DE1428260A1 - Procedure and device for the protection of a centrifugal compressor - Google Patents

Description

30, Carel van Bylandtlaan, Hague, The Netherlands

concerning

Procedure and equipment for the protection of a centrifugal compressor.

The invention relates to a method and device for protecting a centrifugal compressor to to completely or at least almost completely prevent the so-called pumping of the compressor. This Pumping can occur in a compressor when the grass flow velocity is at a certain pumping pressure too low in the compressor or the pressure becomes too high at a certain gas velocity. To counteract this pumping, the compressor has a bypass line or blow-out line, which in normal operation (i.e. with a sufficiently high gas load) is closed by a control valve. As soon as the danger

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of pumping arises - the valve opens more. or less far, so that the gas flow-through the. -compressor stronger 'and thus avoid pumping will. Since branching off or blowing out; gas through the bypass line or the discharge line ■ a loss, in any case always a performance attorney--. entails lust, the valve will only open if this is the case is necessary to avoid pumping.

As already proposed earlier, the control valve can be operated via a controller to which signals are given as a function of the pressure in the compressor and the strength of the gas flow are »For example, according to US Pat. No. 2,000,721, a signal proportional to the discharge pressure of the compressor is generated in the control element which controls Position of the control valve regulated with the SuEime compared two signals. One of these signals is hanging on the flow velocity in the gas supply and the other, depending on the gas flow rate in the bypass line, ■■ "■: .- U ---;

This control can at best only. work properly at a certain pressure level, namely the pressure level to which the control element is set. If the suction pressure fluctuates, the setting of the control element would also have to be constantly changed in order to achieve effective protection against pumping. However, this is almost impractical,. '. "« 9 013/0209 ^BAD0RieINAL

However, no effective protection of the compressor against the danger of the is by means of the known method ■ Pumping possible as soon as the inlet pressure in the one to be compressed Gas is not constant or at least not substantially constant. This phenomenon occurs frequently where a large number of compressors are connected in series.

The invention now provides an effective method of protection against pumping. This procedure is the pressure head with which a compressor works,. practically independent. In addition, this is protection also independent or at least essentially independent of the inlet temperature of the gas to be compressed .

Special embodiments of the invention Protection also enable safe operation of the compressor up to almost the limit of the pumping area without or at least without significant loss of performance. This is particularly important in the event that the Gas load in the compressor fluctuates significantly. Here it is of particular advantage if the area in which the gas load can fluctuate without loss, is kept as large as possible. However, it is a lossless one Operation as a result of too low a gas load (or too high Pressure) is not possible, the resulting losses are kept to a minimum while at the same time

'A stable control of the regulating valve is ensured lsi. 809813/0209. BAD ORK5INAL

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U282BQ

According to the invention, the flow rate through the control valve is regulated by the output signal of a control element to which the quotient of two signals is given as an input signal (and thus as a measured value). One of the two signals (4p) depends on the gas flow through the compressor and the other (p) on the pressure level prevailing in the compressor. The direction of action of the control is such that the output signal of the control element opens the

/ Control valve tries to .as soon as ** ^ C or. - ^) a

^p - ~ Z "

Zp

smaller (or larger) than those set on the control unit Value 'reached.

The signal that is dependent on the grass flow in the compactor is usually a pressure differential signal, which is measured on a throttle, a venturi or a similar arrangement.

The differential pressure meter is preferably connected to the outlet side of the compressor. The dependent of the pressure altitude signal is preferably obtained by measuring the Tora erdruckes of the compressor. By combining the value 4p measured on the suction side of the compressor (IpJ and the value P (Po) measured on the pressure side of the compressor or vice versa (APo and P ₁ ), good results can be achieved. In practice, the best possible control results , if one uses 4p and ρ on the pressure side of the compressor® mlBt, i.e. with the combination 4Po and p «,

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By changing the one set on the control unit The point at which the control valve begins to open can be closer or further to the surge limit be led away from it.

The embodiment of the protection according to the invention described above is particularly useful when the gas load normally well outside the danger area (i.e. the area in which, when the Hegel valve is closed pumping of the compressor would occur) lies and only fluctuates insignificantly. In this case the controller is usually a purely proportional function and more assigned a broad proportional control range. This wide proportional control range is to achieve a stable regulation required. Now occurs, for example, due to a blockage in the discharge of the condensed If the gas shows an unexpected change in its normal state, the dam organ prevents pumping.

However, it is with normal operation of the "compressor" Considerable fluctuations in load are to be expected, with the Surge limit is almost reached or exceeded (so that the control valve work frequently or even constantly must to prevent pumping), protection is achieved by means of a control element with a purely proportional effect as less effective. Due to the relatively wide proportional control range of the control element, the regulation not very economical. If one tries now by introducing an integrating effect, the economic

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speed, the compressor can suffer from rapid fluctuations in load a risk arise.

