長澤金屬除了廢料事業以外，還積極開展石油油罐的清掃事業。
我們在台塑企業 (Formosa Petrochemical) 擁有十三萬公秉 (一億三千萬公升)浮頂式 (FRT) 原油儲罐、5萬千升錐頂式儲油罐(CRT) 等清洗工程的施工實績。
上述工程所需的器材，如COW (原油清洗) 成套設備， AM清洗機，氧氣瓶、可燃性氣體6點自動轉換測量器，熱交換器，氮氣產生器 (PSA) 等，均銷售給臺灣公司，清潔工程也由臺灣公司協助施工。
現在， COW (原油清洗) 技術人員數名也在SKK (係統機工株式會社)SKK（システム機工株式會社） 的協助下在日本COW施工現場進行研習。

NAGASAWA METAL Co.,Ltd
At Taiwan Plastic Co., Ltd.（Formosa Petrochemical）, we have performed 130,000KL Floating Roof Crude Oil Tank Cleaning and 50,00KL Cone Roof Crude Oil Tank Cleaning together with local company in Taiwan.
Fabrication and supply of necessary cleaning system equipment (Crude Oil Washing – COW) Plant Unit, Amplitude Modulation Cleaning Machine, 6 channel Automatic Switching Measurement Equipment for tank inside gas such as Oxygen, Flammable Gas , Heat Exchanger, Pressure Swing Adsorption for Nitrogen Gas, etc. to Taiwan Company. （Please refer to the below photographs）
A couple of special engineers for COW are working together with SKK Co., Ltd. here in Japan and periodic refresher training are being done to improve and maintain their skill.