You can automate service request approvals by creating a workflow using the Workflow Automator. Let’s assume a scenario where you must send a service request for an Apple Macbook to the requester’s approval manager and the department head whenever you get a service request. The service request will be sent to the fulfillment team only after approval from both managers. 


Enabling multistage approval for service requests through workflow automators.


Also, refer to the article below for further reference:

https://support.freshservice.com/support/solutions/articles/211198-setting-hierarchical-approvals-for-service-requests-using-workflow-automator-