According to another feature of the invention appears therefore the use of two control organs connected in parallel is desirable, one of which is 'pure' proportional function and a relatively narrow proportional 'control range and the other both proportional as well as integrating puncture and a relatively broad proportional control range is. The output signals of these controllers are on given an auxiliary relay, which causes the control valve is only activated by the signal that has the greatest flow rate for the control valve releases ». ... ... _ ■

As a rule, both control elements are connected to the same division circuit or the same divider relay (ie circuit or relays which supply the quotient * ~ & · or - ^). In principle, however, different quotients such as-

ΔΡρ

Tr and - = the use of several division ^{circuits p} 2 P1

or divider relays possible

A similar result can be achieved with the help of a single control element, in addition to proportional and integrating also has a derivative or differentiating effect and preferably a broad one has proportional control range.

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The protection according to the invention can be applied in various ways Realize way, for example in a hydraulic, pneumatic or electrical way, whereby the pneumatic embodiment is often used, with such a pneumatic Embodiment can use the output signal of the auxiliary relay (which is used for control with two control organs) - if necessary after prior reinforcement - to the Part of the control are passed on, which triggers the integrating puncture assigned to one of the control organs.

Furthermore, a device can be used in a manner known in another context for preventing saturation the control organ infoige of the integrating function can be used (so-called "anti reset wind-up") ·

The invention is explained in more detail below with reference to schematic drawings of two exemplary embodiments.

Fig. 1 shows an arrangement according to the invention with a individual, and

Pig. 2 shows an arrangement with two control organs connected in parallel.

fig ·. 1 is a schematic representation of a method for compressing natural gas by means of a centrifugal compressor 1. The gas is supplied through a line 2 and leaves the compressor through a line 3. The compressed (Jas is then cooled in a cooler 4

v- and freed in a separator 5 of the condensate that is

en has formed about. The condensate is discharged through a line 6

O '

. · And the compressed gas is discharged through the lines 7 and 8- '' · ^iUhr * | S ^d JE! SSfcW ^{pJi: Lleeead into the corresponding} earth formation "

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pumped back or forwarded to a facility for the production of liquid methane. A gas bypass connects the lines 7 and 2. This gas bypass line contains a control valve 10, which is closed in the “idle state is. If the compressor puffs or is at risk pumping, the cone valve opens to switch off or prevent pumping. The bypass line 9 could also be connected to the outlet side of the compressor at a point further forward, for example immediately in front of the cooler 4.

In the line 3 a throttle 11 is provided which is connected to a pressure difference meter 12. This measuring device generates a signal (4p ₂ ) which is proportional to the pressure difference occurring at the throttle. Next is a pressure gauge. 13 connected to line 3, which generates a _{signal (p 2) proportional to the discharge pressure of the compressor.}

The signals sent out by the measuring devices 12 and 13

are based on a division circuit or a divisor or quo-

AV ₂

tientenrelais 14 given, the output signal is proportional

.P ₂

is. This signal is sent on to a control element 15 which, at 16, can be set to a specific value of the quotient (A), which can also be regulated according to the size. Only one proportional puncture is preferably assigned to the control element. The control element 15 compares the measured value of the quotient sent by the divider or quotient relay 14 --- = - ^mi "fe ^{öe! B} set value A ₉ The output signal 17 of the control element 15 controls the cone valve 10" Iat - ^ "WL ₉ so ist" or * the Hegel valve 10 remains closed

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However, ("for example due to the fact, that at 8 no gas or less gas than usual is withdrawn) ——- <A, the control valve opens

P ₂

each more or less so that the compressor is prevented from pumping. By changing the With the set value A, the instant at which the control valve 10 begins to open is also shifted.

The protection of the compressor according to the invention, explained in more detail above, has the advantage that it is practically independent of the compressor pressure. Occurs, for example, when the pressure rises or falls in the natural gas supply, a change in the pressure head on, the protection against pumping of the compressor remains effective without any change being necessary would.

In the pneumatic embodiment, the display pressure (17) is generally chosen so that the valve 10 opens when the display pressure disappears.

Av ₂

Instead of the quotient, one would also have the quotient

P ₂ ^P 2

take ten r and forward it to the controller 15

Δ P ₂

can. In this case the set value changes as well as the control direction. The valve opens

P ₂ 1 '

of course, as soon as -r- the set value A ¹ (A ¹ = A)

äP

exceeds.

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In Fig. 2, the changes are shown, the ' required if two control organs 15a and 15b are connected in parallel and connected to the same division circuit 14.

The control element 15a has a purely proportional function and, moreover, is proportional narrow proportional control range (e.g. $ 10) set. The control member 16b, which is assigned both a proportional and an integrating function, has a wide proportional control range (e.g. 100-250 ^) compared to the control member 15a. The Andes Control elements 16a and 16b set values differ slightly from one another, namely so that the control element 15b first can go into action. The control range of the control member 15a is on the side of the operating point of the control member 15b, on which the surge line is also located, usually close to the operating point mentioned (at the operating point

The output signals of the control organs are now given to an auxiliary relay 18, which only allows the signal to pass which releases the largest throughput rate for the control valve 10 in each case. In the present embodiment (in the das.Regelventil closes when the pneumatic signal 17 is larger) this means that the relay 18 regularly the smaller of the two signals 15a and 15b emits.

