acids
2. Poor performance if not properly finished

Application:  used for balance rooms

4. Plastics

Advantages

1. Resistant to fungal and bacterial attack

1. Chemical resistant
2. Poor conductor of heat and electricity
3. Easy to be cleaned

Disadvantages

1. Wear out easily  and not heat resistant
2. Easily damaged by laboratory equipment’s

Application: used for Chemistry, biology, physics and medical laboratories

3. Stools

Stools should also be designed to allow enough leg space and appropriate height for people to sit at the bench.

4.  Doors and windows

Doors and windows must be wide enough to provide for natural light and ventilation, be easily accessible and should have restricted openings, which can nevertheless be opened fully in the event of an emergency.

5. Laboratory Drainage System

Laboratory drainage system plays an important role in the supply of water and disposal of laboratory effluents. It consist of taps, sinks and traps. The layout of the drainage system is an important aspect that must be thoroughly considered during laboratory design.

The water supply tanks should be positioned high enough to provide pressure to operate science equipment

Taps: The position of taps and sinks is very important and should be done in accordance to the type of work to be done on a bench. Taps should be placed at the center of the bench or on the sides to allow for communal work. They should not be placed next to electric sockets

Water tap taps should be at least 300mm above benches, and with the sprout at least 225mm above the sink. Sinks should also be provided for washing and rinsing various laboratory wares.   One water tap and a sink is recommended per six pupils spaced around the lab, and each should be large enough for experimental equipment. Another sink and water tap should be included in the fume cupboard.

Sinks can be made of plastic, stainless steel, ceramics etc.There are two types of sinks.

1. Rimless sinks
2. Rimmed  sinks

Rimless sinks

These sinks do not have rims and are fitted tightly on the bench.  

Rimmed sinks,

They have rims that lie over the bench surface. There are two types of rimmed sinks i.e.  Externally rimmed sink and internally rimmed sink. The fittings of the sinks should be such that they should not allow leakage or flooding of the water.

 Rimless and internally rimmed sinks are recommended for use in laboratories because they are easier to wipe out dirt from the bench into the sink

The space between the back of the sink and the bench should always be made watertight to prevent seepage

Traps A trap is a device or fitting under the sink that traps water. Traps serves many functions, these include:

1. They receive waste from the sink and disposes it into the main drainage system.
2. They acts as a dilution tank for corrosive liquids before being discharged so as to protect the piping
3. They also trap insoluble solids flowing down from the sink so as to prevent the piping from being blocked
4. They prevents foul smell from getting back into the laboratory by cutting off the drain interior atmosphere from the exterior air by preventing foul gases in the drain from escaping

The effectiveness of a trap is dependent on the depth of the seal, since the deeper, it is, the more it will resist the pressure inside the drain

All traps must be able to meet the following requirements to be effective:

1. Simple in design
2. Accessible in all parts
3. Made of hard, smooth, impermeable material
4. Self-cleaning in action
5. Be smoothly rounded with no sharp angles or corners
6. Holding minimum amount of water but with effective seal
7. Must not retard the flow of water
8. The most common materials for laboratory water traps are plastic (PVC)

6. Laboratory Gas Supply System

Gas systems are used for distribution of fuel gas in science laboratories.

For efficient distribution of gas in the laboratory, two- way outlet gas taps with safety locks are recommended.

They should not be opened by accidental knocks.

Furthermore, all gas taps not to be used should be properly secured in order to avoid pupil’s accidental opening. However, the master gas switch should be positioned at a readily accessible location and the ON/OFF position be clearly indicated.

Gas tap should be fitted on the demonstration bench, fume chamber and perimeter benching. They should be of robust design, with definite on/off positions and anti-rotate fixing to bench, with non-return valves and restrictors in nozzles.Taps must be spaced around the lab with one tap per student is recommended.

The rubber tubing connecting the gas taps to the Bunsen burner should be of the type suitable for use with the gas being supplied. Both end tubing should be held in position by horse clips to prevent loosening

7. Electric switches

One electrical socket per pupil is recommended. As with gas taps, other sockets should be provided on demonstrations benches, and in the fume cupboard. Electrical sockets should be of robust design and must be away from water taps

.

9.  Pipes and cables

All pipes and cables should be installed in or behind bench walls, or floors. None should be hanging from a ceiling (except for bulbs and other ceiling-mounted data projectors). Pipes and cables should be color-coded according to contents and show the direction of flow.

NB: Gas, electricity and water should all have their master control points that are easily accessible by the lab technician or teacher but not the student

10. Fume chamber

Fume chamber is designed to prevent contamination by drawing out poisonous or dangerous fumes from the laboratory.

 They should be designed in such a way that will only allow fumes to be drawn out of the laboratory and not inside.

Fume chambers consist of transparent panels made of sliding glass that provides a working space for operation.

The services to be installed inside the fume chamber include

1. An electric switch and pilot light
2. A water tap
3. Sink  
4. Two- way gas tap
5. Motor

Based on the type and position of these motors, fume chambers can be classified into two:

       (i)          Direct system

       (ii)         Indirect system

(i) Direct system

The motor is placed directly above the fan in line with the fumes from the lab.

The motor is small and cheap but wears out easily due to direct exposure to fumes hence needs constant replacement

(ii) Indirect system

The motor is placed separately from the fan and is not in line with the direction of movement of fumes from the laboratory.  The motor is big and do not wear out easily, it is however expensive

How to use a fume chamber

Before using a fume chamber, it is important to ensure it is in good working condition.

1. Switch on the fun and adjust the vertical sliding glass to give a reasonable working space.
2. Place your reagents and substances accordingly and ensure that the reaction shall take place as required
3. Close tightly ensuring that no fumes escape out of the fume chamber.

NB/ All fuming chemicals must be opened inside a fume chamber.

11. The shelves

Shelves should be ergonomic and ≤ 2m high, stable and secured to a wall. Stepladders should be provided: height equal to the top shelf, with grab rails and platform.

12. Fire extinguishers

Fire extinguishers are equipment’s used for firefighting.

There are many types of fire extinguishers, these include.

1. Water  fire extinguisher
2. CO2 Fire extinguisher
3. Dry powder fire extinguishers
4. Vaporizing liquid.
5. Foam
6. Fire blanket

13. Emergency showers

Emergency showers are very important because they are used to extinguish fires when somebody is on fire or to wash away chemical from the body surface if spilled upon.

Emergency showers must be placed in an easily accessible position

They should be connected with a water storage tank

They must be regularly tested and properly maintained