ANALYSIS OF THE OPERATION OF AIR DISTRIBUTION SYSTEMS IN COMPRESSOR INSTALLATIONS

ABSTRACT

This article analyzes the results of research on malfunctions occurring in the air distribution system of compressor units, develops technical solutions to improve the efficiency of the lubrication system, and presents the results of their experimental testing. Along with electricity, pneumatic energy, i.e. compressed air energy, is also widely used in industrial enterprises. Information is provided on the significant impact of air distribution systems in compressor units on technological processes, the operation of mining machines and other pneumatic energy consumers that perform the function of compressed air as an energy carrier, and the performance indicators of mining machines and other pneumatic energy consumers. Improving the performance of air distribution systems in compressor units based on distribution processes in compressed air production is discussed.

АННОТАЦИЯ

В данной статье анализируются результаты исследований неисправностей, возникающих в системе распределения воздуха компрессорных установок, разрабатываются технические решения для повышения эффективности системы смазки и представлены результаты их экспериментальных испытаний. Наряду с электроэнергией, в промышленных предприятиях также широко используется пневматическая энергия, то есть энергия сжатого воздуха. Представлена информация о значительном влиянии систем распределения воздуха в компрессорных установках на технологические процессы, работу горных машин и других потребителей пневматической энергии, выполняющих функцию сжатого воздуха в качестве энергоносителя, а также показатели эффективности работы горных машин и других потребителей пневматической энергии. Рассматриваются способы повышения эффективности систем распределения воздуха в компрессорных установках на основе процессов распределения в производстве сжатого воздуха.

Keywords: Compressor devices, air distributor, technological indicators, compressor efficiency, PIK valve, aerodynamic characteristics, vacuum machines.

Ключевые слова: Компрессорное оборудование, воздухораспределитель, технологические показатели, КПД компрессора, клапан ПИК, аэродинамические характеристики, вакуумные машины.

INTRODUCTION

Analysis of the operational efficiency of compressor installations shows that, in most enterprises, they operate with a performance significantly lower than the rated (passport) capacity and with a high specific energy consumption.
As a result of reduced compressor performance and air leaks in the system, the pressure of compressed air delivered to consumers decreases, which causes the actual power output of pneumatic motors to be 30–50% lower than their nominal capacity. Valves are among the most critical components of a reciprocating compressor, largely determining its operational efficiency. During design, calculation, and operation, valves must meet a range of specific requirements. The gas-dynamic efficiency of a valve ensures minimal energy losses. For stationary compressors, these losses should not exceed 10% of the power consumed by the compressor drive. Modern straight-flow valve designs can reduce this figure to 5–8%. High valve tightness is of great importance. It is achieved by optimizing the geometric shapes of the mating parts of the valve’s closing mechanism, properly selecting the movement characteristics of the closing element during operation, and ensuring high-quality surface finishing of the mating areas. To guarantee reliable compressor performance, the mean time between failures for valves used in general-purpose air compressors with a shaft rotation speed of up to 12.5 s⁻¹ (750 rpm) must be at least 4000 hours [1].

In the process of lubricating mechanisms that perform constant movements in technological processes during the operation of compressors, it is advisable to pay special attention to the properties, parameters and cleanliness of the oil, taking into account the constant changes in the initial parameters of the oil, which lead to the deterioration of the mechanisms consisting of moving and rubbing parts, which depend on the degree of contamination of the oil. In many cases, if such situations are not observed and eliminated in a timely manner, they eventually lead to the occurrence of accidents [2].

MATERIALS AND METHODS

In monitoring systems based on monitoring the technical parameters of compressors during continuous operation, a significant contribution to the performance indicators is made by the processes of their lubrication system, and the technical principles of improving their performance significantly reduce the costs of collecting compressed air and producing it under high pressure.

Good maintainability of a valve ensures easy assembly and disassembly under compressor station conditions. This requirement can be met by simplifying the valve’s design.

The wide variety of compressor configurations and their operating conditions has led to the development of numerous valve types, differing in the direction of gas flow through the valve channels, the movement characteristics of the closing element, structural design, and the materials used in their manufacture. Depending on the shape of the closing element, self-acting valves are generally classified as disc-type or plate-type. In piston compressors, if we analyze them mainly from a technological perspective, their lubrication system can be divided into two parts. These, in turn, form the lubrication system for the cylinders and seals, the mechanisms that generate the speed of movement of the compressors [3].

Disc valves are not used in general-purpose air compressors.
Plate valves, depending on the direction of gas flow through the valve’s passage section, are divided into straight-flow and non-straight-flow types. Based on the movement of the plate, valves are grouped into two categories: those with self-springing (flexing) plates and those with floating (non-flexing) plates.

Ring-type valves (see Fig. 1) are widely used both domestically and abroad.

