What Are The Installation Precautions Of Cryogenic Ball Valves? Many Missed The Point.

Buying the right cryogenic ball valve is only the first step, and installing it incorrectly is a waste of money. In LNG, air separation and ethylene projects, valve leaks, frozen cracks and blockages due to improper installation are numerous. Many people focus on choice and ignore the installation process. These easily overlooked details can cost you dearly.
First thing to overlook is that there was no cryogenic treatment verification prior to installation.
Many believe that once the valve is cryogenic treatment at the plant, everything will be fine. In fact, valves may undergo long distances from plant to installation site, outdoor storage, and multiple loading and unloading, which may reduce the effectiveness of cryogenic treatment. Especially if the valve is stored at room temperature for more than 6 months, residual stress canaccumulate again.
The correct method is to check the valve's cryogenic treatment report before installation to determine the treatment temperature and number of cycles. If storage is longer than one year, it is recommended to re-cryogenically treat or to conduct at least a cryogenic simulation test prior to installation. Skip this step and there will be numerous pitfalls later.
The second overlooked point: reverse installation.
Cryogenic ball valves have flow requirements. The valve body is usually marked with a direction arrow or the word ``LOW "indicating the direction in which the medium is flowing. What if the installation is reversed? The sealing surface is subjected to pressure in the wrong direction, and the sealing pair doesnot work properly at low temperature, greatly increasing the probability of internal leakage. Worse, the self-pressurizing structure of the central chamber will fail, and the pressure of the central chamber cannot be released after closing, which in extreme cases may cause the valve body to explode.
During installation, it must be consistent with the flow direction markings, and no marker can be reversed. The mistake may seem basic, but it was actually made in a rush.
Third point ignored: Valve protection during welding is inadequate.
This is the deadliest and most common oversight. Cryogenic ball valves needs to be welded to the pipe during installation. To save time, many construction crews weld directly without any protection.
Is there a problem? Heat generated during welding can damage the valve's internal sealing surface. PTFE valve seats decompose and deteriorate above 260 ℃. Worse, welded heat can enter the valve body, causing the residual stress eliminated to reconstitute, rendering cryotherapy ineffective.
Correct operation: When welded, valve body must be wrapped in wet cloth, especially the seat and sealing cover. At the same time, the valve must be opened to a fully open position, allowing valve ball to leave the seat and preventing heat from acting directly on the sealing surfaces. After welding, let the body cool naturally to room temperature before closing the valve. Skipping this step would turn the installed valve into a ticking time bomb.
A fourth overlooked point: bolts are tightened at will, regardless of material.
At low temperature, the reliability of the connection is directly determined by the quality of the bolt material. Common carbon steel bolts can break below -46°C with cryogenic brittle fracture; using them to tighten flanges is like laying a a landmine.
cryogenic ball valves Flange connections shall be made using cryogenic-specific bolts, usually LC7 or 35CrMoA, and be temperature resistance to -101°C or less. During installation, torque wrench must be used to tighten evenly in three diagonal stages, neither simultaneously nor by hand. bolt tightening is not uniform, the flange surface stress is not uniform, low temperature asynchronous shrinkage, sooner or later will lead to leakage.
The fifth overlooked point: ignore condensation and exhaust.
Many people put cryogenic ball valves into operation immediately after installation without condensation or venting.
During cooling of a cryogenic pipe, moisture inside the pipe condenses into ice, clogging valve passages. Pipes must be purified with dry nitrogen or dry air to remove moisture and impurities completely before test run. At the same time, the valve's drain port must be opened to expel any residual fluid from the valve cavity. Without this step, the valve may freeze during the first cooling cycle, causing the valve stem to block and not open.
Finally, let me emphasize that installing cryogenic ball valves is not simply a matter of tightening them. Cryogenic verification, direction confirmation, welding protection, bolt material, and condensation and exhaust-any one of these five issues can cause problems later. These details are recorded in specifications and accident reports. Don't wait for something to go wrong to realise that an extra half hour of inspection during installation is worth a hundred times more than repairs after production stops.