Structural Features and Types of Cryogenic Pumps for Petrochemical Industry
December 07 08:08:29, 2022
1, the basic concept of cryogenic pump General reference to the use of cryogenic pump Medium temperature slightly higher at minus 30 ° C, low to minus 220 ° C, the designer should take into account the material's low temperature performance, impact resistance ( Mainly Ak), the physical and chemical properties of the medium, in particular, the volatility of these media such as liquid oxygen liquid nitrogen liquid argon liquefied natural gas. Consider the sealing structure based on these properties. Such pumps are generally used packing seal. Seal cost is relatively low. Cryogenic pump is a special pump used to transport liquefied gas, such as liquid oxygen, liquefied natural gas and freezing liquid, liquid nitrogen in petroleum and chemical plants, so it is also called cryogenic system. 2. The type of cryogenic pump A. Piston type, plunger type of such pumps are generally used in the gas filling, chemical processes (such as chemical reactors to add high-pressure nitrogen, nitrogen dioxide, carbon dioxide, etc.), metallurgical engineering Steel mill steel gas, as a transfer pump, the flow is generally not centrifuged, but can effectively provide gas pressure) B. Centrifugal centrifugal cryogenic liquid pump is generally used from a cryogenic liquid container The liquid is delivered to another container or used as a process pump in a fractionation (high flow rate). This pump is generally sealed in the form of a mechanical seal or a labyrinth seal, with a high seal cost. 3, the overall structure Vertical structure: suitable for buried in the ground, will not be affected by motor hot air, air temperature and sunshine, easy to keep cold; can reduce the pump suction height, increase the perfusion head and improve the effective NPSH ; Vertical structure is also conducive to exhaust, so that the suspension shaft height enough to facilitate the installation of shaft seal device, so the pump is also known as vertical cylinder pump. Symmetrical structure: The overall structure of the pump strives to be symmetrically arranged to allow uniform deformation in cold conditions. Double shell: In order to facilitate the cold and facilitate the transport of hazardous medium, usually made of double shells, the inner shell to withstand pumping pressure, the pressure between the inner shell is suction, which may be appropriate to reduce the strength requirements of the inner shell. 2, shaft seal packing: different from the ordinary type, using double packing seal, with a sealed chamber between the two layers, the introduction of a gas (such as nitrogen) from the outside world, from the sealing effect. Mechanical seal: mechanical seal is also different from the ordinary type, the use of double-ended mechanical seal, the seal chamber and the pump body with a buffer chamber, can play the role of cooling, while sealing the hydraulic pressure to adapt to discharge pressure changes for This, are generally equipped with a pressure device, chiller and other ancillary equipment. 3, the bearing: the bearing close to the atmospheric temperature, the general use of thrust ball bearings; the lower bearing for the sliding bearings, submerged in the working medium and run with the working medium for lubrication; in order to prevent the friction caused by heat and liquid vaporization, resulting in damage to lubrication, Good lubricity materials, such as tetrafluoroethylene, graphite, corrosion-resistant nickel alloy, etc .; with the journal bearings on the sliding bearing surface nitriding or surfacing cemented carbide.
Lap Joint Flanges (LJ Flanges) are used on piping fitted with lapped pipe or with lap joint stub ends the combined initial cost of the two items being approximately one-third higher than that of comparable Welding Neck Flanges.
Lap joint flange is having two components, a stub end, and a loose backing flange. Stub end is butt welded to the pipe and Backing flange freely move over the pipe. The backing flange can be of different material than stub material and normally of the carbon steel to save the cost. Lap flange is used where frequent dismantling is required, and space is constrained.
Furthermore, a standard lap joint flange will typically have a longer hub length in comparison to a slip on flange, but this is often considered unnecessary for many applications.
The lap joint flange is practically identical to a slip-on flange except it has a radius at the intersection of the bore and flange face.