Plant Layout: Part-2(IMPORTANCE OF PLANT LAYOUT)

1. It is long-term commitment
2. It facilitates the production process, minimizes material handling, time and cost, and allows flexibility of operations
3. It facilitates easy production flow, makes economic use of the building, promotes effective utilization of manpower, and provides for employee’s convenience, safety, comfort at work, maximum exposure to natural light and ventilation.
4. It affects the flow of material and processes, labour efficiency, supervision and control, use of space and expansion possibilities.

Plant Layout: Part-1(Definition) 

Plant layout refers to the arrangement of physical facilities such as machinery, equipment, furniture etc. with in the factory building in such a manner so as to have quickest flow of material at the lowest cost and with the least amount of handling in processing the product from the receipt of material to the shipment of the finished product.

DEFINITION : Following are the definitions

 “the overall objective of plant layout is to design a physical arrangement that most economically meets the required output – quantity and quality.”

 “Plant layout ideally involves allocation of space and arrangement of equipment in such a manner that overall operating costs are minimized.

DETERMINANTS OF PLANT LAYOUT

1. TYPE OF PRODUCT (size, shape and quality)

2. TYPE OF PROCESS (technology employed, sequencing etc)

3. VOLUME OF PRODUCTIONS- (INCREASE OR DECREASE)

Machine Maintenance : Part-3 (Types of maintenance)

Traditionally, 5 types of maintenance have been distinguished, which are differentiated by the nature of the tasks that they include:

Corrective maintenance:  Corrective maintenance is a maintenance task performed to identify, isolate, and rectify a fault so that the failed equipment, machine, or system can be restored to an operational condition within the tolerances or limits established for in-service operations.

Preventive Maintenance:  Preventative maintenance is maintenance that is regularly performed on a piece of equipment to lessen or reduce the likelihood of it failing. Preventative maintenance is performed while the equipment is still working, so that it does not break down unexpectedly.

In process houses mostly Corrective and Preventive maintenance are performed.

Predictive Maintenance:  Predictive maintenance (PdM) techniques are designed to help determine the condition of in-service equipment in order to predict when maintenance should be performed. This approach promises cost savings over routine or time-based preventive maintenance, because tasks are performed only when warranted.

Zero Hours Maintenance (Overhaul): The set of tasks whose goal is to review the equipment at scheduled intervals before appearing any failure, either when the reliability of the equipment has decreased considerably so it is risky to make forecasts of production capacity . This review is based on leaving the equipment to zero hours of operation, that is, as if the equipment were new. These reviews will replace or repair all items subject to wear. The aim is to ensure, with high probability, a good working time fixed in advance.

Periodic maintenance (Time Based Maintenance TBM): The basic maintenance of equipment made by the users of it. It consists of a series of elementary tasks (data collections, visual inspections, cleaning, lubrication, retightening screws,…) for which no extensive training is necessary, but perhaps only a brief training. This type of maintenance is the based on TPM (Total Productive Maintenance).

Machine Maintenance : Part-2

Objectives of Maintenance Management

The following are some of the objectives of maintenance management:

• Minimizing the loss of productive time because of equipment failure (i.e. minimizing idle time of equipment due to break down).
• Minimizing the repair time and repair cost.
• Minimizing the loss due to production stoppages.
• Efficient use of maintenance personnel and equipments.
• Prolonging the life of capital assets (equipment or machines) by minimizing the rate of wear and tear.
• To keep all productive assets in good working conditions.
• To maximize efficiency and economy in production through optimum use of facilities.
• To minimize accidents through regular inspection and repair of safety devices.
• To minimize the total maintenance cost which includes the cost of repair, cost of preventive maintenance and inventory carrying costs, due to spare parts inventory.
•  To improve the quality of products and to improve productivity.

Machine Maintenance : Part-1

Maintenance Objectives

•  Maintenance is an important factor in quality assurance, which is another basis for the successful competitive edge.

•    Inconsistencies in equipment lead to variability in product characteristics and result in defective parts that fail to meet the established specifications.

•   Beyond just preventing break downs, it is necessary to keep equipment operating within specifications (i.e. process capability) that will produce high level of quality.

