JPS6224680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for stopping a pig midway in a fluid transfer pipe.

[Conventional technology]

Conventionally, when stopping a pig in the middle of an oil pipe,
By closing a valve placed in front of the pig, the oil flow rate is controlled, slowing down the pig's running speed, and stopping the pig.

[Problem that the invention seeks to solve]

The conventional pig stopping method described above has a drawback that the stopping position of the pig is largely influenced by the valve closing timing or the forward running speed of the pig. For example, the valve closing timing is greatly affected by the viscosity characteristics of the oil type, which causes errors in opening and closing, resulting in the pig not being able to stop at an accurate position. There was a problem that variations occurred depending on the conditions and it was not possible to stop accurately at the planned position.

Therefore, if the valve closes at the wrong timing or if the pressure feeding conditions cannot be grasped correctly,
Destroy the valve by smashing the pig into it,
This method has had various problems, such as the pig getting stuck in the electric valve that is in the middle of closing and being damaged, and the fact that the pig stop position cannot be accurately determined, resulting in inaccurate measurement of the transfer amount.

[Means for solving problems]

This invention detects the pig, which is pushed by the downstream fluid and moves from upstream to downstream in the fluid transfer pipe by the upstream fluid, by means of a detection means provided upstream of the scheduled pig stop location. A valve provided on the downstream side is closed to slow down or stop the pig, and then the pig is formed to be substantially thinner than the fluid transfer pipe, and the upstream end is placed at the point where the pig is scheduled to stop in the fluid transfer pipe, and the downstream end is are opened in the fluid transfer pipe on the downstream side of the valve, and the downstream fluid flows out to the downstream side of the fluid transfer pipe, and the pig is moved to a position at the upstream end of the bypass pipe. By stopping the bypass pipe in a closed state, the above-mentioned conventional problems are solved.

[Effect]

Since the valve provided in the fluid transfer pipe is closed and the fluid downstream of the pig flows out of the thin bypass pipe downstream of the valve, the traveling speed of the pig is necessarily reduced. Then, the pig approaches the upstream end of the bypass pipe that opens at the location where the pig is scheduled to stop, closes the bypass pipe at the upstream end position, and stops.

Therefore, regardless of the running speed of the pig or the viscosity characteristics of the transferred fluid, the pig will stop correctly at a predetermined position and will not collide with the valve or bite into the closed valve and cause damage. Accurate transfer amount.

In addition, since the pig can be accurately stopped at the planned stopping point, even when two types of transfer fluids are transferred via the pig, the upstream side of the pig due to an error in the stopping position of the pig, which can be a problem at branch points, etc. There is no mixing of the above fluid and the downstream fluid, and in addition, the timing of opening and closing the valve can be easily determined, so mixing of the upstream fluid and the downstream fluid due to an error in the timing of opening and closing the valve is prevented.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows an oil pipe apparatus for specifically carrying out the method of stopping a pig midway in a fluid transfer pipe according to the present invention.

In the figure, reference numeral 1 is an offshore tanker, and 2 and 2a are first and second base tanks installed at an oil receiving base on land, respectively. A is an oil feed line of the oil feed pipe device, and B is an inert gas (hereinafter referred to as _N2 gas) line.

Oil pipe device A is main oil pipe A ₁ and tanker 1.
Main oil feed pipe A ₁ supplies oil from the tip oil feed pipe A ₂
, a terminal oil transmission pipe A _{3 that} receives the oil transferred by the main oil transmission pipe A 1 into the first base tank 2, and a main oil transmission pipe
A sub-oil pipe _A4 that receives oil from the middle of the land part of _A1 into the second base tank 2a, and a Pig-launching oil pipe _A5 ,
It is composed of a pig recovery oil transmission pipe _a6 , first, second, and third bypass oil transmission pipes _a7 , _a8 , _a9 , and a pressure equalization pipe _a10 .

The main oil transmission pipe _A1 is installed between the offshore cargo handling pier S and the onshore oil receiving base, and a pig launcher 3 is attached to the end on the pier side, and a pig receiver 4 is attached to the end on the onshore side. ing. Furthermore, in the main oil transmission pipe _a1 , there is a first electric valve MV-1 near the pig launcher 3, a second electric valve MV-2 near the boundary between the sea part and the land part, and a third electric valve MV-2 near the pig receiver 4. Electric valve MV-3, 2nd
A fourth electric valve MV-4 is provided between the electric valve MV-2 and the third electric valve MV-3.

The tip oil feed pipe _a2 has the same diameter as the main oil feed pipe _a1 , and one end is connected to the fifth electric valve MV-5.
It is connected to the loading arm 5 installed on the offshore cargo handling pier S, and the other end is connected to the sixth electric valve MV-6.
Through the main oil pipe A ₁ first electric valve MV
-1 and the second electric valve MV-2.
It is connected to branch point A near electric valve MV-1.

The terminal oil pipe _A3 has the same diameter as the main oil pipe _A1 , and one end is connected to the third electric valve MV of the main oil pipe _A1 .
-3 and the fourth electric valve MV-4, the other end is connected to the first base tank 2, and the other end is connected to the first base tank 2. A seventh electric valve MV-7, an air separator 6, and a flow meter 7 are attached.

The sub oil pipe _A4 is branched from the branch point C of the main oil pipe _A1 between the second electric valve MV-2 and the fourth electric valve MV-4, and is connected to the second base tank 2.
A is connected to the piping, and from the branch point C side, the flow control valve CV-1, air separator 6a,
A flow meter 7a is provided. In addition, the pig launching oil pipe _A5 has a smaller diameter than the main oil pipe _A1 ,
A fifth electric valve MV- whose one end is connected to approximately the center of the pig launcher 3, and whose other end is connected to the tip oil feed pipe _a2 .
5 and the 6th electric valve MV-6 are connected at the branch point near the 5th electric valve MV-5, and the flow rate adjustment valves are sequentially connected from the pig launcher side along the way.
CV-2 and air separator 8 are installed.
The pig recovery oil feed pipe _A6 has a smaller diameter than the main oil feed pipe _A1 , has a flow rate adjustment valve CV-3 in the middle, one end is connected to the pig receiver 4, and the other end is the terminal oil feed pipe. a ₃ is connected between the seventh electric valve MV-7 and the air separator 6.

