Internal inspection and maintenance method of 9% Ni liquefied natural gas storage tanks

The present invention relates to an internal inspection and maintenance method of a 9% Ni steel liquefied natural gas storage tank and, more specifically, relates to an internal inspection and maintenance method of a 9% Ni steel liquefied natural gas storage tank having perlite discharge equipment which comprises: a vacuum pump sucking perlite; a manhole; a perlite nozzle fixedly connected for transfer hose discharging perlite to pass therethrough; and a perlite transfer hose fixedly connected to discharge perlite by passing through the manhole and the perlite nozzle.