The choose and buy of triangle pneumatic valve guide 6)

use full copper triangle pneumatic valve, check the testing speech; In the case of the light is enough, can be triangle pneumatic valve in hand straight after observation, no oxidation surface should be raven as a mirror, freckles, without sear; But almost see no pores, no bubbles, no plating leakage, average luster; With the hand touch without burr, grains of sand; Use finger to press the bibcock surface, fingerprint soon spread out, and not easy to scale.