Factors That Make You Decide to Choose a Knife Gate Valve

One of the biggest advantages that make you choose a Knife Gate Valve is the weight and cost. Typically, the weight of a 16-inch knife gate valve is less than 300 pounds, while the weight of various types of ANSI gate valves exceeds pounds or more. The cost of the valve is also comparable to the weight difference.

Link to Afbv Valve

Do you have any questions about valves in your facility? Ask us about them! We gladly offer technical assistance and provide a comprehensive range of all types of valves and solutions for water treatment plants.

The knife gate valve was originally designed for the pulp and paper industry. When pulp accumulates between the knife and the seating surface to prevent flow stoppage, the knife gate valve is used to handle it. It features a sharp edge to cut through the pulp and seal to handle viscous fluids with similar clogging risks.

This type of valve is typically used in the heavy oil industry, wastewater treatment, pulp and paper industry, slurry, and sludge. These devices are usually specified in larger sizes to handle viscous flows in several demanding applications.

Factors That Make You Decide to Choose a Knife Gate Valve

One of the differences between other types of gate valves and the knife gate valve is that the knife gate valve usually has a sharpened disc to better cut through slurry or viscous fluids. Also, the knife gate valve has a short face-to-face length compared to the gate valve, where the latter is larger in dimensions. As a result, the knife gate valve is lighter in weight compared to the gate valve. These are the main differences.

Knife gate valves are commonly found in wastewater treatment plants, chemical plants, mining operations, cement plants, as well as many other industrial applications, while gate valves are typically found in main water networks, distribution networks, and potable water pumping stations.

Advantages and Disadvantages of Using a Knife Gate Valve Compared to Other Types of Gate Valves

Advantages of Using a Knife Gate Valve

Efficiency in Handling Viscous Materials:

The knife gate valve is designed to handle viscous materials and fluids that contain solid particles such as slurry and sludge. The knife blade cuts through the materials easily, preventing clogging.

Compact Design:

The knife gate valve typically has a compact design and short face-to-face length, making it easier to install in tight spaces.

Low Cost:

Compared to other types of gate valves, the knife gate valve is less expensive in manufacturing, installation, and maintenance.

For more JIS Y Type Strainerinformation, please contact us. We will provide professional answers.

Ease of Maintenance:

Maintenance and repair are generally easier and less costly due to the simple design of the knife gate valve.

Better Flow Control:

The knife gate valve provides better flow control when dealing with dense fluids compared to traditional gate valves.

Disadvantages of Choose a Knife Gate Valve

Low-Pressure Limitations:

The knife gate valve is not suitable for high-pressure applications, as it may not provide adequate sealing for such pressures.

Inefficiency in Hygienic Applications:

It is not the best choice for applications requiring high sanitary conditions such as food and pharmaceutical industries, due to the difficulty in thoroughly cleaning it.

Blade Erosion:

The knife blade may erode over time, especially when used with solid or abrasive materials, requiring regular replacement.

Poor Performance with Dry Particles:

The performance of the knife gate valve declines when used with dry particles or granular materials, as the seal may not be tight enough.

Periodic Inspection Requirements:

It needs regular inspections to ensure no leaks and to confirm the cutting and sealing efficiency, which increases long-term maintenance costs.

General Comparison Between Knife Gate Valve and Other Gate Valves

Traditional Gate Valves:

• Suitable for high-pressure applications.
• Provide good sealing for applications requiring hygienic conditions.
• More expensive and heavier than knife gate valves.
• Less efficient in handling viscous materials and solid particles.

Ball Valves:

• Provide tight shut-off and easy operation.
• Can be used in both high and low-pressure applications.
• Not suitable for handling solid or viscous materials.
• More complex and expensive than knife gate valves.

Butterfly Valves:

• Lightweight and easy to install.
• Effective for large flows and low pressures.
• Not ideal for handling viscous fluids or solid particles.
• Less costly than knife gate valves but less durable.

By considering these advantages and disadvantages, the most suitable type of valve can be selected according to the specific application requirements and operating conditions.

I'm a piping designer with afew years of experience, I was doing a project where the engineer wanted to hot tap thur a 4" valve into a 6" line (this is hydrocarbon service). I normally like to use full port ball valves for this but the engineer indicated he want to use a gate valve to save money. I've run across this before so nothing new. As I was filling out the material requisition I had noted that we needed "full port" gate valves to do this hot tap. My boss saw this and said "ALL" gate valves are "full port" regardless, and didn't need to be indicated! ...News to me, But to be honest I really don't know! I've sent to some major valve manufactures, but they ALL seems to be too busy to answer my question. Can ANYBODY help me here!!?? THX! ...Mark Your boss may be stating an industry "truism". That is, unless otherwise stated, people in the industry assumes certain things due to regular industry "commoness".

To my experience, gate valves are usually always "full port". Gate valves are usually only used in on/off service (they are either open or closed), and a full port gives the least pressure lost.

