JPH0618146Y2 - LPG constant pressure liquid sending device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a device for sending a liquid from a room temperature tank of LPG (liquefied petroleum gas) to a supply destination with a constant pressure. Accordingly, the pump power is minimized.

[Conventional technology]

One of the tanks that stores LPG (liquefied petroleum gas) such as propane and butane is a room temperature tank such as a spherical tank,
In many cases, it is necessary to always supply a constant pressure from these room temperature tanks to consumers.

Therefore, as the LPG liquid sending device, a liquid sending pump is attached to a normal temperature tank, and the liquid sending pump pressurizes the liquid to a predetermined pressure and sends it to the supply destination.

[Problems to be solved by the invention]

However, in such an LPG storage facility, LPG such as propane and butane is stored in a room temperature tank, so the internal pressure changes depending on the outside temperature.
In summer it is about 12kg / cm ² , while in winter it is about 4kg / cm ² , and in Butane it is about 5kg / cm ^{2 in the} summer,
It becomes 0kg / cm ^{2 in} winter (both gauge pressure).

For this reason, the capacity of the liquid feed pump must be determined on the basis of the winter season when the pressure difference with the destination to which one-side pressure is fed is maximum, and the capacity of the liquid feed pump becomes excessive in the summer.

Therefore, in the summer, a valve is provided on the discharge side of the liquid feed pump to adjust the valve, and the pump power of the liquid feed pump is wasted.

That is, as shown in FIG. 2 which shows the performance curve of the liquid delivery pump, when the actual lift in winter when the suction pressure is low is h,
For example, the amount Q of water corresponding to the intersection A of the resistance curve R of the pipeline or the like and the head H can be sent, and the axial horsepower at that time is a on the diagram S.
On the other hand, when the suction pressure is high and drops to the actual pump head h ′ as in the summer, the resistance of the pipeline increases because the valve is throttled and the resistance curve becomes R ″. If the same amount of water Q is secured, the axial horsepower of the liquid delivery pump remains a on the line S, and the pump power is wasted by the amount shown by the diagonal lines in the figure.

In particular, in a facility that supplies propane and butane with a single liquid feed pump by switching valves, the pressure difference between summer and winter becomes large, resulting in much waste of pump power and an increase in operating costs. I will end up.

The present invention has been made in view of the above problems in the prior art, and it is an object of the present invention to provide an LPG constant pressure liquid-feeding device that does not waste pump power according to a change in suction pressure and can reduce operating costs. To do.

[Means for solving problems]

In order to solve the above problems, the present invention is directed to an apparatus for feeding LPG from a plurality of room temperature tanks that store LPG at room temperature to a supply destination at a constant pressure, and a method for sucking LPG from the room temperature tank and pumping the LPG to the supply destination. A pump, a flow rate detector for detecting a delivery amount from the liquid delivery pump, a valve provided between the liquid delivery pump and a plurality of room temperature tanks for switching a room temperature tank for delivering LPG, and detection of an open / closed state And a pressure detector that detects the pressure in each room temperature tank,
Among these pressure detectors, the changeover switch that changes over the detection signal from the room temperature tank that sends out the LPG, and the suction pressure detection signal and the flow rate detection signal that are input via this changeover switch control the rotation speed of the liquid delivery pump. And a rotation speed controller for keeping the discharge pressure constant.

[Action]

The pressure in the room temperature tank where LPG is stored is detected by the pressure detector, and the rotation speed of the liquid feed pump is controlled by the rotation speed controller to match the required discharge pressure. By operating with limited pump power, waste is saved and operating costs are saved.

Further, even when different storage liquids are stored in a plurality of room temperature tanks, one liquid feed pump detects the amount of the liquid feed and controls the number of rotations so that a constant pressure can be maintained and pressure fed. become.

〔Example〕

An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the LPG constant pressure liquid feeding device of the present invention.

This LPG constant-pressure liquid-sending device 10 has a single liquid-sending pump 15 by switching two valves 13 and 14 from two room-temperature tanks 11 and 12 that store propane and butane, respectively.
The pressure is fed to the supply destination 16.

As the room temperature tanks 11 and 12, for example, spherical tanks are used, which are pressure resistant containers that can be stored at room temperature.

Valves 1 are provided on the pay-out pipes of these room temperature tanks 11 and 12, respectively.
3, 14 are attached and connected to the suction side of the liquid feed pump 15, and detectors for detecting the open / closed state of the valves are attached to these valves 13 and 14, and input to the rotation speed controller 17. I am doing it.

Further, pressure detectors 18 and 19 for detecting the internal pressure are attached to the room temperature tanks 11 and 12, respectively, and a detection signal is input to the rotation speed controller 17 via a changeover switch 20. .

Further, on the discharge side of the liquid feed pump 15, a flow rate detector 21 for detecting the amount of liquid fed to the supply destination 16 is provided, and a detection signal is input to the rotation speed controller 17, and A pressure detector 22 is also attached to the supply destination 16 and a detection signal is input to the rotation speed controller 17.

