JPH0113000B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for replacing oil accumulated in an oil pipe with an inert gas, for example, when oil transport from an offshore tanker to an onshore tank is completed. The present invention relates to an inert gas replacement and recovery method and apparatus which recovers the inert gas present in the oil pipe when oil transport is restarted.

[Conventional technology]

Generally, in large-scale oil transportation, for example, oil pipes that transport petroleum in and out between tankers and tanks at land bases, oil pipes become stagnant when subjected to unexpected shocks such as earthquakes or tanker collisions. In order to prevent secondary disasters such as oil leaks or spills, the oil stagnant in the oil pipes is replaced with another complete substance after the scheduled import/export operations are completed. Conventionally, as the replacement system, a water or seawater replacement system and an open type (inert gas disposable) replacement system using an inert gas have been widely adopted.

[Problem that the invention seeks to solve]

However, water or seawater displacement systems
Since the oil accumulated in the pipes is replaced with water such as fresh water, industrial water, or seawater, large-scale wastewater treatment equipment for the replacement water is required, and in the case of cold regions, heating equipment is required to prevent freezing. In the case of seawater, corrosion prevention measures are required, and there are various problems such as water being mixed into the oil during replacement and deterioration of quality when product oil is pumped. Ta.

In addition, in contrast, a displacement system using inert gas is necessarily highly safe against fire or explosion accidents during oil transportation, but conventional inert gas displacement systems are based on an open displacement method. Therefore, a large amount of inert gas is required, as a replacement inert gas is released into the atmosphere each time oil is transported, and a large amount of oil mist is mixed with the released gas, resulting in large amounts of air pollution. I had a problem.

Furthermore, these replacement systems have disadvantages in that, because replacement is performed throughout the oil pipe, it takes a long time to complete the operation, and the amount of replacement material is large.

[Means for solving problems]

The structure of the present invention that solves the above conventional problems will be explained using drawings corresponding to embodiments.

First, in the method of the first invention, at the end of the oil conveyance work, the pig G ₁ is moved from one end 3 of the oil conveyance pipe A ₁ to the other end 4 using an inert gas stored in a compressed state in the gas tank 15. When the pig _G1 passes downstream through the gas recovery pipe _B3 , which is connected to the middle of the oil pipe _A1 , the gas recovery pipe _B is removed. Pig stopping means provided on the downstream side of ₃ (MV-2, MV-4, MV-3, CV-3...
etc.), the pig _G1 is stopped at a midway position of the oil feed pipe _A1 , and the oil remaining in the oil feed pipe _A1 in the movement range is replaced with inert gas. ,
In addition, when starting the next oil feeding operation, oil is forced into the oil feeding pipe _A1 from the one end 3, and the oil is used to guide the other pigs.
G ₂ is moved from the one end 3 of the oil feed pipe A ₁ toward the gas recovery pipe B ₃ by pushing the inert gas in the oil feed pipe A ₁ , and at the same time, the inert gas in the oil feed pipe A ₁ is removed. The structure is characterized in that the gas is recovered from the gas recovery pipe _b3 and stored in the gas tank 15 in a compressed state.

Further, in the device of the second invention, a pig launcher 3 attached to one end of an oil feed pipe a ₁ having a gas recovery pipe b ₃ equipped with a valve (CV-6) in the middle is provided with a valve CV-4.
A gas supply pipe _b1 having a valve (CV-2) is connected to an oil receiving pipe _a5 having a valve (CV-2), and a pig receiver 4 and a valve CV-3 are connected to the other end of the oil pipe _a1 . A gas tank ₁₅ is connected to the gas supply pipe _B1 , and a gas compressor 16 is provided between the gas tank 15 and the gas recovery pipe _B3 in communication therewith. The configuration was as follows.

[Effect]

In the method of the first invention, first, upon completion of the oil conveyance work, the pig G ₁ is moved from one end 3 of the oil conveyance pipe A ₁ to the other end 4 using an inert gas stored in a compressed state in the gas tank 15. The residual oil in the oil feed pipe A ₁ is pushed and moved toward the oil feed pipe A 1 , and when the pig G ₁ passes downstream through the gas recovery pipe B ₃ connected in the middle of the oil feed pipe A ₁ , the gas recovery pipe B is removed. Pig stopping means installed downstream of ₃ (MV-2, MV-4, MV-3, CV
-3..., etc.) by closing the above oil pipe a ₁
The pig _G1 is stopped at a midway position, and the oil remaining in the oil feed pipe _A1 in the pig movement range is replaced with inert gas.

The pig stopping means for closing may be the pig stopping means MV-2 provided on the downstream side near the recovery pipe b ₃ branch of the oil pipe, or the pig stopping means further downstream. Any device that can be stopped at an intermediate position of the oil pipe is sufficient, and the intermediate position of the oil pipe where the pig _G1 is stopped is the pig stopping means MV- provided on the downstream side near the branch of the recovery pipe _B3 . It may be on the upstream side of 2 or on the downstream side [that is, the position past the pig stop means MV-2 provided on the downstream side near the branch of the gas recovery pipe _b3 ].

By doing this, for example, oil pipes
It is possible to replace only the underwater part of a ₁ with inert gas, making it possible to complete the work in a short time and efficiently preventing the leakage of accumulated oil into the sea in the event of a break in the oil pipe. be able to.

