Practical Process Engineering

#Steam #Steam_Trap An optimized steam system should: 1- Supply dry steam 2- Drain condensate fast 3- Return condensate The role of steam traps to dispose cold condensate in order to stop mechanical issues like water hammering as well as increase heating efficiency of a chemical plant is obvious. Therefore, steam traps MUST be inspected in a timely and effective manner. They got failed in two ways: 1- Cold (Blocked): no drainage 2- Hot (Leaking): condensate and steam are disposed simultaneously Many operators throttle steam trap outlet valve in case of leaking. But, it may cause cold failure. Moreover, a leaking steam trap is still doing its own job partially to drain cold condensate. In addition, cold failure is not something to be resolved by throttling, because it is happened because of the trap malfunction. So, the author recommends to put more attention to cold failure and do steam trap survey. Several condensate-related equipment issues are listed: 1- Flare failure: It can cause errosion in flare tip, piping, valves, etc. 2- Errosion of steam turbine blades 3- Analyzer failure Water hammering is another important failure that is able to destroy equipment and pipes. Because steam travels fast a long distance in a plant, there are always some chances to have cold condensate in different locations. It is recommended to install one steam trap per 100-150 ft pipe length. Interestingly, superheated steam pipes are susceptible to be filled with not-drained cold condensate. It cause steam header to be moved. Below is a photo of a 400- ft long section of a 24-in pipe that was filled by approximately 3000 Lbm of condensate and displaced more than 7 ft. An appropriately sized leg to collect condesate is necessary. For steam lines up to 4 in., the leg diameter could be the same is pipe diameter. Another picture is provided by the author for the leg sizing. They could estimate the mass of water during water hammering. The results are interesting and show, for example, the minimum weight of slug for a 10 in. pipe could be around 52 Lbm. In the last part, three scenarios to maintain steam traps are surveyed financially. More budget to take care of the traps, the higher five-year internal rate of return. The paper is attached to this post. I strongly recommend it. More information about steam system will be uploaded in comming few days.

Let’s get started with one of the most important topics: STEAM A very informative article was published in current issue of CEP magazine. I’ll share it and summarize it and add more details to it tonight.

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