PulseGuard Ltd. and Inc.
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Fluid Flow Control Animations
Fluid Flow Control Animations


The 9019c Valve has been proven by more than 25 years use
on the landing gear of every aircraft on which you have ever flown.

Cushion Pre-fill Valve 9919c, 9919a necessary to keep

NOTICE - yellow tag

CUSHION PRE-FILL With the preventor connected to the pipework as shown in the appropriate illus. (A-D), but no pressure in the pipe, the preventor cushion bonnet shall be filled through the valve that LDI has provided. Fill to a pressure (calculated on the absolute scale), or 80% (or thereabout) of the theoretical steady state system pressure.

Note: Use only Commercially Pure Nitrogen to avoid "dieseling" or membrane permeation/blistering.


1. Remove 1/4" pipe plug (2). Loosen pre-fill valve 003-150000 (1) by turning 1/2 turn counterclockwise. The sealing point (4) will move away from the valve seat (3).
2. Insert a suitable pressure rated tube or multiple wire braid hose with a 1/4" NPT male end into the pre-fill valve.
3. Connect the other end of the tube or hose to your Nitrogen gas booster (Haskel AG series or similar) assembly. Fill cushion chamber to slightly beyond established pressure in the suction pre-fill system, disconnect pressure line from preventor and replace the plug (2).
5. Allow the gas temperature to stabilize.
6. Start the system and bring it to normal operating temperature.
7. Shut the liquid pumping system down to atmospheric pressure. Nitrogen pressure will have changed with temperature, reconnect pre-fill system as above and bleed or add Nitrogen, as required.

Note: Check Nitrogen pressure after the first moth of operation, then yearly thereafter. Nitrogen pressure varies with temperature. Do not use Preventor pressure figures to determine system performance.
There shall not be any other connection to the Nitrogen cushion bonnet than the cushion pre-fill valve provided by LDI. This prohibits gauges, air lines, and instruments and anything else that will leak and mislead due to temperature change.
During any operation of the system, the cushion pre-fill valve must be capped with the seal plug provided.
The pumping system shall not be started until the above items are complete. All measurement of flow velocity or pressure change shall be accomplished from gauges in the liquid system (close up-stream of the suction acceleration head remover and close down-stream of the discharge acceleration head preventor).

003-15000 Nitrogen Pre-fill Valve diaphragm

secondary containment symbol
For Flexorbers:
SoG & FLo only


toque wheel symbol

spare & services symbol

For LP PipeHugger - PeGs Only

PeG with flanges emphasizing the  valve

Pre-Fill Valve - Low Pressure
Pt Nbr. 2581

Require Pre-Fill Chuck
Ot Nbr. 5560

Chuck 5560 with center pin depressor for use with LP Valve 2581 shown right (see diaphragm)
The cushion pre-fill procedure is similar to other dampers, but the fill connection used is Pt. No. 2581, and this requires that you use chuck - Pt. No. 5560, which has a 1/8 NPT male end, so the hose referred to must have an 1/8" female end.

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Selecting Pulsation Dampeners for Different Pump Systems.
Flow through pulsation dampers are at least 3 times more efficient than T off line accumulators.
Dampeners that do, flow goes through, but pressure pulsation does not.
PulseGuard Pulsation DampersThe Smooth Flow People

Call Toll Free 1-888-DAMPERS (326-7377) / See also: Pulsation-Dampeners.com for a pulsation dampener.

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