Design Considerations

Factors in manifold design

Manifolds offer major advantages when integrated into hydraulic systems. However there are many factors to consider when determining the required circuit, functions and the performance of the manifold. Secondary parameters such as valve selection, port connections and preferred layout, etc need to be considered and decided on before specifying the manifold requirements to the designer.

Following is a brief explanation of some key factors to be considered when specifying the design requirements for hydraulic manifolds.

Custom manifolds

These are specifically design and manufactured to order to suit particular applications and individual customer requirements. The cost of design is in addition to the cost of manufacture and is generally factored into an overall cost of the manifold(s)

Standard manifolds

These are common, industry standard manifolds usually for basic generic applications and are generally manufactured or purchased to be sold as off-the-shelf items against a published price list.

Circuit design

The schematic circuit represents and communicates the function and operation of the fluid power system. The circuit is the ultimate responsibility of the fluid power engineer (generally representing the customer) who has full understanding of the system and the design requirements. This is the person who signs off on the verification and approval of the manifold layout and circuit, prior to manufacture.

Valve selection

As with the fluid power circuit, the correct valve selection for a manifold is vital and is primarily determined by the valve properties and characteristics to suit the application and desired outcome. Valve selection is the responsibility of the engineer/circuit designer. This is the person who knows what specific valves and their performance characteristics are required to produce the desired outcome.
Other relevant factors in valve selection include commercial considerations such as brand preference, time and availability restraints and price.

Size and shape

The shape and size of a manifold can vary to suit almost any individual requirement. Traditionally manifolds are rectangular in shape and sized as small or as large is practically possible.

Occasionally cut-outs, contours or lugs are machined to suit particular mounting requirements. In advanced applications, manifolds are quite complex in shaped and are physically integrated into a machine as an integral or structural member.

Material

The base material selection is usually governed by factors such as system pressure, duty cycle, mass limitations, environmental conditions and engineering specifications. Traditional base materials are aluminum, steel and cast iron.

Aluminum is popular for it's light weight and low corrosive properties, and it's ease of machining. Aluminum is normally maximum rated to working pressures between 210-240 bar, depending on the grade of aluminum and applied safety factors.  Aluminum is not normally accepted in underground mining applications.

Ferrous based steel and cast iron are better suited for high duty cycle applications, especially in mining and industrial equipment. Steel and cast iron rely on suitable surface treatment to minimise surface corrosion.

Stainless steel and brass are usually specified in critically reactive areas such as marine and food processing environments.

Surface Treatment

Surface treatment (also known as surface protection and plating) is generally specified to provide resistance to surface corrosion thereby extending service life. Other benefits of surface treatment may include abrasive resistance, internal protection from specific fluids, improved overall appearance and ultimately, product quality.

While there is a wide variety of surface treatments available, two of the most common for ferrous based manifolds are Zinc Electroplating and Electroless Nickel. Zinc plating is common and relatively economical. Nickel plating is considered to give better protection, particularly in internal galleries etc, but is more expensive. Internal protection is critical for some water-based and synthetic hydraulic fluids.

Anodising is the most common surface treatment process for aluminum. Two benefits of anodising are it's abrasive resistance (by the forming of aluminum oxide) and in some grades, the anodised surface can be coloured to a limited choice..