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Calculation of seismic resistance of a wedge gate valve. JSC "Ust-Kamenogorsk reinforcement plant" (UZAZ), Ust-Kamenogorsk city, Republic of Kazakhstan

   By the order of JSC "UKAZ" specialists of NTC APM performed calculations of seismic resistance of a wedge gate valve with a sliding spindle DN 1000 PN 2.5 MPa CC 13002, taking into account the requirements of GOST 30546.1 in two versions: a gate valve with welded nipples and a gate with branch pipes for a counter flange. Three-dimensional solid-state valve models, created by the customer's specialists using the KOMPAS 3D software, were presented as input data. These models are assembly units, which include parts and subassemblies. The calculation was carried out using the APM StructFEM Prof. complex, which is part of the CAD / CAE Automated Calculation and Design System for Mechanical Equipment and Structures of APM WinMachine. The calculation models were formed as follows: the original models were saved using the universal exchange format STEP 203 and transferred to the APM Studio module; Then automatically builds the finite element grid and transfers it to the APM Structure3D module for later strength analysis. In the initial calculation, the valve model did not pass the strength test, so it was necessary to make changes. After evaluating the calculation results, the customer's specialists together with the STC APM decided to install additional stiffeners on the structure. Primary and corrected models (for example, consider the version of the valve with welded nozzles), transferred by the customer, are shown below.

The model of the gate valve with welding nipples
Primary finite-element valve model
Modified valve model
Modified finite element valve model

To calculate the natural frequencies, a separate model was created, from which the case is excluded. This is completely justified, since the body has significantly higher rigidity than the racks and covers. Consequently, the appearance of the first eigenfrequencies should be expected precisely on the ligament-lid bundle.

Primary finite-element combined rack and cover model for determining natural frequencies
Modified finite element integrated rack and cover model

When calculating for natural frequencies, the account of the presence of the drive was modeled by specifying the concentrated mass at the center of gravity of the drive. As a result, the first five eigenfrequencies are determined, and the first eigenmode of oscillations is of greatest interest, since this value is explicitly needed to select the values ​​of the accelerations characterizing the seismic action on the wedge gate

The first proper form of the primary design model of a united rack and cover
The first proper form of the modified calculation model

When analyzing strength, the seismic action is accounted for by setting two linear accelerations: one in the horizontal direction, and the other in the vertical (GOST 30546.1-98, p.4.2). The account of own weight is realized due to input of a factor of own weight in one of the downloads. The strength calculation results are shown below.

Equivalent stress distribution map with scale limitation of 235 MPa for the primary model
Equivalent stress distribution map with scale limitation of 235 MPa for the modified model

Inelastic deformations occur in all zones displayed on the map of the distribution of equivalent stresses in crimson color. In them, the permissible voltage is exceeded (permissible yield stresses for steel 09Г2С КП245 are 245 MPa at a temperature of +80 ° С). Consequently, the strength condition is not satisfied in this case . In order to eliminate the occurrence of inelastic deformations in problem zones, the customer's specialists, together with the STC APM, decided to install additional stiffeners on the structure. The results of calculating the modified model are shown below.

The value of the maximum operating voltage is 339 MPa. However, this maximum stress is localized in a small volume on the ribs. Despite the fact that its value exceeds the permissible value, with static calculation, the static strength condition, from our point of view, can be considered satisfactory for 09G2S steel; The presence of a stress concentrator affects the fatigue strength. Proceeding from this, it is possible to recommend to make edges from steel 09Г2С, while the body part can be made of steel 20.

The distribution map of the total linear displacements of the original model
Map of distribution of total linear displacements of the modified model

In addition, the performance of the model was evaluated: reactions were determined at the contact points of the spindle with body parts due to an earthquake of intensity 10 points. Comparing the obtained value with the minimum force along the spindle, it can be concluded that the condition of the gate valve working capacity under the earthquake is fulfilled. Moreover, it can be seen that the earthquake has little effect on the operation of the gate valve.