Experimental Study of the Transition of Two Types of Wedge Gate Valves

The object of research is the type of power valves – gate valve or wedge valve. Gate valves or wedge valves take a leading place among power valve. It has minimal hydraulic resistance, an almost linear dependence of the flow rate on the degree of opening, and is widely used on general-purpose pipeline systems. One of the problem areas of such valves is the loss of tightness or the transition of wedge gate valves. In addition, a more complex design increases the likelihood of failure of such valves. To solve this problem, it is proposed to carry out an experimental study of the gate transition depending on the effort of their closure, as well as research the trend of this dependence.<br><br>The studies are carried out on a bench that provides air pressure up to 3.0–3.5 MPa and is equipped with cast-iron and brass valves. Air transition is measured in a volumetric manner, displacing water from the measuring cell. To create a force on the rod that closes the valve, we used a KD-230 torque wrench (Russia) are used, which allows to measure torque up to 230 N⋅m. The experimental technique is as follows. The valve is closed with the necessary force wrench, then the compressor was turned on and the required pressure is reached. Air transition is measured by filling the measuring cell over time, fixed by a stopwatch.<br><br>Processing of the obtained experimental data allows to obtain the following dependences of the relative gap of the valve on the magnitude of the torque for the cast-iron gate valve: Q/√ΔP)=3458∙M(–1,069and for the brass valve: (Q/√ΔP)=6893∙M(–2,435). It is shown that gate valves as well as previously studied valves have one trend: (Q/√Δ)P=С∙M(–g). The degree of torque shows that the larger it is in absolute value, the better the locking characteristics of the valve. So, to ensure the same air transition, the torque on the cast iron valves should have greater values than for the studied brass gate valve.


Introduction
The reliability of pipeline valves in general determines the reliability of any equipment. Timely detection of valve damage will help to avoid unplanned stops and accidents of the heat-power equipment of the station [1][2][3]. Conversely, failure of critical valves can lead to serious events. One can recall the failure of the pulse valve of the pressure compensator at the Three Mile Island NPP (nuclear power plant) [4], which ended in the first serious accident at world nuclear power plants. A similar failure of the PC PRV (pulse pressure relief valve of the pressure compensation system) was noted at the Rivne NPP, Ukraine, but it was detected and eliminated in time. Failure of valves in refrigeration equipment also leads to serious consequences [5]. Thus, the object of this study is the type of power valves -gate valve or wedge valve.
Gate valves or wedge valve take a leading place among power valves. Firstly, when the rod is fully raised, it has the minimum hydraulic resistance, among other types of valves [6,7]. Secondly, the almost linear dependence of the flow rate on the level of the rod lift provides it with a place in automatic control systems or supporting costs, for example, in drainage systems of heaters, on heating mains of heating systems [3]. In addition, such valve has two seating surfaces in series, which increases the reliability of its closure. However, this design is more complex compared, for example, with the design of the valve, which increases the likelihood of failure of such valves [3,6].
The relevance of the work is due to the practical absence of such studies of valve. Analysis of publications on this topic showed the presence of a limited number of works devoted to it [8][9][10]. Therefore, it seems relevant to expand the study of the tightness of valves with various closing efforts on wedge gate valves. So, the aim of this research is to study the tightness of wedge gate valves with different closing forces by constructing the dependence of the relative valve tolerance on the closing force and analyzing this dependence.

Methods of research
Experimental studies were carried out on a bench that provides air pressure with an AK-50 compressor (USSR) up to 3.0-3.5 MPa (Fig. 1). For a smooth air supply to the latch 4, the compressor 2 worked on the receiver 3, with a volume of about 5 liters. Air flow was measured in a volumetric way, displacing water from measuring cell 1. To create a force on the rod that closes the valve 4, let's use a KD-230 torque wrench (Russia), which allows measuring torque up to 230 N⋅m.
The experimental technique was as follows. The valve 4 was closed with a torque wrench with the required force, then the compressor 3 was turned on and the required pressure was reached. Air transition was measured by filling the measuring cell over a period of time, which was recorded by a stopwatch. The experimental results are presented in Tables 1, 2. Note: V air -air volume; t -transit time of the air volume; Mtorque; Q -air consumption (transition); ΔP -pressure drop across the gate valve; (Q /P) 0.5 -complex Continuation of Table 1 Electronic copy available at: https://ssrn.com/abstract=3673864 TECHNOLOGY AUDIT AND PRODUCTION RESERVES -№ 1/1(51), 2020 ISSN 2226-3780 Note: V air -air volume; t -transit time of the air volume; Mtorque; Q -air consumption (transition); ΔP -pressure drop across the gate valve; (Q/P) 0. 5

-complex
The tabular presentation of the results is important for checking the data, but does not give an idea of the nature of the valve transition. For this, it is advisable to process the experimental data according to previously obtained criteria [8].

Research results and discussion
Processing the obtained experimental data allows to obtain the following dependences (Fig. 2, 3). The experiment showed that the gate valves, just as previously studied valves [8] and valves have one trend, namely, obey the equation: where Q -air consumption (transition), ml/s; ΔP -pressure drop across the gate valve, MPa; C -coefficient; Mtorque, N⋅m; g -exponent with M. It is also possible to see that the indicator of the degree of torque is 1.069 for cast iron valve, and 2.435 for brass valve. This means that in order to ensure the same transmission of air, the torque on cast iron valve must have larger values than for the brass.
A visual examination of these gate valves shows that cast iron valve is in operation, while brass valve is brand new. That is, an indicator of the degree of torque allows to evaluate the quality of the seating surfaces of the gate valves.
The dimensional coefficient C also indicates the quality of the seating surfaces, directly relating the valve transition to its value, however, a solid indicator has a significantly greater effect.