In addition, if the pig G 1 is stopped by a pig stopping means other than the pig stopping means MV- ₂ provided on the downstream side near the recovery pipe B ₃ branch of the oil transmission pipe A ₁ , the recovery pipe B ₃ branches. If the pig is located downstream of the pig stopping means MV-2 provided downstream near the branch, the pig stopping means MV provided downstream near the branch.
-2 is preferably closed, but even if this pig stop means MV-2 is not closed, the oil between the downstream side of said pig _G1 and any closed pig stop means may become liquid. (incompressible fluid) and is in a sealed state by the pig G ₁ and the closed pig stop means, so even if the oil pipe on the upstream side of the pig G ₁ is damaged, the pig G ₁ does not move.

In addition, when starting the next oil feeding operation, oil is forced into the oil feeding pipe _A1 from the one end 3, and the oil is used to move the other pig _G2 from the one end ₃ of the oil feeding pipe A1. The inert gas in the oil feed pipe a ₁ is pushed and moved toward the gas recovery pipe b ₃ and the inert gas in the oil feed pipe a ₁ is recovered from the gas recovery pipe b ₃ and transferred to the gas tank 15. Store in compressed form.

In addition, the other pig G ₂ is the gas recovery pipe B ₃ of the oil feed pipe A ₁ .
After reaching the vicinity of the branch or the branch and inert gas recovery is completed, the pig stop means in the closed state is opened without stopping or stopping the other pig G ₂ , and both pigs G ₁ and G ₂ to the other end 4 of the oil feed pipe a ₁ , or when sending oil to a branch oil feed pipe of the oil feed pipe a ₁ , to the downstream side of the branch of the branch oil feed pipe,
The oil feeding operation may be performed by moving the oil from the one end portion 3. At this time, the recovery pipe of the above oil feed pipe _a1
b Pig stopping means installed on the downstream side near the _3- way branch
If the pig _G1 is stopped by a pig stopping means other than MV-2, and the pig stopping means MV-2, which is provided on the downstream side near the branch of the recovery pipe _B3 as a stability measure, is in a closed state, It is preferable to first open the pig stop means MV-2 provided on the downstream side near the branch of the recovery pipe _b3 , and then open the other pig stop means.

This prevents a large amount of inert gas from being released into the atmosphere, and therefore does not cause air pollution due to oil mist. Moreover, since the inert gas is stored in a compressed state, the gas tank 15 can be downsized. Furthermore, in the above-described replacement operation, the inert gas stored in the gas tank 15 in a compressed state is reused and the pig G ₂ is moved under compressed pressure, so there is no waste of both inert gas and energy.

After the inert gas recovery is completed, a small amount of inert gas is sandwiched between the above pigs G ₁ and G ₂ and reaches the other end 4 of the oil feed pipe A ₁ , but since it is a small amount, it usually ends up in the oil tank. There is no problem as the oil mist is separated by the air separator installed in front and is sufficiently removed in the vent tank. Furthermore, if the oil in front of pig G ₁ and the oil in the rear of pig G ₂ are different, the above-mentioned inert gas accompanying the pig will cause the oil to flow through the switching piping that leads the oil to separate oil tanks. It also has the effect of preventing these oils from being mixed together.

In the apparatus of the second invention, when replacing the accumulated oil in the oil pipe a ₁ with inert gas at the end of the oil transport work, _the valve CV-
With valve CV-3 of oil delivery pipe a ₆ closed, valve CV-2 of oil receiving pipe a ₅ is closed, and valve CV-4 of gas supply pipe b ₁ is opened to adjust the pressure. ,
Gas supply pipe b ₁ for compressed inert gas from gas tank 15
Push the pig G ₁ in the pig launcher 3 with an inert gas by sending the oil to the pig launcher ₃ through the oil pipe.
A ₁ oil delivery pipe as a means of moving and stopping the pig
By closing the valve CV-3 of _a6 , the pig is stopped while passing through the gas recovery pipe _b3 , and the oil remaining in the oil feed pipe _a1 in the pig movement range is replaced with inert gas.

By doing this, it is possible to replace only the upstream side of the gas recovery pipe B ₃ branch of the oil pipe A ₁ with inert gas, and the work can be completed in a short time. The oil between the downstream side of the pig G ₁ and the valve CV-3 of the oil delivery pipe A ₆ as a closed pig stop means is a liquid (incompressible fluid), and the oil between the pig G ₁ and the closed valve CV-3 is a liquid (incompressible fluid) Since the pig G 1 is in a sealed state by the pig stopping means CV-3, even if the oil pipe on the upstream side of the pig G ₁ is damaged, the pig G ₁ will not move and will not move when the oil pipe is damaged. It is possible to efficiently prevent accumulated oil from flowing into the sea.

In addition, when starting the next oil transfer operation, the gas supply pipe
While valve CV-4 of b ₁ and valve CV-3 of oil delivery pipe a ₆ remain closed, open valve CV-2 of oil receiving pipe a ₅ and valve CV-6 of gas recovery pipe b ₃ . and oil into the oil receiving pipe.
By sending oil to the pig launcher 3 through a ₅ , the other pig G ₂ in the pig launcher 3 is pushed with oil, and the oil is directed toward the pig _{G 1 stopped} in the oil feed pipe a ₁ . While moving inside the feed pipe a ₁ ,
The gas recovery compressor 16 is operated to recover the inert gas that had been filled in the oil feed pipe A ₁ from the gas recovery pipe B ₃ in the middle of the oil feed pipe A ₁ , and the gas tank 1 is recovered.
Compress it to 5 and put it in.

