Workplace Hazardous Materials Information System - WHMIS

• The Workplace Hazardous Materials Information System (WHMIS) is Canadian legislation covering the use of hazardous materials in the workplace. This includes assessment, signage, labeling, material safety data sheets and worker training. WHMIS closely parallels the U.S. OSHA Hazard Communication Standard.
• Do not confuse this with HMIS®, a hazard/label system of the American Coatings Association (formerly called the National Paint and Coatings Association).

Most of the requirements of WHMIS are incorporated into Canada's Hazardous Products Act and Controlled Products Regulations which are administered by Health Canada. Certain provincial or territorial laws may also apply (see the first link under Further Reading). Enforcement of WHMIS is performed by the Labour Branch of Human Resources Development Canada or the provincial/territorial OHS agencies.

Within the WHMIS framework, chemical products with proprietary formulations or trade secret hazardousingredients must be registered under the Hazardous Materials Information Review Act before thay can be sold or distributed in Canada. Registration numbers under this Act are issued by the Hazardous Materials Information Review Commission (HMIRC). HMIRC is an independent government administrative law agency rather than being directly a part of Health Canada.

Two good comprehensive sources of information about WHMIS are the The Canadian Centre for Occupational Health and Safety (CCOHS) and the Health Canada's Official National Site for WHMIS.

The WHIMS Classification Scheme (See CCOHS info)

WHMIS has six broad hazard classifications:
• Class A - Compressed Gas
• Class B - Flammable and Combustible Material
  • Division 1: Flammable Gas
  • Division 2: Flammable Liquid
  • Division 3: Combustible Liquid
  • Division 4: Flammable Solid
  • Division 5: Flammable Aerosol
  • Division 6: Reactive Flammable Material
• Class C - Oxidizing Material
• Class D - Poisonous and Infectious Material
  • Division 1: Materials causing immediate and serious toxic effects
    • Subdivision A: Very toxic material
    • Subdivision: Toxic material
  • Division 2: Materials causing other toxic effects
    • Subdivision A: Very toxic material
    • Subdivision B: Toxic material
  • Division 3: Biohazardous Infection Material
• Class E - Corrosive material
• Class F - Dangerously reactive material
Canada is working on implementing the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), which will result in changes to the classification of chemicals, labeling, and the content of MSDS's. Health Canada has a web page discussing the implementation of GHS in Canada. It will likely be several years before Canada begins phasing in the GHS but you should expect to start seeing sheets and labels incorporating the GHS'sHazard Statements and Precautionary Statements in the near future.

MSDS Relevance

All materials covered by WHMIS are required to have an MSDS. This means that every worker must have an MSDS for each hazardous substance and be trained in working with that material.A WHMIS regulation, the Controlled Products Regulations (CPR), prescribes what information must be on labels and MSDS's. You can find the 9 required parts as well as information on how to write an MSDS on this CCOHS web page. There is no master list of items subject to the CPR. You can find out how to determine if a material is subject to CPR (PDF file) at the Sask Labour site.

HMIS® - Hazardous Materials Identification System

The Hazardous Materials Identification System, HMIS®, was developed by the National Paint & Coatings Association (NPCA), now known as the American Coatings Association, to help employers comply with OSHA's Hazard Communication (HCS), 29 CFR 1910.1200.

The system utilizes colored bars, numbers and symbols to convey the hazards of chemicals used in the workplace. See below for an explanation of the system.

Alas, the system is proprietary and the NPCA has apparently awarded exclusive rights for HMIS® products and services to a single vendor. In our opinion, this is a totally unacceptable arrangement that runs counter to the facile dissemination of health and safety information.

• Do not confuse HMIS® with WHMIS, which is a set of Canadian Regulations dealing with hazardous materials.
• Do not confuse HMIS® labels (colored bars) with NFPA labels (colored diamonds). The two systems are similar but not identical. See below for more info.
• HMIS® is a registered mark of the NPCA.
• HMIS, a U.S. Federal computerized information management system containing data to ensure the safe transportation of hazardous materials by air, highway, rail, and water. Seehttp://www.dot.gov/pia/phmsa_hmis.htm.
• The U.S. Department of Defense (DoD) used to call their restricted HMIRS (Hazardous Material Information Resource System) HMIS, but changed the name recently to reduce confusion.

