Liquid storage tank protection system and method

A liquid storage tank protection system, comprising:

• a first sensor adapted to sense a percentage of a catalyst gas in a headspace of a liquid storage tank equipped with a two-way breathing valve set to vent the headspace to an ambient gas environment at a high-pressure value and to admit the ambient gas environment into the headspace at a low-pressure value;
• a second sensor adapted to sense pressure in the headspace;
• a controller coupled to said first sensor and said second sensor for generating a first control signal when said percentage of the catalyst gas is less than a catalyst threshold, a second control signal when said percentage of the catalyst gas exceeds said catalyst threshold, and a third control signal when said pressure in the headspace is equal to a low-pressure threshold between said low-pressure value and said high-pressure value;
• a supply of an inert gas at a supply pressure greater than said high-pressure value;
• a first valve coupled to said supply and adapted to be coupled to the headspace, said first valve coupled to said controller wherein said first valve is closed in response to said first control signal and said third control signal, and wherein said first valve is only opened in response to said second control signal wherein a discharge pressure of said first valve is greater than said high-pressure value;
• and
• a second valve coupled to said supply and adapted to be coupled to the headspace, said second valve coupled to said controller wherein said second valve is closed in response to said first control signal and said second control signal, and wherein said second valve is only opened in response to said third control signal wherein a discharge pressure of said second valve is less than said high-pressure value.

A liquid storage tank protection system, comprising:

• a first sensor adapted to be disposed in a headspace of a liquid storage tank equipped with a two-way breathing valve set to vent the headspace to an ambient gas environment at a high-pressure value and to admit the ambient gas environment into the headspace at a low-pressure value, said first sensor sensing a percentage of a catalyst gas in the headspace;
• a second sensor adapted to be disposed in the headspace for sensing pressure in the headspace;
• a controller coupled to said first sensor and said second sensor for generating a first control signal when said percentage of the catalyst gas is less than a catalyst threshold, a second control signal when said percentage of the catalyst gas exceeds said catalyst threshold, and a third control signal when said pressure in the headspace is equal to a low-pressure threshold between said low-pressure value and said high-pressure value;
• a supply of an inert gas;
• a first valve coupled to said supply wherein, when opened, said first valve outputs said inert gas at a discharge pressure that is greater than said high-pressure value, said first valve adapted to be coupled to the headspace wherein said inert gas output from said first valve is introduced into the headspace, said first valve coupled to said controller wherein said first valve is closed in response to said first control signal and said third control signal, and wherein said first valve is only opened in response to said second control signal;
• and
• a second valve coupled to said supply wherein, when opened, said second valve outputs said inert gas at a discharge pressure that is between said low-pressure value and said high-pressure value, said second valve adapted to be coupled to the headspace wherein said inert gas output from said second valve is introduced into the headspace, said second valve coupled to said controller wherein said second valve is closed in response to said first control signal and said second control signal, and wherein said second valve is only opened in response to said third control signal.

A protection system for a produced-water storage tank protection, said protection system comprising:

• a first sensor adapted to sense a percentage of oxygen in a headspace of a produced-water storage tank equipped with a two-way breathing valve set to vent the headspace to an ambient air environment at a high-pressure value and to admit the ambient air environment into the headspace at a low-pressure value;
• a second sensor adapted to sense pressure in the headspace;
• a controller coupled to said first sensor and said second sensor for generating a first control signal when said percentage of oxygen is less than a threshold percentage at which oxygen can serve as a combustion catalyst in the presence of methane, a second control signal when said percentage of oxygen exceeds said threshold percentage, and a third control signal when said pressure in the headspace is equal to a low-pressure threshold between said low-pressure value and said high-pressure value;
• a supply of nitrogen gas;
• a first valve coupled to said supply wherein, when opened, said first valve outputs said nitrogen gas at a discharge pressure that is greater than said high-pressure value, said first valve adapted to be coupled to the headspace wherein said nitrogen gas output from said first valve is introduced into the headspace, said first valve coupled to said controller wherein said first valve is closed in response to said first control signal and said third control signal, and wherein said first valve is opened only in response to said second control signal;
• and
• a second valve coupled to said supply wherein, when opened, said second valve outputs said nitrogen gas at a discharge pressure that is between said low-pressure value and said high-pressure value, said second valve adapted to be coupled to the headspace wherein said nitrogen gas output from said second valve is introduced into the headspace, said second valve coupled to said controller wherein said second valve is closed in response to said first control signal and said second control signal, and wherein said second valve is opened only in response to said third control signal.