The first bypass oil pipe _a7 has an eighth electric valve MV-8 on the way, and is piped as a bypass of the second electric valve MV- ₂ of the main oil pipe a1. The diameter of the first bypass oil feed pipe _a7 (the diameter of the eighth electric valve MV-8) is set extremely smaller than the diameter of the main oil feed pipe _a1 (the diameter of the second electric valve MV-2). Generally, the diameter of the first bypass oil pipe _a7 is set to about 0.5 to 5% in area ratio with respect to the diameter of the main oil pipe _a1 . The second bypass oil pipe _a8 has a ninth electric valve MV on the way.
-9, one end is connected between the fourth electric valve MV-4 of the main oil pipe _A1 and the branch point C of the sub oil pipe _A4 , and the other end is connected to the sub oil pipe _A4. The air separator 6a is connected between the flow control valve CV-1 and the air separator 6a. In addition, the third bypass oil pipe a ₉ has a 10th electric valve MV-10 in the middle, and one end is connected to the main oil pipe
a ₁ 's 4th electric valve MV-4 and 3rd electric valve
Fourth electric valve MV-4 between MV-3
The other end is connected between the flow control valve CV-1 of the sub-oil feed pipe _a4 and the air separator 6a.

Diameters of the second and third bypass oil pipes a ₈ and a ₉ (9th electric valve MV-9, 10th electric valve MV-
10) is extremely small compared to the diameters of the main oil supply pipe _A1 and sub oil supply pipe _A4 (the diameters of the fourth electric valve MV-4 and flow control valve CV-1), and is usually 0.5 to 0.5 in area ratio. It is set at around 5%. The pressure equalizing pipe _a10 is connected to each of the bypass oil pipes _a7 , _a8 ,
It has a small diameter like A ₉ , and there is a 11th electric valve in the middle.
MV-11, and connects the upstream side of the branch point H and the downstream side of the branch point H of the _third bypass oil pipe _A9 by bypassing the fourth electric valve MV-4 of the main oil feed pipe A1. It is piped to. In addition, 9 and 10 in the figure
10a is a vent tank, 11, 12, 13, 13
a, 14, 14a, 14b are drain pumps.

On the other hand, the N ₂ gas system path B is composed of a gas supply pipe b ₁ , first and second gas recovery pipes b ₂ and b ₃ , and a pig back-pushing pipe b ₄ around the N ₂ gas tank 15 . There is.

Gas supply pipe B ₁ has a gas pressure control valve CV in the middle.
-4, and is piped between the N ₂ gas tank 15 and the pig launcher 3. The first gas recovery pipe b ₂ is equipped with an N ₂ gas compressor 16, first and second mist separators 17 and 18, and a gas pressure adjustment valve CV-5 in sequence from the _{N 2 gas} tank 15 side, and the pig receiver 4. 2nd gas recovery pipe b ₃
Attach pressure control valve CV-6 in the middle,
One end is connected between both mist separators 17 and 18 in the first gas recovery pipe _b2 , and the other end is connected to the upstream side of the second electric valve MV-2 (hereinafter referred to as equipment, etc.) in the main oil pipe _a1 . Pig launcher 3 in the center
The side where the pig receiver 4 is located is referred to as the "upstream side" and the side where the pig receiver ₄ is located is referred to as the "downstream side"). Pig reverse push pipe b ₄ has a gas pressure control valve CV-7 and a 12th electric valve in the middle.
MV-12, one end of which is connected to the _N2 gas tank 15
, the other end is the third electric valve MV of the main oil feed pipe _A1
-3 and the third bypass oil pipe _A9 are connected to the branch point G between the branch point E of the third bypass oil pipe A9.

By the way, the main oil pipe _A1 has a first pig detector near the downstream side of the first electric valve MV-1.
PD ₁ has second and third pig detectors PD 2 and PD 3 near the upstream side of the second electric valve MV-2, and a fourth pig detector PD ₂ and PD ₃ near the upstream side and downstream side of the fourth electric valve MV-4. , 5th, 6th, 7th Pig Detector
PD ₄ , PD ₅ , PD ₆ , PD ₇ are the third electric valve MV-
An eighth pig detector PD ₈ is installed near the upstream side of the branch point b of the terminal oil pipe a on the upstream side of _{the third} oil pipe a.
A ninth pig detector PD ₉ is provided between the electric valve MV-3 and the pig receiver 4, respectively.

The second pig detector PD ₂ is installed near the upstream side of the main oil pipe a ₁ to the branch point of the second gas recovery pipe b ₃ , and the second electric valve MV
-2 (or to the branch point of the second gas recovery pipe b ₃ , the first
The installation distance from the branch point d) of the bypass oil pipe _A7 is the pig transfer speed in the main oil pipe _A1 , the second electric valve MV-2, and the third electric valve MV-3.
and the required opening or closing time of pressure regulating valve CV-6, these valves MV-2, MV-3, CV
-6 is set in consideration of the flow rate characteristics when opened or closed.