In addition, the other pig G ₂ is the gas recovery pipe B ₃ of the oil feed pipe A ₁ .
After the active gas recovery is completed by closing the valve CV-6 of the gas recovery pipe _B3 near the branching part or reaching the branching part, the valve CV- ₆ of the oil delivery pipe A6 as a means for stopping the pig in the closed state is closed. Open CV-3 and connect both pigs G ₁ and G ₂
The oil feeding operation may be carried out by moving the oil from the oil receiving pipe A5 to the pig receiver ₄ of the oil sending pipe _A1 . Furthermore, in oil conveying work, different types of oil can be conveyed by using the above-mentioned pig.

An embodiment of the present invention will be described in detail below based on the drawings.

FIG. 1 shows an embodiment of the overall configuration of an inert gas closed-loop replacement recovery apparatus according to the present invention.

In the figure, numeral 1 is an offshore tanker, and 2 and 2a are the first and second tankers installed at an onshore oil receiving base, respectively.
It is a base tank. A is an oil feed line of the present replacement recovery device, and B is an inert gas (hereinafter referred to as N ₂ gas) line.

Oil transmission line A consists of main oil transmission pipe _A1 and tanker 1.
Tip oil feed pipe that supplies oil to main oil feed pipe _A1
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 terminal oil transmission pipe A ₃ that receives oil transferred from the main oil transmission pipe A 1 into the first base tank 2, and a terminal oil transmission pipe A 3 that receives oil from the onshore part of the main oil transmission pipe A ₁ to the second base tank 2a. A receiving sub-oil pipe _A4 , a pig launch oil pipe (oil receiving pipe) _A5 , a pig recovery oil pipe _A6 , and first, second, and third bypass oil pipes _A7 , _a8 , _a9 and pressure equalizing pipe
It consists of a ₁₀ .

The main oil pipe _A1 is installed between the offshore cargo handling pier S and the onshore bearing 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. moreover,
The main oil pipe A ₁ has a first electric valve MV-1 near the pig launcher 3, a second electric valve MV-2 near the boundary between the offshore and land areas, and a third electric valve near the pig receiver 4. A fourth electric valve (pig stopping means) MV-4 is provided between the second 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 separated 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 2a. A flow control valve CV-1, an air separator 6a, and a flow meter 7a are provided in this order from the branch point C side. The pig launching oil feed pipe _a5 has a smaller diameter than the main oil feed pipe _a1 , and has one end connected to the approximate center of the pig launcher 3, and the other end connected to the fifth electric valve of the tip oil feed pipe _a2 .
5th valve between MV-5 and 6th electric valve MV-6
It is connected to a branch point near the electric valve MV-5, and a flow rate control valve CV-2 and an air separator 8 are installed in sequence from the pig launcher side. The pig recovery oil pipe _A6 has a smaller diameter than the main oil pipe _A1 , and there is a flow control valve CV-3 in the middle.
One end is connected to the pig receiver 4, and the other end is connected between the seventh electric valve MV-7 of the unended oil feed pipe _a3 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 this first bypass oil pipe _a7 (or the eighth
The diameter of the electric valve MV-8) is set to be extremely smaller than the diameter of the main oil pipe _A1 (or the diameter of the second electric valve MV-2), and is usually the same as 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-9 in the middle, and one end is connected to the fourth valve of the main oil pipe _a1 .
The electric valve MV-4 is connected between the branch point C of the sub oil feed pipe _A4 , and the other end is connected between the flow rate control valve CV-1 of the sub oil feed pipe _A4 and the air separator 6a. There is.

Further, the third bypass oil pipe _a9 has a tenth electric valve MV-10 in the middle, and one end is connected to the main oil pipe _a1.
The fourth electric valve MV-4 and the third electric valve MV
-3 near the fourth electric valve MV-4, and the other end is connected between the flow rate control valve CV-1 of the sub oil feed pipe _a4 and the air separator 6a.

The diameters of the second and third bypass oil pipes a ₈ and a ₉ (or the diameters of the ninth electric valve MV-9 and the tenth electric valve MV-10) are the same as those of the main oil transmission pipe a ₁ and the sub oil Diameter of feed pipe a ₄ (or 4th electric valve MV
-4 and the diameter of the flow rate control valve CV-1), and is usually set to about 0.5 to 5% in terms of area ratio. The pressure equalizing pipe _a10 has a small diameter like the above-mentioned bypass pipes _a7 , _a8 , and _a9 , and there is a 11th pipe in the middle.
It has an electric valve MV-11, and is piped as a bypass of the fourth electric valve MV-4 of the main oil pipe _a1 . In addition, in the figure, 9, 10, 10a are vent tanks, 11, 12, 13, 13a, 14,
14a is a drain pump.

On the other hand, the N ₂ gas system line 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.

The gas supply pipe _b1 has a gas pressure regulating valve CV-4 in the middle, and is piped between the _N2 gas tank 15 and the pig launcher 3. 1st
Gas recovery pipe b ₂ has an N ₂ gas compressor 16 and a first
and the second mist separator 17, 18 and gas pressure adjustment valve (valve) CV-5 into the _N2 gas tank 15.
They are installed sequentially from the side and are piped between the N ₂ gas tank 15 and the pig receiver 4. Second
Gas recovery pipe _B3 has a pressure adjustment valve (valve) in the middle.
CV-6 is attached, and one end is the first gas recovery pipe.
b ₂ is connected between both mist separators 17 and 18, and the other end is connected to the upstream side of the second electric valve MV-2 of the main oil feed pipe a ₁ (hereinafter referred to as the main oil pipe A 1 where the pig launcher 3 is located) The side is “upstream side”,
The side where the pig receiver 4 is located is referred to as the "downstream side") and is connected to a branch point on the upstream side close to the branch point N of the first bypass oil feed pipe _A7 . Pig reverse push tube B ₄ has a gas pressure adjustment valve in the middle.
It has a CV-7 and a 12th electric valve MV-12,
One end is connected to the _N2 gas tank 15, and the other end is connected to the branch point G between the third electric valve MV-3 of the main oil pipe _A1 and the branch point H of the third bypass oil pipe _A9 . It is plumbed. In addition, 14b in the figure is a drain pump that collects drain from the first mist separator 17.

