Constant- deceleration hydraulic station

I. The medium- and high-pressure hydraulic station in constant-deceleration mode features automatic control of a constant deceleration rate.

During safe braking, the hoisting system can decelerate at a preset constant rate under various load conditions, speeds, and operating scenarios. At the same time, it retains the performance of two‑stage braking. The high‑pressure hydraulic station for deceleration consists of two completely independent single‑unit, single‑pump configurations—each comprising a single unit, a single pump, a dual‑station setup, and an electrical control cabinet. Each set is capable of long‑term independent operation; if one hydraulic station fails, the system can be immediately switched to the other for normal operation. The system employs imported proportional flow valves, variable‑displacement piston pumps, and solenoid valves, all equipped with pressure and temperature sensors that interface with a PLC.

The hydraulic braking system’s piping is entirely constructed from cold-drawn steel tubing, joined by flare‑type fittings, and equipped with imported oil seals. The hydraulic station’s oil circuitry is nickel‑plated, while the housing undergoes phosphating treatment.

Its operating principle is as follows: a constant-pressure variable-displacement piston pump delivers hydraulic fluid through a mesh filter and a fine‑filter, with the pressure being limited by a relief valve. The normal operating pressure of the hoisting mechanism’s braking system is supplied by the energization of a solenoid directional control valve. As the brake‑control lever is actuated, a proportional relief valve adjusts the system pressure to ensure both stable hoisting operation and proper service braking. Once the safety‑braking sequence is initiated, the solenoid valve is de‑energized, activating the constant‑deceleration safety brake. This ensures that, within 0.3 seconds, the hydraulic fluid in the brake circuit returns to the hydraulic power unit and is drained back to the reservoir via the relief valve. Simultaneously, the system pressure drops from its peak value to the initial level, after which the system enters a controlled constant‑deceleration phase, guaranteeing smooth and safe braking under steady‑deceleration conditions.

The constant‑deceleration hydraulic station is an independent, dual‑station hydraulic system featuring electrically delayed, safety‑rated braking with constant deceleration. It can be paired with multi‑rope friction hoists and single‑rope, single‑drum hoists, and includes a motor‑brake function.

II. Technical Parameters and Applications of the Constant-Deceleration Hydraulic Station

1. The technical parameters of the constant-deceleration hydraulic station are as follows:

(1) Rated working oil pressure: ≤14 MPa

(2) Oil pump flow range: 0–14.8 L/min

(3) Fuel tank capacity: 600 L

(4) Oil pump motor: Y132M2-6, B5, 5.5 kW, 960 r/min, AC 380 V / 660 V

(5) Hydraulic oil grade: N46D low‑pour, anti‑wear hydraulic oil

(6) Proportional valve amplifier control signal: 0–10 VDC

(7) Operating oil temperature: 15–65°C

(8) External dimensions: 1310 (L) × 1123 (W) × 1475 (H)

2. Uses

(1) The constant-deceleration hydraulic station is used for single-rope, single-drum and multi-rope friction hoists.

(2) This hydraulic station provides two controllable oil circuits, B and B′, with stepless pressure regulation. It enables brake application and release during hoist operation, normal service braking, and, in emergency safety‑braking mode, a two‑stage braking system—first‑stage braking followed by constant‑deceleration braking. The pressure‑regulation range is 0–14 MPa.

III. Hydraulic Station: System Composition and Operating Principle

This hydraulic power unit is a fully independent dual‑station system, with one station in operation and the other on standby.

1. System Composition

Oil source unit; safety pressure relief device; energy storage unit; oil outlet filtration unit; pressure measurement device; motor brake unit; oil tank assembly; electrical wiring terminal box.

2. Operating Principle

(1) Working principle of the oil source unit:

The unit is driven by a constant-pressure variable-displacement piston pump B, which pumps hydraulic fluid through the mesh oil filter WL and the fine‑filter ZL1. The pressure is limited at the outlet by relief valve Y4, and the system pressure is indicated by electrical contact pressure gauge P1. Below the maximum operating pressure Pmax, the variable‑displacement pump delivers a flow rate of 14.8 L/min; as the pressure approaches Pmax, the flow rate drops sharply, yet the desired pressure is maintained, preventing overheating of the hydraulic fluid due to excessive flow. The threshold for this flow‑limiting behavior is set by remote‑controlled relief valve Y4, with pressure adjustment performed on site. Refer to the commissioning section of the hydraulic station manual for adjustment procedures. In the oil supply circuit, incoming fluid is filtered by filter ZL1; if contaminants clog the filter element, a local pressure differential develops. When this differential reaches 0.35 MPa, a differential‑pressure switch generates a discrete signal, prompting replacement of the filter element and triggering the electrical control system.