In other words, the installation position of the Pig Detector PD ₂ is for gas replacement in the offshore main oil transmission pipe _A1 where the pig moves with _N2 gas on the upstream side and oil on the downstream side, as described below. , the speed of deceleration of the pig due to the closing operation of the second electric valve MV-2 based on the pig passage detection signal of the second pig detector PD ₂ is the same as that between the main oil pipe a ₁ and the second gas recovery pipe b _{3 .}
At the branch point, when the predetermined set speed Vmin is reached and the pig passes the installation position of the third pig detector PD ₃ , the second electric valve MV-2
The first phase that will be the timing for complete closure of
This is the position calculated from the conditions (see Figure 5 I), and the pig has oil on its upstream side and downstream side.
In the case of gas recovery from offshore oil transmission pipe a ₁ moving with N ₂ gas, the second pig detector PD ₂
The pressure control valve CV-6 starts to close when the pig passage detection signal is detected, and the third electric valve starts to open.
MV-3 consists of main oil pipe A ₁ and second gas recovery pipe B ₃
When the pig passes the junction with the third valve, the pressure regulating valve CV-6 has just completed closing and the third
It is required that the position calculated from the second condition is such that the electric valve MV-3 obtains the opening degree Qmin that allows a flow rate higher than the minimum flow rate of the tanker 1 pump (see Figure 5). . However, in reality, the position calculated from the first condition and the position calculated from the second condition do not match, so the second
The installation position of the second pig detector PD ₂ is determined based on the position calculated from one condition where the distance from the electric valve MV-2 is large, and the pressure is determined based on the difference between this and the position calculated from the other condition. The difference in the closing/opening timing of the regulating valve CV-6 and the third electric valve MV-3 is corrected by a timer (see Fig. 5...
In the case shown in the figure, the first condition is when the distance from the second electric valve MV-2 is determined to be large).

The third pig day detector PD ₃ is the main oil pipe A ₁
Branch point d of the first bypass oil pipe a ₇ and the second
The gas recovery pipe _b3 is provided at a position extremely close to the branch point D and the branch point D of the gas recovery pipe b3. Further, the fourth pig detector PD ₄ is provided near the upstream side of the branch point c of the sub oil pipe a ₄ in the main oil pipe a ₁ , The installation distance from the branch point C of the oil feed pipe _A4 and the branch point H of the second bypass oil feed pipe _A8 is the pig movement speed in the main oil feed pipe _A1 , and the flow rate adjustment valve CV-1.
It is calculated and set based on the same conditions as the first condition when determining the installation position of the second pig detector PD ₂ , taking into account the required closing time and the flow rate characteristics at the time of closing.

The fifth pig day detector PD ₅ is the main oil pipe A ₁
It is provided at a position close to the branch point H between the branch point H of the second bypass oil feed pipe _A8 and the branch point C of the sub oil feed pipe _A4 . The sixth pig detector PD ₆ is located between the fourth electric valve MV-4 and the branch point H of the third bypass oil pipe _A9 in the main oil pipe _A1 .
The seventh pig detector PD 7 is installed near the electric valve MV-4, and the seventh pig detector PD ₇ is connected to the branch point H of the third bypass oil pipe A ₉ in the main oil pipe A ₁ and the pig reverse push pipe B ₄ . It is located near the branch point E between the branch point G and the branch point H.

Next, a control system for each mechanism in the oil pipe device will be explained with reference to FIGS. 2 to 4.

FIG. 2 is a flow sheet showing a fully automatic operation system for the N ₂ gas compressor 16.

Since the N ₂ gas compressor 16 in this oil pipe system is operated before and after receiving oil, its operation is not continuous operation but batch operation. Therefore, automatic operation of the N ₂ gas compressor 16 is desirable in terms of saving labor for the operator, and in this embodiment, it is operated as shown in the figure. Note that the arrows drawn between each block in the figure indicate the order of operation. Only the operation of turning on the start switch is performed manually by the operator, and the other blocks surrounded by one-dot chain lines are operated by an automatic sequence.

FIG. 3 shows the pig launcher 3, respectively.
1 is a system diagram and flow sheet showing a pig launch system according to the present invention.

Hydraulic cylinders 21 and 22 operated by a hydraulic unit 20 are attached to the pig launcher 3, and the pins 21 and 22 of each cylinder 21 and 22 are
a, 22a are facing inside the launcher. In the figure, 23 is a sequence control device, PD ₁₀ is a pig detector for detecting the seating of the pig before launching, a ₅ is the oil feed pipe for launching the pig, b ₁ is the gas supply pipe, MV-1 is the first electric valve, G ₁ , _G2 , and _G3 are pigs stored in the pig launcher 3. The pig launcher 3 is configured in this way, and this operation is sequentially controlled as shown in the flow sheet, and each pig G ₁ ,
G ₂ and G ₃ are fired. The pig is stored in the pig launcher 3 manually by the operator.

FIG. 4 is a flow sheet for controlling pressure and flow rate using an electric valve employed in the oil pipe system of this embodiment. In the figure, 30 is the sub oil pipe a ₄ of the oil pipe A 4 ,
Pig launch oil pipe a ₅ , pig recovery oil pipe ₆ , _N2 gas line B gas supply pipe b ₁ , first and second gas recovery pipes
b ₂ , b ₃ , an oil or N ₂ gas flow path indicating a pipe for back-pushing the pig b _{4 ,} etc.; 31 is a flow rate or pressure transmitter attached to the flow path 30; each of the pipes a ₄ , a ₅ , a ₆ , transmitters attached to b ₁ to _{b 4} FIC ₁ , FIC ₂ , FIC ₃ , PIC ₁ , PIC ₂ ,
PIC ₃ and PIC ₄ are shown. Reference numeral 32 denotes an electric valve provided in the flow path 30, which includes flow rate control valves CV-1 to CV-3 and pressure control valve CV- ₄ provided in each of the pipes _a4 , _a5 , _a6 , _b1 to b4. ~CV-7 is shown. 33 is a controller, 34 is a positioner, 35 is a start forced closing circuit, 36 is a contactor, 37 is a sea case circuit, and each of the above parts is installed on a panel. The dotted line arrows in the figure indicate the condition signal paths of each part.

