By: Veejhay B. Limaye
There are different types of layout for spinning mills which varies from Architect to Architect or Textile/Project Consultant.
It is also observed that basically the layouts/drawings of building and M/c layout is prepared and finalized by concern authorities and then Electrical Consultant is introduced in the picture. When the final drawings is kept in front of Electrical Consultant, he had not much choice for selection of place for substation transformer etc. Then he tries to utilize available space.
Initially spending some amount the spinning mill is started, after that the major recurring expenses are electrical bills that is electrical consumption. As per SITRA Norms the unit consumption for spinning mill is 3.564 units (KWH)/kg of yarn.
Now the question is whether the spinning mill�s specific consumption is in the tune of SITRA norms? If yes then you have to accept that the electrical layout of that mill is in order and if not then one has find the reason for that. This specific consumption is directly related with the electrical design and not related to the type of layout, type of building, type of insulation and type of structural design etc.
Hence Electrical design plays a major role in the project of spinning mills because it is directly related to the recurring expenses. The purpose of this article is to develop a new concept for electrical layouts as well as layout of spinning mill.
Now every spinning mill had started energy auditing and started adopting necessary positive changes in electrical system and found that so much energy is saved.
This can be said in the other words, that old mistakes have rectified upto certain level. But prevention is always better than cure. So at least in future the responsibility of electrical consultant increases in designing of electrical layout of spinning mill and he should take adequate care and have a different vision to achieve the target of energy efficient electrical design. He should be sure that his electrical design shall be such that the specific consumption of the spinning mill shall be within SITRA norms or below the norms.
For the concept of designing energy efficient layout of spinning mill. One has to compromise certain things like Architectural vie front elevation etc. Which are not at all related to recurring expense because day today electrical unit charges will go up. So this is a high time to decide whether you have to run your mill with low specific consumption or your outer look out of mill shall be good irrespective of its high specific consumption.
Let us bifurcate the total consumption as follows.
Let us consider the basic consumption i.e. actual M/cs consumption as fixed then B,C,D,E & F components are directly proportional to recurring expenses. Humidification is the independent subject, hence remaining components C,D,E & F is the only area where the skill is to be utilized in electrical design.
CABLE LOSSES :-
1) The cable losses are directly proportional to the length.
2) The losses are proportional to the square of current.
Hence for energy efficient electrical design the main concept in the mind should be that there will be minimum cable length. Hence the selection of panel board position and main panel room and transformer location is very important.
KEY POINT TO REDUCE CABLE LENGTH
Study the common main cable path and try to reduce the common path. (Fig.1.0)
Reduced the common path leads to reduce main cable length.
Use of HT Cable to reduce the length of LT cables, because the current at HT side is very low compare to LT side and since it is proportional to the square of current try to provide transformer nearer to LT Panel.
SELECTION OF L.T. CABLES
This is an independent subject, hence it is very important to select the rating of cables required. The main aspect for selection of cable size is voltage regulation. The variation or voltage regulation should not be more then + or � 2.5% between two far ends.
For Example : For particular current one had selected 240 Sq.mm and cable length is say 85 mtrs. For another feeder assume that the current is same but the length of cable is say 120 mtrs., then one has to calculate the available voltage at the far end and whether it is in the tolerance or not if not then he may require to select the cable of higher size.
The thumb rule should not be applied while selection of cable. If you increase the size of cable then cost also increases but losses reduce if you reduce the size of cable then cost decreases but losses increases. Hence the study of cable economics is very important (Fign. 1.1).
The location of transformer should be nearer to the main LT panel and always prefer to connect the transformer by LT bus duct of sufficient size to main LT panel. Some time the availability of outer space is not possible for transformer and substation then indoor type transformer to be preferred and these may be placed just outside of the LT room or adjacent to the LT room or in LT room and we can place the substation suitably nearer available space and the HT side may be terminated by HT cables. If required then HT indoor breakers can be used for protection of transformer ( fig. 2.1).
All above points are pertaining to reduce the possible cable losses.
Let us calculate the commercial effect of 1 KWH i.e. 1 unit per Hour.
1x24 Hrs x 350 day = 8,400 Units x 3.15 = Rs. 26,460.00
i.e. saving of 1 unit in transformer will lead to saving of Rs. 26,460.00 per ear.