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
8th pig detector PD ₈ is located near the upstream side of the branch point b of terminal oil pipe a ₃ on the upstream side of -3.
A third 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 movement speed in the main oil pipe _A1 , the second electric valve MV-2, and the third electric valve MV-3.
and the time required to open or close pressure regulating valve CV-6, these valves MV-2, MV-3,
It is set taking into consideration the flow rate characteristics when CV-6 is opened or closed.

In other words, the installation position of the Pig Detector PD ₂ is the offshore oil transmission pipe _A1 where the pig moves with _N2 gas on the upstream side and oil on the downstream side, as described below.
In the case of gas replacement, the speed of deceleration of the pig due to the closing operation of the second electric valve MV- ₂ by the pig passage detection signal sent to the second pig detector PD 2 is changed between the main oil feed pipe a ₁ and the second At the branching point with the recovery pipe _b3 , when the predetermined set speed Vmin is reached and the pig passes the installation position of the third pig detector _PD3 , the second electric valve MV-2 is completely closed. This is the position calculated from the first condition such that (see Figure 5), and the offshore oil transmission pipe a where the pig moves with oil on the upstream side and _N2 gas on the downstream side. In the case of gas recovery ₁ , the pressure control valve CV-6 starts to close and the third electric valve MV- starts to open in response to the pig passage detection signal from the second pig detector PD ₂ .
3, when the pig passes the branch point between the main oil feed pipe _a1 and the second gas recovery pipe _b3 , the pressure regulating valve CV-6 has just completed closing, and the third electric valve MV- 3 is required to be a position calculated from the second condition (see FIG. 5) that provides the timing to obtain the opening degree Qmin that allows a flow rate greater than the minimum flow rate of the pump of the tanker 1. However, in reality, the position calculated from the first condition and the position calculated from the second condition do not match, so the position calculated from the one condition that provides a larger distance from the second electric valve MV-2 2. Determine the installation position of Pig Detector PD ₂ , and use the timer to determine the difference in the closing timing of pressure control valve CV-6 and third electric valve MV-3 based on the difference between this and the position calculated from the other condition. (See Fig. 5 - In the case of Fig. 5, the first condition is when the distance from the second electric valve MV-2 is determined to be large.)

The third pig detector PD ₃ is located between the branch point d of the first bypass oil pipe a ₇ and the branch point of the second gas recovery pipe b ₃ in the main oil pipe a ₁ and is very close to said branch point d. located at the location. 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 pipe _A4 and the branch point C of the second bypass oil pipe _A8 is determined by the pig movement speed in the main oil pipe _A1 and the required closing of the flow rate control 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 time and flow rate characteristics when closed.

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 pipe _A8 and the branch point C of the sub oil pipe _A4 . 6th Pig Daytector PD ₆
is provided at a position close to the fourth electric valve MV-4 between the fourth electric valve MV- ₄ and the branch point H of the third bypass oil feed pipe _A9 in the main oil feed pipe A1, and is located near the fourth electric valve MV-4. Daytector PD ₇ has main oil pipe A ₁
It is provided at a position close to the branch point E between the branch point E of the third bypass oil feed pipe _A9 and the branch point G of the pig back-push pipe _B4 .

Next, a control system for each mechanism in the replacement recovery 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 pressure welding machine 16.

Since the N ₂ gas compressor 16 in this replacement recovery device is operated before and after receiving oil, its operation is not continuous operation but batch operation. Therefore N ₂
Automatic operation of the gas pressure welding machine 16 is desirable in terms of saving labor for the operator, and in this embodiment, it is operated as shown in the drawing. 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 manually operated by the operator, and the other blocks surrounded by two-dot chain lines are operated according to an automatic sequence. In addition, PS ₁ and PS ₂ in the figure are pressure switches provided in the mist separators 17 and 18, respectively, and PS ₃ and PS ₄ are the main oil pipes a ₁
A pressure switch is provided.

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 faced into the pig launcher 3. 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 pipe for launching the pig, b ₁ is the gas supply pipe, MV
-1 is the first electric valve, and G ₁ , G ₂ , and G ₃ 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 adopted in the replacement recovery device of this embodiment. In the figure, 30 is a sub-oil pipe of the oil pipe A.
A ₄ , Pig launch oil pipe A ₅ , Pig recovery oil pipe A ₆ ,
_{The oil or _ _}
N ₂ gas flow path 31 is a flow rate or pressure transmitter attached to the flow path 30, and each of the pipes a ₄ , a ₅ , a ₆ , b ₁ to
Transmitter FIC ₁ , FIC ₂ , FIC ₃ , PIC ₁ , attached to b ₄
Shows PIC ₂ , PIC ₃ , and PIC ₄ . 32 is the flow path 30
An electric valve installed in each of the pipes a ₄ , a ₅ , a ₆ , b ₁
Flow control valves CV-1 to CV-3 installed in ~b ₄ ,
Pressure regulating valves CV-4 to CV-7 are shown. 33 is a controller, 34 is a positioner, 35 is a start forced closing circuit, 36 is a contactor, 37 is a sequence 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, various control valves, may adopt a continuous control system using a diaphragm or air cylinder operating device powered by air pressure, but for practical use, it is possible to adopt a continuous control system using a diaphragm or air cylinder operating device powered by air pressure. A control valve powered by pneumatic pressure is recommended for systems that require an air source device and are planned to be installed over long distances with a small number of control loops, such as this replacement recovery device. This would not only require large-scale equipment but also be extremely uneconomical, so in this example, a method of controlling the fluid in the pipeline using electric valves was adopted in order to simplify the ancillary equipment. There is.

