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High temperature high pressure (HTHP) package dyeing machines:
Although package-dyeing machines now being made available are suitable for carrying out dyeing under normal as well as high temperatures, earlier versions were mostly design for dyeing the yarn packages under normal atmospheric pressure conditions. It was only after the advent of the synthetic fibers that dyeing recipes recommending high temperatures became quiet common and hence the machines brought out later were suitable universally, for normal as well as high temperatures. In the earlier models yarn packages used to be mounted on package carriers. The carriers duly mounted on the carriers stands are placed in the package holding dyeing vessel. This dye bath permits the dye liquor to flow through the yarn package in both the directions, i.e. from inside to outside and from outside to inside. The dye liquor is drawn from the main dye bath by means of a pump, and, through a circulation pipeline system, is circulated though the yarn packages as per the circulation programme. Subsequently, they have been yarn-dyeing plants with necessary closing top. The makes the plant into an enclosed system and makes it suitable for high temperatures and high pressure. The next stage of development is rather simple. The system is converted into a totally enclosed HTHP system. Pressure is generated by means of a power circulation pump and arranging closed steam coils, raises the temperature of the dye bath. Increase of steam pressure creates a high temperature. In the case of synthetic and blended yarns, the temperature is raised up to 135° C. In extreme cases, there are provisions to have temperatures up to 140°C. 
The pressure vessels are cylindrical with domed tops. The domed upper end is a lid, i.e. the cover, which is securely locked by a series of boles are be means of sliding tops and packing rings. There is also a provision for a quick locking system. The capacities of machines usually available are 50 Kg., 100 Kg., or 200 Kg. of yarn, in the form of cross bound packages. The height of the machines is according to (a) capacity, (b) type and size of packages, and (c) area necessary for fixing the packages in the vessels and for circulation of the dye liquor. The height of the pressure vessel is selected according to the diameter and capacity of the cylindrical vessel with appropriate internal matching. The overall height of the plant is arranged according to the space required for accommodating the circulation pump below the vessel. Adequate space is provided on top for lifting and handling the yarn carrier. Three or four stanchion legs welded to the sides of the vessel support the vessel. 
The material is loaded into the vessel along with the yarn packages by means of an electrical hoist of a suitable lifting capacity. While deciding the capacity of the electrical hoist, it must be kept in mind that, owing to the presence of the liquor in the yarn or other material, the total weight of the yarn package and the carrier is likely to be more than the original weight with the dry yarn packages. It is convenient to load the machines from the top of the vessels. In addition, enough free space is necessary for closing, locking and manipulating the lid operations. The installation of the plant can be made in two ways as follows: 1) By placing the vessels, pumps, pipes and circulating equipment, etc. in suitably sized pits. This arrangement allows enough operating space around the plan and for the necessary installation of the instruments. 2) In case the preparation of adequately sized pits is difficult, the plant and the vessels can be installed on the ground level. Suitable platforms are required to be constructed for convenient operation of the machine and instruments. It also becomes necessary to increase the height of the building considerably. This arrangement gives better facilities for draining and cleaning as well as installation. |
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