Introduction
The effective work of the basic steam system depends on the operations, ensuring the safety of the process and the equipment’s reliability. Since working with high temperatures and hydraulics may present certain risks for the plant personnel’s health and lives, steam line warm-up and steam trap blowdown are essential for the normal functioning of the system. The first operation is aimed at providing the safe start-up of the boiler, while the second is necessary to remove sediment and sludge. Although the two processes are relatively simple, they are critical for avoiding system malfunction.
Steam Line Warm-up
Steam line warm-up is considered one of the most important operations of the system, as it ensures the safety and reliability of boiling. However, in order to conduct the warm-up correctly, it is necessary to understand its significant aspects, such as the ways to control temperature and pressure and the general principles of its operation (Inveno Engineering, n.d.a). In this part of the paper, the functions and configuration of the steam line warm-up system are discussed in detail.
The main function of this process is connected with starting up the boiling. The warm-up valve is necessary for every boiler with a high rate of steam flowing into the cold system, which increases the risk of water hammer. Since it can cause failure in different steam elements, such as lines and elbows, steam may be released into the surrounding area as a result of malfunction (Inveno Engineering, n.d.b). Therefore, the safety of the plant personnel depends on the secure work of this part of the steam equipment.
The whole warm-up system consists of several elements, the most important of which is the warm-up valve. It is a small but essential component, which is installed in the bypass loop configuration, piped, or tubing (Inveno Engineering, n.d.a). Its size depends on the general peculiarities of the steam system, such as the length and diameter of the steam line, which requires warming up. In the steam distribution systems of 3” or larger, a small valve with the size of ½”, ¾”, or 1”, is needed (Inveno Engineering, 2020). The valve is located around the isolation or in the pressure-reducing valve (PRV), which may be a single-stage or two-stage station.
The process starts with opening the warm-up valve against the large valve. After this, the temperature of the system increases gradually, and the pressure equalizes on both sides of the valves. This procedure ensures easy opening of the larger valve and eliminates the thermal shock, erosion, wire drawing, water hammer, or other issues connected with temperature or pressure differences (Inveno Engineering, n.d.b). It is necessary to understand that the temperature and pressure should be controlled during the whole process to avoid failure.
There are certain requirements for the effective and safe work of the steam line warm-up system. First of all, the design of the valve depends on the type of the steam system: it can be in the form of a needle (in the case of a throttling system) or a globe. The internal permissible leak rate should correspond to the accepted standards, for example, FCI or API regulations. Tubing or the outlet piping should be increased by one pipe diameter. Finally, one warm-up line requires two valves to be installed (Inveno Engineering, n.d.a). If all these requirements are met, the time frame is determined, and the temperature and pressure are controlled, the warm-up is a safe process ensuring the effective steam system work.
Steam Trap Blowdown
Steam trap blowdown is another essential operation of the steam system. This process can be described as removing water from a steam blower while it is active (Rajeena, 2018). The bottom blowdown is the removal of the sediments accumulating at the bottom or in the mud drum of the boiler. The high concentration of sludge may lead to the fouling of heat transfer surfaces and the consequent equipment failure. The surface blowdown is associated with water quality since it refers to the removal of solids from the water surface (“Selection of blowdown systems,” n.d.). Therefore, the purpose of the entire process is to discharge any sludge and sediments that may impede the effective work of the equipment.
The key components of the steam trap blowdown include blowdown piping and valves. The piping should be at least the same size as the boiler’s blowdown tapping. Either one quick-opening or two slow-opening valves are necessary. Moreover, in the case of an additional bottom blowdown connection, a second quick-opening valve can be needed (Barrieau, 2019). Blowdown separator is another critical element of the system since it is used for receiving hot water from the boiler. It reduces the water temperature and allows steam to leave the vessel (“Selection of blowdown systems,” n.d.). Finally, it is important to pipe all the valves on the same side of the boiler.
The following procedures are required in the steam trap blowdown process. First, it is necessary to stop the steam and water supply and open the drain valve. Then follows the blowing through the steam side by opening and closing the steam valve; the waterside should be blown through in the same way. After opening the water and steam valves, the low water fuel cut-off should be tested for proper operation. In order to stimulate the loss of water in the burner, it is required to open the blowdown valve simultaneously with firing the burner (Rajeena, 2018). During the whole procedure, personnel should pay attention to the water level in the boiler and double-check that the shutoff is tight at the end of the blowdown.
In order to eliminate the risk of failure during the process, certain safety requirements should be met. First, to prevent the uncontrolled release of steam to the boiler room, it is necessary to discharge the water into a special vessel where the steam flow can be regulated. Second, according to the environmental standards, the water should be below 140°F before being discharged to the sewer system (“Selection of Blowdown Systems,” n.d.). It is important to understand that to avoid injuries, all testing procedures, such as checking the shutoff, should be performed after the system is cooled down. The whole process ends with the removal of sediments, solids, and sludge.
Conclusion
The present paper aimed to analyze the main operations of the basic steam system, their working principles, and their significance. The warm-up valve regulates the temperature and pressure when high condensation occurs in the steam line. The second process, the steam trap blowdown, serves to remove sediments and sludge accumulating at the bottom of the boiler and on the water surface. Both operations are essential for ensuring the safe work of the boiler, securing the reliability of the equipment, and preventing the plant personnel from injuries.
References
Barrieau, A. S. (2019). A step by step guide to boiler blowdown. Web.
Inveno Engineering. (n.d.a). Steam warm-up valves [PDF document]. Web.
Inveno Engineering. (n.d.b). Steam warm-up valve system for a safe, reliable steam system operation [PDF document]. Web.
Inveno Engineering. (2020). Best practice no. 63: Importance of a steam system warm-up valve. Web.
Rajeena. (2018). What is blowdown valve? Web.
Selection of blowdown systems. (n.d.). Web.