Next, the operation of the present replacement and recovery apparatus configured 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. There is.

(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-1
1 “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 main oil pipe a ₁ with N ₂ gas, first insert the pig G ₁ into the pig launcher 3 and open the first electric valve MV-1. Next, by opening the pressure control valve CV-4, the gas pressure accumulated in the _N2 gas tank 15 is
Pig G ₁ joins G ₁ and moves inside main oil pipe A ₁ while pushing the oil inside main oil pipe A ₁ .
It is replaced with _N2 gas. At this time, _N2 gas is supplied from the tank 15. While the pressure of _N2 gas is controlled by pressure control valve CV-4,
The flow rate on the oil side is controlled by a flow rate control valve CV-3, the differential pressure before and after the pig _G1 is kept constant, and the pig _G1 moves in the pipe at a constant traveling speed.
In addition, in order to prevent wear of pig G ₁ and to switch each electric valve within a fixed time, in this embodiment, the moving speed of pig G ₁ is constant at approximately 1.0.
m/sec flow rate adjustment valve CV-3
controlled by.

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 difference corresponding to the time required for the pig G ₁ to reach the branch point N of the first bypass oil pipe _A7 from the set position of the pig detector PD ₃ . 3 Pig detector PD ₃ sends a gas replacement end signal, so the eighth electric valve MV-8
and the third electric valve MV-3 is closed,
As shown in FIG. 5, the pig _G1 stops at the branch point N, and the inside of the main oil pipe _a1 located above the sea is replaced with _N2 gas.

At the same time as the replacement is completed, the pressure control valve CV-4
is closed, and the pressure control valve CV-6 is closed.
is opened and depressurization of the replacement gas is performed. 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, via mist separator 17
_N2 gas tank 1 by _N2 gas compressor 16
5 will be collected. That is, when the pig G ₁ passes through the second pig detector PD ₂ and is detected, the N ₂ gas compressor 16 is in a no-load operation with the electric motor started, and the pressure regulating valve CV- 6 opens and starts pressure control of the mist separator 17, load operation is started by a signal from the first pressure switch PS ₁ installed in the mist separator 17, and the replacement gas in the main recovery pipe a ₁ is sucked. . When the pressure of the replacement gas in the sea part of the main oil pipe _a1 is reduced to the set pressure of the third pressure switch _PS3 installed in the sea part of the main oil pipe _a1 , the pressure from the pressure switch _PS3 is reduced. N ₂ by signal
The gas compressor 16 is automatically stopped, the pressure control valve CV-6 is closed, and the pressure reduction operation is completed.

In the oil transfer work associated with _N2 gas replacement in the above, the pig G ₁ is accurately stopped at a fixed position on the upstream side of the second electric valve MV- ₂ in the main oil transfer pipe A 1 (in this replacement recovery equipment, For example, during the _N2 gas replacement in the offshore part of the main oil transmission pipe _A1 and the _N2 gas replacement at the branch to the second base tank 2a (described later), it is necessary to accurately grasp the amount of remaining oil in the pipe for bonded processing. This operation is required in order to prevent the pig _G1 from biting into the second electric valve MV-2 which is operating in the closing direction. As mentioned above, in this embodiment, the diameter of the eighth electric valve MV-8 is 0.5 in area ratio with respect to the second electric valve MV-2.
It is set to about ~5%, but this is because when the pig G 1 approaches the branch point of the second gas recovery pipe b ₃ in the main oil transmission pipe a ₁ , the difference between _{the pig G 1 and} the branch point is Pig G ₁ from 〓 between the corner part
If the amount of displacement gas leaking into the forward oil feed pipe _A1 is balanced with the amount of oil sent from the first bypass oil feed pipe _A7 , the pig _G1 will stop at the branch, so the pig The flow rate that G ₁ does not stop midway flows to the first bypass oil pipe A ₇ , and the pig
When G ₁ stops at the branch part 2 of the first bypass oil pipe A ₇ , the branch part 2 is completely sealed by the pig G ₁ to prevent displacement gas from leaking into the first bypass oil pipe A ₇ . It is set in consideration of the above, and changes depending on conditions such as the physical properties of the transfer fluid and the diameter of the transfer pipe.

Method for recovering _N2 gas in oil pipes (when transporting oil through gas-replaced oil pipes) The opening/closing status of each valve after _N2 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-1
1 “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 After gas replacement, the status of main oil pipe a ₁ is determined by pigging it to the upstream side of the second electric valve MV-2.
G ₁ is stopped and the upstream of pig G ₁ is N ₂
replaced with 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 MV-2 at the outlet of the pig launcher 3, the flow rate adjustment valve CV-2, and the pressure adjustment valve CV- Open 6. When oil is started to be received by the oil pump (not shown) of the tanker 1 in this state, the oil passes through the air separator 8 and is drawn into the pig launcher 3 while the flow rate is controlled by the flow control valve CV-2. When hydraulic pressure is applied to the pig G ₂ in the pig launcher 3, the pig G ₂ enters the main oil pipe A ₁ and moves, and at the same time, the movement of this pig G ₂ is
The Pig Detector PD ₁ detects this, automatically starts the _N2 gas compressor 16, and activates the pressure control valve CV.
-6. The replacement gas in the main oil pipe a ₁ is recovered to the N ₂ gas tank 15 by the N ₂ gas compressor 16 via the mist separator 17 .

