Innovative energy conservation measures in overhead cleaners

SITRA has undertaken a research project which has resulted in developing five different innovative methods of energy saving in overhead cleaners. R Prakasam, M Muthuvelan and K Suresh analyse the project

Manufacturing defect free products needs support from other systems generally known as ancillaries, which are not part of the original machines. The ancillary refers to non - productive systems and its power consumption accounts for about 10% to 30% of the machines. Ancillary systems are provided with high-powered drives designed to produce output, especially to meet peak requirements, which will not occur regularly. Textile industry is one among the high-energy intensive quality seeking manufacturing plants. It needs to be effectively managed against waste (fluff) generated out of fibre processing, which affects the quality of the outgoing yarn/fabric. It is imperative for any textile mill to have control over waste removal out of the processing area to ensure better quality. Fluff removal and machine cleaning can be accomplished with the support of Overhead Travelling Cleaner (OHTC) which is an ancillary drive associated with spinning and weaving sections of textile industry Common waste collection system (WCS) is an independent sub-system designated to collect waste from group of OHTC(s). In order to save energy in using overhead travelling cleaners, SITRA has undertaken a research project. It has resulted in developing five different innovative methods of energy saving in overhead cleaners and this paper describes the details of the same.

Overhead travelling cleaners

In modern mills, one overhead travelling cleaner has been serving for every 1008/1200-spindle ring spinning frame. It moves on the rails at a speed of about 16 meters per minute. It takes about 140 seconds to move from pneumafil end to gear end. OHTC is continuously blowing/sucking of air at different component parts of the machine during its traverse motion. It collects approximately 1 to 3 gms of fly from the floor for every to and fro movement. OHTC is stopped at each end of the traverse for more than 60 seconds to collect the accumulated fly/fluff. In general, one overhead travelling cleaner consumes about 17,000 units per year and the waste collected by one OHTC is about 230 gram per shift of 8 hours while processing yarn of 80s count.

Power consumption of OHTC

The actual power consumption of OHTC(s) varies from model to model and one manufacturer to other. It is observed that most of the OHTCs working in the departments belong to the bus bar type family except those working in autoconers. The actual power consumption varies from 0.8 kW to 3.2 kW of different makes.

Waste Collection Suction system (WCS)

Waste management in textile mills adopts various methods for collection and disposal of waste generated during the production process. The Waste Collection System (WCS) is an automatic functionary serving collection and transportation of waste to a common station. This powered system connected with group of overhead traveling cleaning machines is being deployed to collect the waste dropped in the drop boxes and transport it via common suction chute to a specific destination for easy disposal. The WCS has become widely used and most accepted system for waste handling in textile spinning mills especially in those mills built after 1991.

Power consumption of WCS

Measurements have been made for determining the power consumption of suction blower in various spinning mills. It is observed that the capacity of the WCS differs from mill to mill depending upon the number of frames it serves. About 13 frames are grouped under one single system to the maximum. Two parallel systems are deployed for those mills having 25000-spindles capacity. The power consumption of the blower varies from 1.3 kW to 5.1 kW.

a. SITRA PCRA OHTC Eneroptimiser I - PLC based

This system has been introduced in a mill where the spinning section has 11 ringframes of 1008 spindles and each frame is fitted with one OHTC. The traverse time of each OHTC varies from 4.5 to 5 minutes to complete a cycle. Each OHTC(s) are assigned to move in a linear path and at the end of each cycle it has to drop the waste into a drop box. A common waste collection suction system connecting all OHTC(s) to a common station is under operation. The centrifugal blower is located away from the department. The installed blower is capable of creating suction of 230 mm of water column and is driven by 5.0 hp motor. The blower is continuously operated throughout the year except for few holidays. The waste from the waste collection chutes is removed manually once in each shift of the day.

The main components of SITRA PCRA OHTC Eneroptimiser I Control System such as sensors, master control unit, control damper were installed in the mill. After commissioning the unit, the performance of the WCS was observed continuously in terms of quantity of waste collection, variation in energy consumption, rise in temperature of motor etc with the help of precise instruments.

It was observed that the operating time was reduced to about 53%. The energy consumption of the WCS blower was reduced to 57% when compared with previous condition. It is also to be noted that the average waste collection level has not been affected when the working duration of blower is reduced to half of the time.

Economics of the system

The cost benefit analysis of installing SITRA PCRA OHTC Eneroptimiser I PLC based system in a textile mill was worked out as below:

Cost of SITRA PCRA OHTC ENEROPTIMISER I system: Rs 50000 per unit

Previous energy consumption per annum: 58.4 units/day x 360 days = 21024 units/annum

Estimated power saving (minimum): 50% of total consumption

Energy saving per annum: 21024 units/annum x 50/100 = 10512 units/annum

Estimated saving in rupees (at prevailing TNEB cost of Rs 4.30/unit): 10512 x 4.30 = Rs 45201/year

Return on investment (ROI): 45201 x 100/50000 = 90%

Payback period: 13 months.

As can be seen from the above, incorporating SITRA PCRA OHTC Eneroptimiser I - PLC based system ensures a simple payback period of about 13 months. The payback period differs from one mill to other depending on the capacity of the suction blower motor. The payback period will be further reduced in the case of higher capacity blowers installed in the waste collection system due to more savings.

b. SITRA PCRA OHTC Eneroptimiser II - Timer based

An energy efficient control system using off timer circuit named as SITRA PCRA OHTC Eneroptimiser II - Timer based system has been introduced in addition to main contactor provided in the control box to start and stop the OHTC whenever it touches the ends of the ring frame over which it moves in a linear path. The off timer had been incorporated for the study with a feature of extending the delay operation for 0 to 30 minutes in a stepped manner. The study has been conducted in a textile mill near Avinashi, Coimbatore. Initially, the measurement of actual power consumption of existing OHTC connected with a ring frame of 1200 spindles producing yarn of 80s count had been done. The study was continued with the SITRA PCRA OHTC Eneroptimiser II - Timer based system for automatic halting and restarting at both the ends of the ring frame.

