Essay: EVALUATION OF PROCESS CONTROL AND SAFETY PRECAUTIONS IN WET PROCESSING: A CASE STUDY OF RIVATEX EAST AFRICA LIMITED.

CHAPTER ONE
INTRODUCTION
1.0 Introduction
This chapter discusses the inspiration for investigating the process control and safety measures in textile wet processing. Due to the diverse nature of wet processing departments, Rivatex East Africa is taken as the representative facility to provide the case study. For this reason, chapter one of this report elaborates the background to the problem of safety and process control, problem statement, the aim of the study, specific objectives of the study and the scope of the study.
1.1 Background
The wet processing department of a typical textile factory can be divided into: pretreatment, printing, dyeing and finishing. The pretreatment stage involves processes like sizing and desizing, scouring, singeing, and sometimes mercerizing. The printing stage starts from the darkroom where the screens are prepared up to when the prints are imparted onto the fabrics using the machines. Dyeing starts as well from the colour kitchen where the recipes are prepared up to when the final shade is obtained on the fabric. The purpose of finishing is to make sure that the fabric treatments remain permanent even during normal usage by the final consumer.
All these processes require materials in form of chemicals and energy. Most of these processes are done at high temperatures and noise levels. The chemicals, high temperature with noise exposure of the personnel working in this department can have detrimental effects on their performance resulting in high employee turnover and reduced quality of the final product.
During the preliminary survey of Rivatex, it was passively noted that wet processing has a high employee turnover, unclear operating procedures for some personnel and a general concern for safety. This could be externally observed as some electrical cabins had exposure to water and chemical spillage, drainage channels were not properly covered and fire safety measures and equipment had become obsolete in some sections.
It was thus found relevant that a study should be carried to establish the current operating procedures and optimize them to secure a conducive and safe working environment for the wet processing personnel.
1.2 Aim
To assess the process control and safety activities in the wet processing department of Rivatex East Africa Limited in order to develop the safest and optimal process control procedures suitable for both man and machines.
1.3 Objectives
1. Appraise the activities at Rivatex East Africa Limited wet processing department and establish the process and procedure gaps which need future modifications and improvements.
2. Carryout a risk assessment exercise of the wet processing department in order to establish the risk areas and suggest possible solutions for the future.
3. Suggest optimal standard operating procedures and safety measures for Rivatex wet processing department.
1.4 Justification of the study
With reference to the Kenyan occupational health and safety act of 2007, it is important to always evaluate the state of working practices and procedures in order to ensure maximum productivity. A safe work place reduces occurrence of work related accidents, diseases and insurance claims resulting in higher productivity levels and low production costs. (1) This can easily be achieved when the employees are fully aware of the nature of their working environment. It was thus found necessary to carry out an evaluation of the wet processing department in order to establish possible gaps in its procedures which do not comply with the standard operating procedures. After establishment of the gaps, suggestions on how the fill them was suggested considering the guidance obtained from the literature review, OSH ‘act of Kenya 2007, and the Kenya constitution.
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CHAPTER TWO
LITERATURE REVIEW
2.0 Introduction
The Textile Industry involves various functions performed by various departments and persons to convert raw material into final product. Failure of Management to plan for the future and to foresee problems have brought about waste of manpower, of materials, and of machine & time, all of which raise the processing cost and price that the purchaser must pay.
2.1 Textile wet processes
In textile wet processes involve applying chemical treatments to the fabric from either knitting or weaving, for the purpose of improving both performance and appearance. The appearance of the fabric coming from knitting or weaving is often dirty or pale yellow, unsuitable for making apparels or clothing. It thus becomes necessary for the material to go through the following processes in order to make it wearable. The textile wet processing department consists: Gray Inspection, Stitching, Mechanical Cleaning , Singeing, Desizing/Scouring, Bleaching, Mercerizing, Dyeing/Printing, and Finishing stages which all work together to obtain a wearable fabric material.
2.1.1 Gray Inspection
The fabric is checked for inconformity with standards, and all weaving/knitting faults are marked out. Fabric inspection involves three possible steps: perching, burling and mending. Perching is a visual inspection and the name derives from the frame, called a perch, of frosted glass with lights behind and above it. The fabric passes through the perch and is inspected. Flaws, stains or spots, yamknots and other imperfections are marked. Burling is the removal of yam knots or other imperfections from the fabric. The faults are then mended and any knots in the material are then pushed to the back. Mending is the actual repair of imperfections. Knotting should be done carefully and thoroughly so that the repair or holes is not visible.
2.1.2 Stitching
After the goods have been inspected and checked, they are supposed to be classed in the grey room according to quality and stamped. Goods of similar weight, width and construction and the goods which will receive a similar treatment are sewn together, end to end, by circular sewing machines especially constructed for this purpose and each batch is given a number called lot number.[ ] Stitching should be done using proper stitching thread and seam allowance to avoid stitch marks and fabric creases at the seam which may lead to improper colour padding.[ ] For heavy fabrics intended for mercerizing and continuous operations, the seam should be wider (15 mm) and stronger. [ ] The pre-cleaning of grey fabrics is carried out in a separate unit just before cropping and shearing operations. The purpose of brushing is to remove the short and loose fibres from the surface of the cloth. It also removes husk particles clinging to the cloth. Brushing is mainly done to fabrics of staple fibre content, as filament yams usually do not have loose fibre ends. Cylinders covered with fine bristles rotate over the fabric, pick up loose fibres, and pull them away by either gravity or vacuum. The raised fibre ends are cut off during the singeing and shearing operation. Brushing before cropping minimizes pilling. [ ]
2.1.3 Singeing/shearing
2.1.4 Sizing and desizing
The old adage that sizing is the heart of weaving still holds good today given the fact that loom speeds have increased tenfold from those used in shuttle looms. (2) The primary purpose of the sizing process is to obtain the warp threads with minimal deformations that can successfully be woven without major damages which occur during the yarn passage through sliding metal parts of the weaving machine. (3) Sizing thus improves the physical-mechanical parameters of warp threads, thereby reducing warp breakage to a minimum, and achieving the maximum degree of weaving machine efficiency and energy savings. (4) Textile sizing agents are classified into three main types, which include; modified starch, PVA and acrylic size. (5) An environmentally friendly and inexpensive substitute to the widely used poly (vinyl alcohol) (PVA) has also been developed from soy proteins for textile warp sizing. (6)
The presence of sizing ingredients in the fabric hinders processes, such as dyeing, printing, and finishing. (7) To completely remove starch from a fabric, the size must be chemically degraded to make it water soluble. Three chemical methods used to degrade starch into water soluble compounds include, Enzymes, Acid Hydrolysis and Oxidation. (8) The desizing process usually employs enzymes for removal of starch-based size because the enzyme (amylase) only interacts with the molecules of starch, living the cotton cellulose untouched. Other desizing agents like acids, alkali and oxidation chemicals attack the cotton fibre as well as the starch size. (9)
2.1.5 Scouring
The waxy materials on the outer surface and lipids, waxes, pectic substances, organic acids, proteins/nitrogenous substances, non-cellulosic polysaccharides, and other unidentified compounds within the primary wall are responsible for the slightly hydrophobic nature of cotton. (10) Scouring is the essential treatment for the purpose of obtaining a sufficiently hydrophilic fabric. (11) Typical scouring formulation, comprises of caustic (3-8%), surfactant (0.2 – 0.4%), and chelating agent (0.1 – 0.2%), and employs low concentration of surfactant as a wetting agent. (12) . The optimum condition in the scouring machine is at a de-sizing agent to fabric ratio of 20 g/g fabric, with a temperature of the first de-sizing agent tank of 80 C, a temperature of the second de-sizing agent tank of 90 o C, and dipping time of fabric of 7 s. According to these conditions, more than 89% of the sizing agent is eliminated and only 3.52 mg/g fabric of sizing agent remains in the scoured fabric which is in the acceptable range for feeding to the downstream processes. (13) In order to achieve adequate wettability and absorbency using bio-scouring, cellulase + pectinase and cel??lulase + pectinase + protease gives better results than other enzymatic combinations. (10)
