The so treated sheet is then rolled into cylindrical form, either with the treated surface facing inwardly or outwardly, as desired.įIG. Heating and cooling the sheet, as described in step 3 above, causes the heads of the grooves or slots to open as extremely narrow slits which are sufficient to avoid thermal stresses on repeated heating and cooling. The sheet is machined to provided the open-ended grooves, after which the machined sheet is rolled, hammered or shot peened to close the open ends of the grooves. A sleeve with a treated surface, can also be produced from a flat sheet of metal. The method just described is applicable for treating the outer surface of sleeves for use in a pump as described and can also be used for treating internal surfaces, such as the internal surface of cylindrical members. rapidly heating the outer surface of the part to a temperature which exceeds the maximum service temperature differential to be encountered in service, and cooling thereafter, so that the closed slots slightly open to the surface, which will subsequently permit the outer layers of the part to expand both axially and peripherally when subjected to the sudden temperature variations encountered in service without causing thermal stresses in the inner layers of the part. then locally rolling, hammering or shot peening the machined surface, thus closing the surface ends of the slots while retaining cavities in the body of the part andģ. machining narrow open slots, both axially and peripherally on the surface to be exposed to the sudden temperature variations Ģ. The suitable configuration of the surface to be exposed to the sudden temperature variations is achieved in stages by:ġ. However, these sleeves are also subjected to thermal stresses in the same manner as the shaft itself, and are thus subject to failure, requiring a shut down of the equipment for a part replacement.Īccording to the invention to be described herein, thermal stresses in machine components are reduced by providing the surface of the component which is subjected to the sudden temperature variations with a suitable configuration, to be described. To protect or shield the drive shaft from such thermal stresses, one or more sleeves encircling the shaft are used. Because of the sudden temperature variations due to the aforesaid operating conditions, thermal stresses are induced into the drive shaft which could cause failure of the shaft and a shut-down of the equipment. At times, pressure pulsations in the space or cavity behind the impeller cause periodic flow reversal, i.e., hot product fluid flowing toward the mechanical seal through the gap between the housing and the drive shaft. The cold fluid provides a cooling media for the shaft.
![hsmworks machining open ended slot hsmworks machining open ended slot](https://data2.manualslib.com/first-image/i21/104/10341/1034089/hsm-sp-4040.jpg)
This cold fluid flows into the space or cavity behind the impeller and then into the discharge from the impeller. On the impeller side of the mechanical seal, cold fluid, such as cold water, is injected into the system to flow through a gap between the pump housing and the drive shaft. Common practice is to use one or more mechanical seals encircling the shaft which connects the pump impeller and its driving means, such as an electric motor. In the usual centrifugal pump, there is a space or cavity behind the impeller into which product fluid can pass to the system.
![hsmworks machining open ended slot hsmworks machining open ended slot](https://content.instructables.com/ORIG/F43/W1RN/I1TJEVXC/F43W1RNI1TJEVXC.jpg)
The invention can find particular use in components of pumps for pumping hot fluids and the like. This invention relates to the reduction in thermal stresses in machine components which are subjected to sudden temperature variations and which thermal stresses can cause failure of the component.