43.the drain screw of fuel oil sludge tank to be changed with valve or cock.
燃油沉淀柜的排放螺杆应改为阀或旋塞。
英语百科
Oil sludge
Oil sludge or black sludge is a solid or gel in motor oil caused by the oil gelling or solidifying, usually at temperatures lower than 100 degrees Celsius. Oil sludge can be a major contributor to internal combustion engine problems, and can require the engine to be replaced, if the damage is severe.