In English sequence markers are certain group of items that link sentences together. As for IELTS, they are very important in Process diagram to show the sequence (order) .
We will list here several of them with the examples:
Adverbs: first/firstly/first of all, secondly, thirdly, then/ next/ after that/ following that/ subsequently/subsequent to that, finally.
Firstly, the clay is brought to the factory. Secondly, it goes through a purification process. Following that/subsequently/subsequent to that, it is exposed to a heat of 1300 degree in the kiln. Finally,it is delivered to the customers.
Prepositions: At the beginning of…….; At the end of ………..
At the beginning of the process the clay is brought to the factory.
At the end of the process, it is delivered to the customers.
If you want to make more complex sentences use these conjunctions:
when/once/as soon as
Once/when/as soon as the clay is brought to the factory, it is sent to the main chamber.
Before + clause or gerund
Before the clay is packaged, it goes through a process of heating.
After + clause or gerund
After the brick is packaged, it is delivered to the customers.
After that the clay is brought to the next stage where it is heated in the kiln.
Then the end material is packaged, after which it is delivered to the customers.
Other phrases you can use are:
After this step …
Once this stage is completed…
Following this …