255.199 Requirements for design of pressure relief and limiting devices.

(a)Except for rupture discs, each pressure relief or pressure limiting device must:#

(1)be constructed of materials such that the operation of a device will not be impaired by corrosion;#

(2)have valves and valve seats that are designed not to stick in a position that will make the device inoperative;#

(3)be designed and installed so that it can be readily operated to determine if the valve is free, can be tested to determine the pressure at which it will operate, and can be tested for leakage when in the closed position;#

(4)have its support made of noncombustible material;#

(5)have discharge stacks, vents, or outlet ports designed to prevent accumulation of water, ice, or snow, located where gas can be discharged into the atmosphere without undue hazard;#

(6)be designed and installed so that the size of the opening, pipe, and fittings located between the system to be protected and the pressure-relieving device, and the size of the vent line, are adequate to prevent hammering of the valve and to prevent impairment of relief capacity;#

(7)where installed at a district regulator station to protect a pipeline system from overpressuring, be designed and installed in compliance with subdivision (b) of this section to prevent any single incident such as an explosion in a vault or damage by a vehicle from affecting the operation of both the overpressure protection device and the district regulator;#

(8)except for a valve that will isolate the system under protection from its source of pressure be designed to prevent unauthorized operation of any stop valve that will make the pressure relief valve or pressure-limiting device inoperative; and#

(9)where gas pressures are reduced in two or more stages to supply pipelines except field regulators, be designed and installed in compliance with subdivision (b) of this section so that any single incident in one stage will not adversely affect another stage.#

(b)For new installations, and for existing aboveground stations supplying low-pressure pipelines, the minimum separation distance between the overpressure protection device and the regulator or between stages of regulation shall be:#

(1)50 feet (15.2 meters); or#

(2)where it is impracticable because of interfering subsurface structures, not less than 25 feet (7.6 meters) upon approval of the department.#

(c)The requirements contained in subdivision (b) of this section do not apply to those existing stations which, due to their locations or other station protection design features, are adequately protected against any credible single incident affecting the operation of both the overpressure protection device and the district regulator, or which supply integrated distribution systems employing multiple overpressure protection devices of sufficient capacity to prevent overpressuring of the distribution system.#

(d)Notwithstanding the installation date or the retroactivity provided by section 255.2(a) of this Part, when overpressure protection is provided by a monitor regulator, a means must be provided to verify that the regulator is functioning properly.#