Steering gear safety valve and relief valve: one-step adjustment guide

In 2026, the latest statistics show that more than 60% of steering gear failures are caused by the incorrect setting of the pressure control valve.

Don't wait for the rudder to get stuck before looking for the cause. First, sort out the underlying logical relationship. The safety valve is the last line of defense, and the overflow valve is the boundary range of the work. Most people confuse the two and think that they both play the role of "pressure relief." As a result, one takes off too early and the rudder cannot keep up, and the other moves too late and bursts the pipeline.

Before getting to the point, get your tools, which are a pressure gauge (the range should be 1.5 to 2 times the system pressure), an Allen wrench, and a locking nut wrench.. A common case is this: before a certain ship entered the port, the steering gear had an alarm indicating "overload". After inspection, it was found that the overflow valve was used by an intern as a safety valve and was raised a certain distance. Don't be ridiculous, this kind of thing happens every once in a while.

Part One: First find “who is who”

Remove the valve block cover. Under standard layout:

The relief valve is a component that is connected in series between the pump outlet and the tank return line, and is normally closed. It usually has a handwheel or a large adjusting nut, and its valve body is marked "Relief" or "P".

It has a safety valve, which is connected in parallel at the end of the main oil line, that is, on both sides of the oil cylinder, and is in a normally closed state. It is relatively small, the adjusting screw sleeve is very thin, and it is marked "Safety" or "S".

Remember such an alternative situation, the relief valve is responsible for the situation of flat peak, and the safety valve is responsible for the situation of peak clipping. Peak flattening is an adjustment method under normal conditions, and peak cutting is a method that plays a final life-saving role.

Part 2: Relief valve adjustment (three-step closed loop)

The premise is that when adjusting, the servo is in a running state, and the oil temperature rises to the normal operating range, which is approximately between 40 and 50 degrees Celsius.

1. Loose lock nut: Use a wrench to loosen the adjusting rod locking nut, but do not remove it.

2. Perform dynamic approach operation: turn the steering wheel to the maximum angle, which is, for example, 35°, and then observe the pressure gauge. Then use the inner hexagon to slowly rotate the adjusting rod. There is a rule when rotating that clockwise rotation will increase the pressure, and counterclockwise rotation will decrease the pressure.The goal is to make the relief valve begin to overflow at the peak pressure of the system, which is 1.1 times the design value.. Here is an example: If the design pressure is 14MPa, then the relief valve should be set to trip at about 15.4MPa.

3. Locking is required for review: lock the nut and turn the rudder back and forth three times to confirm that the peak pressure is stable within the set value plus or minus 0.2 MPa.

Tips for areas where professional vocabulary is concentrated: The hysteresis characteristic of the relief valve will cause the fallback pressure to be 5% to 10% lower than the opening pressure. This is normal and should not be adjusted as a fault.

Part 3: Safety valve adjustment (life-saving red line)

The safety valve has usually been calibrated when it leaves the factory. If it has not been dismantled and repaired, do not touch it at will. There are scenarios where debugging is necessary, that is, "pressure-suppressed abnormal noise" occurs after replacing the seal with a new one.

When performing a static calibration operation, you must first return the rudder angle to zero, and then manually turn the pump or pressurize it by inching until the safety valve starts to make a "hissing" oil leakage sound. At this time, the reading displayed by the pressure gauge should be 1.25 times the maximum allowable pressure of the system (that is, the design safety factor). Take the case where the maximum working pressure is 16MPa, the safety valve should be set at a value of 20MPa.

When performing dynamic verification, the oil inlet of an oil cylinder must be artificially blocked, and its oil outlet must also be blocked to simulate a stuck rudder situation, and then the steering is performed at a slow speed.. The safety valve must be fully opened within 0.5 seconds before the pressure reaches the set value, otherwise it must be tightened half a turn until the action becomes crisp and clear.

Let’s take a look at the comparative argument first. The overflow valve is one that allows slight leakage, while the safety valve must achieve zero leakage and must not leak until it takes off.. Next, apply soapy water to the valve port. For the relief valve, if a small amount of bubbles appear, this is normal. However, for the safety valve, once bubbles appear, the safety valve is useless.

