Tower internals inspection

Most of my clients now use a digital camera to record tray conditions. For me, this is good for record keeping only, not for decision making as to what tray repairs are needed. I suggest you make a copy of the checklist below, and refer to it when doing your next tower internal inspection. 

A 2-ft tower would be expected to perform satisfactorily with properly designed trays. However, a 2.5-ft tower is the minimum diameter suitable for internal inspection and maintenance. The cost of a tray tower of 2.5-ft has been found to be no more, and from some bids 5 percent less, than the smaller 2-ft. tower. A 2-ft. tower would either be used with packing or with trays inserted from the top on rods with spacers. This would allow removal of the trays for inspection and maintenance. 

A sufficient number of access doors, ladders and walkways shall be provided for safe and easy accessibility to internals and mechanical equipment of the tower for inspection and maintenance. Access doors shall be tight, resistant and easy to operate. Access ladders from the ground should be located in such a position to permit future cell addition. 

A maintenance access is usually located in the bottom top, and intermediate sections of dte tower and is used to gain entry to the tower during shutdowns for internal inspection and component removal. Maintenance accesses must not be located at downcomer sections of the tower. Qtte must be taken at sections of the tower diat contain internal piping to avoid blocking the maintenance, access entrance. Exhibit 10-28 shows typical elevation and orientation requirements for maintenance accesses. 

I didn t know what to do. But fate intervened. A tube leak on an upstream heat exchanger necessitated a short unit outage. The de-ethanizer tower was opened for one day so that we could carry out an internal inspection of the trays. 

Inspecting Tower Internals Compressor Motor Over-Amping... 

The most critical components of a cooling system —the heat exchangers— are seldom available for regular inspection. Therefore the cooling tower usually becomes the primary focus for an inspection of the cooling system, and a subsequent estimation of the degree of cleanliness and condition of internal water-wetted surfaces. Individual tower components and sections need to be regularly inspected and an overall assessment made, with an action plan for improvement if required. 

After treatment of raw water in treatment facilities, clean water may be stored in aboveground or underground tanks or underground clear wells. If left unattended, both internal and external corrosion may pose a stmctural risk because of loss of wall thickness. Hence the need for a periodical inspection of water tanks and towers. With periodic maintenance, water tanks may have a life of over 100 years. 

Top manhole shall be available to add more tower packings, to inspect internals, etc. 

Contract maintenance workers often will not replace the tray manways unless the tray manway is adjacent to a tower external manway. They reason that once the tray manways that are visible from the tower manway are closed, there is no way for someone to inspect the other trays. This problem is not just common— it is imiversal. The maintenance force at the Good Hope Refinery pulled this nasty trick on me at the coker fractionator. Equipped with my crescent wrench, I opened the tray internal manway below the side tower manway. 1 discovered that the 12 trays below this point had their manways stacked in their downcomers. In 1990,1 worked on a project to improve fractionation at the Chevron Refinery crude distillation unit in El Segundo, California. When the tower was opened to implement my design, the tray manways were found lying on the tray decks below the diesel draw tray. The lesson is, inspect each tray and then witness the closure of each tray manway, separately. 

The most satisfactory temperature datum is the vaporizer temperature because this temperature can be accurately estimated and is the temperature about which the entire design of tower and pipestill binges. By using this datum plane, the heat balance consists simply of the sensible heat that is required to (1) cool each product from the vaporizer temperature to its withdrawal temperature and (2) condense the products that are withdrawn as hquids. The reflux that is computed by such a heat balance is about the minimum amount by which the process can function. Upon casual inspection it appears to provide no flow of liquid into the feed plate from higher plates in the column, but rince the decrease in temperature of the bottoms product is not caused primarily by reflux, the heat balance mentioned above actually provides a small flow of hquid into the feed plate. At each ride-draw plate the internal reflux is depleted by the amount of ride-draw product that is withdrawn, as shown in Fig. 

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