Hydraulics Quiz No. 2 — high-pressure pump, pressure regulator and accumulator

In this document

General presentation

This document constitutes the second of the six "Hydraulics Quizzes" of a distance learning course: "This is the second of the six Hydraulics quizzes" p. 24. The trainee must return it "no later than fifteen days after receipt", in a stamped envelope p. 24. A telephone number and a fax are provided for any questions p. 24.

Topics covered

Questions 1 to 12 p. 24 cover:

• the operation of the 5-piston high-pressure pump (intake, compression, "rest" phase), the role of the delivery valve and the priming linked to the pressure regulator bleed screw;
• pressure values proposed as answer choices for the reservoir ("atmospheric pressure", 62, 145 or 170 bar);
• the role of the pressure regulator (setting a minimum, constant or maximum pressure) and the conjunction/disjunction phenomena linked to liquid consumption in the "usage" circuits;
• the composition of the main accumulator: presence of two fluids separated by a deformable membrane, of which a "compressible gas and an incompressible liquid" is among the proposals (12d).

Questions 13 and 14 p. 25 cover the pressure balance between gas and liquid in the accumulator at the membrane's equilibrium, and the constant or oscillating nature (between 145 and 170 bar) of the stored liquid pressure.

Calculation exercise

A guided exercise p. 25 applies the P × V = constant law to an accumulator sphere: solved example with a setting pressure of 62 bar, an empty volume of 400 cm³, resulting in a liquid volume of 229 cm³ at 145 bar. The "your turn" exercise asks to redo the calculation for a 250 cm³ sphere, set at 30 bar, at 170 bar, with answer choices to tick (constant, volume, liquid volume).

The document ends with a space for remarks, time spent, signature and the mention "Keep the carbon copy" p. 25.

Context

The pressure regulator and the main accumulator (sphere) are central elements of the Citroën hydropneumatic system, developed in particular by Paul Magès, who joined Citroën in August 1925 and whose hydropneumatic suspension plans date from 17 February 1944 (Hydropneumatic suspension plans with differential interaction), regulating the pressure of the high-pressure circuit supplying suspension, brakes and steering on models such as the DS or the CX. The values of 145 and 170 bar mentioned in the quiz correspond to the usual disjunction and conjunction thresholds of these systems, known to the brand's technicians — this general knowledge is however not made explicit in the document itself.

Archivist's perspective

This quiz No. 2 confirms the pedagogical structure already identified in other pieces of the same training file, with its layout using numbered red dots and its numerical exercise. It logically completes the first part dedicated to the basics of pressure and braking, visible in Hydraulics Quiz No. 1, and prepares the themes developed later in the series, particularly around the pressure regulator, repeated in Quiz No. 5.

This is not a document directly from the design work of Paul Magès — who retired from Citroën in September 1974 (photographs of Paul Magès' retirement) —, but probably a technical training aid intended for Citroën networks, aiming to transmit and verify the understanding of the principles he helped to invent. The calculation exercise p. 25 clearly illustrates the pedagogical desire to have the physical law governing the accumulator manipulated concretely, rather than limiting it to a theoretical presentation.