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There are several key factors that influence the price of a slide gate when utilized in a pneumatic conveying system. Here are five important considerations:
- Material characteristics
- Contact surface
- Operating environment
- Actuation method
- Electrical classification
Five Factors that Influence Slide Gate Valve Cost
When considering these factors, a deeper assessment of the specific application for a slide gate valve is necessary to get a better idea of cost. Some factors will lead to a more expensive slide gate, while others have subtle effect.
1. Material Characteristics
A critical part of assessing slide gate cost is identifying the characteristics of the material being conveyed. Common considerations include:
- Is the material a powder versus granular or a pellet?
- Is it sticky, corrosive or abrasive?
The latter will require modifications to a slide gate, to ensure a good seal. Modifications required due to conveyed material characteristics will generally lead to increased cost for the valve.
2. Contact Surface
Depending on application parameters, different construction materials are necessary for a valve’s material contact surface. Contact surfaces can range from carbon steel to aluminum, 304 stainless steel, 316 stainless steel, or other sturdy alloys. Material compatibility and abrasiveness will typically dictate the metal requirements for the contact surfaces of the slide gate. As higher grades of metal are needed for material contact areas, the cost of the slide gate valve can increase substantially.
3. Operating Environment
Another factor contributing to slide gate costs is the operating environment – that being, whether the valve will be installed indoor versus outdoor. Outdoor climates can fluctuate from very hot to very cold, depending on geographic location. Although indoor temperatures tend to remain more constant, they can still play a role in the type of slide gate valve selected. When choosing the appropriate seal material, it’s important to account for wear life, melting point, corrosion and potential swelling of the seal. Sometimes, finding a seal material that meets all of these criteria can significantly increase the cost of a slide gate valve.
4. Actuation Method
There are four primary actuation methods typically used in conveying systems:
- Manual actuation – Utilizing a hand wheel, hand crank or chain wheel to actuate a valve open or closed. These would typically be used in low actuation applications, or to perform system maintenance. Manual actuation will help to reduce slide gate costs.
- Pneumatic actuators – Typically used for slide gates designed as process valves. These are good for high cycle rates and when closing through a standing column of material is required. Pneumatic actuators require the availability of plant air to be plumbed to the valve. Pneumatic actuators alone will not significantly affect price in either direction.
- Hydraulic actuators – Utilized for applications that require cutting through a column of material. Hydraulic actuators exert greater force to help the slide gate push through the material. A hydraulic system with a line plumbed to the actuator is required for a slide gate valve to operate, using this configuration. Sourcing this type of actuator will typically add to the overall cost of a slide gate.
- Electric actuators – Another method for use on a process valve. Electric actuators typically only have a 25 percent duty cycle, so they cannot be used in high cycle applications. Electric actuation is utilized extensively in cold, outdoor environments because they are not susceptible to freezing. Electric actuators only require electricity, so they are basically a self-sustaining actuator. Like hydraulic actuators, the cost of a slide gate will increase with electric actuation.
5. Electrical Classification
Any pneumatic, hydraulic or electrically actuated valve controls will fall under a specific National Electrical Manufacturers Association (NEMA) classification. For instance, electrical controls with NEMA 4 requirements are considered water- and dust-protective, whether indoor or outdoor in typical environments. Electrical controls with NEMA 7/9 requirements are designed for hazardous locations (combination of classes, groups and divisions). Review the NEMA enclosure types to determine the most appropriate electrical classifications for your application.
The cost differences between these types of electrical components can be sizeable and have major influence on the overall cost of a slide gate valve.
Importance of Application Engineering
Clearly, specifying a slide gate valve’s application up front saves money. The more initial information that can be provided about a slide gate valve’s application, the more control a customer will have over the price of a valve. If a valve supplier is given all the necessary details, there is less probability for error in adding unnecessary modifications that could increase the total cost of a slide gate valve.
