Final Week 6 eeeeeeeeeeeeeeeeeeeeee.pptx

On analysing a sample of cloth made from cotton; rayon, silk or flax with view of its
reproduction produced thus:
1. Record whether a fabric is in the grey or finished state.
2. Determine which threads constitute warp and which are weft.
3. If in grey, test for the presence of size material by staining with iodine, when the
starch in the size warp turns deep blue in colour, the weft being unaffected.
4. Examine the direction of spinning twist in the yarns and also if either set of threads is
two-fold yarn. If crepe yarns have been used, it may be necessary to test the amount
of twist present.
5. Count the ends and picks per inch in the fabric. If more than 2 warps or wefts are
used, find the number per inch of each yarn type used.
6. Test the yarns for return, i.e. how much longer they are out of the cloth than the
length of the sample from which they were abstracted. By this means, we can
estimate the length of warp required to give the length to cloth and from the weft
regain, we can estimate the length in Reed or length of each pick of weft. In weaving
ordinary classes 10% of cotton goods regain between 4% and according to the
structure, while the weft gain is usually about 5%. These figures apply to grey
cloths only. In finished goods, the regain will differ according to the nature of the
finished applied. Very often, the length of the cloth is increased and its width reduced
on finishing, hence the warp regain may be as low as 1% to 4% while the weft regain
may be 8% to 10 %. “Rigmel” and “Sanforizing” are finishing processes in
which the fabric is pre-shrunk both in warp and weft directions, the advantage being
that the fabric, when made into a garment, will retain its shape; it will not shrink in the
laundering. When analysing these materials, gains of 8% to 10% will probably be
found in both warp and weft.
7. Test the yarns for counts of warp and weft. (The count of the yarn is the number of
length units required to weight on gain). In a grey sample, the warp will probably be
sized yarn and the count recorded will be the sized count. This should be corrected
by making a second test after thoroughly washing the fabric to remove all size and
filling materials. If the sample is a bleached, dyed, or printed cloth, the counts of warp
and weft will be affected by the counts test then made, allowing about 5% in bleached count
= 20s grey count; 38s bleached = 36s grey count.
8. Analyze the sample for weave details, i.e. whether it is plain, twill, satin, or some other
weave, and proceed to develop the draft and peg plan when necessary.
9. When analysing the sample containing rayon yarns, it is important to test for type of
rayon, i.e., viscose, cuprammonium, or Cellulose Acetate, i.e. number of filaments
comprising the rayon thread must be countered and the yarn exactly matched to
obtain true reproduction of the sample. If the fabric is a coloured woven material,
such as poplin shirting or a zephyr check, the warp and weft patterns

1. EE-3111 ELECTRICAL AND ELECTRONIC SYSTEMS Instructor Engr. Neelam mughees

2. Lecture Learning Outcomes Students will be able to: Understand Basics of Electrical Safety Understand Earthing and Grounding

3. Disclaimer This lecture is not designed to qualify you to work on electrical systems. Qualified workers are those with the training and equipment that allow them to work on high and low voltage lines and to get closer than the minimum approach distances. Qualified workers from an electric utility use rubber goods (gloves, blankets, covers) and other protective equipment to protect themselves against accidental contact. As a reminder, if you identify problems with electrical systems, please report them immediately. “Play It Safe, It’s The Law”

4. What is Electrical Safety? Safety should be defined as reduction of risk to a level that is as low as reasonable and as practicable. It is a state of mind and environment that must become an integral part of each working procedure. This is what we mean by built-in or integrated safety and permanently effective. Electrical safety is more important, because we could not apparently realize that, what amount of current a simple cable or a bare conductor carrying or at a glance we could not ascertain whether a conductor is live or dead. This harmless appearance could misguide us. And this is the root cause of most of electrical accident.

5. Electrical Hazard An electrical hazard can be defined as a dangerous condition where a worker could make electrical contact with energized equipment or a conductor, and from which the person may sustain an injury from shock; and/or, there is potential for the worker to receive an arc flash burn, thermal burn, or blast injury. An electric hazard is considered to be removed when protective measures are put in place at the source (remove hazard or deenergize), or along the path (place electrical insulation/barrier between the worker and the electrical hazard). Where PPE is relied upon for worker protection, an electrical hazard is considered to remain and it is still necessary to address safety requirements for other workers in the area.

