Valve leakage often occurs in the connection position of the valve body, valve stem, and stuffing. Most of the valves are cast, so blowholes’occurring is inevitable. But the flow leak out through the valve blowhole is relatively small, so the effect is much smaller, and the blowhole can be detected by the hydraulic pressure test. Stem external leakage is caused by the stem design and material selection. The up and down actions of the stem make the valve open and close. So,if there are problems on the stem design and material selection,the stem could get stuck and closed not completely,then the outside leakage occurs.The leakage flow caused by the stem is usually more than caused by other reasons, so its effects to the environment and equipment are much serious than others.
The main reasons of valve outside leakage：
（1）Packing gland is loosening.
（2）The valve seal packing is imprecision, erosion and abrasion of obstacle.
（3）The choice of valve packing material is improper, or the materials have quality problems.
（4）The packing is aged and weared.
（5）The choice of gasket is improper such as type, material or size, etc.
（6）The seal surface of flange has quality problems.
（7）The connection position of the valve is loosening.
（8）Because of the unreasonable size choice of the pipeline, the valve connection is over loaded.
DBV hopes that this can help you avoid the unecessary lost.Also, our products are certainly much more safe than others.