Temperature, pressure, flow rate in normal process industries,
When controlling industrial quantities such as liquid level, the control end, that is, the various control valves, may adopt a continuous control system using a diaphragm or air cylinder operator powered by air pressure, but for practical use, a dryer A control valve powered by pneumatic pressure is recommended for control in systems where an attached air source device is required, and where the number of control loops is small and the installation is planned over a long distance, as in this example. This would not only require large-scale equipment but also be extremely uneconomical, so in this example, we adopted a method of controlling the fluid in the pipeline using electric valves to simplify the ancillary equipment. It's on.

Next, the operation of the oil pipe system constructed as described above will be explained.

(1) Replacement with _N2 gas up to the offshore branch point and
How to recover _N2 gas.

How to replace gas in the oil pipe (when replacing oil in the oil pipe with _N2 gas) The opening/closing status of _each valve before gas replacement is as follows. ing.

(MV valve opening/closing status) MV-1 “closed”, MV-2 “open”, MV-3
“Open”, MV-4 “Open”, MV-5 “Closed”, MV-
6 “closed”, MV-7 “closed”, MV-8 “open”,
MV-9 “closed”, MV-10 “closed”, MV-11
“Closed”, MV-12 “Closed” (CV valve opening/closing status) CV-1 “Closed”, CV-2 “Closed”, CV-3
“Open”, CV-4 “Closed”, CV-5 “Closed”, CV-
6 “closed”, CV-7 “closed” To replace the _N2 gas in the main oil pipe a ₁ , first insert the pig G ₁ into the pig launcher 3, and then
Open electric valve MV-1. Next, by opening the pressure control valve CV-4, the gas pressure accumulated in the _N2 gas tank 15 is adjusted to the pig _G1.
Pig _G1 moves while pushing the oil in main oil pipe _A1 , and _N2 flows inside main oil pipe _A1 .
It will be replaced with gas. At this time, the pressure of the _N2 gas supplied from the _N2 gas tank 15 is controlled by the pressure control valve CV-4, and the flow rate on the oil side is controlled by the flow rate control valve CV-3, so that the difference between before and after the pig _G1 is controlled. Pig pressure is kept constant
G ₁ moves in the pipe at a constant travel speed. In order to prevent wear of Pig G ₁ and to switch each electric valve within a fixed time, Pig G 1 is
The moving speed of _G1 is controlled by a flow rate control valve CV-3 to be constant at about 1.0 m/sec.

When the pig G ₁ passes through the second pig detector PD ₂ and is detected, the second pig detector PD 2 is detected as shown in FIG.
The second detection signal is detected by Pig Detector PD ₂ .
The electric valve MV-2 begins to close, the flow rate is gradually narrowed down, and the speed of the pig _G1 is reduced.
When the second electrically operated valve MV-2 is completely closed, oil flows only from the first bypass oil pipe _a7 , the pig _G1 becomes even slower, and the upstream branch of the first bypass oil pipe _a7 flows. When it reaches near the point D, the third pig detector PD ₃ detects it, and this detection signal triggers the second gas recovery pipe.
It is confirmed that Pig G ₁ has passed the branch point of b ₃ . 3rd pig detector PD ₃ is pig
After detecting the passage of G ₁ , a timer is used to set a time lag for the pig G ₁ to reach the branch point N of the first bypass oil pipe _A7 from the installation position of the third pig detector PD ₃ . , 3rd
Since the gas replacement end signal is sent from the pig detector PD ₃ , the eighth electric valve MV
-8 and the third electric valve MV-3 are closed, the pig _G1 stops at the branch point N as shown in Fig. 5I, and the inside of the main oil pipe _A1 located above the sea _{is N2.} Replaced by gas. Simultaneously with the completion of the substitution, the pressure control valve CV-4 is closed, and the pressure control valve CV-6 is further opened to perform a pressure reduction operation of the replacement gas.

This depressurization work is carried out when it would be a safety hazard to store the replacement gas, which has reached a high pressure state during the replacement work, in the main oil transmission pipe _A1 for a long period of time after the replacement is completed. This can be omitted if there is no problem with security.
During this depressurization work, the displacement gas in the sea part of the main oil pipe _A1 is replaced by the pressure control valve CV-
6. N ₂ via mist separator 17
_N2 gas tank 15 by gas compressor 16
will be collected. That is, _N2 gas compressor 1
6, the pig _G1 is the second pig detector
When it is detected passing PD ₂ , the electric motor has started and is running without load, and the pressure control valve CV-6 opens and the mist separator 17
When pressure control is started, the first pressure switch installed in the mist separator 17 is activated.
Load operation is started by the PS ₁ signal, and the displacement gas in the main oil pipe A ₁ is sucked. and,
The pressure of the displacement gas in the sea part of main oil pipe A ₁ is the same as that of the third tank installed in the sea part of main oil pipe A ₁ .
When the pressure is reduced to the set pressure of pressure switch PS ₃ , the signal from pressure switch PS ₃
The _N2 gas compressor 16 is automatically stopped, the first electric valve MV-1 and the pressure regulating valve CV-6 are closed, and the depressurization work is completed.

In the above, during the oil conveyance work associated with _N2 gas replacement, the pig _G1 is accurately stopped at a fixed position upstream of the second electric valve MV- ₂ in the main oil conveyance pipe A1 (main oil conveyance pipe In the equipment, for example, in order to accurately determine the amount of remaining oil in the pipe, and to replace the _N2 gas in the offshore part of the main oil pipe A ₁ and the _N2 gas replacement in the branch part to the second base tank 2a (described later), This operation is required to prevent the pig _G1 from biting into the second electric valve MV-2 which is operating in the direction shown in FIG. Note that, as described above, in this embodiment, the eighth electric valve
The diameter of MV-8 is set to about 0.5 to 5% of the area ratio of the second electric valve MV-2, but this is because the diameter of the second electric valve MV- ₂
When the pig G ₁ approaches the branch part of the gas recovery pipe B ₃ , the replacement gas flows from the gap between the pig G ₁ and the corner of the branch part to the main oil feed pipe A ₁ in front of the pig G ₁ . Leak amount and 1st bypass oil pipe
When the oil flow rate from a ₇ is balanced, pig G ₁
The pig will stop at the branch, so the pig
When the flow rate in which G ₁ does not stop midway flows through the first bypass oil transmission pipe A ₇ and the pig G ₁ stops at the branch part N of the first bypass oil transmission pipe A ₇ , the pig G ₁
This is designed to ensure that the branch part 2 is completely sealed and that the replacement gas does not leak into the first bypass oil pipe _A7 , and the conditions such as the physical properties of the fluid to be transferred and the diameter of the transfer pipe are If it is different, it will change.

