1 reply to this topic

[mrtangent]

Dear All,

Background info:
I am leading a re-tray for next year in two small diameter columns => 2 meters.

We are installing over 170 trays in each column.

The tray installers can install the trays in 8 days working at 3 different points within the column ie 6 crews. Our tray spacing is very small about 270-330mm - column dependent. 600 mm at the manways.

Columns are over 60 meters tall.

We have not yet aggreed an inspection plan for the new trays. It is not possible to go through the column once the trays have been installed as the tray spacing is so small that the internal manways cannot be shut without touching the tray above. So each tray must be closed as it is built.

With the company we are using we have had a poor experinece we found a hat left below 7 trays on a re-tray last year. The company has given us many re-assurances that it will not happen again.

Sorry to waffle, but the background is important. So would the experts recommend.

1. Inspecting every tray (possible major delay on the project) also this is higher risk as more people are entering a confinded space, more people in and out ? , but it will assure quality. may be very difficult

2. Inspect a set percentage and install CCTV for monitoring the job to prevent debris ?

Other questions.

1. Have people that have completed full column inspections ever not found anything which would have impacted performance. If so how often and approximatly what percentage of jobs ?

2. Is the typical things that you have found been debris, or poor tray insallation (ie out of level, wrong way around, blocked downcommer ?)

any advice is most welcome as I have never completed or led a re-tray of this scale (nor has anyone in my company).

[Art Montemayor]

Tangent:

Your project seems very similar to the one proposed in:

http://www.eng-tips.....cfm?qid=140955

I believe you will get a lot of answers to your concerns from some of the replies given there.

I consider this a very important project and one that should not be underestimated with regards to important and harmful mistakes - especially since no one in your organization has been through this before.

I would seriously schedule an engineer to physically inspect every tray (during or after the installation) for errors, mistakes, debris, level, etc. You cannot afford to find a major error after you startup the unit.