2.1.6 Bleaching
Bleaching is defined as the removal of unwanted colour from the textile fibres using any of the four major bleaching agents, namely; sodium hypochlorite, calcium hypochlorite, sodium chlorite and hydrogen peroxide. (14) Hydrogen peroxide, due to its biodegradability with reaction products which are non-toxic and non-dangerous is applicable in strongly alkaline medium has almost entirely replaced the conventional chlorine oxidizing chemicals when it comes to giving the most effective bleaching. (15) This process can be done in three main steps, namely; saturating the fabric with the bleaching agent and other necessary chemicals; raising the temperature to the recommended level for the particular textile and maintaining that temperature for necessary duration; and, thoroughly washing and drying the fabric. A new commercial bio-bleaching process for cellulose fibres runs enzymatically with arylesterase enzymes (EC 3.1.1.2) and hydrogen peroxide. The enzyme system catalyses the perhydrolysis of propylene glycol diacetate. During the reaction propylene glycol and peracetic acid as a bleaching agent are formed in situ. (16) After hot bleaching enzymatically pre-treated cotton exhibits similar or even better properties compared to conventionally desized, alkaline scoured and bleached cotton. (17) Studies have also revealed that: increase in temperature increases the rate of bleaching with correspondingly reduction in process time; an increase in concentration of (H2O2) whiteness and weight loss is increases; Hardness of water inversely proportional to whiteness and directly proportional to weight loss; The concentration of peroxide stabilizer is inversely proportional to the whiteness and directly proportional to weight loss. (18)
2.1.7 Mercerizing
Mercerization is a process named after John Mercer in the year 1884 in which textiles (typically cotton) are treated with 18% to 20% caustic soda at 20 oC to 24 oC to improve properties such as fiber strength, shrinkage resistance, luster, and dye affinity. (19) (20) Studies show that the strength of the mercerised yarn is highly affected by the cylinder normal pressure, warm rinsing temperature and caustic soda bath concentration, while the effect of the cold rinsing temperature is witnessed only for higher qualities of cotton fibers and yarns contained in the fabric. (21) Mercerization causes considerable tenacity (tensile strength and elongation) losses of Compact yarns than conventional yarns. (22) In order to achieve better mercerization, causticization for improved color yield can be obtained at 14-16% caustic soda concentration. (23) Caustic soda can be recovered and reused satisfactorily in most textile plants for the purpose of increasing profits and reducing stream pollution caused by effluent discharge.
2.1.8 Dyeing
Dyes are substances applied to a substrate to provide color by a process that can alter any crystal structure of the colored substances. (24) Color is the net response of an observer to visual physical phenomena involving visible radiant energy of varying intensities over the wavelength range 400 to 700 nanometers (nm). (25) Dye molecules contain aromatic rings of benzene or naphthalene with conjugated bonds having delocalized ??-electrons between the carbon and other atoms throughout the structure, known as chromophore or colour-donating unit. The wavelength of absorbed light excites an electron from an occupied orbital to the first unoccupied molecular orbital corresponding to visible light, hence producing colour. (26) In addition to chromophores, most dyes contain groups known as auxochromes or colour helpers, examples being carboxylic acid, sulfonic acid, amino, and hydroxyl groups. (27) Until the initiation of the synthetic dyes in the second half of the nineteenth century, all dyes were derived directly from natural sources such as the leaves, flowers, berries, stems or roots of plants, from insects and shellfish, and a number of minerals. (28)
The process of applying these dyes to a textile substrate is known as dyeing, which can be achieved using several techniques and machines depending on the type of dye and textile material under consideration. dyeing includes sticking plants & rubbing crushed pigments to fabric, extracting natural dyes from crushed fruits, berries and other plants which are boiled into the fabric to give light and water fastness (resistance) into cloth. (29) Conventional Dyeing is often performed using batch, continuous processes and semi-continuous.
Batch Dyeing Process. In this process dye is transferred from large volume dye bath to the material over a long duration to achieve exhaustion of the dye using package, beam, beck, winch, jet and jig processing. Quality of color and dye is Temperature dependent, hence, temperature is maintained up to 100 oC to gain good quality of fabric, but further increase can achieve better quality while damaging the yarn or weave used for the substrate. Fiber, Yarn and fabric can be dyed in machines which either holds the material stationary or circulates. (30)
Continuous dyeing process. This is where a relatively concentrated dye solution is applied evenly across the entire width of the fabric passing through padding or other means. Padding is followed by subsequent fixation of the dye by chemical or thermal means predominantly for woven fabrics. When processing tubular knits, it is recommended that the fabric be subjected to low and uniform tension to maintaining the desired aesthetics because edge lines can occur if good dye penetration is not obtained or if the hardness of the pad rolls is not correct. (31)
Dyeing with CO2. When carbon dioxide is heated to above 31??C and pressurized to above 74 bar, it becomes supercritical, a state of matter that can be seen as an expanded liquid, or a heavily compressed gas with properties of both a liquid and a gas. In this way supercritical CO2, has liquid-like densities, which is advantageous for dissolving hydrophobic dyes, and gas-like low viscosities and diffusion properties, which can lead to shorter dyeing times compared to water. (32)
2.1.9 Printing
Textile printing is essentially a localized form of dyeing in which colored patterns or designs are confined to a restricted area using; Flatbed screen printing, rotary screen printing, engraved roller printing, Heat transfer printing or Digital printing at very low dyebath to fabric ratios. (33) (34) The process involves applying printing ink or paste or dispersions to the fabric, and then fixing to the fiber by heat or heat and steam. The excess dye is removed from the fabric by washing and detergent scouring and the fabric is subsequently dried. The types of dyes used in printing textiles are usually the same classes that confer substantivity to given fiber types by solution dyeing processes, that is, disperse dyes for polyester and disperse/vat dye combinations. Thus, coloration of textiles by pigments containing suitable binders and thickeners is the most used technique for all types of fibres. (35)
Screen printing technology presents a large growth opportunity for manufacturers of clothing utilizing plastisol (PVC) and water-based PA/ PU inks used for most printers. These inks have some serious drawbacks such as inferior wash and weather durability, and poor hand feel and tackiness that limit their use in high-end apparel applications. Some of the products contain plasticizers and have other negative environmental effects. To counter these problems, printing mills have tried silicone inks because of their good washing durability, hand feel, elongation properties and environmental friendliness at the expense of tackiness, high viscosity, stiffness and the inability to create low gloss finishes. (36)
Textile digital printing materialized in the 1990s as a prototyping tool for printing small batches of fabric for niche market products. (37)
2.1.10 Finishing
Finishing in its broad sense is any operation for improving the appearance or usefulness of a fabric after it leaves the loom or knitting machine; including pretreatments such as washing, bleaching and coloration. In wet processing, finishing is used to include all those processes that usually follow coloration for the purpose of adding useful qualities to the fabric, ranging from aesthetics and fashion aspects to high performance properties for industrial needs. (38)
Most of the conventional methods of finish application, such as pad-dry-cure or coating currently being used to impart antimicrobial, anti UV, self-cleaning and Fire resistance finishes, are often accompanied by excessive weight add on, loss of feel and drape, poor durability to washing, loss of mechanical strength and most importantly reduced comfort to wearer. (39)
