Spring-type mechanical seal relies on the axial elastic force of the spring, combined with medium pressure, to press the seal end faces of stationary and rotating rings tightly together, realizing dynamic sealing between the rotating shaft and the equipment cavity. It is widely used in fluid conveying equipment such as rotary lobe pumps. Leakage caused by seal failure is a common fault of such equipment, and the adjustment and control of spring compression amount is the core focus of maintenance work.

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The control accuracy of spring compression amount determines the final effect of maintenance. Insufficient compression amount will lead to insufficient fitting pressure of the end faces, and the medium is prone to leak from the gap; excessive compression amount will aggravate the friction temperature rise of the seal faces, and even burn out the graphite wear-resistant layer on the end faces. The value of compression amount must strictly follow the original technical specifications of the equipment, and the allowable error shall be controlled within ±2mm. The empirical compression amount of conventional pump types is mostly about 15mm. In practice, the dual-position distance measurement method can be used to determine the actual compression amount: first adjust the spring seat to the initial position and fix it, measure the vertical distance from the stationary ring gland to the end face of the shaft sleeve under the free state of the spring and the assembled working state respectively. The difference between the two sets of values is the current actual compression amount. Lock and fix the components only after confirming that the value meets the standard.

Assembly accuracy is the basic guarantee. Multiple key parameters must be verified before installation. In terms of shaft accuracy, the radial runout of the shaft shall be controlled within the range of 0.04-0.06mm, and the axial float shall not exceed 0.5mm, which can be tightened to 0.1mm for some high-precision working conditions. In terms of form and position tolerance, the deflection error of the gland end face shall not exceed 0.05mm, and the concentricity deviation between the gland and the shaft shall be kept in the range of 0.01-0.10mm. In addition, the rotation direction of the spring must be confirmed. The rotation direction of the single-spring structure must be opposite to the rotation direction of the pump shaft to prevent the spring from loosening under the action of torsion during operation. After all assembly is completed, a flexibility test shall be carried out by pressing the moving ring assembly by hand, and it is qualified if it can rebound automatically without jamming after being released.

Standardized disassembly, assembly and cleaning procedures can avoid secondary damage to seals. Hard prying and hitting with tools such as hand hammers and flat chisels are strictly prohibited during disassembly. If components are stuck by medium crystallization or dirt, clean the surface contaminants first before slow disassembly. All sealing parts, especially the seal end faces of stationary and rotating rings, shall be thoroughly wiped clean with acetone or anhydrous ethanol; when assembling O-rings, soapy water is recommended for lubrication, and oily lubricants shall be avoided to prevent erosion of rubber materials. A small amount of grease can be applied to the seal end faces of stationary and rotating rings to avoid dry friction damage during the initial startup phase.

Combined with operation fault characteristics, problems related to compression amount can be quickly located. Abnormal compression amount is the most common cause of seal leakage: when the compression amount is too large, the seal end face is prone to overheating and scorching marks; when the compression amount is insufficient, end face scaling and continuous dripping will occur. In case of serious liquid leakage, it is mostly related to insufficient spring pressure, excessive end face wear or sealing ring failure, and it is necessary to adjust the compression amount or replace failed components accordingly; leakage accompanied by abnormal noise and obvious temperature rise is usually caused by insufficient lubrication, dry friction or medium vaporization, which requires optimization of the equipment's flushing and cooling circuit. If periodic leakage occurs, it is necessary to check pump shaft float or excessive equipment vibration and solve the root cause from the pump body itself.

From the perspective of structural classification, spring-type mechanical seals can be divided into single-spring and multi-spring types according to the number of springs. The single spring has a large pitch and is prone to jamming, making it more suitable for equipment with small shaft diameters; the multi-spring adopts a uniformly distributed small spring structure with more uniform force, suitable for high-speed and large-shaft-diameter working conditions. According to the balance degree, they can be divided into unbalanced type and balanced type. The unbalanced type has all medium pressure acting on the seal end face and is only suitable for low-pressure working conditions below 0.8MPa; the balanced structure can offset part of the medium pressure, adapts to high-pressure environments above 1.0MPa, and has a longer service life.

Bonve pump always adheres to the philosophy of "Wholeheartedly Making Good Rotor Pumps," committed to providing global customers with customized conveying and mixing solutions. If you have technical inquiries, selection needs, case references, or other cooperation intentions related to Bonve rotor pumps, please feel free to contact us.  

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