Comparison of different methods to predict chattering in pressure relief valves

Entity: Universitat Rovira i Virgili (URV)

Confidenciality: No

Education area(s): Enginyeria Industrial

Title in different languages: Comparison of different methods to predict chattering in pressure relief valves

Abstract: Pressure relief valves are safety devices that can be found in any industrial facility. These valves are responsible for avoiding that the equipment of the installation exceeds its maximum allowable pressure. It is, therefore, a critical element in avoiding possible accidents. During the design stage, safety valves must be operated stably, most importantly, ensuring that chattering does not take place. In order to avoid instability, API 520 Part II required that that the pressure losses at the valve inlet were limited to a maximum of 3% of its set pressure. API’s latest edition (2015) indicates that some installations with pressure losses in the entrance greater than 3% have worked stably during their operation. Furthermore, it adds the concept of engineering analysis to check in systematically the possibility of chattering of a safety valve. It has been proved that many of the current facilities are not designed properly. As an example, Otis B., in 2011, conducted a case study of the 25 recorded accidents due to the chattering in Shell's database, which shows that some of them could have been avoided. For example, seven were due to wrong seat selection and one did not take into account the acoustic phenomena in the design phase. This master thesis compares the different calculation methods used by process safety engineering for the validation of installations with safety valves. A total of six safety valves of polypropylene plants located in Tarragona that do not comply with the 3% rule have been analyzed. Three different methodologies of calculation have been applied, two of them use simplified methods, and one uses rigorous methods. It is observed that the prediction of stability with the simplified methods matches up with that of the rigorous method. The final goal is to present to the scientific community a list of recommendations for the validation of the installation of a safety valve in the event of instability. In conclusion, it is recommended using the simplified Melhem method given its simplicity, but only if the safety valve’s blowdown is known accurately.

Subject: Enginyeria química

Academic year: 2016-2017

Language: Anglès

Work's public defense date: 2017-02-10

Subject areas: Chemical engineering

Student: de la Fuente Sánchez, David

Department: Enginyeria Química

TFM credits: 12

Creation date in repository: 2017-10-06

Keywords: pressure relief valve, chattering, method

Title in original language: Comparison of different methods to predict chattering in pressure relief valves

Project director: Basco Montia, Josep