Reciprocating compressor fault diagnosis method based on piston rod settlement displacement signal

Abstract

The invention discloses a reciprocating compressor fault diagnosis method based on settlement displacement signals of a piston rod, which comprises the following steps: arranging two piston rod displacement sensors in a swing plane of a connecting rod at a certain interval along the axis direction of the piston rod to obtain settlement displacement signals of two position points of the piston rod; arranging a key phase sensor at the position of a crankshaft or a flywheel to obtain the position of a crosshead; setting the offset of the crosshead, the filler and the piston; then a linear equation of the axis of the piston rod in a connecting rod swing plane is obtained by taking the column line direction as a horizontal coordinate X and the settlement direction of the piston rod as a Y axis according to the settlement signals of the two positions of the piston rod, X values of a crosshead piston pin, a filler center and a piston position are substituted, and Y values of all points are obtained; and after the Y value exceeds a set offset range, a fault diagnosis alarm is sent out. The technical problem that an existing unit displacement sensor cannot predict inclination of the piston rod, and misjudgment is easily caused can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of reciprocating compressors and relates to a method for diagnosing equipment faults, and in particular to a method for diagnosing faults using compressor piston rod settlement signals. Background Art

[0002] Reciprocating compressors are widely used in industrial fields such as petroleum, mining, metallurgy, chemical industry, food engineering, and natural gas transportation due to their advantages of high compression pressure and stable adjustment of exhaust pressure. Unplanned downtime caused by compressor failure often brings relatively large economic losses to related companies and may even endanger the lives of on-site operators. The application of fault diagnosis technology to maintain the reliable and safe operation of compressor units is of great significance to ensuring the economic benefits of enterprises and avoiding safety accidents.

[0003] The piston rod displacement signal can be used to diagnose packing wear, crosshead settlement and piston runout (piston ring wear). However, when using a piston rod displacement signal, a single point cannot determine the linear position, and the tilt state of the piston rod cannot be accurately judged, which is easy to cause misjudgment.

[0004] Therefore, a new reciprocating compressor fault diagnosis method based on piston rod settlement displacement signal is proposed. Two piston rod displacement sensors are used to obtain the maximum offset of the crosshead, piston and packing inner ring. The overshoot alarm of the two offsets is used to realize the fault diagnosis of the packing and piston ring (or support ring). Summary of the invention

[0005] The purpose of the present invention is to provide a method for fault diagnosis based on piston rod settlement displacement signal to solve the technical problem that the current unit displacement sensor cannot predict the inclination of the piston rod, which easily leads to misjudgment.

[0006] The technical solution adopted by the present invention is to arrange two piston rod displacement sensors at a certain interval along the axial direction of the piston rod in the connecting rod swing plane to obtain the settlement displacement signals of two position points of the piston rod, and arrange a key phase sensor at the crankshaft or flywheel position to obtain the crosshead position; set the offset of the crosshead, the packing and the piston; then take the column line direction as the horizontal coordinate X, take the piston rod settlement direction as the Y axis, and obtain the straight line equation of the piston rod axis in the connecting rod swing plane according to the settlement signals of the two positions of the piston rod, substitute the X values ​​of the crosshead piston pin, the center of the packing and the piston position to obtain the Y value of each point; monitor the change of the Y value of each point during one rotation of the compressor to obtain the change range of the Y value; when the above Y value exceeds the set offset range, issue a fault diagnosis alarm.

[0007] The specific diagnostic steps are as follows:

[0008] 1). According to the manufacturer's design requirements and compressor maintenance experience, set the allowable offset of the crosshead, packing, and upper and lower ends of the piston, Ysmax, Ytmax, Yhumax, and Yhdmax;

[0009] 2). Establish a coordinate system with the neutral line of the column line as the X-axis, the direction of piston rod settlement in the connecting rod swing plane as the Y-axis, and the reference position of the crosshead pin center when the piston is at the bottom dead center (axis side) as the 0 point;

[0010] 3). Arrange the key phase sensor with the piston at the bottom dead center as the trigger point. When triggered, the timing is t(i), and the next trigger timing is t(i+1). Assuming that the compressor speed is uniform between the two triggers, when the time is t between the two trigger points, the angle β between the connecting rod and the column line is