For more Detail

http://www.ilpi.com/msds/ref/hmis.html

Free Online Hazmat/Hazchem Guide

Free Hazmat (Hazardous Materials)/HazChem (Hazardous Chemicals) Guide containing information on Supply Labels, Hazard Warning Panels, Hazard Warning Diamonds, Emergency Action Codes and more

GHS Labels

Hazard Warning Panel

Emergency Action Codes (EAC)

International Operations (ADR)

Blank Plates

Hazard Identification Number (HIN)

Hazard Warning Diamonds

Supply Labelling

Steam Turbines

Power Generation Through Steam Turbines

The basic process behind steam power generation is the “Rankine Cycle”. Water is heated until it is a saturated liquid. From there, it is compressed into steam. The steam is transferred to a turbine where the pressure of the steam is reduced (usually to sub atmospheric pressures) by expansion over the turbine blades. This process produces mechanical work which is latter converted into electricity through generator. The low pressure steam is condensed back to a liquid. The water, now referred to as return water, is mixed with new water, referred to as “feedwater”, and pumped back to the boiler. The figure below shows a common diagram used to describe the Rankine Cycle.

Steam Turbines have different classification criteria. These criterion are;

A-Steam Flow Direction in Steam Turbine

            i) Axial Steam Turbine

            ii) Radial Steam Turbine

B-Working Principle of Steam Turbine

            i) Impulse Steam Turbine

            ii) Reaction Steam Turbine

C-Based on Exit Steam and Application Based

            i) Condensing Steam Turbine

            ii) Non Condensing Back Pressure Steam Turbine

            iii) Extraction Steam Turbine

D-Based on Steam Pressure 

  

i)       Low pressure steam turbine, the turbine with pressure up to 2 ata. 

ii)      Middle pressure steam turbine, the turbine with pressure up to 40 ata. 

iii)     High pressure steam turbine, the turbine with pressure 40 – 170 ata. 

iv)     Very high steam turbine, the turbine with pressure exceeds 170 ata. 

 V)    Super critical pressure steam turbine, the turbine with pressure exceeds 225 ata.

A-Steam Flow Direction in Steam Turbine

i) Axial Steam Turbine 

ii) Radial Steam Turbine

In a radial-flow turbine, steam flows outward from the shaft to the casing.These steam turbines has direction of steam flow perpendicular to the axis of shaft. The unit is usually a reaction unit, having both fixed and moving blades. They are used for special jobs and are more common to European manufacturers, such as Sta-Laval (now ABB).

C-Three Classes of Steam Turbines on the Basis of Exit Steam and Application Based

1-Condensing Steam Turbines

2-Non Condensing (Back Pressure) Steam Turbines

3-Extraction Steam Turbines

1-Condensing Steam Turbine

These turbines Operate with an exhaust pressure less than atmospheric (vacuum pressure).

They experiences the maximum pressure drop through the turbine which results in greater energy extracted from each lbm or kg of steam input.ƒ Turbine efficiency ranges are  approx. 30-40%.ƒ The condenser can be either air or water cooled. Condenser cooling water can be utilized for processes or space heating loads. Condensing tubines areƒ Usually more expensive than Non-Condensing Back pressure turbines. These turbines are not used for Combined Heat and Power Applications. 

2-Non-Condensing Back Pressure Steam Turbine

Steam is expanded over turbine and exhaust low pressure steam is used to meat the thermal heating requirements. Steam is expanded to the extent providing required lower pressure of steam which facility can use. 

These turbines operate with an exhaust equal to or in excess of atmospheric pressure. Exhaust steam is used for lower pressure steam process loads. These turbines are available in smaller sizes and pass large amounts of steam per MW of output (low efficiencies). These turbines ƒ produce less useful work than a condensing turbine, but since the unused steam from the turbine is passed on to process loads, the lower turbine power generation efficiencies (15% to 35%) are not a concern. These turbines areƒ very cost effective when paralleled with pressure reduction valves (PRV), providing an efficient use of the pressure reduction requirements.ƒ Usually less costly than condensing turbines.

