Dual-Face Mechanical Seal: Cartridge Relies on Hand, Non-Cartridge Relies on Craftsmanship

Many maintenance technicians often fall into a misconception, thinking that there is no essential difference between cartridge and non-cartridge dual-face mechanical seals, and that simply tightening them in place ensures normal operation. However, within the industry, the installation threshold and error tolerance between these two are worlds apart.

For a cartridge dual-face mechanical seal, the manufacturer has pre-adjusted the spring compression amount and assembled and positioned the core components, with the shaft sleeve installation position also fixed and locked. On-site, you only need to fit it onto the pump shaft and tighten it according to specifications. Even a novice operator has a less than 10% error rate, making it especially suitable for working conditions like rotor pumps that require high sealing stability. For a non-cartridge dual-face mechanical seal, all components such as springs, rotating rings, stationary rings, and gland are delivered as loose parts. The spring compression, coaxiality, and assembly precision all rely on manual control. Novice operators have a high error rate, making it a core procedure that truly tests the practical craftsmanship of experienced masters.

- Bonve Pump Cam-Type Twin-Lobe Rotor Pump -

Of the problems encountered in daily maintenance, such as seal leakage, heat generation, abnormal noise, and drastically shortened service life, 90% are not due to product quality defects; the root cause is almost always operational errors during installation.

The assembly of a non-cartridge dual-face mechanical seal centers on benchmark positioning and precision control. First, take the central raised positioning step on the shaft sleeve as the core benchmark. Tightly press the bottoms of the spring seats on both sides against this step, then lock the positioning screws. Apply a special lubricant to the auxiliary sealing ring of the rotating ring, install the rotating ring into the spring seat and align it with the positioning groove. Check that the rotating ring floats smoothly in the axial direction without sticking. The flatness of the end faces of both rotating rings must be controlled within 0.1mm, which can be accurately measured with a depth gauge. When assembling the stationary rings, apply suitable lubricant to the auxiliary sealing rings, install the stationary rings into the gland and align them with the anti-rotation pin grooves. Check the fit clearance; the flatness of the stationary ring end faces should also be ≤ 0.1mm.

The core key of assembly is the precise measurement and adjustment of the compression amount of the seals on both sides, which must be measured and calculated separately for the atmospheric side and the medium side.

Calculation of atmospheric side seal compression amount

1. Measure the dimension from the atmospheric side rotating ring end face to the inner step of the shaft sleeve, record as A.

2. Measure the dimension from the stationary ring gland sealing face to the stationary ring end face, record as B.

3. Measure the dimension from the shaft positioning step (which contacts the inner step of the shaft sleeve) to the bearing housing bracket joint face, record as C.

4. Measure the dimension from the seal chamber end face (which contacts the stationary ring gland) to the pump cover joint face, record as D.

Compression calculation formula: E = A - (C + D) - B

Acceptance standard: The calculated value must reach 1/2 to 2/3 of the limit compression amount for that seal model. If the compression amount is too small, adjust the rotating ring installation position and add a positioning shim of corresponding thickness.

- Bonve Pump Dual-Face Mechanical Seal -

Calculation of medium side seal compression amount

1. After installing the shaft sleeve onto the pump shaft and making it contact the positioning step, measure the dimension from the bearing housing bracket joint face to the medium side rotating ring end face, record as F.

2. Measure the dimension from the medium side stationary ring end face to the pump cover joint face, record as G.

Compression calculation formula: H = G - F

Acceptance standard: Same as for the atmospheric side, must be controlled within 1/2 to 2/3 of the limit compression amount. If not met, adjust the rotating ring position or add an adjustment shim.

There are two core taboos throughout the assembly process that must not be ignored: First, the atmospheric side stationary ring is often made of graphite, which has low strength and is prone to breakage. Vigorous or violent operation is strictly prohibited throughout the process, avoiding bumping or damaging the graphite ring caused by excessive shaking of the pump cover or gland. Second, all dimensional measurements must be based on the correct reference joint faces. Choosing the wrong reference will directly lead to inaccurate measurement data, causing errors that are tiny in the beginning but become huge later, ultimately resulting in seal failure.

In summary, the cartridge seal relies on factory standardization and pre-adjustment, which greatly lowers the on-site installation threshold and tolerance cost. The stable operation of the non-cartridge seal, however, depends entirely on the maintenance personnel's control over dimensions, precision, and operational details.

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.  

Service Hotline: 0574-87588986 13586591794  

Official Website: www.bvpumps.com  

Business Email: market@bonvepumps.com  

We look forward to working with you to drive efficiency and innovation in industrial fluid transmission with precision technology.