[0011]

[0012] Among them, r is the crank turning radius, that is, the crank length, L is the connecting rod length, θ is the crank angle,

[0013]

[0014] At this time, the X value Xs of the crosshead pin position is,

[0015] Xs=rcosθ+Lcosβ-(Lr)

[0016] At this time, the X value Xd of the position of the lower end of the piston (shaft side) is,

[0017] Xd=Xs+H1

[0018] Among them, H1 is the piston rod length, that is, the distance from the crosshead pin to the lower end of the piston. This value is the structural dimension of the compressor;

[0019] At this time, the X value Xu of the position of the upper end of the piston (cover side) is,

[0020] Xu=Xd+H2

[0021] Wherein, H2 is the piston length;

[0022] The X value Xt of the filler location is determined by the compression structure design;

[0023] 4). Two piston rod displacement sensors are arranged below the neutral line of the column line (i.e. the center of the piston rod) and in the connecting rod swing plane, and their X coordinates are Xw1 and Xw2 respectively. When the time is t(i)≤t<t(i+1), the piston rod settlement measured is Yw1 and Yw2;

[0024] At time t, according to the piston rod settlement measured by the two displacement sensors, the linear equation of the piston rod settlement is obtained by forming a line with two points:

[0025] y=kx+b

[0026] in,

[0027]

[0028] b=Yw2-kXw2

[0029] 5). Substitute the piston pin position Xs into the above linear equation to obtain the crosshead settlement Yst at time t,

[0030] Yst=kXs+b

[0031] In the time interval of t(i)≤t<t(i+1), record the maximum crosshead settlement value Ystmax and output the Ystmax value. If Ystmax>Ysmax, issue an alarm of "crosshead settlement exceeding value";

[0032] 6). Substitute the packing position Xt into the above linear equation to obtain the packing offset Ytt at time t.

[0033] Ytt=kXt+b

[0034] In the time interval of t(i)≤t<t(i+1), record the maximum value Yttmax of the packing offset and output the value Yttmax. If Yttmax>Ytmax, issue a packing offset over-value alarm.

[0035] 7). Substitute the piston lower end position Xd into the above linear equation to obtain the piston lower end offset Ydt at time t,

[0036] Ydt=kXd+b

[0037] In the time interval of t(i)≤t<t(i+1), record the maximum displacement value Ydtmax of the lower end of the piston and output the value of Ydtmax. If Ydtmax>Yhdmax, issue an alarm of "excess displacement value of the lower end of the piston";

[0038] 8). Substitute the piston upper end position Xu into the above linear equation to obtain the piston upper end offset Yut at time t,

[0039] Yut=kXu+b

[0040] In the time interval t(i)≤t<t(i+1), record the maximum displacement value of the upper end of the piston Yutmax and output the Yutmax value. If Yutmax>Yhumax, issue an alarm of "excessive displacement of the upper end of the piston".

[0041] Advantages and positive effects of the present invention:

[0042] The beneficial effect of adopting the present invention is that after the piston rod deviates, the crosshead settlement, packing deviation (wear) and piston deviation (piston ring wear) can still be accurately predicted, and the diagnosis result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the geometric dimensions of the sensor installation and fault diagnosis point positions of the present invention; DETAILED DESCRIPTION

[0044] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figure 1 As shown, two piston rod displacement sensors 2 (eddy current) are arranged at a certain interval along the axial direction of the piston rod in the connecting rod swing plane to obtain the settlement displacement signals of the two position points of the piston rod, and a key phase sensor is arranged at the crankshaft or flywheel position to obtain the crosshead position; set; the offset of the crosshead, filler and piston; then take the column line direction as the horizontal coordinate X, take the piston rod settlement direction as the Y axis, and obtain the straight line equation of the piston rod axis in the connecting rod swing plane according to the settlement signals of the two positions of the piston rod, substitute the X values ​​of the crosshead piston pin, the center of the filler and the piston position to obtain the Y value of each point; monitor the change of the Y value of each point in one rotation of the compressor to obtain the change range of the Y value; when the above Y value exceeds the set offset range, a fault diagnosis alarm is issued.

