Mechanical Engineering Measurements

Thermometry and Psychrometry

• Dry bulb temperature measures the air temperature
• Wet bulb temperature measures the temperature of the air when it is fully saturated with water vapor
• Inclined water gauge is used to measure water pressure less than 200 mm

Centrifugal Fans

• Smooth flow of air and conversion of velocity energy into pressure energy takes place in the spiral casing
• Re-entry of discharged air is prevented by the spiral casing
• Efficiency of the fan and reduction in power cost can be obtained with well-designed blades

Axial Flow Fans

• Maximum permissible speed is 5200 m/min
• Maximum water gauge developed is 13.5 cm
• Water gauge developed and quantity circulated depend on more than 250 pa

Refrigeration

• Refrigerant used in refrigerant circulation system is Freon-12
• Harmless refrigerant is Carbon dioxide
• Profilometer is used to measure the cross-section of irregular shapes

Safety and Extinguishers

• Ammonia should not be used in underground mines as it forms an explosive mixture with air if present above 20% by volume
• The best extinguisher for fires involved in live electrical equipment is CO2 type
• The best extinguisher for fires due to oil is Foam type
• The best extinguisher for gaseous fires is CO2 type

Mining and Quarrying

• When a quarry is abandoned, the coal and OB dump should be separated by digging a trench 3-5 m wide
• Coal stock should not exceed 100 te
• The height of the coal stock should not exceed 1.5 to 3 m
• The ignition temperature of bituminous coal is 20°C

Isolation Stopping

• Isolation stopping in degree I and II gassy coal mines should have a minimum thickness of 2 m
• The isolation stopping should be explosion-proof if the minimum CH4% behind the stopping is 2%
• The minimum thickness of the explosion-proof isolation stopping is 4.5 m
• Isolation stopping should have a minimum depth of locking in shale of 75 cm

Stoping and Mining Methods

• Temporary stoping is constructed before depillaring is undertaken
• Stoping should always be kept white washed on the surface and at the roof, floor, and sides for 1 m outbye for every detection of cracks
• During the process of sealing a fire area below ground, the atmosphere near the stoping should be tested frequently for 20 m

Dams

• The thickness and height of the temporary dam are 1 m and 2 m, respectively
• The thickness of the permanent water dam is 6 m

Electric Cap Lamp

• The electric cap lamp is intrinsically safe
• The flame of a flame safety lamp while testing for CH4 spires of jumps at 3%

Automatic Detectors

• Automatic detectors give either audio or visual alarm when the percentage of inflammable gas exceeds 2%

Health Hazards

• Tuberculosis is caused due to inhalation of quartz dust

Fire Fighting

• The method of dealing with fire in a mine where heating is in the initial stages and its exact location is known is digging out and extinguishing
• Spraying the surface with a liquid cement sand mixture (1:3) in dealing with fire is known as plastering

Stone Dust Barrier

• A stone dust barrier may fail to arrest an explosion if there is a crack in the roof of the roadway over the barrier

Open Stope Method

• Open stope method is used for ore of high grade
• The thickness of the bed in open stoping is 2 to 3 m

Pillar Left

• The pillar left to support the upper level is called the sill pillar

This quiz assesses knowledge of measurement instruments and techniques in mechanical engineering, including temperature and water gauge measurements.