The closing element of a ring-type valve is a flat ring with various outer diameters, a width of 5–12 mm, and a thickness of 1–3 mm. The working rings are pressed against the valve seat by the force of cylindrical springs.

Ring-type valves have several significant and difficult-to-eliminate drawbacks: a complex design and manufacturing process, a large mass of moving parts (rings), a low flow-area coefficient, and difficulty in maintenance under production conditions. In ring-type valve designs, the plate-shaped closing elements are positioned perpendicular to the gas flow. As a result, the gas stream changes direction twice, which increases the valve’s gas-dynamic resistance.

Among plate valves, the most advanced are the straight-flow valves, which have become widely used in general-purpose reciprocating compressors. A typical representative of this type is the PIK valve. Currently, most general-purpose compressors are equipped with these valves (see Fig. 2).

The closing elements of the PIK valve are rectangular plates with a thickness of 0.2–0.5 mm. Plate 5 is rigidly clamped between the end and the seat 3, as well as by the lift limiter 4. The valve consists of a stack of assembled seats 3, plates 5, and side plates 2, all tightened together with clamping rings 6 [4].

Figure 1. Suction and discharge ring valves of a reciprocating compressor

PIK valves offer several significant advantages: a low mass of moving parts, a larger effective flow area compared to ring and disc valves, and reduced gas-dynamic resistance. However, this valve also has serious drawbacks — its structural complexity and, consequently, poor maintainability.

The rigid attachment of the valve plate to its seat causes a constant bending moment to act on the plate during operation. Prolonged exposure to this stress leads to the concentration of fatigue stresses at the bend point, eventually resulting in plate failure. This structural flaw reduces the valve’s mean time between failures. In the process of lubricating mechanisms that perform constant movements in technological processes during the operation of compressors, it is advisable to pay special attention to the properties, parameters and cleanliness of the oil, taking into account the constant changes in the initial parameters of the oil, which lead to the deterioration of the mechanisms consisting of moving and rubbing parts, which depend on the degree of contamination of the oil. In many cases, if such situations are not observed and eliminated in a timely manner, they eventually lead to the occurrence of accidents.

Figure 2. Straight-flow PIK valve

The main ways to improve the performance of air distribution components in reciprocating compressors can be summarized as follows.

RESULTS AND DISCUSSIONS

Increasing wear resistance of valves.

As noted earlier, this issue received considerable attention at the All-Union Scientific and Technical Conference on Compressor and Vacuum Machines [5].

The destruction of plates and the wear of valve sealing edges occur as a result of the impact of the plates against the seat and the lift limiter. Therefore, to increase the durability of valves, it is necessary to eliminate the causes leading to the failure of plates and the wear of sealing edges in air distribution components.

The aerodynamic characteristics of valves have a significant impact on the technical and economic performance of piston compressors.

The relatively low durability of PIK valves, the difficulty of monitoring the condition of operating air distribution components, and their limited maintainability have prompted efforts to improve them and to design new, more advanced configurations.

As is well known, air distribution in reciprocating compressors is carried out by valves, which have a significant impact on the efficiency and key performance indicators (such as output capacity and specific energy consumption) of the pneumatic system. Compared to ring-type valves, straight-flow PIK valves are considered the most efficient [6].

A PIK valve consists of plates, locking strips, two clamping rings, and valve seats. During operation, valve replacement may be required. Since PIK valves are of a disassemblable design, their functionality can be restored by replacing worn components. In particular, replacing the plates restores the valve’s working capacity.

PIK plates are typically made of spring steels SANDVIK 7C or 20C. However, analysis of PIK valve performance has shown that the components most affecting its efficiency and service life are the plates and the valve seat.

To enhance the efficiency of the PIK-type valve, we propose manufacturing the valve plate from V95 alloy. V95 is a high-strength, heat-treatable aluminum alloy containing zinc, magnesium, and copper — one of the strongest known aluminum alloys. It is used for heavily loaded structures operating under high compressive stress. The alloy’s strength and hardness are due to the formation of solid crystalline phases within its structure.

CONCLUSION

Depending on the direction of the applied load (transverse or longitudinal), the material exhibits different mechanical properties — a phenomenon known as anisotropy. V95 also demonstrates adequate corrosion resistance under normal conditions, except when subjected to severe localized stresses.

Comparative tests of three valve types have shown that a valve equipped with a plate made of V95 material increases compressor productivity by 2% compared to standard PIK valves and by 10% compared to ring-type valves.

The modernized valve also reduces the specific energy consumption by 1.5–2% compared to PIK valves and by 8–9% compared to ring-type valves. Thus, using V95 alloy plates in straight-flow valves allows a 13–15% reduction in energy consumption for compressed air production, while simultaneously increasing output by 10% compared to ring-type valves.

References:

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