Key Considerations When Evaluating/Selecting Valves and Gates

Ricky Patel, engineering associate, Lorenz Conveying Products

When evaluating/selecting valves and gates for a system, what are the key factors to consider?

Often, the selection of items for a project tends to come down to the bottom line: price. Secondly, the lead time: how fast can the product be delivered? While these both are important factors, they should not be the top priority when choosing a valve or gate. It is important to consider valves/gates based on the specific application they will be used for and evaluate based on the features they have that will support their use in that specific application rather than a few generic key factors. The criteria used in selection can be grouped into three areas: system, product and usage.

 Systems can be classified into two types: pneumatic conveying or gravity feed. A pneumatic conveying line (operating in pressure or vacuum) will require valves/gates designed to meet the system specifications. Pressure, line size, and flow rate will define which model will meet the requirements. Dilute or dense phase systems are another factor to consider. The main difference between the two types will be the seals and the body. Valves/gates of both types will feature seals that will suit the application.

Valves and gates used in gravity feed can be much simpler than the ones used for pneumatic conveying. They will not require the extensive sealing mechanisms required to seal air pressure/vacuum.

Manufacturers of valves or gates will often offer various actuation methods including manual, fluid power (pneumatic/hydraulic), or electric.

Environmental temperature as well as indoor/outdoor installation should also be considered. Valves/gates designed for outdoor usage will feature weather seals and covers.

The product characteristics will not only specify what type of valve/gate may be suitable, it will also determine which options a manufacturer may suggest. These options tend to vary the materials of construction and seal seat material to match the product.

How the valve/gate is to be used cannot be forgotten. Valves and gates can be classified into two main types: open/close and diverting.

Open and close valves/gates accomplish one basic function: the starting and stopping of material flow. How this is accomplished can vary. Each type of valve/gate will have a performance limit based on its design. For example, a gate made for occasional use to shut off material during maintenance only will quickly fail if used for a high-speed batching operation (opening and closing several times per minute). However, a gate meant for a high-speed batching operation, while capable of being used for occasional material shut off, is likely overkill for the application. Additionally, open and close type valves/gates can be used partially open or closed for metering applications.

Diverting valves/gates will change the material flow from one stream to another. Again, just as with open and close type valves/gates, how the diversion is accomplished can vary and each type will have certain characteristics which make it more or less suitable for the application.

Another major usage condition for both on/off and diverter valves/gates is what will the gate be subject to when opening or closing. When opening, will it have a static head of material on it? When closing, will there be a moving or static stream of material? These are important details that are required when a valve/gate is being specified.

Choosing a valve or gate is not always as simple as picking from a catalog. Most manufacturers have trained sales and engineering staff, which when provided with a complete picture of the application including the system details, the material properties, and the usage requirements, can help to select the correct valve/gate to suit the application.

Ricky Patel joined Lorenz Conveying Products in 2010 as an engineering associate. As part of the engineering team at Lorenz he is involved with quoting and estimating, product improvement and development, product support, and process improvement. Patel has written several articles for industry publications. He was graduated from Centennial College with a degree in Electro-Mechanical Engineering Technology in 2002, and from the University of Western Ontario with a Bachelors of Engineering Science in Integrated Engineering in 2007.