2.2 Process control in the textile wet processes
Figure 2.1: process control activities in wet processing
2.2.1 Grey inspection Process control parameters and procedures.
2.2.2 Singeing Process control parameters and procedures.
Burner position, flame height, flame intensity, and speed are the major process control parameters which have to be kept under constant consideration. Proper working of guide rollers and expanders, and immediate quenching bath after singeing of cold water to lower down the temperature of cloth should also be ensured for consistent quality in singeing. Failure to ensure these controls not only leads to faults, but may also leads to hazards. Management decision here is also important for selection of machine which reduces the manual control. Oshthoff is one such machine which is having much automatic function and can result consistent singeing quality. (40)
2.2.3 Desizing Process control parameters and procedures.
Enzyme concentration, wet pick-up, pH, temperature, reaction time. In desizing process parameters, and manual work should be carried out efficiently so that no re-desizing batch would occur, final testing according to QMS should be properly carried out for desizing. Efficiency of Desizing can be judged by QC of desized fabric which arbitrarily grade desized fabric. It should not be less than 85%. Thus by stricter control during desizing it is possible to achieve 85% desizing efficiency. Using required concentration of enzyme. It has been reported, that optimum concentration of enzyme for this purpose is 0.25% W/V9. Higher concentrations do not increase desizing efficiency to any appreciable extent but simply add to the chemical cost of the operation. Similarly other process parameters like digestion time for enzyme, temp. & pH of the process should be maintained carefully.
2.2.4 Scouring Process control parameters and procedures.
Steam pressure, time of boiling, caustic alkalinity in process and in effluent. Of the process parameters which need to be controlled here, caustic alkalinity at the time of drain should not be less than 10% of the starting concentration in order to maintain impurities in the suspended form. For this purpose a periodic check of alkalinity in the kiering solution is desirable during the course of scouring operation. Quality Control checks determine efficiency of scouring & should be maintained under norms.
2.2.5 Bleaching Process control parameters and procedures.
Concentration of bleaching agent, pH, time of reaction, residual Cl2/H2O2 in drain. Bleaching is carried out either by conventional batch methods using a kier or by semicontinuous pad steam method or by continuous J box system. Record should be kept of each of the wet processes operation in a log book maintained by the department & various controls listed should be scrupulously entered.
2.2.6 Mercerizing Process control parameters and procedures.
Concentration of caustic, Speed of the mercerization machine, dwell time, pick-up, temperature of mercerizing liquor, residual alkalinity. In mercerizing, an hourly check of the strength of the caustic soda in mercerizing liquor is necessary for the uniform degree of mercerizing especially for goods meant for subsequent dyeing and for goods mercerized by wet on wet method. All the measures are aimed at obtaining a well mercerized fabric without undue shrinkage and wastage of costly caustic soda thereby enabling the mills to produce quality mercerizes fabric at optimum cost. A well mercerized fabric should not give a Barium Activity number below 135. Increase in luster % by 5-7 units due to mercerization can be considered satisfactory.
2.2.7 Dyeing Process control parameters and procedures.
Besides testing of dyestuffs and pigments for their strength before using in dyeing the scope of the laboratory should be further extended to include cheaper dye combinations and quality of water to be used for dyeing. This can help the department to prevent dyeing problems like; inconsistent shade, blotchy dyeing, filtering, spots, resists, poor washing off, and poor fastness caused by poor water quality. (41) As regards process control while dyeing, checkups of the concentration of chemicals, especially caustic soda and hydrosulphite, temperature of dyeing, the density of the package, time of reversal of cycles, and pump pressure should be taken regularly.
2.2.8 Printing Process control parameters and procedures.
The dyestuff and pigments as well as other auxiliaries used in printing should be tested as per the quality manual before accepting them for use in bulk production. Besides this it is always desirable to check the basic cloth for width variation, creases, absorbency, whiteness etc. which would otherwise lead to higher percentage of damages. The desired consistency of the printing paste and its suitability on storage is also an equally important check. Fastness characteristics of the prints should be checked for all the designs as a routine quality control measure.
2.2.9 Finishing Process control parameters and procedures.
Proper selection of finishing ingredients such as starches, gums, resins, catalysts, softeners etc. And it is many a time said that the final finish decides the quality of the fabric for which the consumer pays. Comparative evaluation of resins and costly auxiliaries should be critically made before their use in bulk. On the other hand resin finished fabric should be invariably tested for physical properties such as tensile and tear strength, abrasion resistance, wrinkle recovery angle and wash-n-wear or D.P. Ratings as the case may be, whereas chemical test would include nitrogen and formaldehyde determination, resistance to acid or alkali hydrolysis, chlorine retention and subsequent loses on scorching etc. These should conform to the various standards laid down by different authorities.
2.3 Risks and hazards in textile wet processes
The textiles sector contains many hazards and risks to workers, ranging from exposure to noise and dangerous substances, to manual handling and working with dangerous machinery. (42)
2.3.1 Risk assessment procedure for health and safety in wet processing
The legal requirement for risk evaluation or assessment applies to all employers. The process for carrying out a risk assessment can be broken down into a series of steps: (43) 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.
Step 1 Identifying hazards and those at risk
Looking for those things at work that have the potential to cause harm, and identifying workers who may be exposed to the hazards. Using workers’ knowledge helps to ensure hazards are spotted and workable solutions implemented. Consultation encourages workers to commit themselves to health and safety procedures and improvements. A risk assessment should cover all workers regardless of whether they are employed on long- or short-term contracts. Where there are persons employed by another organization on site, there is a duty on the two employers to cooperate and safeguard the health and safety of workers. Risk assessment should take account of differences in workers, such as by gender, age, or disability. For example, older employees may learn differently than a younger worker, and also have different concepts of risk due to a lack of experience. Different prevention measures may be required for these worker groups. Work, its organisation and the equipment used should be adapted to the worker, not the other way around. Workers with disabilities should be considered specifically in the risk assessment process. For example, people with disabilities may be subjected to bullying, which can lead to work-related stress. Consultation with workers with disabilities is vital to ensure a risk assessment is appropriate.
Step 2 Evaluating and prioritising risks
Evaluate how likely it is that the hazard will lead to harm or injury, and how severe that injury is likely to be. Consider what control measures are in place and whether they are sufficient. It is essential that the work to be done to eliminate or prevent risks is prioritised. The focus for cost-effective and sustainable risk management should be on collective protection and preventative measures.
