The valve for a reciprocating compressor .... For the Head of the enterprise like and sounds like that it is too small. "Well, the valve, well, it's where it's in the compressor, I still do not understand." I have Petrovich there, he knows everything. "
But in fact, behind this are serious costs. After all, the valve by 50% is the most important gas distribution in the piston compressor. As a result of long-term analysis, data have been obtained to judge that the percentage of wear of other friction-friction parts in the piston compressor does not significantly affect the operation of the compressor itself, as a percentage of valve wear.
If the valve has lost its tightness, then you get a whole bunch of little pleasant factors, such as an increase in the temperature of compression and the passage of a compressed medium between the stages. That, accordingly, leads to a decrease in productivity.
What is productivity? This is the volume of compressed environment that your production equipment is urgently needed, in order to make profit for you.
It turns out that? Petrovich does not care about your longing for profit.
On 90% at it all valves "hiss", but he regularly receives the salary. What do you get in this case? The compressor, due to loss of performance, lasts longer to maintain the required pressure. Does it last longer? Hence, it consumes more electricity. Excess energy consumption is the 1st factor of profit reduction.
But God forbid that you still lack productivity? Petrovich with a light hand starts a backup compressor with an electric motor with a capacity of 600 kW. This is no longer a factor; it is a direct attempt on profit at the end of the year. The second factor is the cost of purchasing valves and repair kits that, by the way, reach 40-50% of the cost from the valve itself. So, the valves usually change 2-3 times a year.
Well, what to do ... Accessories. How's the top? Quite an expensive consumable. The cost of a set of valves is more than 1 500 000 Tenge. This is 3 000 000 or 4 500 000 Tenge per year. Maybe it's not much ... And if there are 5 compressors in the enterprise ...?
At present, enterprises using piston compressors use valve designs of the past century.
PIK Valve
which do not ensure the nominal operation of the piston compressor due to unsatisfactory tightness. Similarly, the valves currently in use have a low "fail-safe" life, which leads to additional costs for the purchase of new or repair of old valves.
Energy-saving valves for piston compressors ESCL, SLK, fully replacing the valves SGID, SGID m, PIC, NCP, VKT, NDT, VDT, etc.
ESKL Valve:
1. Ideally suited only as a suction valve of the 1st stage.
2. Warranty period of the valve "to failure" 5 000 hours.
3. Actually increases the compressor's capacity by 5% due to absolute tightness by suction conditions.
4. Absence of metal traces of wear.
5. Absolute noiselessness of the valve.
6. Can be used as a non-return valve.
SLK valve:
1. Ideal, starting with 1 stage of the discharge side and above.
2. Warranty period of the valve "to failure" 15 000 hours. Confirmed by industrial operation for 10 years.
Structures of self-acting valves.
Self-acting valves belong to the number of the most critical parts of reciprocating compressors. They have a significant effect on the two most important characteristics of a reciprocating compressor: economy of operation and reliability. They are presented with a number of requirements that cannot simultaneously be satisfied. Different requirements for valves and their operating conditions led to the appearance of a variety of valve designs. Consider the requirements for valves, and only those designs that are most widely used.
Valves should provide as little gas dynamic resistance as possible to the flow of gas flowing through them; have a developed cross-section; open under the influence of a small difference in pressure before and after the valve, and in the open state to work without vibrations of moving elements. Deviation from this requirement leads to an increase in the energy required to push the gas and reduce the economy of the compressor.
The closing of the valve (the seating of the closing element in the seat) under the action of the spring element must occur in a timely manner, that is, at the time when the pressure difference before and after the valve becomes zero. If the suction valve is operated with a delay, then some of the gas is forced back into the suction chamber before the compression process begins, which leads to a decrease in productivity and an increase in the specific operation of the stage. At a delay with closing of the delivery valve the part of the compressed gas from the injection chamber returns to the working chamber, this leads to a decrease in productivity and an increase in the specific work.
Gas flow due to delay may cause the so-called "dynamic non-density of the valve", named so because it is caused by imperfection of the dynamics of motion of the valve plates.