Method for recovering _N2 gas in oil pipes (when transporting oil through gas-replaced oil pipes).

The opening/closing status of each valve after N ₂ gas replacement is as follows.

(MV valve opening/closing status) MV-1 “closed”, MV-2 “closed”, MV-3
“Closed”, MV-4 “Open”, MV-5 “Closed”, MV-
6 “closed”, MV-7 “closed”, MV-8 “closed”,
MV-9 “closed”, MV-10 “closed”, MV-11
“Closed”, MV-12 “Closed” (CV valve opening/closing status) CV-1 “Closed”, CV-2 “Closed”, CV-3
“Open”, CV-4 “Closed”, CV-5 “Closed”, CV-
6 “Closed”, CV-7 “Closed” N ₂ The status of main oil pipe A ₁ after gas replacement is as follows: Pig G ₁ is placed upstream of the second electric valve MV-2.
has been shut down and the upstream of pig _G1 has been replaced with _N2 gas. To recover the gas in the main oil pipe _A1 , first, insert the previously used pig _G1 and another pig _G2 into the pig launcher 3. Next, the original fifth electric valve MV-5 of the loading arm 5, the first electric valve MV-1 and the second electric valve at the outlet of the pig launcher 3.
Open MV-2, flow control valve CV-2, and flow control valve CV-6. When the pump of the tanker 1 starts receiving oil in this state, the oil passes through the air separator 8 and is sent into the pig launcher 3 while the flow rate is controlled by the flow rate control valve CV-2. After joining G ₂ , pig G ₂ enters the main oil pipe A ₁ and moves at the same time.
The movement of this Pig G ₂ is the first Pig Detector.
The PD ₁ detects this, and the N ₂ gas compressor 16 automatically starts, and the replacement gas in the main oil pipe a ₁ is replaced by the N ₂ gas compressor 16 via the pressure control valve CV-6 and the mist separator 17. It is collected into the _N2 gas tank 15.

In this case, the flow rate of oil received from the tanker 1 is controlled by the flow rate control valve CV-2, but if the set flow rate is equal to or lower than the suction capacity of the gas compressor 16, The _N2 gas compressor 16 has a receiving oil flow rate and
Load operation and no-load operation are repeated depending on the difference in suction capacity of the N ₂ gas compressor 16. This load operation and no-load operation are performed by detecting the pressure inside the mist separator 17 by the first pressure switch PS ₁ installed in the mist separator 17. Note that if the received oil flow rate exceeds the suction capacity of the _N2 gas compressor 16, the main oil pipe a ₁
The N ₂ gas pressure inside will gradually increase as the pig G ₂ moves, but the suction pressure of the N ₂ gas compressor 16 is controlled by the pressure control valve CV-6 and the load will be kept constant. Oil can be accepted if the pump discharge pressure of the tanker 1 has a capacity higher than the N ₂ gas pressure that has risen at the end (to the branch of the second gas recovery pipe b ₃ and the main oil transmission pipe a ₁ ).

Next, Pig G ₂ is the second Pig Detector PD ₂
When detected, the pressure control valve CV-6 is automatically closed after the timer setting time as shown in Figure 5, and the third electric valve is closed.
MV-3 is opened and N ₂ gas recovery ends. Furthermore, when the pig _G2 , which is being pushed by the oil and moves, passes through the branch point of the second gas recovery pipe _b3 , the pressure control valve CV-6 is completely closed at the same time. Second
A large amount of oil does not flow into the mist separator 17 via the gas recovery pipe _b3 . Even after N ₂ gas recovery is completed, the movement of pig G ₂ does not stop, and the oil received last time, pigs G ₁ and G ₂ , and the oil received this time move inside the main oil pipe A ₁ to the pig receiver 4 side. move towards. and the 9th pig detector at the entrance of pig receiver 4.
When PD ₉ detects passage of the upstream pig G ₂ , the third electric valve MV-3 closes, the seventh electric valve MV-7 opens, and the two pigs G ₁ ,
G ₂ is stored in the pig receiver 4. Next, the sixth electric valve MV-6 is opened, the first electric valve MV-1 and the flow control valve CV-2 are closed, and normal oil reception is started.

(2) Gas recovery and replacement method for all oil pipelines Method for recovering gas in oil pipelines (when recovering replacement gas in oil pipelines) The opening/closing status of each valve after gas replacement is as follows.

(MV valve opening/closing status) MV-1 “closed”, MV-2 “open”, MV-3
“Closed”, MV-4 “Open”, MV-5 “Closed”, MV-
6 “closed”, MV-7 “closed”, MV-8 “closed”,
MV-9 “closed”, MV-10 “closed”, MV-11
“Closed”, MV-12 “Closed” (CV valve opening/closing status) CV-1 “Closed”, CV-2 “Closed”, CV-3
“Closed”, CV-4 “Closed”, CV-5 “Closed”, CV-
6 “Closed”, CV-7 “Closed” Insert pig G ₁ into pig launcher 3. Next, the original fifth electric valve MV-5 of the loading arm 5, the first electric valve MV-1 at the outlet of the pig launcher 3, and the third electric valve
Open MV-3, flow control valve CV-2, and pressure control valve CV-5. When tanker 1's pump starts receiving oil in this state,
The oil flows through the air separator 8 and the flow control valve
The oil is fed into the pig launcher 3 while the flow rate is controlled by CV-2, and when the feeding pressure is applied to the pig G ₁ inside the pig launcher 3, the pig G ₁ moves and the first pig detector PD ₁ detects the passage of the pig G ₁ . Upon _{detection of}
7 and 18, and is recovered to the _N2 gas sink 15 by the _N2 gas compressor 16, similar to the _N2 gas in the sea part of the main oil pipe _a1 .