Step 3 Deciding on preventive action
Identifying the appropriate measures to eliminate or control the risks. List the preventive measures needed in order of priority, then take action, involving the workers and their representatives in the process. Targeting the underlying problems is the most cost-effective method of risk management.
Step 4 Taking action
Risk assessment is the first step to successful risk management. Put in place the preventive and protective measures through a prioritisation plan (most probably all the problems cannot be resolved immediately) and specify who does what and when, when a task is to be completed, and the means allocated to implement the measures. Interventions should be agreed with the workforce, either directly or through worker safety representatives. The agreed solutions should be carefully implemented, monitored and evaluated. The information arising from the risk assessment must be shared with the appropriate persons. Action should be supported by appropriate training.
Step 5 Monitoring and reviewing
The assessment should be reviewed at regular intervals to ensure it remains up to date. It has to be revised whenever significant changes occur in the organization or as a result of the findings of an accident or ‘near miss’ investigation.
2.3.2 Risk assessment on textile finishing requirements and considerations
Risk assessment on textile finishing requires knowledge of the properties of chemicals and the reactions involved in the concerned chemical processes. Due consideration should be given to the factors listed in the following paragraphs.
Physical form of the chemicals; the physical forms of the chemicals used in textile finishing have pronounced effects on the hazards of the chemicals. For those in the state of gases, vapours, fumes, aerosols, airborne particulates, the risk of entry into the human body as well as the risk of fire and explosion is increased. It should be noted that aerosol, particulate and powder forms of combustible materials can form explosive/flammable mixtures with oxidizing agents, including air.
Chemical changes; if chemical change is involved, the chemical reaction and the products should be studied. The hazards associated with the chemical reaction as well as hazardous properties of the reactants and products in textile finishing processes should be identified. Special attention should be paid to any possible side reactions and by-products.
Temperature and pressure changes; Many physical and chemical changes may evolve heat, causing a rise in temperature during the finishing processes. They may result in: formation of hazardous gases, vapours or fumes; pressure increase in the container causing explosion; rapid bubbling causing splashing of hot hazardous fluids; or increase in reaction rate generating even more heat. These effects can be intensified if there is no effective means to dissipate the heat evolved which may result in localised heating and superheating of the reaction mixture. It should also be noted that some exothermic reaction initiated by a rise in temperature may auto-accelerate and the reaction rate may become out of control.
Scale of the process; the scale of the process determines the amount of hazardous chemicals involved. Change in the scale affects the heating effect of the operation as well as heat dissipation and pressure change in the system. Extent of exposure The extent of exposure to hazardous chemicals is affected by: frequency, duration and mode of exposure; rate of generation and concentration of the hazardous chemicals in the atmosphere; and effectiveness of control and protective measures in minimizing the exposure.
Working environment; the working environment ranging from the containers holding the chemicals to the general conditions of the workplace is an important aspect in the risk assessment of textile finishing. The following factors should be considered: size and shape of the container where chemical or physical changes take place, especially the headspace in the container and passage for release of pressure; if the container cannot withstand or release the increase in pressure, explosion may occur; presence of nearby ignition source, if explosive/flammable mixtures are encountered; whether processes undertaken or chemicals stored or used are sensitive to air, moisture, temperature or light; and ventilation of the environment.
2.3.3 Prevention measures for occupational hazards
2.3.3.1 Access to safety and health information
The Hazard Communication Standard of the Occupational Safety and Health Act requires that all employees be informed of the hazards associated with the chemicals they are exposed to or could be accidentally exposed to. In addition to chemical hazards, OSHA requires workers be trained to recognize many other types of hazards. Hazards may include chemical, explosion and fire, oxygen deficiency due to confined spaces, ionizing radiation, biological hazards, safety hazards, electrical hazards, heat stress, cold exposure, and noise. (44)
2.3.3.2 Ensuring a Safe Working environment
Involving employees in the identification of high risk factors through an approved process to improve workplace conditions and safety provides a platform for; enhancing employee motivation and job satisfaction, improving problem solving capabilities, increasing the likelihood that employees will accept changes in the job or work methods, and improving labor relations. (45)
2.3.3.3 Safe operation of machines
Regardless of the particular risk reduction measures selected for a particular machine, there are some general safe operating rules that must be observed: Avoid working alone in the area so that someone is available to provide or summon assistance in the event of an emergency; Read and adhere to the manufacturer’s operating instructions and warnings. Receive training in proper operation and demonstrate competency to an experienced and authorized operator for each type of task to be conducted before operating independently; Know the emergency stop/shut-down procedures for the specific machine operated; Inspect machines/equipment prior to each operating shift to ensure that: Points of operation and surrounding areas are clean of debris and other hazards. Shields/guards are in place and controls and interlocks or other safety devices are accessible and operating properly (pay attention to the point of operation, as well as the area behind, to the side, and above the machine). Machine components are in good working condition (do not use damaged equipment). Labels and warnings are present and legible. ‘ Inspect ancillary hazard control devices for proper operation, such as dust collectors used with wood working equipment; Follow the manufacturer’s recommendations for routine cleaning and preventative maintenance. Do not use compressed air for cleaning of debris; Do not wear loose clothing or jewelry while operating machines; Confine long hair, including restraint of ponytails and beards; Wear appropriate work attire and prescribed Personal Protective Equipment, including, at a minimum, safety glasses and closed-toed shoes; Ensure unimpeded access to all operating controls, emergency shut-down devices, and electrical panels/shut-offs servicing the equipment; Ensure adequate lighting to safely operate the equipment; and If a machine is designed to be anchored to the floor, then it must be securely attached. (46)
2.3.3.4 Safe handling of chemicals
Dyes may present hazards to health. The following precautionary measures should be considered: As dyestuff powders may form airborne dust, they should be dispensed under local exhaust ventilation; the choice of low-dusting dyes such as those in granular, dust-suppressed or liquid form can reduce exposure; High-speed mixers should not be started until any dry dye is wetted out and the stirrer blades are covered. The vessels should be fitted with lids to prevent emission of aerosols or droplets during high-speed mixing; Walls should have smooth and impervious surfaces capable of being washed down, and floors should be smooth but non-slippery and preferably designed with a fall to a channel or drain for easy removal of cleansing water. The floors should be properly constructed to fit the type of material stored and to withstand rigorous impact from containers of all kinds. Dye stores should be well lit and ventilated; Separate storage areas should be provided for dyestuffs and other chemicals, as spillages of chemicals require frequent floor washing operations, which create a moist atmosphere not conducive to the good storage of dyes; all dye containers should be kept in good condition. They should be stored on pallets or platforms to facilitate cleaning of the floor. Lids should be kept close all times. The scoop used to transfer powdered dyes should enclose the powder to the greatest practicable extent, i.e., it should have a curved base and a partial canopy; Eating, drinking and smoking in the dye store should be strictly prohibited. Workers should wash their hands carefully before eating, drinking, or smoking; Protective clothing including impervious overalls, gloves, head coverings and footwear should be provided to and worn by dye handling workers; Respiratory protective equipment should be provided for use: on the recommendation of the dyestuff manufacturer; where persons are exposed to significant quantities of dust, for example during the cleaning of dye stores or following spillages of dyestuffs; and when dyestuffs in finely divided powder form (instead of ordinary granular form) are being handled. (47)
CHAPTER THREE
METHODOLOGY
3.0 Introduction
3.1 Study population
The study will consider a universe of 39 employees working in processing department which include 4 in grey inspection, 2 in dyeing, 4 on stenter, 4 on printing, 2 scouring, 2 mercerizing, 2 screen preparation, 6 design, 5 maintenance , 4 supervisors and 4 managers.