3-Extraction Steam Turbine

The other type of steam turbine used in CHP applications is called an extraction turbine. Basically these turbines are hybrid of Condensing and Non-Condensing turbines. In these turbines, steam in extracted from the turbine at some intermediate pressure. This steam can be used to meet the facilities steam need. The remaining steam is expanded further and condensed. Extraction turbines can also act as admission turbines. In admission turbines, additional steam is added to the turbine at some intermediate point. The figure below schematically shows the process of an extraction steam turbine.

Cooling Tower: Performance calculation

First you should collect all the data as given below. Be sure that the data collected for these temperatures is most accurate because of lower absolute level of generally ~40°C average temperatures, an error of 0.5°C due to manual data collection & judgment will cause more than 1.2% error in the result at one calculation. Repeating such errors may result in cumulative errors of more than 10% in totality giving you totally absurd results.

So the basic point is that collect the data on regular basis, keep a watch to have a feel of real values & then proceed.

Actual Data
Cooling water flow rate - 4134 M3/hr
Cooling water inlet Temp - 44.0 °C
Cooling water exit Temp - 35.0 °C
Inlet air-wet bulb - 30.0 °C
Inlet air-dry bulb - 38.8 °C
Exit air-wet bulb - 40.7 °C
Exit air-dry bulb - 42.0 °C

Now follow step by step procedure for the calculation.

Step-1
Calculate waterside actual heat load, which is as below

Qw = 4134 x 1000 x (44 – 35) / 1000000
= 37.21 Gcal/Hr

Step-2
Calculate absolute humidity at wet bulb of inlet air, which is at 30°C in this case. This is a function of wet bulb temperature only.

The equation for the same is

1.4478310678E-10*(Tw^7)-2.6920*10e-8*(Tw^6)+1.99053*10e-6*(Tw^5)-6.65614*10e-5* (Tw^4)+0.00131879344*(Tw^3)+0.00125483272*(Tw^2)+0.291649083*Tw+3.802441

Where Tw is wet bulb temperature in °C. So,

H1 = 27.29 Kg/ ‘000Kg of dry air

Step-3
Calculate absolute humidity at dry bulb of inlet air, which is at 38.8°C in this case. It will give you saturation level of humidity, say H2.

Step-4
Find out &% Saturation. Of course it can be done from Psychometric charts but then you wont be able to use powerful Excel Tool for simulation of your cooling tower that’s why these equations are generated.

You can also use any good Excel Add-IN for Psycho properties if available.

Here, it will be %Sat = H1/H2

Step-5
Based on % Saturation find out the enthalpy content of moist air at inlet condition. Again I did it using self-developed equations ~10 years back.

I found it to be Hin = 26.196 Kcal/Kg of wet air.

Step-6
Similarly find out the moist air enthalpy at exit condition, which is

Hex = 41.630 Kcal/Kg of wet air

Step-7
Similarly, find out the absolute humidity at wet bulb for exit condition, which is 50.74 Kg/ ‘000 kg of dry air in this case.

Step-8
Calculate airflow based on heat load and enthalpy difference, which shall be as below

A = 4134000 x (44-35)/(41.630 – 26.196)
= 2410652 Kg/hr

Now based on Absolute Humidity difference, calculate amount of water evaporated as below

W = 2756000 X (50.74 – 27.29)/1000
= 64654 Kg/hr

Step-9
Now heat required for evaporation of this water can be calculated based on average latent heat of water evaporation at the inlet & exit temperature.

Average water temperature = 39.5 °C
Latent heat = 575.33 Kcal/Kg

Hev = 64654 x 575.33
= 37.20 Gcal/Hr

This is matching with the heat load of waterside hence, calculation is correct due to accurate temperature measurements.

So L/G comes out to be = 1.715 in this case.

Now we will see the NTU calculation & efficiency of tower, use of NTU method for predictions etc.

Step-1
First consider the cooling water exit temperature ‘twex’ in column A in excel sheet so i.e. 35°C in this case.

Put h’ in column B which is the enthalpy of saturated air at twex and can be calculated by the equation

h’=9.446443x10-13x(twex^8)-1.433603766x10-10x(twex^7)+5.39506924*10-9(twex ^6)+3.02962638*10-7(twex^5)-0.0000272854755*(B7^4)+0.00096596975*(B7^3)-0.005340108*(B7^2)+0.458708485*B7+2.219286635

Put tawet in column C starting with actual wet bulb temperature of entering air, which is 30°C in this case.

