Reflections on the R&D of PFBV (SSV) Progressive Divider for Centralized Lubrication Systems

In grease‑lubricated systems, progressive lubrication represents one of the widely‑adopted configurations for centralized lubrication. Thanks to its simple structure, convenient monitoring and low overall unit cost, progressive dividers are extensively deployed in construction machinery, wind turbines, small port machinery (reach stackers, container handlers, etc.), new‑energy equipment, automated machinery and other traditional heavy‑industry facilities.

Among progressive dividers, the SSV modular divider stands out for its compact footprint, high‑volume manufacturability, fast parallel‑port connection and cost‑effective performance, making it the most popular variant. The SSV series from a well‑known German brand has gained particularly wide acceptance across the Chinese market.

Numerous online resources and videos have covered progressive dividers in detail, including schematic diagrams, internal construction, parallel‑port connection schemes, machining processes, dimensional tolerances and grease‑volume calculation, so these topics will not be elaborated here. Our company is the first player globally to represent progressive dividers with hydraulic functional schematic diagrams. This approach enables hydraulic specialists to rapidly gain in‑depth understanding of progressive dividers, breaking down technical barriers between grease lubrication and hydraulics for quick comprehension of product construction and working principles.

Outlet No.1 delivers grease; solid red lines denote the pressure supply port (Port P).

Outlet No.2 delivers grease; solid red lines denote the pressure supply port (Port P).

Domestic competitors have achieved mass‑scale production of divider assemblies for wind‑turbine lubrication systems. In‑depth product research covers material selection, cylindricity and fit tolerances, oil‑groove routing, plunger‑stroke limiting and other key parameters. Sealing remains an indispensable subject across the fluid‑power industry, and this article focuses specifically on the metal‑to‑metal sealing performance at outlet ports of the PFBV (SSV‑type) progressive divider.

For the metal‑to‑metal sealing structure at outlets of the modular PFBV divider (SSV counterpart), a common perception prevails: given the low back‑pressure at progressive divider outlets, any properly threaded fitting will suffice for connection. Existing market‑proven products perform adequately under normal operating conditions. Nevertheless, rigorous engineering assessment is required to verify product performance under extreme working conditions.

Deviations exist between actual machined tapers of check‑valve fittings and drawing specifications. Some suppliers deliver components with a 17° sealing cone, which have already been commercialized for field service. Per DIN 2353, single ferrule fittings adopt a 24° sealing cone for S06, L06 and LL06 series. In current domestic supply chains, check‑valve fittings with 17° and 20° cone angles are mass‑produced; one US‑branded domestic product, for instance, features a 20° cone. In real‑world batch production, mating between fittings and divider bodies commonly defaults to either 20° or 17° cone geometry.

During the original design phase of the modular PFBV divider (SSV equivalent), thorough studies were conducted on oil‑circuit routing. Grease delivery volumes, especially for Outlet 1 and Outlet 2, went through repeated calculation and field validation tests. Our current grease‑metering error can be controlled at 5 % or lower; this topic will be discussed in a separate article.

Let’s continue our discussion on the 24° cone‑sealing design, as illustrated below:

Comparative analysis reveals that several degrees of taper deviation may appear insignificant for grease sealing. When a copper fitting with a 22° cone is fully tightened, micro‑deformation occurs. Hard‑on‑hard line‑contact sealing forms between the deformed copper cone and the divider sealing surface. Plastic deformation of the 22° copper cone achieves optimum sealing engagement against the divider seat. Our divider bodies adopt a 24° cone profile complying with DIN 2353 and ISO 8434‑1. We hold that high‑quality products shall be designed based on such standard specifications, which help customers save lead‑time and generate tangible value.

We have accumulated substantial practical experience for special service conditions such as ultra‑low‑temperature applications, and key‑component optimization has benefited from technical guidance from senior international specialists. Guided by the top‑priority principle of reliability, we pursue maximum performance improvement through innovation. Technical exploration knows no bounds, and many design details — even seemingly straightforward ones — carry hard‑won experience and lessons. As practitioners within the dry‑grease lubrication sector amid China’s transition from a manufacturing giant to a manufacturing powerhouse, we sincerely welcome technical exchanges and cooperation with customers, suppliers and industry peers for mutual progress.