Tank / Pressure Vessel Drying

Tank / Pressure Vessel Drying

 

Watkins Hire's customer was awarded a contract at a Petro chemical plant to chemically clean, dry, test and reline a tank which holds ammonia for the production of chemicals. These processes usually take around six weeks to complete with the removal of the old lining the cleaning, drying and testing. Historically the longest part of the project is the drying part that is undertaken after the tank has been cleaned. This has taken up to three weeks to completely dry to a relative humidity of less than 20%.

 

The internal of the tank relative humidity needs to be below 20% to ensure the new lining attaches to the metal tank in the correct way to stop the ammonia corroding the tank. Previously they have utilised refrigerant de-humidifiers and desiccant dehumidifiers but the process drying time was only increased by 20% (the drying time was only reduced to 16 days from the 22 previous project).

 

They contacted Watkins Hire Ltd heat for hire division KwikHEAT to gain our advise on speeding up the project and if KwikHEAT could provide a better solution to the drying application. A solution and proposal was provided to supply, install and commission a KwikHEAT MH170 indirect fired warm air heater to dry out the tank.

 

 

Why did we not install a de-humidifier?...If you heat up the air it (by a chemical process) increases the airs capacity to hold more moisture. Watkins Hire Ltd heat for hire division KwikHEAT undertook tests on the MH170 , on the day of the test the ambient temperature of 18.5 Celsius and a humidity level of 77.2% relative humidity was recorded. A 27 metre length of ducting was installed to simulate our clients exact installation, the KwikHEAT was then put into operation, the temperature increased to 66 Celsius (a delta T of 47.5 Celsius) and the relative humidity was reduced to less than 1%.Data from the test was supplied to the customer with a prediction to cut their process drying time by one third from 16 days to 10 days.

 

As the tank had suitable pipework to allow the heated air to be extracted out of the tank it was decided that only heating equipment was required to achieve the required duty inside the tank to reach the desired atmosphere before a new lining could be applied. KwikHEAT was awarded this project and the equipment was delivered, installed and commissioned on the same day.

 

The tank took less than one week to completely dry out the tank to less than 10 % relative humidity which allowed the customer to focus on other projects bringing their timetable forward and saving their customer valuable time on the shut-down. Another factor that helped was that when the new lining was applied because the tank was warm the lining inside the tank dried quicker (1 day when usually it took 3 days), this also helped speed up the process.

 

The customer and their customer were extremely pleased with the whole drying process and the time savings during the project and would not hesitate to utilise the KwikHEAT 170 indirect fired heater again and when another application (that is a little out of the ordinary) comes to light he will call us for an opinion.

 

The KwikHEAT 170 was 62.5% quicker drying out the tank compared to using refrigerant de-humidifiers and desiccant dehumidifiers.