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The part 16c of the control member 1513, which is on the integrating puncture is related, is preferably • fed by the output signal of the relay 18. In prop. 2 the character 17 is therefore passed through an amplifier 19 to the named part, which leads to faster triggering the integrating 'effect. Also, a device that prevents the Control organ is saturated as a result of the integrating puncture (anti reset wind-up).

If the load on the compressor 1 (insofar as it relates to the gas output at 8) approaches the surge limit, then first comes the control member 15b in action, be there Operating point is exceeded first. Since the operating point of the control member 15b is relatively close to the Pump limit can be set, the operation of the compressor remains economical, because it occurs, for example as a result of the gas diversion through the bypass line, no losses occur as long as the operating point of the Control organ 15b (as far as it relates to the gas discharge at 8) is not exceeded, since then the control valve closed is. If the operating point is only slightly exceeded, the cone valve only opens easy, so that only minor losses occur.

If another load change brings the compressor closer to the dangerous zone or even into the

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¹ danger zone itself, the other control element 15a can immediately take action and open the control valve immediately. If there is no such control element 15a, the risk of pumping for the compressor is very great, since the control element 15 "b cannot open the valve 10 in time due to the wide proportional control range and the effect resulting from the integrating puncture.

On the other hand, there is also a constantly unstable

Regulation (due to the narrow proportional regulation range of the control element 15a) no cause for concern, since the control element 15b finally does the regulation again takes over as soon as a signal of suitable size could be generated by the integrating function.

Ultimately, the integrating function offers a guarantee that there is no difference in continuous operation of the compressor with the control valve open to a greater or lesser extent between the measured value and the set value, which could otherwise lead to the compressor pumping.

Claims

"809813/0209

Claims (1)

1A-27 Η2826Θ Claims Γ 1 .J Procedure for protecting a centrifugal compressor, against pumping, using a gas bypass line or blow-out line with a control valve, whose flow rate is regulated by a controller, which depends on the pressure level and gas flow in the Compressor receives signals, characterized in that the flow rate of the control valve is regulated by the output signal of a control member to which the quotient of two signals as Input signal (Heßwert) is given, one of which (Δρ) from the gas flow in the compressor and the other (p) depends on the pressure level in the compressor, with the control in its direction of operation is dimensioned so that the output signal of the control element tries to open the control valve, as soon as - = - (or ^ -) a smaller (or, . greater) than the value set on the control unit. 2. The method according to claim 1, characterized in that g e k e η η · shows that the signal, which is dependent on the gas flow prevailing in a compressor, is a pressure difference signal is measured on a throttle, a venturi or a similar arrangement. 3. The method according to claim 1 or 2, characterized in that - 809813/0209 - 14 - ■ -1A-27 259 mark ty that from the gas flow The compressor-dependent signal is measured on the outlet side of the compressor. 4ο method according to claim 1 to 3, characterized that the signal dependent on the pressure level can be obtained by measuring the outlet pressure of the compressor "receives» 5 ο method according to claim 1 to 4, characterized g e - indicates that the control organ has proportional, integrating and derivative functions. 6 ο Method according to claim 1 to 4, characterized in that two parallel-connected Find control organs use, one of which purely proportional puncture and, moreover, a relatively narrow proportional control range, the others, on the other hand, have a proportional as well as an integrating function and, moreover, a relatively broad proportional control range is assigned and the output signals of these control organs are given to an auxiliary relay, which the control valve can only respond to the signal that releases the greatest flow rate for the control valve. 7. A suitable for the protection of a centrifugal compressor described in the preceding claims BATH
8098 13/0209 r, ■ 15 - ^1Α " ²⁷ * 142826Θ Facility, characterized that there are pressure gauges for those in the compressor prevailing pressure head, a pressure differential meter for the gas flow through the compressor, a to the Divider or quotient relay connected to the outputs of these measuring devices, one to the output of the divider Quotient relay switched control on which the desired value of the quotient of the pressure difference and pressure can be set and a connection for connecting the divider or quotient relay output having with the control of the control valve. 8. Device according to claim 7, characterized in that a control member with proportional, integrating and derivative or differentiating function is provided. 9. Device according to claim 7, characterized in that two control elements are provided, both of which are connected to a divider or quotient relay, one of these control elements having a purely proportional function and, moreover, a relatively narrow proportional control range and the other both proportional and integrating function and a relatively broad proportional control range assigned, and the output of both control organs is connected to an auxiliary relay that consists of the two BADORiGINAU
809813/0209 - 16 - ^U - ²⁷ 259 U2826Q input signals the one who can select the in each case the largest throughput for the control valve releases, and also a connection for connecting the Auxiliary relay output is provided with the control of the control valve .. 10 »Device according to claim 9, characterized in that it identifies that the integrating part of the control organ to which an integrating function is assigned is, if necessary, connected to the output of the auxiliary relay via an amplifier. 11. Device according to claim 9 or 10, characterized in that means are provided that prevent saturation of the control by the integrating puncture. 809813/02 (19