In this case, the flow rate of the oil received from the tanker 1 is controlled by the flow rate control valve CV-2.If the set value of the flow rate is equal to or lower than the suction capacity of the _N2 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
The _N2 gas pressure in a ₁ is as the pig _G2 moves,
Although it gradually increases, the suction pressure of the _N2 gas compressor 16 is controlled by the pressure control valve CV-6 and the load is kept constant, so it is _less than Oil can be accepted if the oil pump discharge pressure of tanker ₁ has a capacity higher than the N ₂ gas pressure that has risen at branch point 1).

Next, Pig G ₂ is the second Pig Detector PD ₂
When detected, the pressure control valve CV is automatically operated as shown in Figure 5.
-6 is closed, the third electric valve MV-3 is opened, and N ₂ gas recovery is completed. In addition, Pig G ₂ , which is pushed by oil and moves, is the second gas recovery pipe.
When passing through the branch point b ₃ , the pressure control valve CV-6 is completely closed at the same time, so a large amount of oil flows through the second gas recovery pipe b ₃ to the mist separator 17. It does not flow into. Even after _N2 gas recovery is completed, Pig _G2 does not stop moving, and the oil it received last time,
The pigs G ₁ and G ₂ move inside the main oil pipe a ₁ toward the pig receiver 4 side with the oil received this time. When the ninth pig detector PD ₉ at the inlet of the pig receiver 4 detects passage of the upstream pig G ₂ , the third electric valve MV-3
is closed, the seventh electric valve MV-7 is opened, and the two pigs G ₁ and G ₂ are housed in the pig receiver 4.

Next, the sixth electric valve MV-6 opens, and the flow rate control valve CV-2 and the first electric valve MV open.
-1 is closed and normal oil reception begins.

(2) Gas recovery and replacement methods for all oil pipelines.

Method for recovering gas in oil pipes (when replacing gas in oil pipes is recovered and transporting oil) 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-1
1 “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” Insert pig G ₁ into pig launcher 3.
Next, the loading arm's original fifth electric valve MV-5, the pig launcher 3 outlet first outlet valve MV-1, and the third electric valve MV-
3. Open flow control valve CV-2 and pressure control valve CV-5. Tanker 1 in this state
When the pump starts receiving oil, the oil flows through the air separator 8 and is sent to the pig launcher 3 while the flow rate is controlled by the flow rate control valve CV-2. When the oil feeding pressure is applied to the pig G ₁ in the pig launcher 3, G ₁ moves, and when the first pig detector PD ₁ detects the passage of the pig G ₁ , the N ₂ gas compressor 16 is activated, and the displacement gas in the main oil feed a ₁ is transferred to the pressure regulating valve CV-
5. The _N2 gas is recovered into the gas tank 15 by the N2 gas compressor 16 via the mist separators 18 and 17, 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 that has pushed the pig _G1 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 rate control valve CV-2 and the first electric valve MV open.
-1 is closed and normal oil reception is started. In addition, when recovering N ₂ gas, the mist separators 17 and 18 separate oil from the N ₂ gas, but the mist separators 17 and 18
The oil stagnant in each drain pump 14b,
14 and sent into the oil 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-1
1 “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 entire length of the main oil pipe A ₁ with N ₂ gas, first insert the pig G ₁ into the pig launcher 3, and then open the first electric valve MV-1 and the third electric valve. Open valve MV-3. Pressure regulating valve CV
-4 is opened, the gas pressure accumulated in the _N2 gas tank 15 is applied to the pig _G2 , and while pushing the oil in the main oil pipe _A1 , the pig _G2 pumps _N2 gas inside the main oil pipe _A1 . The oil in the main oil pipe _A1 flows through the pig recovery oil pipe _A6 , and is controlled by the flow rate control valve CV-3.
Sent to base tank 2. When the pig G ₂ is detected by the ninth pig detector PD ₉ at the inlet of the pig receiver 4, the flow control valve CV-3 and the pressure control valve CV-
4 is closed, the total length of main oil pipe _A1 is
It will be in a state where it is replaced with N ₂ gas. after that,
The pressure control valve CV-5 is opened, and the inside of the main oil pipe _A1 is replaced in the same way as in the _N2 gas replacement method in the sea part of the main oil pipe.
After the N ₂ gas is depressurized, 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
(In the case of _N2 gas replacement) Collect the replacement gas upstream of the fourth electric valve MV-4 and pass it to the second base tank 2a via the recovered main oil pipe _A1 and sub oil pipe _A4 . carry out oil transportation. 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-1
1 “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
MV-3, flow control valve CV-2, and pressure control valve CV-5 are opened. When the tanker 1's oil feed pump starts receiving oil in this state, oil flows into the pig launch oil feed pipe _a5 ,
Flow through air separator 8 and flow rate adjustment valve CV-2
It is fed into the pig launcher 3 while its flow rate is controlled by . When the oil feed pressure is applied to the pig G ₁ in the pig launcher 3, the pig G ₁ enters the main oil feed pipe a ₁ and moves toward the downstream side within the oil feed pipe a ₁ . At this time, move pig G ₁ first.
The Pig Detector PD ₁ detects this and starts the N ₂ gas compressor 16, and the replacement gas in the main oil pipe a ₁ is compressed into N ₂ gas via the pressure control valve CV-5 and the mist separators 18 and 17. The gas is collected by the machine 16 into the _N2 gas tank 15. 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 oil feed pipe _a4 . Pig _G1 , which has been running inside the main oil pipe _A1 , is connected to the fourth electric valve MV-
4 runs inside the main oil feed pipe A ₁ until it is completely closed, and at the point 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 ₄ are moved. It stops between the branch point and the 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 pressure control valve CV-
5 is closed.