In the rotation speed controller 17, the pressure detectors 18 and 19 used for liquid transfer to the room temperature tanks 11 and 12 are selected by the changeover switch 20 to input a detection signal, and the required discharge is made from this pressure signal. The number of rotations of the liquid feed pump 15 corresponding to the pressure is calculated, and a control signal is output to the liquid feed pump 15 to control the number of rotations of the liquid feed pump 15.

Further, even when the pressure that should be made constant based on the detection signal of the pressure detector 22 of the supply destination 16 changes, the rotation speed controller 17 controls the rotation speed of the liquid feed pump 15 to keep it constant. To do.

According to the LPG constant pressure liquid-feeding device 10 configured as described above, 2
If one of the two room temperature tanks 11 and 12 to be pressure-fed, for example, the changeover switch 20 is switched to detect the pressure of the room temperature tank 11 and the valve 13 leading to the liquid supply pump 15 is opened, Controller 17
And the liquid delivery pump 15 that matches the discharge pressure required for the supply destination 16
Is calculated, and a control signal is output to an inverter or the like of the power supply device of the driving motor of the liquid feed pump 15 to operate the liquid feed pump 15.

This will be described with reference to the performance curve of the liquid delivery pump 15 shown in FIG.

First, when the pressure in the room temperature tank 11 is low in winter or the like, it is necessary to increase the discharge pressure to the supply destination 16, and assuming that the actual head is h, the resistance curve R is obtained from the piping system or the like. .

Further, when the number of rotations of the liquid feed pump 15 is N, the lift curve H and the shaft horsepower diagram S are also as shown in the figure, and the pumping amount is Q and the shaft horsepower is point a on the diagram S. Becomes

Next, when the pressure in the room temperature tank 11 rises in the summer or the like, the suction pressure of the liquid feed pump 15 rises and the actual lift decreases to h ', while the resistance of the piping system changes. Since this is not done, the resistance curve R is translated into a resistance curve R '(broken line).

Also in this case, if the same pumping amount Q as in the winter season is secured, the intersection X between the pumping amount Q and the resistance curve R'is obtained.

Therefore, the rotation speed controller 17 calculates the rotation speed N ′ at which the rotation speed of the liquid feed pump 15 is lowered to obtain a lift curve H ′ (broken line) passing through the point X, and the liquid feed pump is operated at this rotation speed N ′. Drive 15

The shaft horsepower corresponding to the lift curve H'when the number of revolutions is N'is a straight line S '(broken line), and the shaft horsepower required when the pumping amount is Q is a point b on the diagram S'. It can be seen that the pump power decreases.

In this way, the pressures in the room temperature tanks 11 and 12 are detected by the pressure detectors 18 and 19, and the number of rotations N and N'of the liquid feed pump 15 corresponding to the discharge pressure required at the supply destination 16 is obtained to operate. The pump can be operated efficiently without waste of power.

In the above embodiment, the case where two normal temperature tanks are switched and used by one liquid feed pump has been described, but it is also applicable when a plurality of normal temperature tanks are switched and used. Also, LPG is not limited to propane and butane.

[Effect of device]

As described above in detail with reference to the embodiment, according to the LPG constant-pressure liquid-feeding device of the present invention, the pressure in the room temperature tank storing LPG is detected by the pressure detector and required by the rotation speed controller. Since the rotation speed of the liquid feed pump is controlled so as to match the discharge pressure, the liquid feed pump can always be operated with the minimum required pump power, and operating costs can be saved. Further, even when different storage liquids are stored in a plurality of room temperature tanks, a single liquid feed pump detects the delivery amount and controls the number of revolutions to maintain a constant pressure for pressure delivery. You can

[Brief description of drawings]

FIG. 1 and FIG. 2 are a schematic configuration diagram and an explanatory diagram of a performance curve according to an embodiment of the LPG constant pressure liquid sending device of the present invention. 10 ... LPG constant pressure liquid sending device, 11, 12 ... Room temperature tank,
13, 14 ... Valve, 15 ... Liquid feed pump, 16 ... Supply destination, 1
7 ... Revolution speed controller, 18, 19, 22 ... Pressure detector, 2
0 ... Changeover switch, 21 ... Flow rate detector.

Claims (1)

[Scope of utility model registration request] 1. An apparatus for feeding LPG from a plurality of room temperature tanks that store LPG in a room temperature state to a supply destination at a constant pressure, and a liquid supply pump that sucks LPG from the room temperature tank and pressure-transmits the LPG to the supply destination. A flow rate detector for detecting the amount delivered from the pump, a valve provided between the liquid delivery pump and a plurality of room temperature tanks for switching the room temperature tank for delivering the LPG and a detector for opening / closing state, and each room temperature tank The pressure detectors that detect the internal pressure, respectively, and L of these pressure detectors
The changeover switch that switches the detection signal from the room temperature tank that sends out PG, and the suction pressure detection signal and the flow rate detection signal that are input via this changeover switch are used to control the number of revolutions of the liquid feed pump to keep the discharge pressure constant. The LPG constant pressure liquid-feeding device, comprising: