A valve can include a valve body, a rotatable gate, a neck extending from the valve body, a shaft extending from the rotatable gate and through the neck, and a seal assembly configured to rotatably seal the shaft to the neck. The seal assembly can include a first stage seal having a first working temperature and coupled to the shaft at a first stage seal location, and a second stage seal having a second working temperature and coupled to the shaft at a second stage seal location farther from the valve body than the first stage seal location. The first working temperature can be higher than the second working temperature, and the seal locations and the first stage seal can be configured to prevent a second stage operating temperature at the second stage seal location from exceeding the second working temperature.

A valve comprising a valve body including a first end and a second end spaced apart along a longitudinal axis, a central portion disposed between the first end and the second end, wherein the first end and the second end define a first flow passageway and a second flow passageway, respectively, and wherein the central portion defines an interior chamber, wherein the first end of the valve body includes a bore, and a removable seat disposed in the bore and defining at least in part the first flow passageway.

A valve comprising a valve body including a first end and a second end spaced apart along a longitudinal axis, a central portion disposed between the first end and the second end, wherein the first end and the second end define a first flow passageway and a second flow passageway, respectively, and wherein the central portion defines an interior chamber, wherein the first end of the valve body includes a bore, and a removable seat disposed in the bore and defining at least in part the first flow passageway.