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ECS Equipment - Atmosphere Revitalization Section

SUIT CIRCUIT ASSEMBLY

Suit Circuit Relief Valve The suit circuit relief valve protects the suit circuit against overpressurization. The valve has automatic, open, and close positions. Two externally mounted microswitches provide telemetry signals when the open or close position is selected.

Suit Circuit Relief Valve
Suit Circuit Relief Valve
In the automatic position, the valve responds to pressure sensed by the aneroid; it cracks open at approximately 4.3 psia to prevent overpressurization of the suit loop by allowing oxygen to flow to the cabin. At 4.7 psia, the valve is fully open and flows approximately 7.8 pph at +90' F. The valve reseats at approximately 4.3 psia. In the open position, the valve handle displaces the poppet from the seat to open the valve, regardless of pressure. In the close position, if the valve fails to reseat, the automatic poppet is left open, but an auxiliary poppet is closed, maintaining pressure.

Suit Gas Diverter Valve The suit gas diverter valve is a manually operated, two-way valve (one inlet and two outlets) with a solenoid override in one direction. The valve is on the ECS package above the oxygen control module. When the valve handle is pushed into the cabin position, oxygen is directed into the cabin; pulling the valve handle to the egress position shuts off flow to the cabin.

Suit Gas Diverter Valve
Suit Gas Diverter Valve
An automatic closed-to-cabin feature is provided. If cabin pressure falls to below the normal level while the valve is set to CABIN, a solenoid is energized by the cabin pressure switch and the main spring returns the valve to the EGRESS position. Electrical power is also supplied to the diverter valve when the oxygen demand regulator valves are set to egress.

Cabin Gas Return Check Valve The cabin gas return check valve is a spring-loaded, flapper-type valve. The valve has automatic (AUTO), OPEN, and EGRESS (closed) positions. In the automatic position, the valve automatically permits cabin gas to return to the suit circuit. When the cabin is depressurized, the suit circuit pressure closes the valve, preventing back flow into the cabin. The open and egress positions provide manual override of the automatic position.

Cabin Gas Return Valve
Cabin Gas Return Valve
C02 Canister Selector Valve and C02 and Odor Removal Canisters The CO2 canister selector valve is a dual-flapper-type valve that routes flow through the C02 and odor removal canisters. The valve has primary and secondary positions. One flapper is at the inlet to the canisters: the other, at the outlet.

Canister Selector Valve
Canister Selector Valve
Each canister contains a cartridge filled with LiOH and activated charcoal. The primary canister cover has a debris trap, which may be replaced before, but not during, flight. A relief valve in the cartridge permits flow to bypass the debris trap if it becomes clogged. The canister selector valve is sufficiently leakproof to permit replacement of cartridges, with the cabin unpressurized.

Suit Circuit Fans The suit circuit fans maintain the circulation of conditioned oxygen in the suit circuit. Each suit circuit fan is operated by a 28-volt d-c brushless motor, and each fan moves approximately 24 cfm at 25,000500 rpm. Fan operation is controlled by the suit fan selector switch.

Suit Circuit Sublimator The sublimator rejects suit circuit heat to space if the suit circuit heat exchanger is inoperative. It has a water inlet and a stream outlet that is vented overboard. Water and suit circuit gas both make a single pass through the unit, which comprises a stack of modules of several layers of porous plates, water, steam, and suit circuit gas passages.

Suit Circuit Heat Exchanger The suit circuit heat exchanger is a duct-shaped unit of aluminum plate-and-fin construction. It has a single pass for both the coolant and the suit circuit gas and is used to remove excess heat in the ARS. Heat is transferred to the HTS coolant supplied to the heat exchanger.

Water Separator Selector Valve The water separator selector valve is a manually operated, flapper-type valve that enables selection of either of two water separators. The valve handle is pushed in for separator No. 1 and pulled for separator No. 2.

Water Separator Selector Valve
Water Separator Selector Valve
Water Separators Two water separators are connected in parallel, but only one is used at a time. Saturated gas and free moisture fed into the separator come in contact with the inlet sensor blades, which direct the flow onto a rotor at the proper angle. Most of the entrained moisture collects on the rotating perforated plate, which centrifuges the water into a rotating water trough. A stationary pilot tube, picks up the removed water and discharges it to the WMS. The pitot purnping action creates a dynamic head of pressure sufficient to ensure positive flow from the water separator to the WMS. Water passing through the perforated plate collects on a rotating conical drum and is fed into the water trough. The oxygen flow drives the rotating parts of the separator. A water drain boss on each separator drains the cavity between the rotating drum and the outer shell of the unit. Plumbing attached to each drain boss carries water away from this area and dumps it into a surge (collection) tank outside the suit circuit.

