The situation of using NSH type on-line normal pressure calibrator for safety valves in Yahekou Power Plant to check DRESSOR safety valves of boilers has been presented

and the system structure and operatinal steps of said calibrator being briefed. Based on the designed accuracy of sampler

sensor and amplifer selected for the said calibrator

the measurement error of seat-leaving pressure for the testing system has been analysed. Through veriffcation of real-trip by raising pressure

it is found that the repeatability error and the measuring error of said calibrator aren’t all exceeding 1%

satisfying the requirements of National Standard and ASME Standard. practice shows

on the basis of comparison with traditional methods

the said calibrator has high accuracy

less time-consurming

and good security. The performance testing and seatleaving pressure setting of a single safety valve can be completed only in 10min under normal operation condition of the unit

having remarkable economic benefits.