When Pig G ₁ is detected passing by the 8th Pig Detector PD ₈ , the 7th electric valve MV-7
is opened and the oil pushing the pig G ₁ passes through the air separator 6 and the flow meter 7 and is sent to the base tank 2. Next, when the passage of pig G ₁ is detected by the ninth pig detector PD ₉ , the third electric valve MV-3 closes and the pressure regulating valve
CV-5 is closed, the pig _G1 is stored in the pig receiver 4, and the recovery of _N2 gas is completed.

Next, the sixth electric valve MV-6 opens, and the flow control valve CV-2 and the first electric valve MV open.
-1 is closed and normal oil reception begins. Note that when recovering N ₂ gas, the mist separators 17 and 18 separate the oil in the N ₂ gas, but the oil remaining in the mist separators 17 and 18 is collected by each drain pump 14b and 14, and the oil is It is sent into the pipe.
The oil remaining in the vent tanks 9, 10 is similarly recovered by each drain pump 12, 13. Further, oil remaining in the pig launcher 3 and the pig receiver 4 is similarly recovered by drain pumps 11 and 14, respectively.

Method for replacing _N2 gas in oil pipes The opening and closing status of each valve before replacing _N2 gas is as follows.

(MV valve opening/closing status) MV-1 “closed”, MV-2 “open”, MV-3
“Closed”, MV-4 “Open”, MV-5 “Closed”, MV-
6 “closed”, MV-7 “closed”, MV-8 “closed”,
MV-9 “closed”, MV-10 “closed”, MV-11
“Closed”, MV-12 “Closed” (CV valve opening/closing status) CV-1 “Closed”, CV-2 “Closed”, CV-3
“Open”, CV-4 “Closed”, CV-5 “Closed”, CV-
6 “closed”, CV-7 “closed” _N2 gas is supplied to the entire length of the main oil pipe _A1 by first inserting the pig _G2 into the pig launcher 3, and then passing the first electric valve MV-1 and the third electric valve. Open valve MV-3. Pressure control valve CV-
When 4 is opened, the gas pressure accumulated in the _N2 gas tank 15 is applied to the pig _G2 , pushing the oil in the main oil feed pipe _A1 , and the Pig _G2 converts the inside of the main oil feed pipe _A1 into _N2 gas. As the oil is replaced, the oil in the main oil feed pipe _a1 flows through the pig recovery oil feed pipe _a6 , and is sent to the first base tank 2 under the control of the flow control valve CV-3. Pig G ₂ is the 9th Pig Detector PD ₉ at the entrance of Pig Receiver 4
When the passage is detected by the flow control valve,
CV-3 and pressure control valve CV-4 are closed, and the entire length of the main oil pipe _a1 is replaced with _N2 gas. After that, the pressure control valve CV-5 is opened, and the main oil pipe a ₁
After depressurizing the _N2 gas in the main oil pipe _a1 in the same manner as in the _N2 gas replacement method above the sea, the first electric valve MV-
1. The third electric valve MV-3 and the pressure control valve CV-5 are closed, and the N ₂ gas replacement of the entire length of the pipe is completed.

(3) Oil supply and N ₂ gas replacement method for the second base tank 2a.

Oil supply to the second base tank 2a (all lines are
(if replaced with _N2 gas).

The replacement gas on the upstream side of the fourth electric valve MV-4 is recovered, and after the recovery, the oil is sent to the second base tank 2a via the main oil feed pipe _a1 and the sub oil feed pipe _a4 . The opening/closing status of each valve when all lines are replaced with _N2 gas is as follows.

(MV valve opening/closing status) MV-1 “closed”, MV-2 “open”, MV-3
“Closed”, MV-4 “Open”, MV-5 “Closed”, MV-
6 “closed”, MV-7 “closed”, MV-8 “closed”,
MV-9 “closed”, MV-10 “closed”, MV-11
“Closed”, MV-12 “Closed” (CV valve opening/closing status) CV-1 “Closed”, CV-2 “Closed”, CV-3
“Closed”, CV-4 “Closed”, CV-5 “Closed”, CV-
6 “Closed”, CV-7 “Closed” Insert pig G ₁ into pig launcher 3. Next, the original fifth electric valve MV-5 of the loading arm 5, the first electric valve MV-1 at the outlet of the pig launcher 3, and the third electric valve
Open MV-3, flow control valve CV-2 and pressure control valve CV-5. In this state, when the tanker 1 pump starts receiving oil, the oil flows into the pig launching oil feed pipe _a5 , passes through the air separator 8, and enters the pig launcher 3 while being controlled by the flow rate control valve CV-2. sent. When oil feeding pressure is applied to the pig G ₁ in the pig launcher 3, the pig G ₁ enters the main oil feeding pipe a ₁ and moves downstream within the oil feeding pipe a ₁ . At this time, the first pig detector PD ₁ detects the movement of the pig G ₁ , the N _{2 gas} compressor 16 is started, and the displacement gas in the main oil pipe A ₁ is brought to the pressure as described above. Control valve CV-
5. Via mist separators 18 and 17
_N2 gas tank 15 by _N2 gas compressor 16
will be collected.