It was observed that the operating time was reduced by about 33%. The energy consumption has reduced by 33% when compared with previous condition. This method can be adopted for the mills processing fine counts where the fly liberation is less. This system is not suited for the mills processing coarser counts, as the fly liberation will be more.

Economics of the system

Cost of SITRA PCRA OHTC ENEROPTIMISER II system: Rs 7500 per unit

Previous energy consumption per annum: 2.03 units/hr x 24 x 360 days = 17539 units/annum

Estimated power saving (minimum): 33% of total consumption

Energy saving per annum: 17539 units/annum x 33/100 = 5788 units/annum

Estimated saving in rupees (at prevailing TNEB cost of Rs.4.30/unit): 5788 x 4.30 = Rs 24888/year

Return on investment (ROI): 24888 x 100/7500 = 332%

Payback period: 4 months.

As can be seen from the above, the payback period is just 4 months for installing SITRA PCRA OHTC Eneroptimiser II - Timer based system.

c. SITRA PCRA OHTC Eneroptimiser III - Optical

Another design of using the optical sensor to sense the position of the OHTCs on the ring frames had been designed and named as SITRA PCRA OHTC Eneroptimiser III - Optical system. This system will start running the blower fan of the WCS only during the needed time. This system has been designed and installed in a textile mill near Annur, Coimbatore. It was noticed that the waste collection level by the WCS blower does not get affected by installing this system.

It was observed that the operating time of the WCS blower was reduced by about 41%. Simultaneously, the energy consumption reduced by 41% when compared with previous condition.

Economics of the system

Cost of SITRA PCRA OHTC ENEROPTIMISER III system: Rs 40000 per unit

Previous energy consumption per annum: 36.43 units/day x 360 days = 13115 units/annum

Estimated power saving (minimum): 40% of total consumption

Energy saving per annum: 13115 units/annum x 40/100 = 5246 units/annum

Estimated saving in Rupees (at prevailing TNEB cost of Rs 4.30/unit): 5246 x 4.30 = Rs 22558/year

Return on investment (ROI): 22558 x 100/40000 = 56%

Payback period: < 2 years

It can be seen from the above that the payback period is less than 2 years for installing SITRA PCRA OHTC Eneroptimiser III - Optical system in the mills.

d. SITRA PCRA OHTC Eneroptimiser IV - Curve system

In most of the textile mills built before 1995, one overhead travelling cleaner (OHTC) has been serving for 5 to 8 ring frames having 432/440/480/504-spindles. OHTC moves on the rails at a speed of about 12-16 meters per minute driven by a traverse motor and collects the waste from the floor through suction nozzles by means of a suction fan driven by a separate motor. It takes about 240 to 390 seconds to move from one end to other end. The waste deposition is bare minimum on the floor at the ends of each ring frames when compared with other area. But the suction fan of the OHTC, which is working continuously on the curvi-linear path, continues to consume the same energy irrespective of the amount of waste it collects from the floor. Therefore, the suction fan of the OHTC can be stopped allowing traverse motor only to function during the movement over each curved path to save power.

In general one overhead travelling cleaner consumes about 8,000 units per year. Based on the above-mentioned criteria, an energy saving control system has been designed and developed using position sensors and Programmable logic controllers (PLC) to achieve the energy savings on OHTC(s) working in a textile-spinning mill. The developed control system can automatically switch on and off the suction fan whenever the OHTC touches the ends of the ring frames.

It was observed that the operating time of the suction fan was reduced by about 10 minutes/hr. The energy saving to the tune of 18% had been realised compared with previous condition. It was also to be noticed that the average waste collection level has not been affected.

Economics of the system

The cost benefit analysis of using SITRA PCRA OHTC Eneroptimiser IV system had been worked out and illustrated below.

Cost of SITRA PCRA OHTC Eneroptimiser IV system: Rs 30000 per unit

Previous energy consumption per annum: 1.10 units/hr x 24 x 360 days = 9504 units/annum

Estimated power saving (minimum): 18% of total consumption

Energy saving per annum: 9504 units/annum x 18/100 = 1710 units/annum

Estimated saving in rupees (at prevailing TNEB cost of Rs 4.30/unit): 1710 x 4.30 = Rs 7353/year

Return on investment (ROI): 7353 x 100/30000 = 25%

Payback period: 4 years.

It can be seen from the above that the payback period is about 4 years for installing SITRA PCRA OHTC Eneroptimiser IV -Curve system in textile mills.

Energy efficient blower fans for overhead cleaners

One more energy saving concept of using energy efficient fans in the place of existing suction/blower fan in the overhead cleaners has been implemented in a textile mill near Palladam, Coimbatore. The details of energy saving achieved are given below. An energy efficient SITRA Excel Fan has been designed with 4% lower diameter, 3% less weight and same width. The existing blower fan was replaced by this fan and the energy measurements as well as performance data were taken for 7 days continuously.

It was noticed that an appreciable energy saving of about 20% is possible in using SITRA Excel fans with a quick pay back period of less than 6 months. In addition, the instantaneous current value is reduced by 23% and the suction performance is not affected.

(The authors are with the South India Textile Research Association, Coimbatore)