Put w as absolute humidity at tawet in column D that is calculated from the same formula as shown in Part-I of this post.

Put hcal as humidity at tawet using the formula given above for h’ in column E.

Put ha as humidity at actual wet bulb temperature of entering air, which is 30°C in this case. Yes, that means initially in the first row of calculation sheet hcal & ha will be same. This is in column F.

Now put calculation of difference of h’ – ha in column G.

Step-2
In first row G will be automatically zero.
Now in second row consider the twex 2 = (Twin – Twex)/19 + twex 1
i.e. twex 2 = (44 – 35 ) / 19 + 35
= 0.474 + 35 = 35.474°C

Copy this formula in column A for next 19 rows. This gives you incremental evaluation of tower step by step along the total tower height from 35° at exit at bottom to 44° at inlet at the top.

Copy h’ formula in column B for the same no of rows.

Step-3
Now put any assumed figure for tawet in column C, w in column D, hcal in column E.

Now calculation for ha will change which will come from actual L/G ratio of tower calculated in Part-I.

Use the following formula for ha in second row onwards.

ha 2 = ha1 + L/G * (twex 2 - twex 1) + (w 2 – w 1) / 1000 * twex 1
= ha1 + 1.715 * (35.474 – 35.00) + (w 2 – w 1) / 1000 * 35.0

Based on other figures it will vary.

Now since you have assumed tawet, hcal will be different from ha. Put this difference in next column G.

Now either change tawet manually to make the difference Zero in column G or use goal seek from excel. This will give you tawet, which is supposed to be the actual wet bulb temperature of air exiting from the tower at the top finally.

This will complete first part of NTU calculation after completing all the rows.

Step-4
Now in next column i.e. H; put (h’ – ha) value which is Column B – Column F and copy it down till the last row.

Put reciprocal of column H in column I. This will give you 1/ (h’ – ha) value and copy it down till the last row.

Now in next column J, leave first row blank & start from second row where you should put average of first & second row in column I. This will give you average of 1 / (h’ – ha) for first & second value. Copy this formula also down till the end of rows.

Step-5
Now in column K, put NTUL as calculated below (From second row as column J starts from second row).

NTUL = Column J x (twex 2 - twex 1)
= Column J x (35.474 – 35.0)

Copy this formula in all rows.

In column L, put progressive summation of NTUL calculated in column K i.e. in each row of column L, use previous row of column L + same row of column K.

This value at the end of last row will give your towers total NTU for liquid side.

Step-6
Repeat all calculations in next two columns for NTUG similar to Step-5 above and find out final value of gas transfer units. The only difference is to use the following formula to calculate NTUG in column M.

NTUG = Column J x (ha 2 - ha 1) ha is in column F.

Use progressive sum again in column N.

Now I will give you guidelines on using these calculations for prediction of performance, prediction of new conditions, calculation of existing system and how to improve it in the next part of this post.

Ways to Save Energy in Pumps

Here is my experience based on energy audits of pumping systems in various chemical, metal, textile & petrochemical units.

• Design systems with lower capacity and total head

1. Do not assume these requirements are fixed.
2. Calculate flow requirement based on actual mathematical nos without margins in each stage & then add 10-20% straightforward as Normal capacity of the pump. For example if process side heat load in an exchanger is based on normal flow of say 100 M3/hr then do not consider cooling water requirement for peak condition of 120 or say 140 M3/hr. Just calculate it based on normal flow of 100 M3/hr at this stage.
3. Total head requirements can be reduced by: lowering process static gage, pressure, minimizing elevation rise from suction tank to discharge tank, reducing static elevation change by use of siphons, lowering spray nozzle velocities, lowering friction losses through use of larger pipes and low-loss fittings, and eliminating throttle valves.
4. After calculating total requirement of Flow & Head this way, simply add 10-20% in both parameters as design margin based on your judgement about process variation. This should be your normal capacity. You still have higher margins becasue rated condition are further higher than these values.
5. Also keep in mind that worst conditions dont come all simultaneously. You can still meet few peak demands.
6. Dont worry about undersizing of your pump. You can add later & this approach is beneficial in overall longer run as you can switch your additional capacity ON & OFF.
7. This can give you a saving of ~10-20% in your pumping system. A thorough review is must.

