Lubricating oil adjustment for the light oil station of the compressor unit
Thread Content
On the lubricating oil control pipeline of the company’s light oil station, there are two control valves: one is used to regulate the pressure at the outlet of the screw pump, while the other, a self-acting control valve, is used to control the pressure in the main oil supply line. Since the pressure in the main oil supply line can already be regulated using the valve located near the pump, why is a self-acting valve still needed? On-site operations also suggest using that valve; the self-acting valve hasn’t been touched yet. Please help me understand this, I’m a newcomer to the workplace~ Thank you!
The self-acting control valve on the main fuel supply pipe serves to stabilize the pressure. In many applications, there is only one self-acting pressure regulator at the pump outlet, with no pressure regulator on the oil supply main.
This is the oil circuit in our company. Do you mean that this isn’t part of the standard configuration? The self-acting pressure regulator for the main oil supply line isn’t necessarily included by default – is that the case for you?
The main settings on the pump are the rated outlet flow rate and outlet pressure. Self-regulating valves are convenient, as they can be adjusted according to the amount of usage.
The self-acting valve at the pump outlet functions as a flow-diverging regulator; it already serves to regulate the oil pressure in the back circuit； Is a regular self-acting valve installed at the end of the oil circuit as an extra safety measure?
This stand-alone control valve is a downstream control valve used to regulate the pressure in the lubricating oil pipeline; this pressure should be lower than the pressure at the pump outlet. When the pressure after the control valve decreases, opening the control valve further will lower the pressure at the pump outlet. By closing the control valve at the pump outlet, the pressure can be maintained at a stable level. The control valve at the pump outlet is adjusted based on the characteristics of the pump, while the stand-alone control valve is adjusted according to the characteristics of the pipeline. This is how you operate it on-site: 1. It’s possible that the stand-alone control valve is already preset at the time of manufacture ； 2. You replaced the stand-alone control valve with a control valve; the stand-alone control valve was already set to its maximum position. Therefore, you do not feel the effect of the stand-alone control valve. It is recommended that during the next start-up, the pump outlet valve be set to automatic control; then the stand-alone control valve should be turned down to the minimum position, after which it should be adjusted gradually so that both the outlet pressure and flow rate of the pump meet the requirements of the process.
Thank you for such a detailed answer. The pressure in the lubricating oil main is lower than the pressure at the pump outlet. What you mean is: two self-acting control valves work together, using the pressure behind the self-acting control valve in the lubricating oil main pipe as a reference to influence the pilot-operated self-acting valve at the pump outlet ahead, thereby maintaining stable pressure in the lubricating oil main pipe. What we do now is adjust the pressure at the pump outlet and the pressure in the lubricating oil main line; over time, the accuracy of both self-acting valves has decreased to some extent, yet these valves have not been calibrated. Is that the correct way to understand it?
The pump outlet pressure is higher than the pressure in the final fuel supply line. The regulator ahead serves to maintain the pump outlet pressure within a certain range, while the regulator behind ensures that the oil pressure reaching the compressor remains constant; these two regulators are not designed to control the same pressure. It can be understood as one being a major adjustment and the other being a fine-tuning.
I encountered the same situation at a gas station when I first started working there; I didn’t pay attention to it at the time, and no one mentioned anything either. Now it seems that it’s done in order to achieve more precise control of oil pressure. The alarm and interlock settings for oil pressure in your system must be set quite low – with an outlet pressure of 0.8 MPa, I guess your alarm and interlock levels are below 0.2
L-0.2Mpa, interlock LL-0.15Mpa； Currently, we keep the pressure at the pump outlet at 0.4 Mpa, while the pressure in the lubricating oil main line is between 0.3 and 0.4 Mpa. Over these past few days, it seems that everyone agrees on the need to maintain a stable pressure in the lubricating oil main line. I’m wondering if, due to the presence of the oil cooler, it’s necessary to prevent internal leaks by keeping the oil pressure higher than that of the circulating water; the pressure of the circulating water is generally around 0.35 Mpa. Even in the event of an internal leak, it would be the oil leaking into the water
Thank you for your reply; it has deepened my understanding