Do the companies apply LOPA after a Hazop study?

Yes, of course some companies do. However LOPA methodology, which is often an extension of HAZOP, involves analyzing the layers of protection for a HAZOP’s high risk scenarios.

This includes identification of separate initiating event frequencies and known reliabilities, including documented failure frequencies; and determination of the probability of Failure on Demand of a process’ existing safeguards and then comparing it to risk tolerance criteria that have been established by the operating company.

Yes. Companies may go for LOPA after HAZOP study

In PROCESS SAFETY MANAGEMENT, the HIERARCHY of HAZARD Identification and RISK control starts with HAZOP, then LOPA for additional protection layers and ends with SIL Analysis to ascertain the SIF for any instrumented functions.

So applying LOPA after HAZOP is the correct procedure. Hence, Yes, is the answer. 

You may refer to AIChE for the guidelines as to decide the order of HAZARD identification and Risk Management. 

yes. The Layer of Protection Analysis (LOPA) allows to determine the risk associated with the various hazardous events by utilizing their severity and the likelihood of the events being initiated.The Impact Event and its severity are entered into equipment and units have been considered.

LOPA can be conducted alone but normally it is preceded by HAZOP.

The application of LOPA after the HAZOP depends on the criticality of the process involved and  the corresponding risk identified.

hazop is the structured and systematic examination of a complex planned or existing process or operation in order to identify and evaluate problems that may represent risk to personnel and equipment. than LOPA is the standard approach for detrmine the safety inegrity level

Yes. Some Companies are following this method.

A LOPA (Layer of Protection) study is a semi-quantitative appraisal of scenario risks, usually carried out on unacceptable risk scenario’s identified in the HAZOP study.

Yes, of course some companies do. 

Hazop and LOPA support each other. However typically yes, a Hazop comes first. However a LOPA can be applied before Hazop (or without HAzop) e.g. to an existing system design to confirm the design integrity,  perhalps to an old asset designed and comissioned pre 2000.

Yes,

Hazop study is very useful in pre commissioning or initial state of the project, some process or plant which is already exist  Hazop found unacceptable risks required to implement layers of Protection , A LOPA (Layer of Protection) study is a semi-quantitative appraisal of scenario risks, usually carried out on unacceptable risk scenario’s identified in the HAZOP study.