Method and apparatus for safeguarding pipe-lines against an inadmissibly high internal compressive load by a control valve with a pneumatic drive

Claim 1

A method for safeguarding a pipe-line against an inadmissibly high internal pressure and an inadmissibly large rate of pressure increase, comprising the following steps: a. generating a first, pressure, signal as a function of the momentary pressure in said pipe-line; b. continuously applying said first pressure signal to a pressure ratio regulator for generating, at an output of the pressure ratio regulator, a second signal as a function of said first signal; c. applying a presettable constant pneumatic pressure to the power input of a power amplifier; d. applying said second signal to the control input of said power amplifier for generating a third, pneumatic pressure, signal at the output of said power amplifier, said third pressure signal being a function of said second signal; e. applying said third signal to a drive chamber of a regulator valve connected to said pipe-line; the pressure in said drive chamber opposing the valve opening pressure constituted by the internal pressure in said pipe-line, whereby an increase of the internal pressure in the pipe-line causes an increase of pressure in said drive chamber until the pressure in said drive chamber reaches a threshold value set for said presettable constant pneumatic pressure, and whereby said internal pressure, upon exceeding said threshold value, causes opening of said regulator valve; f. differentiating said third signal with respect to time to obtain a pressure differential characterizing the rate of pressure change in the pipe-line; g. comparing said pressure differential with a reference value; and h. depressurizing said drive chamber if said pressure differential exceeds said reference value, whereby said reguLator valve is opened by said internal pressure.

Claim 2

A method for safeguarding a pipe-line against an inadmissibly high internal pressure and an inadmissibly large rate of pressure increase, comprising the following steps: a. generating a first, pressure, signal as a function of the momentary pressure in said pipe-line; b. continuously applying said first pressure signal to a pressure ratio regulator for generating, at an output of the pressure ratio regulator, a second signal as a function of said first signal; c. applying a presettable constant pneumatic pressure to the power input of a power amplifier; d. applying said second signal to the control input of said power amplifier for generating a third, pneumatic pressure, signal at the output of said power amplifier, said third pressure signal being a function of said second signal; e. applying said third signal to a drive chamber of a regulator valve connected to said pipe-line; the pressure in said drive chamber opposing the valve opening pressure constituted by the internal pressure in said pipe-line, whereby an increase of the internal pressure in the pipe-line causes an increase of pressure in said drive chamber until the pressure in said drive chamber reaches a threshold value set for said presettable constant pneumatic pressure, and whereby said internal pressure, upon exceeding said threshold value, causes opening of said regulator valve; f. differentiating said third signal with respect to time to obtain a pressure differential characterizing the rate of pressure change in the pipe-line; g. comparing said pressure differential with a reference value; and h. depressurizing said drive chamber if said pressure differential exceeds said reference value, whereby said reguLator valve is opened by said internal pressure.

Claim 3

An apparatus for safeguarding a pipe-line against an inadmissibly high internal compressive load, comprising in combination: a. a regulator valve disposed in said pipe-line and arranged to be openable by the internal pressure in said pipe-line; said regulator valve including means defining a chamber means for receiving pneumatic pressure to oppose the valve-opening force of said internal pressure; b. a pressure ratio regulator having an input and an output; c. means connecting, at least indirectly, the inside of said pipe-line with said input of said pressure ratio regulator, for applying, to said input, a first signal as a function of the momentary pressure in said pipe-line to generate, at said output of said pressure ratio regulator, a second signal as a function of said first signal; d. differentiating and comparison means for differentiating pressure with respect to time and for comparing a reference value with the pressure differential, said differentiating and comparison means having an input and an output; e. means connecting said output of said pressure ratio regulator at least indirectly to said input of said differentiating and comparison means; and f. depressurizing means connected to said output of said differentiating and comparison means and to said chamber means of said regulator valve for depressurizing said chamber means if said differential exceeds said reference value, whereby the internal pressure in said pipe-line causes opening of said regulator valve.

Claim 4

An apparatus for safeguarding a pipe-line against an inadmissibly high internal compressive load, comprising in combination: a. a regulator valve disposed in said pipe-line and arranged to be openable by the internal pressure in said pipe-line; said regulator valve including means defining a chamber means for receiving pneumatic pressure to oppose the valve-opening force of said internal pressure; b. a pressure ratio regulator having an input and an output; c. means connecting, at least indirectly, the inside of said pipe-line with said input of said pressure ratio regulator, for applying, to said input, a first signal as a function of the momentary pressure in said pipe-line to generate, at said output of said pressure ratio regulator, a second signal as a function of said first signal; d. differentiating and comparison means for differentiating pressure with respect to time and for comparing a reference value with the pressure differential, said differentiating and comparison means having an input and an output; e. means connecting said output of said pressure ratio regulator at least indirectly to said input of said differentiating and comparison means; and f. depressurizing means connected to said output of said differentiating and comparison means and to said chamber means of said regulator valve for depressurizing said chamber means if said differential exceeds said reference value, whereby the internal pressure in said pipe-line causes opening of said regulator valve.