[0046] The specific diagnostic steps are as follows:

[0047] 1. Set the allowable offsets of the crosshead, packing, and upper and lower ends of the piston, Ysmax, Ytmax, Yhumax, and Yhdmax, according to the manufacturer's design requirements and compressor maintenance experience.

[0048] 2. Establish a coordinate system with the neutral line of the column line as the X-axis, the direction of piston rod settlement in the connecting rod swing plane as the Y-axis, and the reference position of the crosshead pin center when the piston is at the bottom dead center (axis side) as the 0 point.

[0049] 3. Arrange the key phase sensor 1 with the piston at the bottom dead center as the trigger point of the key phase sensor 1. When triggered, the timing is t(i), and the next trigger timing is t(i+1). Assuming that the compressor speed is uniform between the two triggers, when the time is t between the two trigger points, the angle β between the connecting rod and the column line is

[0050]

[0051] Among them, r is the crank turning radius, that is, the crank length, L is the connecting rod length, θ is the crank angle,

[0052]

[0053] At this time, the X value Xs of the crosshead pin position is,

[0054] Xs=rcosθ+Lcosβ-(Lr)

[0055] At this time, the X value Xd of the position of the lower end of the piston (shaft side) is,

[0056] Xd=Xs+H1

[0057] Among them, H1 is the piston rod length, that is, the distance from the crosshead pin to the lower end of the piston. This value is the structural dimension of the compressor.

[0058] At this time, the X value Xu of the position of the upper end of the piston (cover side) is,

[0059] Xu=Xd+H2

[0060] Among them, H2 is the piston length.

[0061] The X value Xt of the filler position is determined by the compression structure design.

[0062] 4. Two piston rod displacement sensors 2 are arranged below the neutral line of the column line (i.e., the center of the piston rod) and in the connecting rod swing plane. Their X coordinates are Xw1 and Xw2 respectively. When the time is t(i)≤t<t(i+1), the measured piston rod settlement is Yw1 and Yw2.

[0063] At time t, according to the piston rod settlement measured by the two displacement sensors 2, the linear equation of the piston rod settlement is obtained by forming a line with two points:

[0064] y=kx+b

[0065] in,

[0066]

[0067] b=Yw2-kXw2

[0068] 5. Substitute the piston pin position Xs into the above linear equation to obtain the crosshead settlement Yst at time t,

[0069] Yst=kXs+b

[0070] In the time interval of t(i)≤t<t(i+1), record the maximum crosshead settlement value Ystmax and output the Ystmax value. If Ystmax>Ysmax, issue a "crosshead settlement exceeding value" alarm.

[0071] 6. Substitute the packing position Xt into the above linear equation to obtain the packing offset Ytt at time t,

[0072] Ytt=kXt+b

[0073] In the time interval of t(i)≤t<t(i+1), record the maximum value of the packing offset Yttmax and output the Yttmax value. If Yttmax>Ytmax, issue a "packing offset exceeding value" alarm.

[0074] 7. Substitute the piston lower end position Xd into the above linear equation to obtain the piston lower end offset Ydt at time t,

[0075] Ydt=kXd+b

[0076] In the time interval of t(i)≤t<t(i+1), record the maximum displacement value Ydtmax of the lower end of the piston and output the Ydtmax value. If Ydtmax>Yhdmax, issue an alarm of “excessive displacement value of the lower end of the piston”.

[0077] 8. Substitute the piston upper end position Xu into the above linear equation to obtain the piston upper end offset Yut at time t,

[0078] Yut=kXu+b

[0079] In the time interval t(i)≤t<t(i+1), record the maximum displacement value of the upper end of the piston Yutmax and output the Yutmax value. If Yutmax>Yhumax, issue an alarm of "excessive displacement of the upper end of the piston".

