Nasa expendable launch vehicle payload safety requirements: requirements table



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11.2.2.13.16. The effects of the discharge from relief devices shall be assessed and analyzed to ensure that operation of the device cannot be hazardous to personnel or equipment. Items to be analyzed are thrust loads, noise, impingement of high velocity gas or entrained particles, toxicity, oxygen enrichment, flammability, and oxygen deprivation.

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11.2.2.13.17. All relief devices shall be vented separately unless the following can be positively demonstrated:

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11.2.2.13.17.1. The creation of a hazardous mixture of gases in the vent system and the migration of hazardous gases into an unplanned environment is impossible.

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11.2.2.13.17.2. The capacity of the vent system is adequate to prevent a pressure rise more than 20 percent above MOP or exceed 10 percent of the set pressure of the valve in accordance with ASME Code, Section VIII, Division 1, Appendix M, Paragraph M-7. The analysis shall assume that all relief valves connected to the vent system are open and flowing full capacity.

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11.2.2.13.18. Both the inlet and discharge sides of a relief valve shall be hydrostatically or pneumatically tested. When the discharge side has a lower pressure rating than the inlet side, they are to be hydrostatically or pneumatically tested independently. Prior approval of the plan for pneumatic testing shall be obtained from the PSWG, Range Safety, and Center Pressure Systems Manager.

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11.2.2.13.19. Pressure relief valves shall be tested for proper setting before installation and annually thereafter.

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11.2.2.13.20. Pressure relief devices shall be marked in accordance with ASME Code, Section VIII, Division 1, Paragraphs UG-129, UG-130, UG-131, and UG-132 as applicable.

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11.2.2.13.21. A pressure relief valve shall be installed as close as is practical downstream of each pressure reducing device (regulator, orifice) or downstream of any source of pressure such as compressors, gas rechargers, and tube bank trailer whenever any portion of the downstream system cannot withstand the full upstream pressure. The criteria for “withstand” is that the upstream pressure shall not exceed the MAWP of any pressure vessel or component downstream of the regulator or pressure source.

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11.2.2.13.22. A three-way valve with dual relief valve is required where continuous operation of the system is needed during relief valve calibration.

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11.2.2.13.23. Pressure system relief devices shall have no intervening stop valves between piping being protected and the relief devices or between the relief device and the point of discharge except as allowed by ASME B31.3, Paragraph 322.6.1. When a shutoff valve is allowed in accordance with the ASME code, the valve shall have provisions for being locked in the open or closed position. The valve shall have permanent marking clearly identifying its position (OPEN or CLOSED).

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Safety wiring is an acceptable means of locking shutoff valves in the open or closed position.

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11.2.2.14. Ground Support Pressure System Supports, Anchors, Clamps, and Other Restraints

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11.2.2.14.1. All piping supports, anchors, hangers, and other restraints shall conform to the requirements of ASME B31.3, Paragraph 321.

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11.2.2.14.2. Line Restraints

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11.2.2.14.2.1. Where line restraint is required, anchors, guides, pivots, or restraints shall be fabricated or purchased and assembled in such a form as to secure the desired points of piping in relatively fixed positions.

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11.2.2.14.2.2. Line restraints shall permit the line to expand and contract freely in opposite directions away from the anchored or guided point.

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11.2.2.14.2.3. Line restraints shall be designed to withstand the thrust, torsional forces, and load conditions of operation.

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11.2.2.14.2.4. Line restraints shall contain the line in case of line failure.

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11.2.2.14.2.5. The support shall be capable of withstanding no less than two times the available force as a result of thrust generated from component failure under pressure.

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11.2.2.14.3. All relief valves and attached vent piping shall be designed to withstand any thrust caused by venting fluids.

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11.2.2.14.4. All rigid tubing assemblies shall be supported by rigid structures using cushioned steel clamps or suitable multiple tube, block-type clamps.

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11.2.2.14.5. Tubing supports within consoles or modules shall be spaced according to the maximum spacing listed in Table 11.3.

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Table 11.3. Spacing for Tubing Supports Within Consoles or Modules.

Nominal Tubing Diameter (inches)

Maximum Distance Between Tubing Support (inches)

1/8 through 3/8

1/2 through 3/4

1 and over

18

25

30



11.2.2.14.6. Tubing supports between consoles and modules shall be spaced according to the maximum spacing listed in Table 11.4.

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Table 11.4. Spacing for Tubing Supports between Consoles or Modules.

Nominal Tubing Diameter (inches)

Maximum Distance Between Tubing Support (feet)

1/8 through 3/8

1/2 through 7/8

1 through 2

4

6

9



11.2.2.14.7. Components within a system shall be supported by a firm structure and not the connecting tubing or piping unless it can be shown by analysis that the tubing or piping can safely support the component with a safety factor of 3 against yield.