•      Unnecessary breakdown also leads to the increase in cost of the production.

Impact of Poor Maintenance

1. Production capacity: Machines idled by breakdowns cannot produce, thus the capacity of the system is reduced.
2. Production costs: Labor costs per unit rise because of idle labor due to machine breakdowns. When machine malfunctions result in scrap, unit labor and material costs increase. Besides, cost of maintenance which includes such costs as costs of providing repair facilities, repair crews, preventive maintenance inspections, spare parts and stand by machines will increase as machines break down frequently.
3. Product and service quality: Poorly maintained equipment produce low quality products. Equipment that have not been properly maintained have frequent break downs and cannot provide adequate service to customers. For example, winding and unwinding rollers of Jigger machine are not maintained properly, they may results uneven dyeing or uneven colour pick up due to tension variation in the fabric across the width.
4. Employee or customer safety: Worn-out equipment is likely to fail at any moment and these failures can cause injuries to the workers, working on those equipments. For example, boiler used in process house, if not maintain properly (removing of scale), it may burst and cause injuries to the boiler attendants.
5. Customer satisfaction: When production equipments break down, products often can not be produced according to the master production schedules, due to work stoppages. This will lead to delayed deliveries of products to the customers.

Handling of dyes & Chemicals-method & precautions: Part-4 (Some important hazards and safety aspects)

•    Direct contact of dyes & chemicals with skin or eyes may cause irritation. If this occurs, flush thoroughly with water. If irritation persists, get medical attention.

•      Gloves to be used while handling dyes & chemicals.

•    Prolonged inhalation of dyes & chemicals should be avoided especially personnel who is dealing with storage of the finishing chemicals. It is recommended to use toxic fume/vapour respirators approved by competent authorities.

•      The method of storage and handling of dyes & chemicals is one among various reasons for inconsistency performance. In most of the process houses the dye & chemicals storerooms are maintained in most disorderly manner. Often the dye & chemicals containers are kept in open condition thereby the dye powders/pastes/chemicals get exposed to varying climatic conditions especially, extreme humidity and temperature. Therefore they should be stored in dry and cool conditions as per the recommendation of manufacturers.

Handling of dyes & Chemicals-method & precautions: Part-3 (Safety Program)

 (c) Emergency preparedness: To establish the plan and procedures for emergency response. Emergency preparedness is vital to reduce injuries, ill-health and other damages, as quick and correct response is necessary in case of emergencies. In textile finishing, common emergency situations involving chemicals include fire, explosion, spills or release of hazardous chemicals, splashing of hot fluid, and any situation which result in personal injuries and acute illnesses.

(d) Hazard communication: To establish appropriate means of communication of safety and health matters to employees. This includes the provision of information, instruction and training to enable employees to do their jobs safely; and

(e) Monitoring and review: To monitor the effectiveness of the safety measures and review and revise periodically to cope with new requirements or significant changes in the concerned processes and /or materials

Handling of dyes & Chemicals-method & precautions: Part-2 (Safety Program)

A chemical safety programme for textile processing should include the following major elements:

(a) Risk assessment: to identify the hazards and evaluate their risks in the processes. Risk assessment is a process to evaluate what chemicals or processes would cause harm at work in terms of frequency of exposure, likelihood and consequence. Based on the assessment results, suitable safety measures could be developed to reduce the risks.

(b) Control of risks: to adopt and maintain suitable preventive and protective measures to control the risks associated with the identified hazards; The primary consideration is to adopt appropriate preventive measures to directly control the hazards at source, such as by elimination or substitution. For instance, certain azo dyes likely to form carcinogenic substances during dyeing process should be replaced by non-hazardous or less hazardous ones. These carcinogenic substances may also be regulated by the Factories and Industrial Undertakings (Carcinogenic Substances) Regulations. In case elimination or substitution is not possible, segregation of the chemicals or the process is an effective safety measure. Protective measures such as the use of personal protective equipment should only be considered as a supplementary means in addition to engineering controls to minimize workers’ exposure to the hazards.

