Information which is contained in Hazard & Operability (HAZOP) studies is highly sensitive since it can reveal the vulnerabilities of a system and potential ways in which to bypass safeguards. Through the design of systems involving collaboration along a value chain, at some point this information is shared between several parties. In this paper, we propose a methodology for the secure exchange of safety information whilst preserving sensitive information for the application of modular Hazard & Operability (HAZOP) studies. We use homomorphic encryption in a workflow for the sharing of information between plant owners and operators as well as module vendors. We apply encryption to the risks from different modular HAZOPs (mHAZOPs), and combine and compare them without disclosing the risk level. Our contribution is a privacy-preserving protocol for mHAZOP comparison during the integration of modular process and equipment. We provide an exemplary implementation of the protocol and demonstrate the protocol's privacy and correctness.