Starting up a new refinery unit is a very complicated process involving a detailed sequence of procedures to ensure worker safety and avoid damaging sparkling new pieces of expensive equipment.

Part of the process includes what is known as flushing – pumping a series of gases and liquids through the unit to check that pipes and valves are fully sealed and welded, equipment and instruments are working properly and to dislodge construction waste and anything else that should not be there. The startup commences with drying the feed and reactor systems to remove residual moisture after lines are pressurized with water (known as hydro-testing) to ensure mechanical integrity.

The startup team that runs through these procedures is focused on every minor detail and ensure seamless operations during flushing, Robbert Roozendaal, the start-up manager of ExxonMobils new API Group II unit in Rotterdam, told LubesnGreases.

It is all new, its never been used so you want to make sure there are no little surprises, Roozendaal said.

Surprises can include welding slag, grinding debris, salt and rust in pipes and valves. But the list of other, more unusual objects the startup team finds is startling.

Theres hard hats, theres gloves, jewelry, nuts and bolts. You find everything. Its amazing.

Roozendaal recounted the moment when the startup team discovered something altogether more unusual than accidentally discarded work wear.

During the drying phase, the team circulated nitrogen, as per the startup sequence, and ran a test for moisture levels. The moisture analyzer is connected to the reactor section via a set of restriction orifices – also called a choke tube – to let down the pressure from the high-pressure reactor system to the low-pressure analyzer system. The team noticed that the moisture analyzer kept showing unusually high values and very small flow to the analyzer itself.

It took some detective work to figure out what the issue was, but the engineers soon figured it out. The startup team uncovered a tightly lodged brown paper lunch bag.

We knew it was soft because going in that direction it moved, and this way it got stuck, Roozendaal gestured. When we took out the choke tube, we found a brown paper lunch bag, which blocked most of the flow. The lunch bag itself was very wet, likely from an earlier hydro-test.

They found the bag in time. Had it been found after oil was introduced into the system, it could have been a genuine problem.

You cannot simply open up a flange – its dangerous. Thats why we like to do the flushing early.

After the drying step, hydrogen is introduced for a high-pressure leak test, which is done before feed, or oil, is introduced.

You dont want to introduce any hydrogen in these systems before you know for sure that you have a full circulation, he said.