In the closed state, the valve must ensure the tightness of the working chamber. Gas flow through the closed valve, caused by a not sufficiently tight fitting of the plate to the seat, causes the so-called "static non-density" of the valve, which also causes a decrease in the productivity of the stage and an increase in the specific work.
Valves should have a small amount of "dead space", since any "dead volume" reduces the performance of the compressor. Plates and springs of valves (or only plates of self-closing closing organs) should have sufficient strength, i.e. they must for a sufficiently long time to withstand the static and dynamic (shock) loads that arise during the operation of the valve. In other words, the valve must have the required reliability, i. E. keep working capacity for a given operating time. Insufficient reliability of the valves entails an increase in operating
costs, a decrease in the volume of output, when the compressor participates in the process, etc. In operating conditions, the valves should provide convenient installation, dismantling and repair. Thus, the main requirements for valves are associated with ensuring the economical and reliable operation of the compressor.
In modern piston compressors, the cost of power to overcome the resistance of the valves is about 20% of the nominal. Given the huge fleet of piston compressors, reducing these costs is an urgent task.
No less urgent is the problem of increasing the reliability of valves. As the experience of operating piston compressors shows, the greatest number of their downtime is caused by the failure of the valves.
To create a valve that fully meets the above requirements is not easy. At their designing difficulties arise as the speed of the crankshaft increases, the average speed of the piston, the gas density, i.e. when the requirements of profitability and reliability become increasingly contradictory.
The variety of requirements imposed on the valves was the reason for the appearance of very different designs of self-acting valves.
Direct-flow valve PIC-A.
The PIK is the most common type of valve, the design of which was created in the 70s of the
last century.
The valve is a set of the same type of elements, consisting of a saddle and an elastic plate. The saddle has, on the one hand, flow channels for gas passage, separated by bridges, on the other hand, a wedge-shaped bevel, serving as a stop for the plate when the valve is opened. The plate consists of several languages connected by a common jumper. Each closing element covers two to four channels. The plate is clamped along the U-shaped contour between adjacent saddles. The valve is assembled with a special device.
It is used in general air compressors, as well as in the first stages of medium and high pressure compressors with a pressure drop on the valve of no more than 4 MPa.
PIK valve is not recommended for work on contaminated, coking gases and easily flammable gases.
Tubular ring valves; CGT.
They consist of a saddle with concentric channels for gas passage, connected by radial bridges, annular plates overlapping these channels and a plate-lift limiter, which also has concentric channels that are shifted relative to the seat channels along the diameter of the valve. In the lift stop there are springs pressing the plates to the seat and closing the valve. The entire valve is pulled together by a stud located in the center. In the limiter or in the saddle, the beads are made to guide the plate as it moves. Ring valves can be made either with an annular, concentrically arranged spiral spring, separate for each plate, or with point springs arranged around the circumference of each ring.
As the speed of compressors increases, shock loads in the plates increase. At the same time, on the one hand, the plate breaks down more often, on the other, the plate hits the stopper, bounces off it and for some time makes oscillatory movements between the seat and the stop, thus preventing the passage of gas. To mitigate the impact force make damping devices in the form of gas chambers, complicating the design of the valve and increasing the cost of the valve.
Ring valves are easy to manufacture, have high density, relatively small "dead space". However, due to the low efficiency (low value of the flow area), the ring valves are currently used mainly at medium and high pressure stages, in compressors compressing easily volatile gas (hydrogen, helium, etc.), also in compressors without lubrication and compressing the polluted gases (natural, coke, etc.).
Disc valves VDT; NDT.
They differ from the ring structures only in that the rings of the closing plates are connected by bridges and form a disk.
The valves have one or more disc springs, which serve to increase the overall stiffness of all spring elements to the end of the valve opening. Sometimes in the valve additionally install several point coil springs to create some pre-tension. To reduce the impact force of the plate against the limiter and to extinguish its vibration over the working plate, an elastic plate is installed, called a damper plate.
Disk valves are more complicated in design than ring ones. They require more labor in production, but at the same time they are more effective, since with the same fitting diameters in disc valves, a larger number of channels and rings of smaller width can be made, thereby increasing the cross-section. The presence of flat springs allows reducing the height of the limiter of lifting the plate and, in the case of a suction valve, reducing the "dead volume".
