Regarding the flushing scheme for mechanical seal PLAN11 52
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I would like to ask the experts here! It’s a centrifugal pump using propane as the medium, with an outlet pressure of around 1.7 MPa. The sealing system employs a PLAN11 52 flushing approach. Questions: 1. Is the vent line at the top of the oil tank connected to a ground flare, and under normal conditions, should the vent valve be open or closed? 2. If the vent valve on the top of the oil tank is kept open, how can we determine whether there is a leakage in the sealing system (since the pressure should be released in that case)? 3. What are the consequences if the vent valve on the top of the oil tank is kept closed?
The standards of API682. Using 11+52 is intended to prevent the medium from leaking into the atmosphere; a normally closed mechanism causes the medium to leak inside the liquid storage tank, where it can be discharged through a flare (throttle orifice). Leaks in the sealing system can be detected by monitoring the liquid level and gauge pressure in the sealed tank. Once there is a leak in the secondary seal, medium will also leak into the atmosphere under normal operating conditions, though in small quantities. Propane is only flammable and explosive; if it were a highly toxic gas, it would be completely unacceptable
It is normally open to the flare line; if there is a leak in the internal mechanical seal, the pressure will increase and an alarm will be triggered. If the oil level drops too quickly, it is due to a leak in the external seal
The valve on the top of the 52-seal tank should remain open; there is a flow-limiting orifice plate in this area. Under normal circumstances, the small amount of leakage from a seal is directly vented to the flare, so the pressure does not rise or rises only slightly. When the leakage from the seal is significant, the pressure can rise above 0.1 MPa; at this point it signals that maintenance is needed{:9002:}
52 is the most commonly used; it’s necessary to understand your process in detail, and we can discuss this privately
Does anyone know why the design features a flow-limiting orifice plate? So how is throttling achieved? One needs to thoroughly understand the design
The more I look at it, the more it resembles Lanzhou Petrochemical{:9010:}
Our company’s propane pumps also use this design; the sealing coolant in them is a 50% ethylene glycol water solution. However, the exhaust valve of the cooling tank remains closed at all times, so that any leakage in the mechanical seal can be detected promptly through the pressure gauge on the cooling tank. If the exhaust valve were kept open, small amounts of leakage would go unnoticed
Normally open, with a orifice plate on it; pressure is generated when leakage becomes excessive