[0080] The beneficial effect of adopting the present invention is that after the piston rod deviates, the crosshead settlement, packing deviation (wear) and piston deviation (piston ring wear) can still be accurately predicted, and the diagnosis result is more accurate.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A reciprocating compressor fault diagnosis method based on the piston rod settlement displacement signal, comprising the following steps: Along the axis direction of the piston rod, two piston rod displacement sensors are arranged at a certain interval within the connecting rod swing plane to obtain the settlement displacement signals of two position points of the piston rod. A key phase sensor is arranged at the crankshaft or flywheel position to obtain the crosshead position; Set the offsets of the crosshead, packing, and piston; Then, taking the column line direction as the abscissa X and the piston rod settlement direction as the Y axis, according to the settlement signals of the two positions of the piston rod, obtain the straight line equation of the piston rod axis within the connecting rod swing plane, substitute the X values of the crosshead piston pin, packing center, and piston position, and obtain the Y values of each point; Monitor the change of the Y values of each point during one rotation of the compressor to obtain the change range of the Y values; When the above Y values exceed the set offset range, a fault diagnosis alarm is issued.

2. The reciprocating compressor fault diagnosis method based on the piston rod settlement displacement signal according to claim 1, the specific steps are as follows: 1). Set the allowable offsets of the upper and lower ends of the crosshead, packing, and piston, Ysmax, Ytmax, Yhumax, Yhdmax, according to the manufacturer's design requirements and compressor maintenance experience; 2). Establish a coordinate system with the column line neutral line as the X axis, the piston rod settlement direction within the connecting rod swing plane as the Y axis, and the reference position where the crosshead pin center is located when the piston is at the bottom dead center position as the 0 point; 3). Arrange the key phase sensor with the piston at the bottom dead center as the trigger point of the key phase sensor. When triggered, record the time t(i), and record the time t(i + 1) for the next measurement trigger. Assuming the compressor speed is uniform between the two triggers, then when the time is t between the two trigger points, the angle β between the connecting rod and the column line is in, r is the crank throw radius, that is, the crank length, L is the connecting rod length, θ is the crank angle, At this time, the X value Xs of the position where the crosshead pin is located is, Xs = rcosθ + Lcosβ - (L - r) At this time, the X value Xd of the position where the lower end (shaft side) of the piston is located is, Xd = Xs + H1 Where, H1 is the piston rod length, that is, the distance from the crosshead pin to the lower end of the piston, and this value is the compressor structure size; At this time, the X value Xu of the position where the upper end (cover side) of the piston is located is, Xu = Xd + H2 Where, H2 is the piston length; The X value Xt of the position where the packing is located is determined by the compression structure design; 4). Arrange two piston rod displacement sensors below the column line neutral line (i.e., the piston rod center) within the connecting rod swing plane, and their X coordinates are Xw1 and Xw2 respectively. When the time is t(i) ≤ t < t(i + 1), the measured piston rod settlement amounts are Yw1 and Yw2; At time t, according to the piston rod settlement amounts measured by the two displacement sensors, obtain the straight line equation of the piston rod settlement amount in the way of two points forming a line y = kx + b Where, b = Yw2 - kXw2 5). Substitute the piston pin position Xs into the above straight line equation to obtain the crosshead settlement amount Yst at time t, Yst = kXs + b Within the time interval of t(i) ≤ t < t(i+1), record the maximum value of the crosshead settlement Ystmax, output the value of Ystmax, and if Ystmax > Ysmax, issue an alarm of "excessive crosshead settlement"; 6). Substitute the packing position Xt into the above linear equation to obtain the packing offset Ytt at time t, Ytt = kXt + b Within the time interval of t(i) ≤ t < t(i+1), record the maximum value of the packing offset Yttmax, output the value of Yttmax, and if Yttmax > Ytmax, issue an alarm of excessive packing offset; 7). Substitute the lower position of the piston Xd into the above linear equation to obtain the lower piston offset Ydt at time t, Ydt = kXd + b Within the time interval of t(i) ≤ t < t(i+1), record the maximum value of the lower piston offset Ydtmax, output the value of Ydtmax, and if Ydtmax > Yhdmax, issue an alarm of excessive lower piston offset; 8). Substitute the upper position of the piston Xu into the above linear equation to obtain the upper piston offset Yut at time t, Yut = kXu + b Within the time interval of t(i) ≤ t < t(i+1), record the maximum value of the upper piston offset Yutmax, output the value of Yutmax, and if Yutmax > Yhumax, issue an alarm of excessive upper piston offset.

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