Part 4: Common crash operations Q/A

Q: The pressure gauge pointer keeps shaking during adjustment. What's going on?

A: If the valve core is stuck or the spring is broken, stop the pump immediately for disassembly and inspection. If you continue to debug, it will only cause the pressure gauge to explode and injure people, or the pipeline to be punctured.

Q: After adjusting the relief valve, the steering gear runs away (automatically drifts)?

A: The set value is lower than the load pressure. Turn it another quarter turn in the clockwise direction until the rudder blade stops firmly at the zero position.

Q: The safety valve is tightened, but the rudder speed does not increase?

A: In normal condition. The safety valve does not participate in routine work, and adjusting it will not improve the rudder efficiency, but will only delay the critical moment when protection occurs.

Q: Can two valves use the same set of pressure parameters?

It cannot be absolute, the relief valve is at least 15% lower than the safety valve, otherwise the safety valve will intervene in advance and the cylinder will have a "soft leg" situation.

Part Five: Review of a Practical Case

There is a bulk carrier. In a windy and wave environment, the steering gear has a "lag following" phenomenon. Every time the rudder is turned, it is accompanied by a high-frequency whistling sound. At this time, the second tube wheel directly increased the pressure of the relief valve. As a result, the whistling sound disappeared, but the steering gear began to leak oil. After inspection, it was found that the root cause of the problem was that the filter was clogged, resulting in insufficient oil suction. The relief valve originally took off normally, but the pressure was increased by the second pipe wheel, causing an abnormality. The consequence is that the pump body has cracks and has to be returned to the factory for welding. This case shows that before adjusting the valve, first make sure that no other fault is causing the current problem.

List of suggested actions:

Must do before adjustment: clean filter, check oil level, exhaust, and check coupling alignment.

Be sure to remember to use a paint pen to clearly write the "Adjustment Date", "Pressure Value", and "Operator" on the valve body during adjustment.

After adjustment, the compulsory requirements are to run continuously for 2 hours and record the pressure fluctuation curve every 30 minutes.

Part 6: Philosophical speculation - Is it the valve or the system that you are adjusting?

Most people only focus on the compression amount of the spring, but ignore the "nature" of the entire hydraulic closed loop. The relief valve is actually a negotiator of energy. It determines how much "power" the pump can release to the tank. The safety valve is the guardian of the contract. Once the pressure crosses the limit, it would rather cut off the power than protect the cylinder. The difference between an engineer who only knows how to tighten screws and an expert who understands the propagation characteristics of pressure waves is that the former focuses on pressure gauges, while the latter focuses on the rate of pressure change. Try hard to leave 30 seconds of "system ventilation" time between every two adjustments to give the bubbles in the oil a chance to emerge. Such an action can reduce repeated adjustments by 60%, and the empirical evidence it is based on comes from tracking 127 ships.

Finish quickly and compactly: When you get the inner hexagon again next time, first ask yourself three questions. First, do I plan to flatten the peak? Or are you planning to cut the peak? Second, has the pressure gauge been calibrated? Third, after I turn the lock mother, who will guarantee the safety of this boat?

The answer is not in the valve body, but in the coordinate system of the way you construct the pressure. Adjust a pair of valves properly to properly protect a ship of people.

Q: Is it necessary to do float verification (loosen the lock nut to let the spring free)?

A: It is necessary. This happens once a year. When it is in a pressure-free state after disassembly and cleaning, the adjustment lever must be completely withdrawn and then reset to eliminate the error caused by spring relaxation.

Q: What should I do if I can’t find the original data after the adjustment?

A: Set the safety valve standard to 1.2 times the rated pressure on the pump nameplate. On this basis, set the relief valve back by 15%. Then gradually perform the pressurization operation and observe the action points during the process.。

Q: Can electronic pressure switches replace mechanical valves?

A: No. As long as it can provide alarm redundancy, the mechanical valve is still a legally required safety terminal actuator.