When the passage of pig G ₁ pushed by oil is detected by the sixth pig detector PD ₆ , this detection signal activates the fourth electric valve MV.
-4 is closed, the flow rate control valve CV-1 is opened, and the oil is sent to the second base tank 2a through the sub-oil sending pipe _a4 . Main oil pipe a ₁
The Pig G ₁ that was running inside is the 4th electric valve.
The MV-4 runs inside the main oil feed pipe A ₁ until it is completely closed, and when it is completely closed, the 7th pig detector PD ₇ of the main oil feed pipe A ₁ and the pig reverse push pipe B Stop between the _4th branch point and
Replacement gas recovery ends. When the replacement gas recovery is completed, the _N2 gas compressor 16 stops, and the third electric valve MV-3 and the pressure control valve
CV-5 is closed.

Next, the pig G ₁ stopped between the seventh pig detector PD ₇ of the main oil pipe A 1 and the branch point of the pig reverse push pipe B ₄ is transferred to the third pig detector PD ₇ of the main oil pipe A _1. In order to return to the branching point _E with the bypass oil pipe _A9 , as shown in FIG.
10 will be held. Next pig back push tube b _4th
12 Electric valve MV-12 and pressure regulating valve
CV-7 is opened, and the displacement gas stored in the _N2 gas tank 15 flows through the pig back-pushing pipe _b4 to the main oil pipe _a1 , and is stopped in the oil pipe _a1. Press Pig G ₁ and Pig
_G1 moves to the upstream side, and the oil on the upstream side of the pig _G1 passes through the third bypass oil pipe _a9 , and is sent to the second base tank 2a via the sub oil pipe _a4 .

When the passage of the pig G ₁ is detected by the seventh pig detector PD ₇ , the pig G ₁
A time difference is set by a timer for the time it takes to reach branch point E from the installation position of Pig Detector PD ₇ , and a pig back push end signal is sent from the 7th Pig Detector PD ₇ , and the 10th electric valve MV-10 No. 12 electric valve MV-1
2 and pressure regulating valve CV-7 are closed, the pig _G1 stops at the branch point E, and the pig reverse push operation is completed.

As mentioned above, the purpose of the operation of pushing back the pig _G1 and stopping it at a certain position (branching point H) is to reduce _the N ₂
When replacing gas, connect the pig to the first bypass oil pipe.
This is the same as stopping at branch point 2 in _a7 .

During the pig pushback operation, the first electric valve MV-1 closes, the sixth electric valve 6 opens, and the flow rate control valve CV-2 closes, so that the oil from the tanker 1 is transferred from the tip oil pipe _A2 . The oil enters the main oil pipe _a1 and is normally accepted into the second base tank 2a.

_N2 gas replacement to the second base tank 2a Oil on the upstream side of the fourth electric displacement valve MV-4 (the downstream side of the fourth electric displacement valve MV-4 has been replaced with _N2 gas) to the second base tank 2a. The opening/closing status of each valve before N ₂ gas replacement is as follows, and the two pigs that were collected and inserted into the main oil transmission pipe _a1 after collection are collected into the pig receiver 4.

(MV valve opening/closing status) MV-1 “closed”, MV-2 “open”, MV-3
“Closed”, MV-4 “Closed”, MV-5 “Closed”, MV-
6 “closed”, MV-7 “closed”, MV-8 “closed”,
MV-9 “open”, MV-10 “closed”, MV-11
“Closed”, MV-12 “Closed” (CV valve opening/closing status) CV-1 “Open”, CV-2 “Closed”, CV-3
“Closed”, CV-4 “Closed”, CV-5 “Closed”, CV-
6 “Closed”, CV-7 “Closed” To replace the _N2 gas upstream of the fourth electric valve MV-4, first insert a pig into the pig launcher 3.
When G ₁ is inserted and the first electric valve MV-1 and pressure control valve CV-4 are opened, the gas pressure accumulated in the N ₂ gas tank 15 is
Join _G2 . Pig _G2 moves while pushing the oil in main oil pipe _A1 , and moves inside main oil pipe _A1 .
It is replaced with _N2 gas. The oil on the upstream side of the _fourth electric valve MV-4 of the main oil feed pipe A1 flows through the sub oil feed pipe _A4 and the second bypass oil feed pipe _A8 , and the flow rate is controlled by the flow rate control valve CV-1. Meanwhile, it is sent to the second base tank 2a.

When the passage of pig G ₂ is detected by the fourth pig detector PD ₄ , the flow control valve CV-
1 starts to close, the flow rate is gradually narrowed down, and the moving speed of pig G ₂ is slowed down. When the flow rate control valve CV-1 is completely closed, oil flows only from the second bypass oil pipe _a8 , and the pig
G ₂ becomes even slower, and the second bypass oil pipe a ₈
When the pig G 2 approaches the branch point C of the sub oil pipe A ₄ , the fifth pig taker PD ₅ detects this, and this detection signal confirms that the pig G ₂ has passed the branch point C of the sub-oil pipe A 4 .

After the fifth piglet protector PD ₅ detects the passage of the pig _G2 , the time required for the pig _G2 to reach the branch point of the second bypass oil pipe _A8 from the installation _position of the fifth piglet protector PD5. The 5th Pig Teter is set up with a time difference using a minute timer.
A gas replacement end signal is sent from PD ₅ , and the 9th
Electric valve MV-9 and pressure control valve
Since CV-4 is closed, the pig _G2 will surely stop at the branch point H of the second bypass oil pipe _A8 , and the fourth electric valve MV- of the main oil pipe _A1 will be stopped.
The upstream side of 4 is replaced with N ₂ gas.

As mentioned above, _the operation to decelerate pig _G2 and stop it at a certain position ₍ branch point This is the same as when stopping at the branch point d of the first bypass oil pipe _a7 .