3.2 Sampling design
From the universe of 39 employees, a sample size of 19 employees was selected at random using the stratified sampling techniques to represent the whole department.
3.3 Establishment of the current processes and procedures
So as to get reliable observations, impromptu visits to the factory floor were made and photos of the risk areas which need improvement and modification were obtained.
3.4 Identification of the risky areas and practices
3.5 Development of standard operating procedures
3.6 Data collection instruments
Questionnaires were used to obtain information regarding the daily operation procedures and safety measures from the sample of 20 employees selected systematically based on their specific sections within the processing department. Since some information especially regarding safety is taken to be sensitive in some factories, names and sections of the respondents were held confidential between the researcher and respondents to prevent reprimanding and ensure openness and accuracy in the findings.
Interviews through casual discussions were also held to obtain information which could not be obtained using the questionnaires.
3.7 Analysis of findings
The obtained data and information was analyzed using Microsoft excel spreadsheets.
3.8 Presentation of findings
The obtained findings from observations, interviews and questionnaires are presented in comprehensible charts and graphs and sentences.
CHAPTER FOUR
RESULTS AND DISCUSSION
4.0 Introduction
This chapter presents the current process control and safety measures and issues at Rivatex East Africa Limited as obtained from the observations, interviews and questionnaires.
4.1 Duration of employment
To determine the reliability of the information, respondents were asked to state how long they have been working in the department. The information obtained is shown in the table below.
Table 4.1: duration of personnel employment at REAL wet processing department.
Duration Number of employees
Less than 3 months 1
3 ‘ 6 months 0
6 months to 1 year 2
2 years and above 16
Total number of respondents 19
Figure 4.1: distribution of employment duration at REAL wet processing department.
Since most the respondents have worked in the department for more than 2 years, it can be assumed that they are familiar with the daily activities and processes of the department. The information provided will give a representation of what exactly is done by all the employees in the department.
4.2 Training for the job
After establishing the duration of employment, respondents were asked to state if they have ever received specific training from the factory for the tasks they were assigned to in the department. This was to establish if they knew exactly what they is expected from them and how their tasks contribute to the attainment of the organizational objectives and goals. The respondents were required to tick a yes for having received training and for not receiving any specific training. The results obtained from the 19 respondents are shown in table below.
Table 4.2: percentage of trained personnel at REAL wet processing
Response Frequency
Yes 12
No 07
Total 19
Figure 4.2: percentage distribution of trained personnel
From the questionnaires, 37 % of the respondents said that they have never received any specific training from the factory regarding what they are supposed to do on their daily schedules. Of these 37 %, some said they use the knowledge gained from their previous experiences to execute their daily their tasks. Some said the training would not be very necessary since what they do is very obvious and routine.
63 % of the respondents said they had received training on their specific daily tasks. Of these who said had received training, most of them were graduates practicing the profession and others were trained by fellow workers who had left the department for other things. The training from fellow workers was more informal and depends on the individual’s level of curiosity and interest in a particular process. As the individual picked interest in a particular machine, he is told by the operator what is done and in his absence, the one told what is to be done takes over from the old operator.
4.3 Occurrence of accidents
To justify the need for safety evaluation, the respondents were asked if they have ever witnessed or encountered an accident during the course of their work. This was aimed establishing the major causes of accidents so as to develop the most appropriate measures which can prevent future occurrences. The response obtained is shown in table below.
Table 4.3: occurrence of accidents at REAL wet processing
Ever witnessed an accident? Frequency
Yes 08
No 11
Total 19
Figure 4.3: occurrence of accidents at REAL wet processing
From the questionnaires and interviews, 58 % of the respondents said they have never witnessed of encountered an accident in the department since they started working for the factory. Among these were the new recruits who had spent less than 2 years working for the department.
42 % of the respondents said they have ever witnessed an accident in the department and recommended a need for more safety awareness among the employees. The accidents that were witnessed include: operator’s hand getting clamped between rollers; fingers cut off by a machine handle; explosion of electric motors due to failure; spillage of chemicals to operator’s eyes during application to machines; rolling of fabric rollers due to improper or accidental unwinding from the stands; flames from electrical faults; operators hurt on starting the machine because they were in harm’s way; and operators loosing fingers to falling and moving metals.
4.4 Occupational health
The respondents were asked if they have ever got complications resulting mainly from the nature of their daily tasks. During interviews, 4 of the respondents said yes, but only 2 could give the details as shown below.
Table 4.4: respondents with occupational health concerns
Occupational hazard Number of employees
Yes 04
No 15
Total of respondents 19
Figure 4.4: percentage of respondents with occupational health concerns.
Of the 4 who said to have complications from the line of work, 2 claimed they acquired allergies from the dust and inhalation of chemicals, 2 claimed to have persistent headache and fatigue, 1 claimed to have back compilations from the over bending and lifting of heavy weights, 1 claimed to have issues with the eyes which cannot easy properly especially under a lot of light and 1 claimed to have general body weakness.
4.5 Process control
This section outlines the daily activities carried out by the personnel in various section of wet processing department as obtained from the factory floor through interviews, observations and questionnaires.
When asked about what they do on a daily basis, most respondents said they: report for shift, wear overall, clean the machines, and run the machines following the instructions from the shift in charge. They don’t need to memories the activities since it is the responsibility of the shift in-charge. From the questionnaires, some knew the specifics of their daily tasks, while others relied on the instructions from supervisors and managers as shown in the table below.
Table 4.5: level of initiative at REAL wet processing
Response Number of employees
Wait for instructions from supervisors 11
Know what exactly to do 08
Total 19
Figure 4.5: level of initiative at REAL wet processing
Since 42% of the respondents know what to do based on daily routine tasks, it is possible that given power and audacity, they can work towards the improvement or degradation of the process through unconscious modifications as time goes on.
58% of the respondents wait for instructions from the supervisors before they can do anything. This can put a lot of strain on the supervisors and managers especially in case one or more processes have hiccups which immediate attention. This can mean that the process has to stop until the supervisor or manager reports to provide a go-ahead. Most the respondents who said they wait for the supervisors and managed were engaged in processes which can be easily regulated using basic standard operating procedures which can be easily read and followed and the supervisor would then be required to confirm if what they are doing is in line with the stipulated standard operating procedures.
4.6 Observed operating procedures
4.6.1 Grey room activities
Storage
Figure 4.6: fabric storage at REAL
Inspection
Figure 4.7: fabric inspection machines at REAL
4.6.2 Sizing and desizing
Figure 4.8: singeing, sizing and desizing machine at REAL
4.6.3 Mercerizing
Figure 4.9: mercerizing machine at REAL
4.6.4 Dyeing
Figure 4.10: HT-HP Jigger dyeing machine at REAL
4.6.5 Printing
Figure 4.11: rotary screen printing machine at REAL
4.6.6 Raising machine
Figure 4.12: raising machine at REAL
4.7 Identified unsafe areas which need attention
Figure 4.13: The expired fire extinguishers in grey room which need removal and replacement
Figure 4.14: steps entering the bottom of mercerizing machine [they need balustrades]
Figure 4.15: Improper drainage of caustic behind the mercerizing machine [needs proper drainage]
Figure 4.16: The moving bar which cutoff the employee’s fingers on the stenter machine
Figure 4.17: The drainage channels with rusted and worn-out covers which need renovation
Figure 4.18: An open electrical cabinet used for drying wet cloth.