(2) Working principle of the energy storage device:

When the hoisting system is brought into operation, after starting the hydraulic station motor, the system oil pressure rises to near the maximum working pressure Pmax (which is set by the Y4 relief valve and read on the P1 electrical contact pressure gauge). At this point, the oil flows through the check valve DF1 to charge the accumulator X. Only when the charging pressure reaches the specified value—causing the pressure relay JP1 to switch to a logic state of “1”—can the hydraulic system be considered ready for normal operation, and the electrical control system may proceed to normal hoisting tasks. Should the oil pressure in X drop for any other unknown reason, causing the logic state of JP2 to change from “0” to “1,” the system will deem the accumulator pressure too low to function, and the electrical control will issue an alarm, prompting maintenance personnel to verify the pressure settings corresponding to the logic states of JP1 and JP2; these settings are detailed in the subsequent commissioning section. The accumulator’s oil pressure is indicated by the P3 pressure gauge. When the accumulator X does not require pressurized oil—such as during shutdown or maintenance—the shut-off ball valve QF3 can be used to drain the oil back into the reservoir.

(3) Working principle of the safety pressure-regulating device:

The normal operating oil pressure of the hoisting brake system is maintained by energizing solenoids G1 and G1’. As the brake control lever is actuated, a BL proportional relief valve regulates the system pressure, ensuring both normal hoisting operation and proper service braking. Once the safety‑braking sequence is initiated, solenoids G1 and G1’ are de‑energized, activating constant‑deceleration safety braking. This ensures that, within 0.3 seconds, the hydraulic fluid in the brake chambers flows back through lines B and B’ to the hydraulic power unit and is drained to the reservoir via relief valves Y1 and Y1’. Simultaneously, the system oil pressure drops from its maximum value Pmax to the initial pressure. Px (i.e., the setpoint oil pressure for Y1 and Y1’), immediately transitions into the constant-deceleration programmed control phase, ensuring that the braking system performs smooth and safe braking under constant-deceleration conditions. During this process, G6 and G6’ are energized, and TS, along with Y1, Y1’, and BL, must all be engaged. After a delay of Δt = 0–10 seconds, the programmable control system dynamically monitors the main unit’s operating speed; upon determining that the speed has fallen below the minimum threshold, valves G3 and G4 are actuated according to their closing‑time schedule, while BL is simultaneously controlled via its closing‑time schedule to reduce the oil pressure to zero, thereby concluding the automatic constant-deceleration control.

When constant deceleration fails—i.e., when the constant‑deceleration phase is too brief and the operating speed does not achieve the desired change—the G2 and Y2 valves are immediately activated in parallel to engage secondary braking. The BL valve operates at the Vmax signal voltage as specified by the closing table, while the brake oil pressure is maintained at the set secondary‑braking pressure PⅡ, which is adjusted by Y2. After a delay, the programmable control system dynamically monitors the main drive’s operating speed; if the speed falls below the minimum threshold, the G3 and G4 valves are actuated after the delay specified in the closing table, thereby completing the secondary braking sequence.

When the secondary braking system fails—during the brief interval when the secondary brake is engaged and the operating speed does not decrease—the G2, G6, and G6’ circuits are locked out. The control system then activates the primary wellhead braking sequence as specified in the closing table, immediately reducing the system’s hydraulic pressure to zero and ensuring reliable braking of the hoisting system.

(4) Working principle of the oil filtration device:

The device comprises high-pressure ball valves QF1 and QF1’, filters ZL2 and ZL2’, differential pressure transmitters YC2 and YC2’, check valves DF2 through DF5, and solenoid valves G7 and G7’. In addition to filtering and isolating the hydraulic fluid, its most critical function lies in the wellhead‑level primary braking system: by means of G7 and G7’, B‑line and B’-line can be connected to form two additional return‑oil paths, thereby significantly enhancing the safety of the hoisting system during emergency braking.

(5) Working principle of the pressure-measuring device:

This device provides pressure-sensing functionality during operation and comprises a pressure transmitter YB, pressure controllers JP3 and JP4, and a pressure gauge P2 to regulate the system’s operating conditions.

(6) Operating principle of the motor brake:

This device provides pressure relief for the brake oil in the motor rotor system and controls the release and application of the brake. During normal operation and service braking, it operates automatically in response to the system’s oil pressure. When G5 is energized, it ensures that, during final braking, oscillations caused by high‑speed gear impacts between the reducer and the motor are prevented. Furthermore, during primary braking at the wellhead, G5 is de-energized, triggering an emergency application of the motor brake to prevent severe impact between the motor rotor and the reducer’s high‑speed gears.