Handling of dyes & Chemicals-method & precautions: Part-1 (Introduction)

•      To ensure safety and health at work of employees engaged in textile processing, a carefully planned chemical safety programme is essential.

•      The risks arising from the hazards have to be assessed and control measures set up with their effectiveness monitored. The programme should also include emergency planning and training of employees.

•     The chemical safety programme should be organized and integrated into the general safety management system of the workplace. In addition, sufficient resources should be assigned to the development, implementation and maintenance of the programme

Balancing of machines for complete process house :Part-6 Finishing (Softener application)

For finishing purpose stenter machine (4 chambers) will be used and fabric will be given softening treatment.

Machine working speed: 40 m/min, M/c utilization= 80%

Total production per shift (8 hours or 480 min)= (speed x utilization x 480)/100

= (40 x 80 x 480)/100 = 15,350 meter

Total fabric to be dyed= 50,000/-

15,350 meter fabric treated in 8 hours

50,000 meter…………= (8 x 50,000)/15,350 = Approx 26 h

Balancing of machines for complete process house :Part-7 Finishing (Zero-Zero)

For this purpose one Sanforizing (zero-zero) is needed to dimensionally stabilize cotton fabric.

Machine working speed: 40 m/min, M/c utilization= 80%

Total production per shift (8 hours or 480 min)= (speed x utilization x 480)/100

= (40 x 80 x 480)/100 = 15,350 meter

Total fabric to be dyed= 50,000/-

15,350 meter fabric to be preshrunked in 8 hours

50,000 meter…………= (8 x 50,000)/15,350 = Approx 26 h

Balancing of machines for complete process house :Part-5 Dyeing

For this purpose one CDR (Continuous Dyeing Range - Open width) is required

Machine working speed: 40 m/min, M/c utilization= 75%

Total production per shift (8 hours or 480 min)= (speed x utilization x 480)/100

= (40 x 75 x 480)/100 = 14,400 meter

Total fabric to be dyed= 50,000/-

14,400 meter fabric treated in 8 hours

50,000 meter…………= (8 x 50,000)/14,400 = Approx 28 h

Balancing of machines for complete process house :Part-4 Mercerization

For this purpose one Mercerizing machine (chain type) is required.

Machine working speed: 40 m/min, M/c utilization= 75%

Total production per shift (8 hours or 480 min)= (speed x utilization x 480)/100

= (40 x 75 x 480)/100 = 14,400 meter

Total fabric to be mercerized= 50,000/-

14,400 meter fabric treated in 8 hours

50,000 meter…………= (8 x 50,000)/14,400 = Approx 28 hrs

Balancing of machines for complete process house :Part-3 Scouring and Bleaching

For this purpose one Pre-treatment Range (PTR) is required.

Machine working speed: 60 m/min, M/c utilization= 80%

Total production per shift (8 hours or 480 min)= (speed x utilization x 480)/100

= (60 x 80 x 480)/100 = 23,040 meter

Total fabric to be pretreated= 50,000/-

23,040 meter fabric treated in 8 hours

50,000 meter…………= (8 x 50,000)/23040 = 17.36 hrs

Balancing of machines for complete process house :Part-2 Processing on  Singeing cum desizing machine

This will be used to remove protruding fibre from the surface of fabric by singeing process followed by  desizing of fabric.

Let Machine working speed: 120 m/min, M/c utilization= 75%

Total production per shift (8 hours or 480 min)= (speed x utilization x 480)/100

= (120 x 75 x 480)/100 = 43,200 meter

Total fabric to be singed and desized= 50,000/-

43200 meter processed in 8 hours

For 50,000 meter = (8 x 50,000)/43200 = 9.25 hours

Balancing of machines for complete process house :Part-1 (Introduction)

•      Machine balancing is a most important part of any process house to run production smoothly.