Next, insert the pig G ₁ that is stopped between the seventh pig detector PD ₇ in the main oil pipe A 1 and the branch point of the pig reverse push pipe B ₄ into the main oil pipe A _{1 .}
In order to return to the branching point _E with the third bypass oil feed pipe _A9 , first, as shown in FIG.
10 will be held. Next, turn the pig back-push tube b ₄ .
12 Electric valve MV-12 and pressure regulating valve
CV-7 is opened, and the displacement gas stored in the N ₂ gas tank 15 flows into the main oil pipe a ₁ through the pig reverse push pipe b _{4 .}
When the pig G ₁ that is stopped inside is pressed, the pig G ₁ moves upstream, and the oil on the upstream side of the pig G ₁ passes through the third bypass oil pipe A ₉ and flows into the sub oil pipe A ₄ and then sent to the second base tank 2a.

The passage of the pig G ₁ is detected by the seventh pig detector PD _7. A timer is used to set a time difference corresponding to the time required for the pig G ₁ to reach the branch point H from the installation position of the seventh pig detector PD ₇ . , a pig reverse push end signal is sent from the 7th pig detector PD _7, and the 10th electric valve MV-10 and the 12th electric valve MV-12 are activated.
and pressure control valve CV-7 is 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 to push back the pig _G1 and stop it at a certain position (branch point H) is to
This is similar to the case where the pig is stopped at the branch point N of the first bypass oil pipe _A7 during _N2 gas replacement.

Note that during the pig reverse push operation, the first electric valve MV-1 closes and the sixth electric valve MV-6 closes.
opens, the flow rate control valve CV-2 closes, and the oil from the tanker 1 enters the main oil supply pipe _A1 from the tip oil supply pipe _A2 , and is transferred to the second base tank 2a.
Regular oil intake will be carried out.

_N2 gas replacement for the second base tank 2a.

The oil on the upstream side of the fourth electric valve MV-4 (the downstream side of the fourth electric valve MV-4 has been replaced with _N2 gas) is recovered into the second base tank 2a, and after recovery, the oil is transferred to the main oil transmission pipe _a1. Collect the two pigs inserted into the pig receiver 4.

The opening/closing status of each valve before _N2 gas replacement is as follows.

(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-1
1 “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 ₂ 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 pumped.
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
When it reaches near the branch point H of A ₈ , the fifth pig detector PD ₅ detects this and uses this detection signal to pig the branch point H of the sub oil pipe A ₄ .
It is confirmed that G ₂ has passed.

After the fifth pig detector PD ₅ detects the passage of the pig G ₂ , the pig G ₂ moves from the installation position of the pig detector PD ₅ to the second bypass oil pipe a ₈
The 5th pig day detector PD ₅
A gas replacement end signal is sent from the 9th electric valve MV-9 and the pressure control valve CV-.
4 is closed, the pig _G2 will definitely stop at the branch point of the second bypass oil pipe _A8 ,
The upstream side of the fourth electric valve MV-4 of the main oil pipe _a1 is replaced with _N2 gas.

As mentioned above, the operation to decelerate pig _G2 and stop it at a certain position (branch point H) and the purpose _of the operation are as follows:
When replacing _N2 gas, connect the pig to the first bypass oil pipe.
This is the same as stopping at branch point 2 in _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 these pigs come into close contact with the fourth electric valve MV-4, causing the opening operation of the valve MV-4. The upstream side of pig G ₂ and the downstream side of pig G ₁ may be It is necessary to equalize the _N2 gas pressure on both sides. This pressure equalization operation is performed using the 11th motorized valve MV of the pressure equalization pipe _A10 .
-11 is opened, the main oil pipe _a1 on the upstream side of pig _G2 and the downstream side of pig _G1 are communicated with each other, and the _N2 gas on the high pressure side is released to the low pressure side.

When the pressure equalization operation is completed, the 11th electric valve MV
-11 will be closed.

After doing this, the fourth electric valve MV-4,
Third electric valve MV-3 and pressure control valve
When CV-4 and CV-5 are opened, _N2 gas compressor 16
is activated, and the pigs G ₁ and G ₂ start moving toward the pig receiver 4 inside the main oil pipe a ₁ . The _N2 gas on the downstream side of pig _G1 in main oil pipe _A1 is supplied through pressure control valve CV-5 and mist separator 18,1.
7 and is recovered to the N ₂ gas tank 15 by the N ₂ gas compressor 16 as described above. When the passage of the upstream pig G ₂ is detected by the ninth pig detector PD ₉ at the inlet of the pig receiver 4, the pressure regulating valve CV-4 is closed, and after further pressure reduction work, the pressure regulating valve CV-4 is closed. -5 and 1st
The electric valve MV-1 and the third electric valve MV-3 are closed, and the work of collecting the pigs G ₁ and G ₂ into the pig receiver 4 is completed. Note that a small amount of oil remaining between the pigs G ₁ and G ₂ is separated by the mist separator 18 and collected into the first base tank 2 by the drain pump 14 .

