JPS6031254B2 - Differential pressure converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential pressure converter (D, P, T
In particular, the present invention relates to a differential pressure converting device that is provided with an overload protection device to prevent damage to D, P, and T and modulation of accuracy due to overload.

D, P, and T are instruments that detect the difference in pressure between the A side and the B side using strain gauges. As shown in FIG. 1, in the conventional OPTI, the bellows 2 receives the differential pressure applied to the A side and the B side, and applies a strain corresponding to the differential pressure to the strain plate 4 provided at the center thereof.

A strain gauge is attached to the strain plate 4, and an unbalanced voltage is obtained by the strain of the strain gauge, and this value is converted into a differential pressure. In the above-mentioned measurement, in order to perform the measurement accurately and accurately, it is necessary to avoid giving an excessive load to the DPTI. In the conventional type, the bellows 2 is used as a protection mechanism against overload.
There is a stopper 3 that suppresses the deformation of the strain plate 4.
is designed so that it does not deform. The bellows 2 can withstand overloads greater than this, and the safe permissible load is determined in consideration of the withstand pressure of the bellows 2. However, since DPTI is generally intended for low differential pressure measurement, the safe allowable load is only several times the measurement rating.

Nowadays, when it is required to detect minute differential pressures in high-pressure lines, this safe allowable load is not sufficient.

In other words, since high-pressure lines have high atmospheric pressure, this safe allowable load may be exceeded if a leak occurs in the measurement system piping, or if one side is modulated when measuring differential pressure from a different pressure source. There are many things. The present invention has been made in view of the above-mentioned circumstances, and is capable of withstanding overloads that conventional differential pressure converters cannot withstand without being destroyed, and that can detect the differential pressure with high precision. The purpose is to obtain a conversion device.

That is, without relying on the withstand pressure of the parts, the differential pressure is made zero in the event of an overload, so that the bellows, which is the lifeblood of the DPT, is never overloaded.

An embodiment of the present invention will be described below with reference to the drawings. The differential pressure converter of the present invention comprises an OPTI, a three-point set valve 5, and a protection device 22, as shown in FIG.

(The three-point set valve 5 is a DPT used when the measurement is stopped.
It is a pause device for I. ) A protection device 22 is installed in parallel with the OPTI and closer to the pressure source than the DPTI. The protection device 22 is configured as follows.

That is, the pressure guide pipes 7 and 6 on the A and B sides are connected to both ends of the sill 20 in parallel with the differential pressure converter 1. A piston 23 is slidably disposed within the cylinder 20, and the inner space of the cylinder 20 is divided into two parts by the piston 23.
It is divided. A seal ring 21 is attached to a contact portion around the piston 23 with the cylinder 20, and is designed to seal a gap between the sliding surfaces of the piston 23 and the cylinder 20. A spring 24 is fitted between both ends of the piston 23 and both ends of the cylinder 20. Bypass circuits 25 are provided on the side walls near both ends of the cylinder 20, and when the piston 23 moves near the ends of the cylinder 20, the internal spaces of the cylinder 20 at both ends of the piston 23 communicate through this bypass circuit 25. It looks like this. In this differential pressure converter, when the differential pressure between the pressure guide tubes 7 and 6 on each side of A and B is small, the piston 23 is located at the center of the cylinder 20 by the spring 24, and the cylinder 20 is moved as shown in FIG. The space is divided into two spaces connected to each other on the A and B sides. When the differential pressure increases, the piston 23 moves against the force of the spring 24 due to the difference in pressure applied to both sides of the piston 23.

When the piston 23 passes the inlet of the bypass circuit 25, the two spaces on both sides A and B are connected through the bypass circuit 25, so a flow is generated from the high pressure side to the low pressure side, and is applied to both ends of the differential pressure converter 1. This prevents the differential pressure from becoming excessive. If the subsequent differential pressure on both sides of the piston 23 becomes smaller,
It returns to its original state (the state shown in FIG. 2) by the force of the spring 24. As explained above, the differential pressure detection device of the present invention has D
It is possible to protect the DPT from unexpected overloads due to PT operation errors, overloads due to pressure transient phenomena accompanying the operation of the pond, or abnormalities in loop system equipment.

Furthermore, since it can always be used within the measurement range, the life of the DPT is extended, zero shift does not occur, and performance such as linearity is maintained.

Moreover, in this case, just using a pair of cylinders and pistons can handle high pressure on either side.
It is possible to provide a differential pressure converter that has a simple structure, is compact, and is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a conventional differential pressure converting device, and FIG. 2 is a schematic explanatory diagram of a differential pressure converting device of the present invention. 1... Differential pressure converter, 6, 7... Impulse tube, 20... Cylinder, 21... Seal ring, 22
...Protective device, 23...Piston, 24...
...Spring, 25. ．．・．． ．．・Bypass circuit. Figure 1 Figure 2

Claims (1)

[Claims] 1. A differential pressure converter that detects the pressure difference between two fluids, a cylinder connected in parallel to the differential pressure converter, and a cylinder that divides the internal space of the cylinder into two spaces each connected to the two fluids. The cylinder includes a piston that slides within the cylinder, and a spring provided between the piston and each end face of the cylinder, and a spring is provided near both ends of the side wall of the cylinder when the piston moves near both ends of the cylinder. A differential pressure converting device characterized in that it has a bypass circuit that connects two spaces within the cylinder.