•      Let us take example of dyeing of 50,000 meter 100% cotton medium weigh quality (150 gsm) fabric to understand this

Process flow:

To start it, let us have following process flow:

Grey cotton fabric------Singeing & Desizing------Scouring------Bleaching-------mercerizing-----dyeing-----finishing----finish folding

Let us have following type of machines to carry out processing of 100% cotton fabric:

•      Singeing cum Desizing

•      Scouring & Bleaching (Pretreatment renage-PTR)

•      Mercerizing

•      Continuous dyeing range (CDR)

•      Softening & Drying on stenter

•      Sanforzing (Zero-zero)

Cleansing action of soap: An application of ionic micelles formation:

Let us take an example of oil or grease stick on the cloth (Fig i). When it come in contact with soap solution, the stearate ions arrange themselves around it in such a way that hydrophobic parts of the stearate ions (R) are in the oil or grease and the hydrophilic parts project outside the oil droplet. 

(http://ask.learncbse.in/uploads/db3785/original/2X/c/c4f7b8ae6a369163f36e62787cda96f3f1a2cdf2.png)

As hydrophilic part is polar, these polar groups can interact with the water molecules present around the oil droplet. As a result, the oil droplet is pulled away from the surface of the cloth into water to form ionic micelle which then washed away with the excess of water. In fact, the stearate ions of soap molecules help in making a stable emulsion of oil with water which is washed away with excess of water.

Micelles or associated collids

There are some substances which at low concentrations behave as normal strong electrolytes, but at higher concentrations exhibits colloidal behavior due to the formation of aggregates. The aggregated particles thus formed are called micellies. these are also known as associated colloids. The formation of micelles takes place only above a particular temperature called Kraft temperature (Tk) and above a particular concentration called critical micelle concentration (CMC). On dilution, these colloids revert back to individual ions. Examples of such type of substances are soap and detergents. For soap, the CMC is 10^-4 to   10^-5 mol/L. These collids have  both lyophobic and lyophilic parts. Micelle may contain as manyas 100 molecules or more. 

Mechanism of Micelles formation:

It can be explain by taking an example of soap. Soap is sodium salt of higher fatty acid and may repersented as RCOONa, e.g sodium stearate viz. CH₃(CH₂)₁₆COO^-Na⁺  or sodium palmitate viz. 

CH₃(CH₂)₁₄COO^-Na⁺  . When we dissolve it in water, it dissociates in to RCOO^-  and Na⁺ ions. The RCOO^- ions consists two parts i.e., non-polar long hydrocarbon chain (R) called the tail, which is hydrophobic (water repelling) and the polar  COO^-  called the head, which is hydrophilic i.e water loving. The RCOO^-  ions are therefore present on the surface of water with its COO^-  group in water  and hydrocarbon chains R staying away from water and remain at the surface.

However, at higher concentration, these ions do not remain on the surface but pulled into the bulk of the solution. As a result, at higher concentration, the RCOO^-  ions form an aggregate of spherical shape with their hydrocarbon chains pointing toward the centre and COO^-  part outwards on the surface of the sphere. An aggregate thus formed is known as "ionic micelle".

(http://eng.thesaurus.rusnano.com/upload/iblock/383/micelle1.jpg)

Detergency

It is a process by which soil is removed from a surface and undergoes solubilization or dispersion.

Result of several physicochemical phenomenons taking place at the interface of three phases : surface/soil/detergent.

The phenomenons are :

– Wetting of surface

– Removal of soil from surface

 – Avoiding re-deposition of soil on surface.

Basic Principal:

1.Wetting of surface: The detergent must come into contact with the surface so that adherence forces of detergent with subtract of surface should be higher than  adherence forces of soil with subtract of surface

          F_{detergent/surface} > F_{soil /surface}   ( Here F = adherence force )

It lower the superficial tension of the detergent solution and the interfacial tensions between aqueous bath, soil and surface

2.Removal of soil:The detergent solution wets the surface, is absorbed by it and lowers the surface’s attraction to allow the soil to separate itself from the surface.

3.Avoiding re-deposition

Chemical reactions

 – lipids undergo saponification

 – mineral soil undergoes solubilization

 – soil undergoes emulsification

 Liquid soil = hydrophobic ; detergent solution = hydrophilic.

Preparation of detergent

During the preparation of detergents, long-chain hydrocarbon obtained from petroleum fractions is converted into an organic aid through a series of steps.  The organic acid is then neutralized with sodium hydroxide, NaOH solution to produce a detergent. Examples are of detergents are: Sodium alkyle sulphate and sodium alkylbenzene sulphonate.

(Above pictures taken from https://image.slidesharecdn.com/soapanddetegents-150725134721-lva1-app6891/95/soap-and-detegents-8-638.jpg?cb=1437832077)

Dispersing Agents (Solid in water):

These are organic compound. A solid material dispersed in a liquid requires an additive to make the dispersion process easier and more stable – this is the role of the dispersing agent, or dispersant. Dispersing Agents function in a manner similar to emulsifying agents. The difference is that solid particulate matter, rather than insoluble oils, is dispersed. The nature of the lyophilic part of the surfactant molecule must be such that it adsorbs onto the particle's surface. These assist the process of dye particles size reduction and help to dissolve dye particles in water. Pigment colour paste one of the most known example in which dispersing agent is used to disperse pigment in water. Disperse dye also contains dispersing agents.

How they work?

When we shake solid (like sand) in water, it seems that solid is dissolved. However after some time solid particles are separated out from water. These solid particles attract each other. That is why they come together and separate out from water. To separate these particles from each other, there is a need of energy. Also, solid particles must be stabilised after they have been separated from each other. The particles will move to each other and glue together again when particle-particle repulsion is insufficient. The spontaneous process of gluing together of solid particles in a liquid is called flocculation. The functionality of a dispersant is to prevent flocculation. Dispersants do their job because the molecules adsorb on the solid-liquid interface and assure repulsion between the particles.

What is the difference between Soaps and Detergent:

Soaps

Soap is made from fat and alkali by specification method. There are not suitable for delicate clothes.  They work well in hot water. They don't produce lather with hard water and are not able to clean the cloth. Lot of water is needed to remove soap from the cloth.

Detergents

Detergents are carbonic compounds which are not alkaline. They are suitable for delicate clothes. They clean both in hot and cold water. They clean the cloth even in hard water. They are removed very easily so less quantity of water is needed.

     3. Emulsifying Agents (Oil in water)

When water and oil are mixed together and vigorously shaken, a dispersion of oil droplets in water - and vice versa - is formed. When shaking stops, the phases start to separate. 

However, when an emulsifier is added to the system, the droplets remain dispersed, and a stable emulsion is obtained.

An emulsifier consists of a water-loving hydrophilic head and an oil-loving hydrophobic tail. The hydrophilic head is directed to the aqueous phase and the hydrophobic tail to the oil phase. 

2. Detergents

Detergents are surfactants that help remove soils from solid surfaces. Over and above reducing water's surface tension, detergents must adsorb onto the soil's surface to aid in spontaneous release. Detergents must also keeps the soil suspended to prevent re-deposition. 

Ø  Detergents are surfactants used  for removal of dirt.

Ø  Detergency involves:

•      Initial wetting of the dirt and the surface to be cleaned.

•      Deflocculation and suspension, emulsification or solubilization of the dirt particles
•      Finally washing away the 

dirt.http://d25smtqkk0nuqw.cloudfront.net/wp-content/uploads/2015/11/biorf11.gif

Following can be understand from the above figure:
1. Dirty Substrate (Any textile material)  come in contact with detergent or surfactant in the presence of water
2. Detergent molecules start coming toward dirt or soil. As the dirt is oily in nature hydrophobic tail come in contact with dirt and hydrophilic head of detergent molecule remain in water.

3. Slowly detergent surrounded dirt particles and pulling them out of substate
4. All the dirt particles removed from the substrate.

a)    Wetting agents: Wetting agent is a surfactant that when dissolved in water, lower the contact angle and reduce the surface tension of a liquid. According to the nature of the liquid and the solid, a drop of liquid placed on a solid surface will adhere to it or no. which is the wettability between liquids and solids. When the forces of adhesion are greater than the forces of cohesion, the liquid tends to wet the surface and vice versa.

To more clarification example of behavior of water and mercury in test tube can be taken. The surface of liquid water (meniscus) has a concave shape because water wets the surface and creeps up the side. The surface of Mercury has a convex shape it does not wet glass because the cohesive forces within the drops are stronger than the adhesive forces between the drops and glass.