Next, after the pig G ₂ stops at the branch point H on the upstream side of the fourth electric valve MV-4 of the main oil pipe a ₁ , it opens the fourth electric valve MV-4 and stops at the branch point H. Pig G ₂ at the branch point E and pig G ₁ stopped at the branch point E are to be collected into the pig receiver 4, but if there is a difference in N ₂ gas pressure between the upstream side of pig G ₂ and the downstream side of pig G ₁ . , the two pigs G ₁ and G ₂ start moving during the opening operation of the fourth electric valve MV-4, and the pig G ₂ comes into close contact with the fourth electric valve MV-4, causing the opening operation of the valve MV-4. The upstream side of Pig _G2 and the Pig
It is necessary to equalize the _N2 gas pressure downstream of _G1 . This pressure equalization operation is performed using the _11th
Open the electric valve MV-11, connect the main oil pipe A ₁ on the upstream side of Pig G ₂ and the downstream side of Pig G ₁ , and release the N ₂ gas pressure on the high pressure side to the low pressure side. Let me do it. When the pressure equalization operation is completed, the 11th electric valve MV-11 is closed.

After doing this, the fourth electric valve MV-
4. When the third electric valve MV-3 and pressure control valves CV-4 and CV-5 are opened, the _N2 compressor 16 is started, and the pigs _G1 and _G2 are connected to the main oil feed pipe.
Start moving inside a ₁ toward the pig receiver 4. Downstream side of pig G ₁ in main oil pipe A _1
N2 gas passes through the pressure control valve CV-5 and mist separators 18 and 17 as described above.
_N4 gas tank 15 by N2 _gas compressor 16
will be collected. When the passage of the upstream pig G ₂ is detected by the ninth pig taker PD ₉ at the inlet of the pig receiver 4, the pressure regulating valve is activated.
CV-4 is closed, and after further pressure reduction work, pressure control valve CV-5 and the first
Electric valve MV-1, third electric valve MV-
3 is closed, and the work of collecting the pigs G ₁ and G ₂ to the pig receiver 4 is completed. In addition, Pig
A small amount of oil remaining between G ₁ and G ₂ is separated by a mist separator 18 and collected into the first base tank 2 by a drain pump 14 .

Although the above embodiment describes the case where the main oil pipe _a1 is replaced with N2 gas, the present invention is not limited to this, and _{the N2} gas line B may be replaced with a water supply or recovery line. A water displacement method can also be used. In addition, in the above embodiment, the first
It goes without saying that the method for stopping a pig midway according to the present invention can be used when there are a plurality of base tanks 2 and second base tanks 2a, or in a fluid transfer pipe system in which the N ₂ gas line B is omitted.

〔Effect of the invention〕

This invention detects the pig, which is pushed by the downstream fluid and moves from upstream to downstream in the fluid transfer pipe by the upstream fluid, by means of a detection means provided upstream of the scheduled pig stop location. A valve provided on the downstream side is closed to slow down or stop the pig, and then the pig is formed to be substantially thinner than the fluid transfer pipe, and the upstream end is placed at the point where the pig is scheduled to stop in the fluid transfer pipe, and the downstream end is are opened in the fluid transfer pipe on the downstream side of the valve, and the downstream fluid flows out to the downstream side of the fluid transfer pipe, and the pig is moved to a position at the upstream end of the bypass pipe. Since the pig is stopped with the bypass pipe closed, the pig can always be accurately stopped at a predetermined position regardless of the running speed of the pig or the viscosity of the transferred fluid. Therefore, if the pig crashes into the valve,
The amount of transferred fluid can be accurately measured without causing damage to the valve while it is closed.

In addition, even when a different type of fluid (oil) is transferred through a pig, the pig can be stopped exactly at the planned stopping point, so the fluid on the upstream side of the pig can be easily stopped due to an error in the stopping position of the pig, which can occur at branch points, etc. There is no mixing of the fluids on the downstream side, and since the timing of opening and closing of the valves can be easily determined, it is possible to prevent mixing of the fluids on the upstream side and the fluid on the downstream side due to timing errors in opening and closing the valves.

[Brief explanation of the drawing]

Fig. 1 is a piping explanatory diagram showing the first example of the practical oil pipe system of the present invention, Fig. 2 is a fully automatic sequence block diagram of an N ₂ gas compressor, and Fig. 3 is an explanation of the main parts of a pig launcher. Fig. 4 is a block diagram showing the automatic sequence block diagram of the pig launcher, Fig. 4 is a block diagram showing the liquid control situation using the electric valve, Fig. 5 is
, FIG. 6 is an explanatory diagram of the operation of stopping the pig in a fixed position. a ₁ ... Main oil pipe (fluid transfer pipe), a ₇ ... 1st bypass oil pipe (bypass pipe), PD ₂ ... 2nd
Pig detector (detection means), MV-2...second electric valve (valve).

Claims (1)

[Claims] 1. A pig that pushes downstream fluid and moves from upstream to downstream in a fluid transfer pipe by upstream fluid is detected by a detection means provided upstream of a scheduled pig stop location, and the pig is stopped. Closing the valve provided downstream of the planned location to slow down or stop the pig,
Thereafter, it is formed to be substantially thinner than the fluid transfer pipe, and has an upstream end opened at a location of the fluid transfer pipe where the pig is scheduled to stop, and a downstream end opened into the fluid transfer pipe downstream of the valve. Fluid transfer characterized by causing the downstream fluid to flow out of the bypass pipe to the downstream side of the fluid transfer pipe, moving the pig to a position at the upstream end of the bypass pipe, and stopping with the bypass pipe closed. How to stop a pig in the middle of a pipe. 2 Claims characterized in that the bypass pipe is stopped in a closed state by moving the pig to an upstream end position of the bypass pipe and using the pig to stop the downstream fluid flowing into the bypass pipe. A method for stopping a pig midway in a fluid transfer pipe according to item 1. 3 Move the pig to the upstream end of the bypass pipe and close the valve provided in the bypass pipe,
A method for stopping a pig in a fluid transfer pipe according to claim 1, characterized in that the pig is stopped in a state where the bypass pipe is closed.