A bearing oil cooler is a kind of heat exchanger, also known as a coil heat exchanger or multi-loop tube exchanger. It is connected by two standard pipes of different sizes to form a concentric sleeve. The outside is called a shell Cheng, the internal one is called Guan Cheng. Through these two different media, the shell side and tube side can flow in the opposite direction (or the same direction) to achieve the effect of heat exchange. Bearing oil coolers are mainly used for oil cooling of various large vertical motor bearing seats, reducer gearboxes, and other lubrication systems. The whole installation is immersed into an oil tank for direct heat exchange. For example, Daying River, Xigu, Deshan, Vietnam SE SAN, and other upper guide bearings all use coiled pipe coolers. Fits these applications: Wind power, Hydropower, Petrochemical.

heat exchanger
bearing oil cooler
Oil bearing Cooler(1).jpg

Three characteristics of bearing oil cooler(coil heat exchanger) structure:

  1. The bearing oil cooler/coil type heat exchanger uses a seamless steel tube as the outer tube for fluid transportation, and the tube bundle of the copper tube is bent into a laminated spiral casing body and is fixed with a steel bracket. It is welded and consolidated with the sleeve-type main body, and the two ends of the sleeve are respectively exported with refrigerant and cooling water to connect to the waterway

  2. The two ends of the tube bundle of the heat exchanger are respectively connected to the liquid separator and the collecting and dispersing cavity tube, which effectively promotes the equalization of the refrigerant in and out, realizes rapid division and accumulation, and makes full use of the heat exchange efficiency of each tube

  3. The tube bundle inside the steel tube is bent into a stacked spiral structure. After multi-directional anatomy, it is found that the tube bundle is difficult to maintain the distribution of forks at the rotation of the casing body, but the molecular tubes are squeezed or slightly angled toward the center of the tube bundle. Twist-like distribution, but because the impact of the high-pressure refrigerant flow rate on heat transfer is much greater than the impact of tube row changes on heat transfer, this change can be ignored. Due to this structural feature, the cooling water is under the effect of centrifugal force by the double influence of the spiral shape of the casing body and the slightly twisted band of the tube bundle extending between the flow channels, resulting in integrated heat transfer of the wall-side circulation and the complex scouring boundary layer. 

hydroppwer station
hydropower station

How to deal with the failure of the heat exchanger?

1. Leak handling
The spiral plate heat exchanger is composed of two closed and independent spiral passages. If there is a cross leakage in the passage, it is difficult to determine the cross leakage point. In order to accurately detect the leakage point, a drilling method is used. When drilling, the drilling position should be set on the same spiral channel at one end of the heat exchanger, and it should be arranged in a crisscross shape. When drilling, it should also try to ensure that iron filings do not fall into the heat exchanger to make it The passage is unobstructed.
2. Flooding to suppress leaks
In a channel that has never been drilled, use a pressure water pump to fill the heat exchanger with water and form a certain pressure. At this time, the position of the heat exchanger leakage will leak out and flow to the other channel (drilled through the hole). Channel), and drip water from the layer closest to the leakage point (At this time, the end of the heat exchanger drilled through the hole should be placed downward). By the position of the dripping water, you can determine which layer is there. For internal leakage, cut a section of the undrilled head of the same layer of the heat exchanger as an observation hole, and the specific leakage point can be accurately determined from the observation hole.
3. Repair of internal leakage

  • Digging holes: After determining the position of the internal leakage point, start cutting holes from the outermost layer of the heat exchanger corresponding to the leakage point. The order is from the outside to the inside until the layer with the internal leakage point is cut. until. The cut hole should be oval, and the size of the outer layer is larger, and the size is gradually smaller inward. Generally, the size of the hole on each layer differs by 40mm. If the location of the leak is deeper, the hole cut in the outer layer should be larger. 

  • Removal of slag: After the hole is cut, the oxide slag remaining on each layer of the board should be carefully cleaned. This is when the repaired board is butt welded, whether the repaired board and each layer of the spiral board can be closely welded The key is to clean the oxide slag with the chisel and the small hand grinding wheel used to trim the mold and pay attention to the cleaned slag as far as possible to prevent it from falling into the heat exchanger.

  • Equipped with replenishing board: In order to ensure the quality of repair, the sheets cut from each layer of the heat exchanger are no longer used, and the replenishing board is reconfigured. The additional replenishing board should be used with the heat exchanger spiral plate. With the same material and plate thickness, its periphery should be 15mm-20mm larger than the holes cut on each layer of the heat exchanger, and it is also elliptical and made into an arc that is consistent with the curvature of each layer of the heat exchanger. 

  • Welding internal leakage points and replenishment boards:

  1. When welding internal leaks, carefully check whether the leaks are cracks or blisters. If necessary, use a hand wheel to clean the leaks and grind out the grooves to ensure welding quality.

  2. J422 electrode is used for welding repair, the diameter of the electrode is 3.2mm, the current is controlled between 100-120A [1], the leakage point is welded first, and then each layer of repairing board is welded, sequentially from the inside to the outside layer by layer.

  3. The elliptical repair plate is closely attached to the inner arc surface of the heat exchanger for welding, and its purpose is to "convenient operation and ensure welding quality".

  4. In order to smoothly install the elliptical repairing plate into the heat exchanger, a piece of round steel can be welded on the repairing plate, and then the elliptical repairing plate can be removed after spot welding.

  5. Short round steel braces are also welded between each layer of replenishment plates (mainly to increase the mutual rigidity of the elliptical replenishment plates). The number of short round steel braces welded on each layer of the repairing plate is determined by the size of the repairing plate. Generally, 23 welds are welded on the larger outer layer of the repairing plate, and the inner layer of the repairing plate is welded 1~ 2 pcs.

  6. It should be done during welding. After each layer of the elliptical repairing plate is welded, the welding position should be carefully checked. If there is a sand hole, repair welding should be carried out to ensure the welding quality of each layer.