Series 415 steam safety valves feature a stainless steel spring, a top guided stem and non-stick Teflon? disc to metal seating to assure positive shutoff.是什么意思_Series 415 steam safety valves feature a stainless steel spring, a top guided stem and non-stick Teflon? disc to metal seating to assure positive shutoff.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句