6. Electrical Injuries There are basically two ways to be injured by electricity. One is by electric shock and the other is by arc flash. Electric shock is the passing of electric current through the body. Electrical contact can cause involuntary physical movements. The electrical current may prevent you from releasing your grip from a live conductor throw you into contact with a higher voltage conductor cause you to lose your balance and fall cause severe internal and external burns kill you. A household 125-volt circuit can deliver 15 amps. Current as low as 15/1000 of 1 amp (15 mA) can cause breathing to stop. A 15-Amp circuit contains many times the current needed to cause death.

7. Electrical Injuries An arc flash is a release of energy caused by an electric arc. The flash causes an explosive expansion of air and metal. The blast produces a dangerous pressure wave a dangerous sound wave shrapnel extreme heat extreme light. These dangers can result in blast injuries, lung injuries, ruptured eardrums, shrapnel wounds, severe burns, and blindness. Arc flash injuries can also result in death.

8. Electrical Safety Tips

9. Electrical Safety Tips

10. Electrical Hazards and Their Prevention Watch this video to note down the major Electrical Hazards and their prevention https://www.youtube.com/watch?v=ggJo6m8NZtA

11. Lightning Protection We have already studied it. However, watch this video to understand how lightning protection systems work: https://www.youtube.com/watch?v=TBbybbmcguo

12. DISTINCTION BETWEEN GROUNDING AND EARTHING Grounding implies connection of current carrying parts to ground. It is mostly either generator or transformer neutral. Hence it is popularly called ‘neutral grounding’ or ‘system grounding’. Grounding is for equipment safety. Earthing implies connection of non-current carrying parts to ground like metallic enclosures. Earthing is for human safety . It is also called ‘equipment grounding’. Under balanced operating conditions of power systems, earthing system does not play any role. But during ground fault condition, it enables the ground fault current to return to the source without endangering human safety. G rounding Earthing

13. Grounding System and circuit conductor grounding is an intentional connection between the electric system conductors and grounding electrodes that provides an effective connection to ground (earth). The grounding provides the return path for the leakage current and hence protect the power system equipment from damage. When the fault occurs in the equipment, the current in all the three phases of the equipment become unbalanced. The grounding discharges the fault current to the ground and hence makes the system balanced.

14. Grounding The basic objectives being sought are to Limit over voltages due to lightning, Limit line surges, or unintentional contact with high-voltage lines, Stabilize the voltage to ground during normal operation, and Facilitate overcurrent device operation in case of ground faults.

15. Earthing All exposed metal parts of electrical equipment (including generator frames, mounting bases, electrical instruments, and enclosures) should be bonded to a grounding electrode. The earthing is achieved by connecting the parts of the installation to the earth by using the earth conductor or earth electrode in intimate contact with the soil placed with some distance below the ground level.

16. Earthing The basic objectives being sought are the following: to maintain a low potential difference (almost zero volts) between nearby metal members, and thereby protect people from dangerous electric-shock-voltage exposure in a certain area, to provide current-carrying capability, both in magnitude and duration, adequate to accept the ground-fault current permitted by the overcurrent protection system without creating a fire or explosive hazard to buildings or contents, to provide an effective electrical path over which ground-fault currents can flow without creating a fire or explosive hazard, and to contribute to superior performance of the electrical system (e.g., suppression of differential and common-mode electrical noise).

17. Ungrounded Systems The system without neutral grounding is known as the ungrounded system, or in other words, in the ungrounded system, none of their conductors is connected to the ground. The main feature of the ungrounded system is its ability to remove the earth faults without interruption. The fact that any one contact occurring between one phase of the system and ground is unlikely to cause an immediate outage to any load may represent an advantage in many plants. But the self-cleaning process of the ungrounded system become disappear when the length of the conductor becomes excessive.

18. Grounded Systems In most cases Grounded Systems are designed so that circuit protective devices will remove a faulty circuit from the system regardless of the type of fault. A phase-to-ground fault generally results in the immediate isolation of the faulted circuit with the attendant outage of the loads on that circuit (Fig. 2.46). However, experience has shown in a number of systems that greater service continuity may be obtained with grounded-neutral than with ungrounded-neutral systems.

19. Where are Ungrounded Systems Required? Although the NEC requires the majority of electrical systems to be grounded, some are actually required to be ungrounded. There are only five different electrical power systems/subsystems noted in NEC Article 250.22 where the code committee has determined the hazards of grounding to outweigh safety benefits of grounding . One of these system types is an isolated power system, which is a distribution power system of limited size, typically for use in hospital operating rooms. These areas are required to have an ungrounded system because it would be considered unacceptable to have a power outage during a surgical procedure.

20. Any Questions?