This exposes the personnel to electric shock and electrical related fires.
Figure 4.19: Exposed steam valves with a cloth for condensing steam into water.
This can cause serious injuries to personnel in the event of valve explosion.
Figure 4.20: Broken ceiling in the dye house laboratory which needs renovation
Figure 4.21: Obsolete air conditioning system in the laboratory
Figure 4.22: Faulty electric sockets being by-passed
Figure 4.23: Chemical bath needs a shower
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CHAPTER FIVE
RECOMMENDATIONS AND CONCLUSION
5.0 Introduction
5.1 Safety Protocol on the Factory Floor
There are various measures that can and should be taken to minimize accidents on the factory floor and to ensure a safer working environment.
5.1.1 Protective Gear
Care should always be taken when handling dyes and chemicals as they can be hazardous or toxic to health as a result of respiratory sensitization from exposure to reactive dyes. Exposure to dust, dyes and chemicals can arise from dye handling, poor storage conditions, damaged containers, spillage, and from dust which has previously settled in the workplace. Exposure to hazardous substances is minimized by wearing the appropriate gear, which includes, gloves, goggles or glasses, boots and dust masks when handling or transporting certain dyes and chemicals, especially caustic chemicals and acids. It is not necessary to always wear protective gear and at times it may be restrictive and increase risk but all workers must be made aware of potential dangers and guidance provided on MSDS should always be followed. In case of exposure to contamination, the person should run to eye washes and showers or hoses to decontamination.
5.1.2 Environment
The working environment should be as dry as possible to prevent accidents. Signs informing people of damp and wet floors must be displayed when required. Dust should also be minimized or extracted to reduce inhalation of particles. Exit passageways and stair cases must never be blocked with obstacles, and all stairs should have hand rails. Emergency exit doors should never be locked. Proper lighting and ventilation need to be ensured and machinery must be well maintained to avoid accidents. Head height should be sufficient in all areas to avoid accidents. Hazardous waste must be disposed of properly in accordance with manufacturers’ guidelines (MSDS) and national policies.
5.1.3 Training
Proper Training on the use and maintenance of machinery and other equipment; Health and Safety; and Fire Hazards and Emergency, needs to be provided. Training should be repeated regularly – at least once a year. Health and Safety training would include information on the potential hazards of solvents and chemicals; preventive measures that can be taken to avoid accidents and to minimize exposure to all dyes and chemicals; and measures to take if such accidents or exposure do occur. Fire Hazards and Emergency Evacuation training involves holding regular fire drills and all workers should be trained in the correct use of fire extinguishers and fire hoses. These should be easily available throughout the factory and regularly checked by a qualified assessor.
5.1.4 Lifting and Carrying Heavy Objects
According to the HSE, it has been shown that musculoskeletal injuries are the most common type of injuries in the textile industry. (48) Care should be taken when moving heavy objects, as is often required on the factory floor. Most musculoskeletal injuries occur due to improper ways of carrying or moving heavy objects. This can be minimized by sharing the weight between two workers or by using wheeled trolleys, and maintaining the correct posture when lifting and carrying these objects. These risks can also be better managed by identifying and assessing which tasks would cause serious risks of acute injury for example from lifting, or chronic injury from repetitive upper body work. The weights of sacks and boxes should be kept to 25kg or below and there should be job rotation and training provided on ways to prevent such injuries.
5.2 Process control chart for wet processing
From the observations of what happens in the wet processing department of Rivatex east Africa limited, the activities can be aligned into the following process control chart for easy tracking and order.
Figure 5.1: recommended process control chart for REAL wet processing department.
5.3 Recommended standard operating procedures
Standard Operating Procedures describe how individual processes are carried out and ensure consistency within the factory. Consistency of processing is key to delivering quality goods batch after batch. If correctly implemented, SOPs will improve quality, increase productivity, reduce waste and save costs. All factory processes, however simple, should have a written SOP that provides step by step details of what needs to be done in order to carry out a task such as: The equipment used; Temperature, humidity and lighting requirements; Timings; and Chemicals used.
5.3.1 Grey room Standard operating procedure
Safety
Always wear black gaggles to prevent the effect of inspection light; avoid lifting the beams alone as this can affect your back and chest in the long run; use a jerk for placing the fabric beams onto the unwinders; always wear a lab coat to keep yourself clean; use the transportation trollies for moving fabric; wear musk when handling fabric as it tends to give off fluff which can be dangerous for your lungs; don’t operate the machines when alone as this can be dangerous in case of emergency help. Always report any safety concerns to the immediate supervisor.
Equipment:
1. Inspection table
2. Fabric inspection machine (Nazer, L 90P, Pakistan)
Key Accessories
Nipper, Pointer, Cutter, Comb etc.
Safety measures:
1. Smoking inside the inspection area is strictly prohibited.
2. Fire extinguishers are placed in the inspection area and all are trained to use it.
3. No fabric stack is placed in front of electric panels.
Inspection procedure
Operation staff:
Cloth doffer, cloth mender, inspector
Machine set up:
Machine set up Parameter range Set value
1) Roller speed 100-1500 rev/hour. 590-600 rev/hour.
2) Light N/A Artificial light
3) Length measuring meter N/A Attached with the machine.
Checks list before inspection:
1. 1 .Machine parameters are set
2. Man power is made available
3. All the tools/accessories are made available
4. Fabric is made ready for inspection.
Investigation:
In the inspection table the operator finds out faults in the fabric and analyses their intensity by visual inspection. Some of the common weaving faults are: Stop mark, Pick faults, e.g.-miss pick and double pick, Wrong density /drawing, Pattern or design break, Selvedge faults, e.g.-lashing in, cut selvedge, Oil stain, Crack, hole, Missing ends, . Slubs. The intensity of some of the major and common weaving faults are marked with points (Numerical value) ranging 1 to 6, 6 being the highest point for every faults. The defects found and the points given against them are recorded in the grey fabric inspection sheet in the case of solid dyed fabric and in yarn dyed fabric inspection sheet for yarn dyed fabric. The measured length, fabric sort, yarn lot, machine number etc. are also written down at the tail end of each fabric piece. Apart from these two forms another from called grey fabric inspection daily production sheet is filled to keep the record of total inspected grey fabric in the shifts in a day. At the bottom of this sheet total amount of rejection is also shown. All the data entered in this form are done according to various sort, construction and quality.
Acceptance of fabric:
Any piece of fabric with the rating of total 36 points faults per 100 linear meter is allowed to pass as ‘A’ grade fabric. 36-50 is the point range for ‘B’ grade fabric. Any piece having more than 50 points is graded as ‘C’ which is rejected. A minimum of 20 meter ‘A’ grade fabric is allowed to pass with other long pieces. Pieces less than 20 meter is recorded as cut pieces.