• Emphasize on Efficiency first

1. Despite the tendency to emphasize initial cost, you will save cost in the long run by selecting the most efficient pump type and size at the onset.
2. The choice of a pump depends on the service needed from the pump. Considerations are flow and head requirements, inlet pressure or net positive suction head available, and the type of liquid to be pumped.
3. Maximum attainable efficiency of a centrifugal pump is influenced by the designer's selection of pump rotating speed as it relates to "specific speed." Purchasers need to be aware of this, as well as the decision criteria for determining the type of pump to use.
4. Consider LCC (Life Cycle Costing) option instead of initial cost only. Click here to learn more about LCC Analysis.
5. Remember ENERGY is the most expensive "commodity" today.
6. People generally loose ~80% more money due to non LCC approachover a period of its service life.

• Divided Use

1. Design or select no of pumps based on different possible scenarios & always follow the operation philosophy of bulk & makeup supply for any system.
2. This approach saves at least 10-15% over conventional selection of equal size pumps.
3. This helps in putting the smaller pump on auto mode with header pressure switch so that excess pump capacity can be turned on/off.
4. Two pumps can be operated in parallel during peak demand periods, with one pump operating by itself during lower demand periods. Energy savings result from running each pump at a more efficient operating point and avoiding the need to throttle a large pump during low demand.
5. Analternative is to use one variable-speed pump and one constant-speed pump. Use or selection depends on the process behaviour e.g. how fast the demand is changing? How many time it is changing? Is my process critical? etc.

• Avoid end of curve operation

1. Generally in case of cooling water pumps head & flow both are selected with plenty of margins, comfortable to the cushion needed by selection manager. This results in near end curve operation without throttling. This is worst operation of pumps in almost every situation. Avoid it.

• Use pumps as drives

1. Use them as drivers / turbines to recover pressure energy that would otherwise be wasted.
2. Practically all centrifugal pumps will perform as turbines when operated in reverse.
3. A hydraulic power recovery turbine can recover pressure energy when used to drive a generator, or assist the driver of a pump or a compressor.

Useful Tips on Use of ASD/VFD for pumps

ASDs are ideally suited for variable-torque loads from centrifugal pumps, fans, and blowers when the system load requirements (head, flow, or both) vary with time. Conditions that tend to make ASDs cost-effective include the following:

1. High horsepower (greater than 15 to 30 hp)—the higher the pump horsepower, the more cost-effective the ASD application.
2. Load type—Centrifugal loads with variable-torque requirements (such as centrifugal pumps or fans) have the greatest potential for energy savings. ASDs can be cost-effective on positive displacement pumps, but the savings will generally not be as great as with centrifugal loads.
3. Operating hours—In general, ASDs are cost-effective only on pumps that operate for at least 2,000 hours per year at average utility rates.
4. High utility rates—higher utility energy charges provide a more rapid payback on an investment in an ASD.
5. Availability of efficiency incentives—where they are available, electric utility incentives for reducing energy use or installing energy-saving technologies will reduce payback periods.
6. Low static head—ASDs are ideal for circulating pumping systems in which the system curve is defined by dynamic or friction head losses. They can also be effective in static-dominated systems—but only when the pump is carefully selected. A thorough understanding of pump and system interactions is critical for such applications.
   
   
   
   
   Courtesy of  Profmaster

Condition Monitoring through Vibration in Motors

Vibration	Operation Condition
Less than 0.10 in/sec	Good Operating Condition
Between 0.10 in/sec – 0.20 in/sec	Satisfactory
Between 0.20 in/sec – 0.35 in/sec	Correct to Extend Life
Between 0.35 in/sec – 0.5 in/sec	Un Satisfactory (Mechanical Wear)
Over 0.50 in/sec	Severe wear (Correct as early as possible)

Source: Longo sales and services

Fabric Testing through Flame

Manufacturing Process of Fabrics

Cotton Fabric

Cotton fiber undergoes several process to reach the stage of final cloth. The processes are as mentioned below:

Ginning

Ginning is the method of separating the cotton fibers from the seedpods, and sometimes with the sticky seeds. This is done in the cotton field with the help of machines.

Spinning
Spinning is the succeeding step to ginning. This process involves the making of yarn from the cotton fiber. The cotton yarns are made of different thickness in this stage.