Suit Circuit Regenerative Heat Exchanger The suit circuit regenerative heat exchanger is of the aluminum plate-and-fin type. Heat from the circulating warm coolant is transferred to the oxygen, which makes a single pass through the unit while the coolant makes two passes.

Suit Temperature Control Valve The suit temperature control valve is a manually operated diverter valve that controls coolant flow through the suit circuit regenerative heat exchanger. The valve has two positions, one to increase the temperature, the other to decrease the temperature.

Suit Temperature Control Valve
Suit Temperature Control Valve
Suit Isolation Valve The suit isolation valve is a manually operated, two-position dual-ball valve. In the Suit Flow position, suit-circuit gas is directed through the valve into the PGA, and from the PGA back into the suit circuit. In the Suit Disconnect position, the valve keeps the gas in the suit circuit, bypassing the PGA's and preventing flow in either direction between the suit circuit and PGA's.

Suit Isolation Valve
Suit Isolation Valve
Setting the valve handle to suit flow loads a solenoid-operated spring return mechanism. A signal from the suit circuit pressure switch energizes solenoid, which releasing the return mechanism, which turns the valve to Suit Disconnect. The ACTUATOR OVRD lever enables manual release of the return mechanism to the SUIT DISC position. A valve position indicator switch provides a telemetry signal for SUIT DISC position.

Carbon Dioxide Partial Pressure Sensor The carbon dioxide partial pressure sensor, in the suit circuit assembly, is a single-beam, dual-wavelength, filter photometer with ratio readout. The sensor operates on the infrared-absorption principle. It measures the amount of infrared energy absorbed by the carbon dioxide in a gas sample that passes through the sensor, by comparing transmitted energy of two different wavelengths in the infrared spectrum. (One wavelength is absorbed by carbon dioxide; the other is a reference.) This establishes an amplified ratio signal that is indicated as a d-c voltage proportional to the partial pressure of carbon dioxide in the gas sample.

The sensor has two sections: optics and electronics. The optics section has the infrared energy source (a small tungsten lamp), a collimating lens, a lens that reimages the source on the dual filter, an aperture to fix the source image on the dual filter, and a lens that reimages the chopped and filtered source image onto the detector target. The electronics section detects and decodes the signal, computes the ratio and, then, reads out a continuous d-c voltage proportional to the partial pressure of carbon dioxide in the gas sample. The sensor provides an electrical signal to the PART PRESS C02 indicator and a telemetry signal to indicate the carbon dioxide level in the gas supplied to the astronauts.

SUIT LIQUID COOLING ASSEMBLY

Cabin Fan The fan motor is of the brushless, d-c type; it operates on 28 volts dc with an input power of 62 watts average, 210 watts peak. The fan circulates cabin gas and can move approximately 5 pounds of air per minute at 13,000 rpm. The fan permits operation at sea level for checkout purposes. An input voltage of 15 volts dc is provided for this purpose.

Water-Glycol Heat Exchanger The water glycol heat exchanger transfers heat from the warm water returning from the LCG to the coolant of the heat transport section. This heat exchanger is of the crosscounterflow, single-pass water and multipass coolant type.

Liquid Garment Cooling Valve The liquid garment cooling valve is a manually operated diverter valve that controls water flow to the water-glycol heat exchanger. Part or all of the water may be manually diverted around the heat exchanger to provide varying degrees of cooling, depending on astronaut needs.

Liquid Cooling Valve
Liquid Cooling Valve
Water Accumulator The water accumulator consists of an aluminum housing, diaphragm, spring, diaphragm piston guide, and diaphragm piston. The system water pressure opposes the spring action in the accumulator to maintain the correct pressure level in the water loop. The accumulator serves as a reservoir to make up for system leakage and volumetric changes due to temperature fluxuations.

Water Pump The water pump is of the diaphragm type; it circulates water through the suit liquid cooling assembly. A voltage regulator steps down the LM-supplied 28 volts dc to 161 volts dc for pump operation.

Portable Recharge Adapter The portable recharge adapter serves as the connection between the PLSS drink line and the multiple water connector of the suit liquid cooling system. Bleed-off capability is provided in the adapter to relieve pressure in the event of overfilling of the system. Both astronauts are disconnected from the cooling system when recharging.

Suit Umbilical Water Hoses The water umbilical hoses transport water between the LCG and the suit liquid cooling assembly. The hoses are flexible silicon rubber, covered with Beta cloth.

Multiple Water Connector The multiple water connectors are quick disconnects that connect the water umbilical hoses to the LCG receptacle on the astronauts outer suit. The connectors provide dual flow into, and out of, the LCG. Poppet valves minimize leakage during connecting and disconnecting.


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