Background

Our client is a large chemical processing operator specializing in the production of paint pigment, specifically the purest form of white. To make the pigment as white as possible, low pressure and high temperatures (572 Fahrenheit) were required. With chlorine the gas, the environment was highly toxic. The application was measuring the level in a chlorinator that was used to improve the purity of the paint pigment.

As chlorine is a bleaching agent, the paint pigment was going into the Chlorinator which was then used to create the white colour. Purity of the whiteness is critical; if you don’t match to 99.8% purity the pigment is discarded. In this low-pressure environment and due to the toxicity of the chlorine gas, our client had three pressure measurement points on the vessel. If two of the three 3 tapping points were to plug up the equipment would shut down for safety, and manual rodding out would be required. This was a highly dangerous task given the hazardous nature of the environment and would also require a considerable length of time to undertake – often between five and eight days.

Solution

Following the successful implementation of the Autorodder at a large refinery in Scotland, the project’s lead engineer mentioned Clearguard to their colleague within the Paint Pigment Industry – our client. This referral motivated our client to contact Clearguard with the intention of trialling the instrument in their tapping points. However, rather than implement an Autorodder in all three of the pressure measurement points the decision was made to run a controlled trial:

  • Tapping point 1: With the Autorodder (blue line as shown in the below graph).
  • Tapping point 2: Without the Autorodder (green line as shown in the below graph).
  • Tapping point 3: Moved to a ‘vapour space’, where it would never become blocked (red line as shown in the below graph).

The process conditions required some detailed discussions, as the Autorodder’s main components needed to be manufactured out of an exotic material that can withstand the process conditions. Clearguard’s representative in the UK visited the site, sending us photographs enabling us to create a ‘mock-up’ to accompany our recommendation. The engineers on site approved the recommendation.

 

Result

As evidenced by the graph below, the results of the Autorodder trial were fascinating and the key outcomes extraordinary – including:

  • The pressure measurement point depicted in red is a tapping point located in the ‘vapour’ part of the process vessel. This tapping point rarely gets blocked and is used as the reference point.
  • The pressure measurement point depicted in green is one of the tapping points immersed in the liquid phase of the process. Note the spikes which are the result of high-pressure nitrogen gas being used to ‘blow’ open the tapping point. Since the actual process pressures are very low, any ‘blow down’ using nitrogen causes the pressure inside the vessel to spike above the maximum operating set point. In the event the pressure exceeds the maximum operating set point, two out of three safety shutdown systems initiate a unit shutdown which can be seen occurring on two occasions (between the black lines) in a 30-day period.
  • The pressure measurement point depicted in blue is the second tapping point on which the Autorodder was installed. The optimum pressure point is depicted by the pale blue line which is a lesser pressure than the maximum operating set point. Best practice is to keep the process pressure inside this vessel on this pale blue line. Note how the trend where the Autorodder was installed follows the blue line and matches the reference pressure measurement point depicted in red. Also note how there is no pressure spike. The Autorodder was stroked frequently to keep the tapping point bore clear, allowing for unimpeded pressure measurement. Furthermore, even during the stroking cycle the Autorodder scraper did not create any induced error or pressure spike.

Overall, the threat of lost production caused by pressure spikes from ‘blowing down’ a plugged tapping point was eliminated, which would often require five days of equipment shutdown to rod out the tapping points and bring the unit up to process parameters. Our client was extremely satisfied to see a return on their investment in just 17 days of implementing the Autorodder.

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