Rejection of fabric:
Any area of the fabric that contains: Objectionable (too frequent) presence of weaving faults like stop/starting mark and pick faults; Oil or grease spot; Crack/holes, floats and warp end miss etc. are cut to a separate pieces and recorded as rejected; and any fabric having points more than 50 is graded as ‘C’ and also rejected.
Machine area cleaning:
Inspection area is cleaned twice a day by the helpers.
Storage:
The grey fabrics thus inspected are piled separately according to lot and sort/quality or construction and to store; store upon receiving the production sheet physically checks and receives the fabric.
5.3.2 singeing/shearing Standard operating procedure
Safety
Always wear a lab coat to keep yourself clean; never start the flames when the fabric is not not running as this can lead to fire hazards; wear musk when handling fabric as it tends to give off fluff which can be dangerous for your lungs; don’t operate the machines when alone as this can be dangerous in case of emergency help; always make sure the machine is properly threaded and clean; avoid excessive exposure to high temperatures by keeping a safe distance whenever necessary; Always report any safety concerns to the immediate supervisor.
5.3.3 Desizing Standard operating procedure
Safety
Always wear a lab coat to keep yourself clean; wear and eye gaggles musk when mixing the desizing recipe and handling fabric as it tends to give off fluff which can be dangerous for your lungs; wear gloves when handling chemicals to avoid chemical burns; don’t operate the machines when alone as this can be dangerous in case of emergency help; always make sure the machine is properly threaded and clean; avoid excessive exposure to high temperatures by keeping a safe distance whenever necessary; Always report any safety concerns to the immediate supervisor.
Procedures
Nature of Size: Prior to desizing spoofing test.
Action: Select correct method of desizing
%Wet pickup during Desizing: Pick up should not be less than 110%.
Action: If pickup variation is there then adjust pressure.
Concentration of desizing agent and other ingredients: HCl-5gpl, Cellulase enzyme 3-5gpl.
Impregnation and dwell time: Nonionic wetting agent 3-5gpl. Dwell time checked during padding. Ensure optimum dwell time.
Temperature: During desizing in the bath (exothermic reaction may rise the temperature. Acid desizing is done at room temperature. Enzyme desizing is done depending on the enzyme.
Action: Regulate the steam supply. In acid desizing replenish the acid solution or provide water cooling system.
pH: Depending on the Enzyme
Desizing efficiency: Standard- Not less than 85%.
5.3.4 Mercerization and scouring Standard operating procedure
Safety
Always wear a lab coat to keep yourself clean; wear and eye gaggles musk when mixing the desizing recipe and handling fabric as it tends to give off fluff which can be dangerous for your lungs; wear gloves when handling chemicals to avoid chemical burns; don’t operate the machines when alone as this can be dangerous in case of emergency help; always make sure the machine is properly threaded and clean; avoid excessive exposure to high temperatures by keeping a safe distance whenever necessary; Always report any safety concerns to the immediate supervisor.
Procedures
Moisture Control: More moisture pickup by the fabric means more NaOH and hence more effect. Drying cylinders are kept before mercerization tank to have the same moisture content in the fabric throughout for uniform results. Other technique is wet on wet mercerization, where fabric is pre wet but it requires high precaution.
STANDARD: Free from moisture.
METHOD: By sufficient steam in drying cylinder.
Caustic soda solution while padding:
STANDARD: 25% or 50-520 Tw.
METHOD OF CHECKING: Twadle meter or titration.
NECESSARY ACTION: Adjust the concentration according to the requirement. Concentration of NaOH will never change in tank from start to end but then also at a later stage the concentration on Twadle meter increases because the density of solution may increase due to the impurities from the fabric like thickening agent.
Temperature of Padding Solution:
Ideally it is carried at room temperature. If the temperature is more, then it is because the moisture in the fabric is more. Water and NaOH leads to exothermic reaction which will increase the temperature. So dry the fabric properly. If still temperature increases then check water cooling line.
Dwell time:
45-60 Seconds.
Wet pick up of NaOH: Wet pick up is generally 120-125% but it should be perfectly uniform throughout the width and length. Pick up is studied by taking original weight of fabric and weight of fabric after padding. Pick up is checked randomly.
Washing:
First compartment after mercerization tank is recuperator. Here the caustic soda should not be more than 100 Tw. If its % is very low then take less water. (Because if more water is present then NaOH associates itself with more water molecule and its size becomes bigger which is very difficult to remove from the core of the fibre while washing and chances are that we do not get proper washing).
ACTION: Adjust the flow of water.
Temperature of Recuperator:
Here the hot washing is carried out. Live steam is blown in water. So the temperature should not be less than 900C.
Caustic soda left on the fabric:
Removal of 100% caustic is very difficult and uneconomical. It should not be more than 1% on fabric and if the quantity is more than 1% then check the washing efficiency, efficiency of recuperator and adjust the flow of water.
Souring:
This treatment is carried out when bleaching is performed on the fabric. In grey mercerization it is not performed. Removal of NaOH is very difficult and hence acid neutralization is very cheap and easy. Removal of alkali by water consumes very high amount of water.
STANDARD: Extract of fabric must be neutral after the souring treatment.
Fabric after washing:
Check the extract of fabric by pH indicator or pH paper
STANDARD: pH must be neutral. If fabric is acidic then adjust flow of water, if alkaline in nature then adjust souring percentage.
5.3.4 Dyeing Standard operating procedure
Safety
Always wear a lab coat to keep yourself clean; wear and eye gaggles musk when mixing the desizing recipe and handling fabric as it tends to give off fluff which can be dangerous for your lungs; wear gloves when handling chemicals to avoid chemical burns; don’t operate the machines when alone as this can be dangerous in case of emergency help; always make sure the machine is properly threaded and clean; avoid excessive exposure to high temperatures by keeping a safe distance whenever necessary; Always report any safety concerns to the immediate supervisor.
Procedures
Standard procedure for ‘pre bleaching’
Load fabric, Add viscavin ‘ dosing 5 minutes ‘ run 10 minutes, Add primasol jet and ffc, Add caustic ‘ dosing for 10 minutes ‘ raise to 60 oC, Add peroxide ‘ don’t mix with water just transfer, Raise temperature to 95o C, Run 30 minutes only, Cool and drain, Hot wash at 90 oC for 10 minutes, Hot wash at 85 o C for 10 minutes, Add acid and raise temperature to 50 o C, Check pH and set to 5.5-6.5, Add kfp ‘ run 10 minutes ‘ check residual peroxide, and Drain and fill for dyeing
Standard procedure for 65% cotton dyeing
Fill for dye bath ‘ set the temperature at 50 oC; Add Primasol jet and FFC ‘ take water from the machine; add Sarabid l dr ‘ water from the machine; Add salt ‘ water from the machine; Add acid ‘ water from the machine; check pH and set to 5.5 – 6.5; Add dyes ‘ dilute with fresh water and dose for 20 min; Raise the temperature to 65 oC; Run 30 minutes; Add soda ash – mix with fresh water and dose for 20 minutes; Run dyeing time according to recipe sheet; Check sample after 15 minutes; Do not cut more samples unless advised; Drain at the end of dyeing time; Do not run more time unless advised; Wash at 50 o C for 10 minutes; Wash at 50 OC with acid for 15 minutes; and finally Drain and fill for after treatment
Standard procedure for 85% cotton dyeing
Fill for dye bath ‘ set the temperature at 50 oC; Add primasol jet and ffc ‘ take water from the machine; add sarabid ldr ‘ water from the machine; Add salt ‘ water from the machine; Add acid ‘ water from the machine; check ph and set to 5.5 – 6.5; Add dyes ‘ dilute with fresh water and dose for 20 min; Raise the temperature to 85 oC; Run 30 minutes; Add soda ash – mix with fresh water and dose for 20 minutes; Run dyeing time according to recipe sheet; Check sample after 15 minutes; Do not cut more samples unless advised; Drain at the end of dyeing time; Do not run more time unless advised; Wash at 50 c for 10 minutes; Wash at 50 c with acid for 15 minutes; and finally, Drain and fill for after treatment
Standard after treatment process ‘ very light shades
Fill water; hot wash at 85 o C for 20 minutes; Cold wash and check the shade; Fill ‘ add acid ‘ set pH to 5.5 ‘ 6.5; Add softener.