While selecting the transformer the technical specification are to be carefully studied the selection of transformer should not be on commercial terms but it should be combination of both i.e. commercial and technical.
Now there are some manufacturers who manufacturers low loss transformer with some additional cost. Since the losses are directly proportion to the square of the current, the transformer of higher rating shall have low losses but the cost will high.
Hence it is important to calculate the losses of transformer for the actual working load and accordingly one can easily decide the rating and selection of transformer. Another aspect of transformer selection is magnetizing current generally all manufacturers specify this below 3% but some manufactures specify 1.5% or 1.25% also, then it is very important to know the commercial effect of magnetizing current. (fig. 1.3)
The transformer with high magnetizing current will draw more reactive current and to compensate this, more shunt capacitors are required to improve power factor. The transformer with low magnetizing current will draw less reactive current and hence lesser shunt capacitors shall be required to compensate power factor and there will be saving in cost of additional capacitors, switching devices required for additional capacitors, cost of cable required for connecting the additional capacitors and besides that the self consumption of additional capacitors (Fig. 1.4).
Hence selection of transformer is very important to control the recurring expenses.
The major two aspects for electrical designing of spinning mill is covered. Now another important subject directly related to recurring expenses is Illumination system. Use of Electronic Ballast definitely saves about overall 35% energy bill in illumination system but unfortunately there are only very few manufacturers who�s electronics ballasts are successfully working. In some cases it is observed that problems in 40W tube arises oftenly by using electronic ballast hence it is also very important to select the electronic ballast as well as tube. If the above things are followed it is possible to achieve the specific electrical consumption not only in the limit of norms but below of that.
General electrical terms, we have studied towards energy efficient electrical design.
LAYOUT OF SPINNING MILL :
To achieve some thing our view towards that subject should be wide and without preconcept (traditional). One should not compare with other existing systems. But he should look through the other angle to achieve the target.
Let us study the general types of layout of spinning mill. Generally we can divide the spinning mill in two types. One is H. Plant at one side and second is H. Plant at two sides. i.e. for 25,000 spindles and 12,500 spindle x 2 spindles respectively.
Now let us study the probable location of L.T. Room and PDB�s.
In this Fig. 2.0 you will observed that comparatively �B� location of LT room is near the load centre but main draw back is the PDB of H. Plant is far way @ more than the 65 mtrs.
In this Fig. 2.1 you will find that at �A� or �B� position is near the load centre but the main cable running for other side of PDB�s increases.
In this Fig. 2.2. it is seen that all PDBs are placed in the centre and location of L.T. Room is at �A�. Here it is observed that the cable length is minimum. Electrically this is comparatively energy efficient layout. The main panel should be the as near as load centre, Since the major load is at ring frame the ideal design shall be near the Ring Frame that is load centre. Considering the above aspect the following layout is prepared. Now whether it is practically workable or not it is to be discussed with concern authorities but as a technical person anybody had to accept that this shall be the ideal electrical design for spinning mill.
A � L.T. Panel
B & C � Compressor Room for Prep. & Ring Frame respectively.
Generally both side H. Plant are preferred for initial cost and convenience. In fig. 2.3 the location of L.T. Room is just nearer to the ring frame trench i.e. PDB of Ring Frame and Post Spinning. If possible transformer can be erected in the room or just outside of the post spinning as shown.
A typical layout shown in fig. 2.4 in which an open space is shown open to sky. The L.T. Room is adjacent to Ring Frame and Post Spinning section two locations of compressor room is also shown. Compressed air is very energy intensive only about 5% input electrical energy is converted to useful energy and rest is loss as heat. Use of compressed air for clearing is rarely justified. If pressure requirements are widely different e.g. 3 Kg/Cm2 then it is advisable to have two separate compressor system and the location of compressor is preferably near the load centre, hence the two separate compressor room have shown in fig.2.4. This may increase the overall efficiency of Air system. Now let us see the utility of open space which is open to sky. If we can provide the double glass framed window for the both sheds towards open to sky side the utilization of day light will definitely save in lighting consumption at least in day time.
Hence considering major recurring expenses of electrical losses, efficiency of air system, optimum utilization of natural light. This energy efficient layout of spinning mill is prepared.
About the author:
Veejhay B Limaye of Miraj has authored this article and his contact details are: Phone: 0233-2222350, fax. 2221514
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