They allow visual checking of chambers and flames . pyrex glass , protected with alloy mesh , provides large viewing area . cast iron frame and housing . automatic , spring loaded shutter 允许视觉检查燃烧室和火焰。派热克斯耐热玻璃，合金网保护，提供大视觉范围。铸铁框架。自动弹簧负载门。
Features a modular design concept which facilitates complete maintenance and assembly by retaining the spring load . first and second check valve spring modules are not interchangeable 特点在于模块设计概念，通过保持弹簧负载促使日常维护和总成的完善。第一和第二止回阀弹簧模块不能互换。
The 775qt series features a modular design which facilitates maintenance and assembly by retaining the spring load . check modules are threaded into the valve adapter for leak proof operation 775qt系列特点是模块化结构，通过保留弹簧负载简化维护和组装。止回阀模块通过螺纹旋进阀门适配器内，提供无泄漏运行。