〔Effect of the invention〕

The first invention is to move the pig from one end of the oil pipe to the other end by pushing the remaining oil in the oil pipe using inert gas stored in a compressed state in a gas tank when oil transport work is completed. When the pig passes downstream through a gas recovery pipe connected to the middle of the oil pipe, a pig stopping means provided on the downstream side of the gas recovery pipe is closed to stop the pipe from running midway through the oil pipe. Stop the pig at the above position, replace the oil remaining in the oil pipe within the pig movement range with inert gas, and then pump the oil from the one end above when starting the next oil pipe. The oil is press-fitted into the pipe, and the oil moves the other pig from the one end of the oil pipe toward the gas recovery pipe by pushing the inert gas in the oil pipe. Since the gas is recovered from the gas recovery pipe and stored in the gas tank in a compressed state, the following effects can be obtained regardless of the structure of the inert gas channel.

In other words, (i) For example, it is possible to replace only the underwater part of an oil transmission pipe with inert gas, which allows the work to be completed in a short time, and also prevents stagnant oil from being pumped into the sea when an oil transmission pipe breaks, etc. It is possible to efficiently prevent the outflow of. (ii) It does not release a large amount of inert gas into the atmosphere, does not cause air pollution due to oil mist, and is economical because there is no need to install air pollution prevention equipment. (iii) Since the inert gas is stored in a compressed state, the gas tank can be made smaller and the equipment area can be reduced. (iv)
Since the inert gas stored in a compressed state in a gas tank is used as it is to move the pig under compressed pressure and replace oil with inert gas, it is rational and there is no waste of inert gas or energy. Further, the amount of replenishment of inert gas can be reduced.

Further, in a second invention, a gas supply pipe having a valve and an oil receiving pipe having a valve are connected to a pig launcher attached to one end of an oil supply pipe having a gas recovery pipe having a valve in the middle, and the oil receiving pipe has a valve. The other end of the feed pipe is equipped with a pig receiver and an oil delivery pipe having a valve, and a gas tank is connected to the gas supply pipe, and a gas tank is connected between the gas tank and the gas recovery pipe. Because the system is equipped with a gas compressor connected to This problem has been solved, and the inert gas replacement and recovery equipment has been downsized.

That is, it can be applied to all types of oil, including volatile oil types, and is safe and does not deteriorate the quality of the oil. Of course, there is no risk of air pollution from wastewater treatment equipment, so there is no need to install equipment to prevent pollution. Since the entire oil feeding process is installed in a closed system, operating costs are low, and the loss of inert gas is minimal, so replenishment is less and labor can be saved. Since the inert gas in the oil pipe is compressed by a gas compressor and put into the gas tank, the gas tank can be made smaller and the pig can be moved directly using the compressed inert gas. It has various excellent effects such as being efficient and rational. Since it is configured to partially replace and recover inert gas, it is possible to replace only the underwater portion of the oil pipe with inert gas, minimizing the amount of inert gas used, and The replacement recovery equipment can be downsized and operating costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of an inert gas replacement and recovery device according to the present invention, Fig. 2 is a sequence block diagram of a fully automatic system for an _N2 gas compressor,
Fig. 3 is an explanatory diagram of the automatic firing system for large pigs, Fig. 4 is a block diagram showing the pressure and flow rate control situation using a large electric valve, and Figs.
FIG. 6 is an explanatory diagram of the operation of stopping the pig on the upstream side of the electric valve. 3...Pig launcher, 4...Pig receiver, 15... _N2 gas tank, 16... _N2 gas compressor, _a1 ...Main oil feed pipe (oil feed pipe), _a5 ...Oil feed for pig launch Pipe (oil receiving pipe), a ₆ ... Oil pipe for pig recovery (oil sending pipe), b ₁ ... Gas supply pipe, b ₃ ...
Second gas recovery pipe (gas recovery pipe), CV-2...flow control valve (valve), CV-4, CV-6...pressure control valve (valve), CV-3...flow control valve (valve) Pig stopping means), MV-2, MV-4, MV
-3...Electric valve (pig stopping means).

Claims (1)

[Scope of Claims] 1. At the end of the oil transport work, the pig is directed from one end of the oil pipe to the other end using an inert gas stored in a compressed state in the gas tank to remove residual oil in the oil pipe. The pig is pushed and moved, and when the pig passes downstream through a gas recovery pipe connected to the middle of the oil feed pipe, the oil feed pipe is closed by closing the pig stop means provided downstream of the gas recovery pipe. The pig is stopped at a midpoint position, and the remaining oil in the oil pipe within the pig movement range is replaced with inert gas, and when the next oil pipe is started, the oil is removed from the one end above. The oil is press-fitted into the oil pipe and the oil moves the other pig from the one end of the oil pipe towards the gas recovery pipe by pushing the inert gas in the oil pipe. A method for replacing and recovering an inert gas, comprising recovering the gas from the gas recovery pipe and storing the gas in a compressed state in the gas tank. 2. A gas supply pipe with a valve and an oil receiving pipe with a valve are connected to a pig launcher attached to one end of the oil pipe that has a gas recovery pipe with a valve in the middle, and the other end of the oil pipe has a gas recovery pipe with a valve. is equipped with a pig receiver and an oil delivery pipe having a valve, and a gas tank is connected to the gas supply pipe, and a gas compression pipe is connected between the gas tank and the gas recovery pipe. 1. An inert gas replacement and recovery device characterized by being equipped with an inert gas replacement and recovery device.