Weaving
Weaving is the most important process in the making of cotton cloth. In this process, two yarn is placed to make warp and weft of a loom which successively turn them into a cloth.
 
Fabric finishes and treatments
After weaving the cotton fabric passes through different processing stages till it reaches to the state of final product. The stages are mentioned below, but it is not necessary for the fabric to undergo all the process for e.g. grain bags cloth are used unbleached.

• Singeing - This process burns off the fibers sticking in the goods.
• Desizing - This process involves removing the size material from warp yarns in woven fabrics.
• Scouring - The cleaning part of the fabrics are involved in this process.
• Bleaching - The fabrics are bleached here to make it more whiter and lighter.
• Mercerizing - In this process, the fabric is immersed in alkali to make it more strong, shining, durable, shrink free and stretch free.
• Dyeing - This process involves the changing of the fabric color by the treatment with a dye.

Finishing - In this process, the fabric is treated with some chemicals or other useful agents to make it qualitatively more better, for e.g. cotton is made sun protected by treating it with UV protecting agent.

Leather Fabric

Pre-tanning

• Animal skin is cleaned and salted to prevent decay.
• The hide or pelt then is sent to tannery for trimming and sorting.
• Next, it is soaked in water to restore moisture content, which is lost during salting process.
• It is treated mechanically with rollers and blades to remove fat/muscle and flesh (Fleshing).
• During liming the skin is soaked in lime solution to remove the hair, inter-fibrillary protein and epidermis.
• In De-liming the hide or pelt is washed in water containing ammonium chloride or ammonium sulphate to neutralise it.
• Bating involves treating the leather with digestive enzymes to remove non-fibrous protein.
• Scudding is done with a blunt knife to remove remaining hair roots, skin pigmentation, and surface fats.
• Lastly, it is put in sulphuric acid to lower the pH.

Tanning

Tanning is the process where the leather gets the necessary feel and physical characteristics. In this process, the collagen, an insoluble fibrous protein, which carries the major property of the hide or pelt gets less susceptible to decay and are kept flexible. This is done by removing the water molecules from the gap of protein molecules and replacing it with chemicals that retain flexibility.

The main tanning processes are mineral/chrome tanning, vegetable tanning and oil tanning.

• Mineral/chrome tanning is the most common and modern method, which uses chromium salts. This makes leather water proof and stretchable.
• Vegetable tanning, or bark tanning is the process where the hide is soaked in a solution of bark of oak/chestnut which is chopped or boiled. The leather becomes moldable and can be tooled. Moreover when dry, the leather will not stretch.
• Oil tanning is a process where fish and animal oil is used. The leather becomes very soft and flexible. It cope up with wetted condition without causing damage to the leather. Chamois leather is best example of oil tanning.

Lubricating, Dyeing and Finishing

After tanning, the leather undergoes different processes according to the use of the final product.

• Vegetable-tanned leather which are used for shoe soles is bleached, lubricated and then run through rolling machines to make it firm and glossy.
• Chrome-tanned leather, for shoe uppers, is split and shaved and then placed in a rotating drum for the dyeing process using several types of coloring materials to give color fastness and durability.
• Before or after dyeing, it is rolled in a fat liquor containing emulsified oils and greases. Next, the leather is pasted on glass or ceramic frames and then passed through drying tunnels with controlled heat and humidity.

In the finishing process, the leather is coated with grain surface which contains finishing compound. This is brushed under a revolving brush-covered cylinder. For smooth finish, the leather is treated with a mixture of waxes, shellac or emulsified synthetic resins, dyes, and pigments (to avoid painted look). Glazing is done to achieve polished surface.

Silk Fabric

From Cocoon to Yarn
Silk from cultivated silkworms is more used though silk of wild worms is also valuable. The worms feed on mulberry leaves and increases their body size by nearly 10,000 times in a short span of time. The worm ceases to eat by the end of thirty days and attach itself to a piece of straw and begins to spin its cocoon. After the spinning of cocoon and before the hatching of the worm into a moth, the cocoon is soaked in hot water unraveling and producing long size thread. This fine thread is the basic component of silk yarn and fabric.

