How to select valve in different temperaturesadmin
When choose valve in high temperature, housing material and the inner member material which has a high temperature and strong body should be considered, such as: stainless steel, two-side stainless steel. The material can not be used due to high temperature and bonding, plastic deformation, creep. The gap is not too small. When the temperature is very high for the type of valve has a throttle butterfly. Body structure can be considered with a heat sink, trim using thermosetting material. If the temperature has exceeded the metal can withstand temperature range, consider using a ceramic lined special valves, cooling jacket structure may also be used, by circulating cooling water. So that the internal metal remains within the allowable stress range.
When the temperature is below -29 ℃, should choose low temperature resistant housing materials and trim materials. In the low temperature range of -29 ~ -196 ℃, requiring housing materials and trim materials have sufficient impact toughness. Special means must be maintained by the heat capacity of the valve, so that the cooling load from the action, but also of the filler material and the tank section is maintained at a temperature above 0 ℃.
Preventive measures have boosted exception. After the valve is closed, the valve chamber portion of the liquid will be left. With the increase of time, these residues will be left in the valve chamber portion of the liquid. As time increases, the residual liquid in the valve chamber, the atmosphere will gradually absorb the heat back up to room temperature and re-vaporized. After vaporization, the rapid expansion of its volume, an increase of about 600 times, which will produce high pressure and acting on the valve body, this is called abnormal pressure. This is a phenomenon unique cryogenic valves. This abnormal pressure, cause the valve plate is pressed against the seat causes the valve plate can not be opened. At this high pressure will be washed out in the flange out or filler; even bonnet rupture caused a serious accident.
Therefore, in order to avoid this situation, pressure balance hole or vent should be set, this method is relatively simple and has been widely used in valve industry.