Paper on Heat Stress

Topics: Temperature, Heat, Thermodynamics Pages: 5 (1286 words) Published: April 8, 2013
Heat Stress Exercises- Bhaskarla Krishna Harika

Question 1:
(5 marks)

Herbicide spraying is taking place with a hand-held spray. The sprayers carry a container of weedkiller on their backs and the spraying covers a large area which they are covering on foot.

The sprayers have just come back from annual leave, this being their first week back.

To protect themselves against the herbicide, they are wearing cotton coveralls and gloves.

On the day when spraying is to take place, the temperatures are measured at 11am.

They are:

Globe temperature 43.50C
Air temperature32.00C
Natural wet bulb temperature 20.00C

* Calculate the WBGT

* What work-rest program would you recommend?

* What work-rest program would you recommend for workers who had been back for two weeks?

* Suggest some other ways to prevent effects of heat stress in this case.

* WGBT= (0.7*NWB) + (0.2*GT) + (0.1*DB)
= (0.7*20.0) + (0.2*43.5) + (0.1*32.0)
= 25.9⁰C
* Work-rest program:
Since the workers have returned from a break around one month, they have to acclimatize themselves before taking full work load. The exposure time to heat must be shortened with frequent rest breaks. On an average an unacclimatized worker should rest for 15 min per hour. Such a work-rest cycle gives the worker’s body opportunity to lose excess heat. Thus preventing unwanted heat stress before acclimatisation. * Work-rest program for workers who have been back for 2 weeks: A time period of 2 weeks is sufficient for a worker to acclimatise himself to the work conditions. Since the WGBT is less than 27⁰C and the nature of work is moderate, the worker can carry on with his normal schedule. However, work should be planned in such a way that hectic part of the job can be done in the early morning when heat is not pressing. Heavy work should be avoided when the temperature is at its peak. Planning the work schedule ahead and educating the workers similarly goes a long way in avoiding heat stress or strain. * Other ways to prevent heat stress:

There are different ways to prevent heat stress and its side effects. It has already been mentioned that the workers are wearing cotton overalls which is one the most important method of preventing heat stress since they assist the body in evaporation of sweat thereby bringing down body’s core temperature. A few other ways to prevent heat stress are as follows:- * Drinking water (preferably slightly salted) in small quantities at regular intervals throughout the day to maintain the electrolyte balance of blood. * Keeping the skin dry and clean helps in preventing heat rash. * Resting in cool and shaded areas allowing the skin to cool itself. * Changing work style like mid-day resting and sharing tasks between more workers. *

* Question 2:
* (5 marks)
* Gardeners have to spend time digging a plot for replanting. The soil is fairly light. * The afternoon temperatures are as follows: * Globe temperature 36.50C * Air temperature280C * Natural wet bulb temperature 200C * They are wearing light summer clothing * Calculate the WBGT

* What work-rest program would you recommend for workers returning from the Christmas shutdown in January? * What work-rest program would you recommend for workers who had been back for two weeks?

* WGBT= (0.7*NWB) + (0.2*GT) + (0.1*DB)
= (0.7*20) + (0.2*36.5) + (0.1*28) = 24.10C...