Washing and bleaching of the silk threads
The natural fiber extracted from the silkworm holds some glutinous substance (gummy substance or glue) which is removed by washing and bleaching.

Weaving
Weaving is a process where the fabric is created by interlacing the warp yarns and the weft yarns. It is either done by machines or hand. Hand woven fabric is better than the machine woven. It can make delicate designs with different colored thread. Modern machines use lances, projectiles, a jet of compressed air to shoot the weft-yarn between the warp-yarns. It leads to greater yield and productivity.

A good quality of silk begins with a warp of approximately 2,000 threads for one meter width. 1,600 threads or 1,800 threads are considered to be poor quality fabric. Loosely woven fabrics are difficult to sew.

Dyeing, Printing and Finishing
There are two main types of silk fabrics. One which is yarn-dyed or dyed-woven, like taffeta, duchess satin and many pattern-woven fabrics. The other type is piece-dyed fabrics, which is carried out after weaving, like crepes, twills, etc. The dyeing process gives the silk different shades.

Printing is giving pattern to the fabric. It is either done by block-printing method, roller-printing method or screen printing. Screen printing is widely used in silk fabrics.

Embroidery process gives embellishment and the perfect finish to the fabric to make it look more beautiful.

All fabrics has to be finished. It is here the fabric gets the desired appearance and feel. Finishing process is either physical or chemical. It give treatments like crease-proofing, water-proofing, fire-proofing, etc.

Final soaking in a chemical solution
This process helps to preserve the sheen and luster of the silk fabric. It adds weight and makes the fabric soft, smooth, easy to iron and wrinkle resistant.

Bleaching of Fabrics

Bleaching is an operation to remove the colored impurities from textile fibers. Cotton in its natural form contains so many minerals, waxes, proteins and coloring matters, etc. In order to attain a bright substrate for dyeing, bleaching or printing and to make the fabric uniformly water absorbent, a pretreatment is essential. 

So the first and foremost textile processing operation is called pretreatment, that remove remove the unwanted matters, such as color, minerals, waxes and oils and stains from the greige material. The pretreatment operation utilizes a lot of water and the quality of water plays a vital role in the cleansing of textile materials. Better the quality of water, better will be the processed goods.

As water and its quality play a very important role in wet processing, let us have a brief look into the quality of water required for wet processing, with an emphasis on reactive dyeing. We get water from various sources, like river, ponds, shallow wells and deep bore wells. According to the source of water, it contains many dissolved and suspended impurities. The water from a running river, contains many dissolved salts (solids) like Sulphates, Chlorides, silicates, Carbonates and Bicarbonates of heavy earth metals like Calcium, Magnesium, Iron, Aluminums, Sodium etc. The ratio of these salts varies according to the source of water. The general requirements of the water used in textile processing are given below: 

The water should be colorless, clear and free from suspended impurities.

Should not be hard and have the tendency to deposit, scale on fabric or on water supply structures.

It should be non-corrosive.

It should be free from metals such as iron, manganese, aluminums and copper

It should neither be too alkaline or acidic.

Color is normally an indication of the presence of suspended and dissolved salts that may affect the fiber/yarn/fabric. So it has to be removed from water prior use in processing, by a suitable de-coloration technique.

Turbidity or Suspended solids are due to a fine suspension of inorganic salts like (clay. silica, calcium carbonate) or organic finely divided vegetable matter like algae, micro-organism etc. This should also be removed using a suitable filtration technique.

Dissolved solids - in water treatment and analysis this term is called Total Dissolved Solids (TDS). The TDS reflects the presence of unwanted elements in dissolved form, which has to be removed using a suitable method. Good quality water should not have a TDS more than 150 ppm.

pH value – Water with a pH value of more than 7 is alkaline and one below 7 is acidic. Most of the textile processing treatments are dependent on pH values.

Hardness (Calcium and Magnesium) – the presence of Calcium and Magnesium salts in water is called hardness of water. 

Temporary Hardness: The presence of bicarbonates of Calcium and Magnesium in water is called temporary hardness. When the water containing these salts are heated to boil, the soluble bicarbonate salts will become insoluble carbonates and precipitate and the hardness disappears.

Permanent Hardness: The presence of carbonates, sulphates and chlorides of Calcium and Magnesium are called permanent Hardness, as this hardness cannot be removed by simple heating.