SISTEMAS PRESION/VACIO

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Documentation logs shall be developed and maintained throughout the life of the pressure vessel. A recording system must be maintained which accounts for all maintenance operations, tests, and inspections performed with or on the pressure vessel. It shall include pressure and temperature history, and results of inspections conducted.

Pressure relief devices shall be used to limit the maximum pressure to below MAWP.

4.8 Relief Devices

Relief devices are required on all pressure vessels unless they have potentially hazardous fluids. Vessels containing potentially hazardous fluids must have a design pressure that exceeds 4 X worst case pressure due to failure (2 fault tolerant) .

Relief devices are required downstream of all regulators when the upstream pressure exceeds downstream design pressure.

The following is a list of relief device design requirements:

- Relief devices shall be set no greater than 110 % of MOP.

- Relief device settings shall not exceed the MAWP of the pressure vessel or system.

- Relief device must be able to handle the worst case capacity.

- There shall be no shutoff devices between the relief devices and the pressure source.

- Relief devices shall be adequately supported for discharge thrust impulse forces.

- Relief devices shall vent out of the work area.

- Relief valves shall be inspected and calibrated every 2 years. All GSE relief valves shall have identification of the calibration and inspection dates.

4.9 Gauges

Gauges are required downstream of all regulators, on all storage vessels (GSE), and between isolation valves (trapped volumes). Trapped volumes can over pressurize causing failure of system. The requirement for gauges can be approved (waiver, deviation, or variance) by safety if isolated volumes, by design, cannot over pressurize.

The following is a list of gauge design requirements:

- The system MOP shall be less than or equal to 75 % of the gauge scale.

- Gauges shall have a one piece shatter-proof window and a blow out back (or equivalent) to allow unrestricted venting.

- All gauges shall be inspected and calibrated every 2 years. All relief valves shall have identification of the calibration and inspection dates.

4.10 Flex hoses and rigid tubing

The facility user must ensure that all flex hoses and tubing meet the following requirements:

- Flex hoses and rigid tubing shall have a minimum design burst factor of 4.

- ASME/ANSI B31. Piping or rigid tubing shall be used in lieu of flex hose wherever possible.

- Flex hose shall be restrained properly at every 6 feet and at both ends for pressures greater than 150 psi.

- Flex hose shall be proof tested annually to 1.5 X MAWP and tagged in accordance with paragraph 3.10.

- Piping and rigid tubing shall meet ANSI/ASME B31.1 and B31.3.

4.11 Vents

Pressure systems shall be designed so that pressure cannot be trapped in any part of the system without vent capability.

The following vent design requirements must be meet:

- Vent system outlets shall be in a location normally inaccessible to personnel and shall be identified/marked.

- Incompatible venting fluids shall be separated sufficiently to prevent mixing.

- All vent outlets shall be designed so as to prevent accumulation of vented fluid in dangerous concentrations.

- Vent lines shall be adequately supported for discharge thrust impulse forces .

- Each line venting into a multiple use vent system shall be protected against back pressurization. All venting fluids shall be compatible.

4.12 Bonding and grounding

All pressure systems containing flammable/combustible fluids shall be bonded and grounded.

Bonding and grounding design requirements:

- Grounding shall provide a discharge path between distribution piping/tubing and earth to prevent the buildup of static electricity.

- Bonding is required for all flammable/combustible pressure systems. Piping/tubing shall be bonded to ground at the end termination’s and at 100 feet intervals.

4.13 Testing

Proof test verifies workmanship and integrity of joints. All new, modified, repaired or, replaced system components shall be hydrostatic proof.

Testing requirements:

- Tested as a system to 1.5 X MOP (1.25 X MAWP for pneumatic testing) for at least 5 minutes.

- Pre and post inspections are mandatory for all systems. System shall be considered failed if there is any permanent set or damage in any manner when subjected to a proof test.

- No system level proof test is required on sensitive hardware such as certain types of gauges, regulators, relief valves, burst disks, and pressure transducers. All untested components shall be calibrated every two years.

- Tag identification for non-flight pressure vessels or systems must identify proof pressure, date of proof pressure, MOP of system, and identification number. For flight pressure vessels or systems, certification logs must document proof testing.

- Proof testing is required for flex-hoses annually.

- Systems requiring proof testing after arrival at GSFC shall provide document of previous component and system testing (if any).

- Remote testing will be required if the system or vessel does not have at least a Design Burst Factor (DBF) greater than 4 or if the integrity of the system or vessel has been compromised. Adequate exclusion zone(s) will be