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11.2.2.14.8. Hazardous pressure system piping shall be installed with sufficient flexibility to prevent static or dynamic flow-induced loads and thermal expansion or contraction from causing excessive stresses to be induced in the system, excessive bending moments at joints, or undesirable forces or moments at points of connection to equipment or at anchorage or guide points.

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11.2.2.15. Reserved

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11.2.2.16. Ground Support Pressure System Pumps

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11.2.2.16.1. The Standards of the Hydraulic Institute should be used as a guide in selecting a safe pump.

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11.2.2.16.2. Gear pumps shall not be used for high pressure applications involving flammable and/or hazardous fluids.

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11.2.2.16.3. The inlet pressure of hydraulic pumps shall be controlled to prevent cavitation effects in the pump passage or outlets.

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11.2.2.16.4. Hydraulic pumps required to provide emergency power shall not be used for any other function.

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11.2.2.16.5. Hydraulic pressure systems shall have regulators with a pressure relieving or self-bleeding feature.

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11.2.2.16.6. Pumps used in hypergolic propellant systems shall be of the centrifugal type specifically designed for pumping hypergolic propellants.

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11.2.2.17. Ground Support Hydraulic System Hardware

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11.2.2.17.1. General Ground Support Hydraulic System Design

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11.2.2.17.1.1. For all power-generating components, pump pulsations shall be controlled to a level that does not adversely affect system tubing, components, and support installation.

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11.2.2.17.1.2. When two or more hydraulic actuators are mechanically tied together, only one lock valve shall be used to hydraulically lock all the actuators.

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11.2.2.17.1.3. The ambient operating temperature for hydraulic systems shall not exceed 275oF for systems using petroleum-based fluids.

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11.2.2.17.1.4. Fluids for systems operating at temperatures higher than 275oF shall be fire resistant or fireproof for the intended service.

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11.2.2.17.1.5. Where system leakage can expose hydraulic fluid to potential ignition sources, fire resistant or flameproof hydraulic fluid shall be used.

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11.2.2.17.1.6. All hydraulic piping installations shall be designed, installed, and tested in accordance with ASME B31.3.

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11.2.2.17.1.7. Pressure snubbers shall be used with all hydraulic pressure transmitters, hydraulic pressure switches, and hydraulic pressure gauges. Exception: Pneumatic pressure gauges are excluded from this requirement.

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11.2.2.17.1.8. A gauge indicating accumulator gas pressure shall never be used to indicate equivalent hydraulic pressure.

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11.2.2.17.1.9. Pressure system relief devices shall have no intervening stop valves between piping being protected and the relief devices or between the relief device and the point of discharge, except as allowed per ASME B31.3.

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11.2.2.17.1.10. When a shutoff valve is allowed in accordance with the ASME code, the valve type shall have provisions for being secured in the open or closed position.

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11.2.2.17.1.11. The shutoff valve shall have permanent marking clearly identifying its position (OPEN or CLOSED).

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11.2.2.17.1.12. Thermal expansion relief valves shall be installed as necessary to prevent system damage from thermal expansion of hydraulic fluid.

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11.2.2.17.1.13. The thermal relief valve setting shall not exceed either the system test pressure or 120 percent of the system MOP.

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11.2.2.17.2. Ground Support Hydraulic System Accumulators and Reservoirs

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11.2.2.17.2.1. Accumulators and reservoirs that are pressurized with gas to pressures greater than 150 psig shall be designed, constructed, tested, certified, and code stamped in accordance with ASME Code, Section VIII, Division 1 or Division 2.

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11.2.2.17.2.2. Hydraulic system reservoirs shall be provided with a fluid level indicator. If a sight glass is used for a liquid level indicator, it shall be properly protected from physical damage.

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11.2.2.17.2.3. Only inert gases shall be used in pressurization accumulators in systems operating at pressures in excess of 200 psig or temperatures over 160oF unless adequate fire and explosion resistance is demonstrated.

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11.2.2.17.2.4. For a gas-pressurized reservoir, the gas pressure shall be controlled by an externally nonadjustable pressure regulating device to control the gas pressure in the reservoir.

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11.2.2.17.2.5. Hydraulic systems having reservoir filling caps shall include design provisions that will automatically vent the reservoir opening.

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11.2.2.18. Ground Support Hypergolic Propellant System Hardware. The minimum design requirements for all mobile, or portable equipment used to handle hypergolic propellants (Nitrogen Tetroxide [N2O4 ], Hydrazine [N2H4,] Unsymmetrical Dimethylhydrazine [UDMH], Aerozine 50 [A-50], Monomethylhydrazine [MMH]) shall comply with NASA-STD-5005 Standard for The Design and Fabrication of Ground Support Equipment and the requirements described below.

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11.2.2.18.3. Components used in any fuel or oxidizer system shall not be interchanged after exposure to the respective media.


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