Standard after treatment process ‘ medium shades
Fill water; soap at 85o C for 20 minutes; hot wash at 70 o C for 10 minutes; Cold wash and check the shade; Fill ‘ add acid ‘ set ph to 5.5 ‘ 6.5; Add softener. For light and medium shades there is no fixing and you must use baa softener.
Standard procedure – after treatment ‘ dark shades
Fill water; [2]Soap at 95 oC for 20 minutes; [3] hot wash at 90o C for 10 minutes; repeat step 2 and 3 until the water is clear; Cold wash and check shade and color in the water; Fill water followed by acid to set pH to 5.5 to 6.5; add fixing agent; Add softener. Dark colors can use softeners. But you can’t use softeners for turquoise combination. So please be careful and select the softener according to the recipe sheet.
All machines should run at 130 rpm
5.3.5 Printing Standard operating procedure
Safety
Always wear a lab coat to keep yourself clean; wear and eye gaggles musk when mixing the desizing recipe and handling fabric as it tends to give off fluff which can be dangerous for your lungs; wear gloves when handling chemicals to avoid chemical burns; don’t operate the machines when alone as this can be dangerous in case of emergency help; always make sure the machine is properly threaded and clean; avoid excessive exposure to high temperatures by keeping a safe distance whenever necessary; Always report any safety concerns to the immediate supervisor.
Procedures
5.3.6 Finishing Standard operating procedure
Safety
Always wear a lab coat to keep yourself clean; wear and eye gaggles musk when mixing the desizing recipe and handling fabric as it tends to give off fluff which can be dangerous for your lungs; wear gloves when handling chemicals to avoid chemical burns; don’t operate the machines when alone as this can be dangerous in case of emergency help; always make sure the machine is properly threaded and clean; avoid excessive exposure to high temperatures by keeping a safe distance whenever necessary; Always report any safety concerns to the immediate supervisor.
‘
Procedure
Fabric Shrinkage and Twist Control
Some fabrics are relatively unstable when they leave a dyeing machine and if washed would shrink and or twist leading to customer dissatisfaction. Some of the problems of variable shrinkage can be traced to different greige sources, so it is important to segregate greige from different sources and treat them as different fabrics even if they have the same nominal specification.
There are a number of processing methods which can reduce shrinkage and twisting of unstable fabric. Santex relax driers are useful for weft knitted fabrics. It is recommended that a pin entry on these machines is used to control over-feed into the fabric and to hold open width fabric at a controlled width.
Stenters are used to carry out a multitude of tasks in a finishing department and can have several features including: Controlled over-feed to compress fabrics and reduce shrinkage; Pyrometers to measure the actual fabric temperature; Moisture meters; Pick/course counters; Gravimetric fabric weight measurement; Bow and skew control; Auto-levellers on pad troughs to ensure uniformity of finish application; Pad mangles to apply performance finishes; Steam boxes to reduce ripples formed by over-feeding mechanism; Cooling cans to cool and condition fabric; Vacuum slots to remove lint / excess moisture; Scrubbers to reduce air emissions; Heat recovery.
Particular recommendation is made for course/pick counters to ensure fabric stability and pyrometers to ensure fabrics are subjected to the correct temperature for correct period of time, essential for pre and post setting. However, stenters and other finishing equipment are not good for on-line final examination as they don’t provide sufficient time to carry out a thorough examination of the fabric. There often no opportunity to test finished fabric, hence testing should always be completed before examination. Sanforisers and compactors are used as the final process to apply the final compression to the fabric to ensure the required stability is achieved.
Application of chemical finishes
Most chemical finishes are applied by a mangle at the entry to a stenter. Harder rollers, operating under higher pressure results in fabric having less moisture present as it enters the stenter and it therefore requires less energy to dry the fabric. Well maintained mangles apply chemicals in a more controlled and uniform manner. Consistent application is improved through the use of auto-levellers to control the liquor levels and fabric immersion times. Simple softeners, lubricants, fixatives and anti-static finishes are considered relatively non-critical in terms of process control but SOP’s are still required to ensure mistakes are not made. Performance finishes such as resins, flame retardants and water-repellents are far more critical and it is highly recommended that pyrometers are used to control these processes. For some fabrics that require long curing times (such as FR finishes) it is worth considering the purchase of a baker rather than using a stenter at slow speeds. Bakers hold large quantities of fabric so can still give a high throughput.
5.4 conclusion
Based on the findings obtained from the study,
‘
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‘
Appendices
QUESTIONNAIRE FOR WET PROCESSING DEPARTMENT
Introduction
This questionnaire is for MIT 832 – Processing Techniques coursework project for assessing the state of safety and operation efficiency at wet processing department of Rivatex East Africa Limited. The information to be obtained is solely intended for study purposes so as to improve the state of safety in the departments. No one will be liable accountable or punishable from the findings of the study as no specific identities will be required for the assessment purpose. Please spare some few minutes to complete the following questions. Your honest and sincere cooperation during this survey will greatly determine the accuracy of the findings.
1. How long have you worked at Rivatex? [tick as appropriate]
Less than 3 months
3-6 months
6 months to 1 year
2 years and above
2. Have you ever had training on the job?
Yes No
3. If yes, ? How did this training help if any, in carrying out your tasks?
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..
4. Have you ever witnessed or heard of an accident while working?
Yes No
5. If yes please give brief description of the incident.””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””?
6. Do you have any health complications related to your line of work?
Yes No
7. If yes in 6 above, have you visited the hospital for diagnosis and treatment?
Yes No
8. If yes in 7 above, what was the diagnosis?
…………………………………………………………………………………………………..
9. When you report on shift? What are the first tasks you carry out””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””?
10. What steps or procedures do you follow when doing your work””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””””?
11. Do you use any chemicals in your area of work?
Yes No
12. If yes, please state some of the chemicals.
i. ””””””””””’.
ii. ”””””””””””’
iii. ”””””””””””’
iv. ”””””””””””’
13. Do you have any recommendations on how to make your job:
a. Safer
””””””””””””””””’
””””””””””””””””’.
””””””””””””””””..
b. Easier and more productive
””””””””””””””””””””””””””””””””””””””””””””””””””””’.
THANKS FOR YOUR COOPERATION