In the case of a slab gate (through conduit?), I suppose you can have a hole that is not "full port", although I don't know why one would do that, and I haven't seen one.

In my opionion, it doesn't hurt to state full port gate.

Many "oldtimeers" sort of "sneer" at this as something an inexperienced person does. I don't share that opinion. There are lots of people in my industry now that could benefit from having the obvious stated.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums? Mark-

My experience agrees with Hench's. I'd suggest looking at some valve catalogs such as one from Edward Vogt at . Print out the dimension sheet for CL-150 gate valves (page 5 of the .pdf) and toss it on your boss' desk. Ask him what exactly dimension D, the seat diameter, means. For a 4" valve it's listed as 2.75" which I suspect does not fall into his definition of "full port". What I've seen in my industry (petroleum refining) is that larger valves tend to be full port while smaller valves tend to be reduced port. For a hot tap, it's best to just be sure and specify "full port".

jt Hench, jte,

You are correct. I took a look at Flowserve's documents, and they do reference conventional AND full port.

I have talked to my colleagues, and they, as myself, are surprised by this. We are currently looking into it more. This is great - I will learn another new thing today.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums? Well... I am chalking this up to one of those regional industry truisms.

Evidently, I (and 11echo's boss I guess) come from an area/industry where we only use full port gate valves, even though evidently, reduced port is more commonly used elsewhere.

I called Flowserve USA, and they confirm that they sell a whole bunch of conventional port gate valves into the oil and gas industry.

I will have to be more diligent in the future when I fill out my gate valve datasheets.

Thanks to Hench and jte. It is greatly appreciated. Stars to you guys.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums? I want to thank ALL participating authors here. I in deed marched into my boss office and "showed" him a copy of these data sheets! ...He hmmm'd and haaa'd abit but finally bowed to my newly found knowledge. Only thing that would have made it better if he was an a$$, but normally he's a nice guy, so didn't want to "rub it in" too much! *G*
THX for the brownie points!!! ...Mark
Maybe someone will add some discussion here as to why some gates are standard and other full.
Seems to me that probably they both have same bodies whether cast or forged, same bonnets, stems, packing ... whatever.

Also, are ports same size among all manufactured brands as per API, ASME standards?

I can see that full would have slightly enlarged bore, but am not sure if the pre-machined disc blank could not be the same part for both port types.

So, what is the basic advantage of buying standard rather than full port valve? Can whatever cost savings for standard ports be really significant?

Another question:
Please compare the Classes such as 150, 300, 600, 800, 900, , , as opposed to ANSI Classes such as , , and . (Of course, pressures would be temperature dependant for any material) but what engendered such oddly numbered classes? They do not seem to have an evenly numbered metric correlation. So, is it some historical consideration associated with a particular industry? shopper,

Refer to the following standards for the minimum port openings allowed:

For valves manufactured to API 600 (generally cast valves, flanged and butt-weld, like is made by Crane Valve)
API 600, Sect. 5.3.3.1, Table 4, Minimum Port Diameters.

For valves manufactured to ANSI/API 602 (generally small forged valves, threaded, socket-weld and flanged, like is made by Vogt)
ANSI/API 602, Sect. 5.2, Table 1, Minimum Diameter of Equivalent Flow Passageway.

Generally, for forged valves per API 602, a standard port is a reduced port. As well as system block valves, these valves also include vents, drains and instrument connections. As far as system block valves are concerned, they are usually 2" and below for forged and for pipe sizes this small, pressure drop is usually not a problem. And yes, cost is a big factor; a forged full port valve body is the body for the next valve size up. The valve weight and cost can be double or triple.

For cast valves per API 600, the minimum port allowed is considered to be full port.

Note that 'full port' really means 'considered as full port for flow calculations'. Full port does not mean full size un-obstructed bore. Although the minimum bores are established in the standards noted above, the actual bore diameter will vary from manufacturer to manufacturer.

If you need a straight through bore of a certain diameter (for hot-tapping for example) you need to be specific about that in your purchase specifications and verify that on your approval and certified drawings. Don't trust catalog info, some major valve companies contract with valve manufacturers all over the world so the valve you get might not match the one shown in the catalog but it should meet all of the standards and specifications.

I hope this helps


NozzleTwister
Houston, Texas .... While I have over 25 years in the valve distribution industry, I would never consider myself an expert. My experience is that even when a manufacturer presents the valve as "full port" it may not be suitable for hot-tap applications. In the wedge style gate valve, the seat rings are angled to match the wedge disc. While the outside edge of the seat ring may match the "full bore" of the valve body, the lower inside mating surface of the seat is may protrude into the flow path. Using a full bore tap will damage this lower portion of the seat ring, and compromise the sealing surface between the wedge and seat.
That is not much of a technical description, but I hope you get the picture. I have also seen valves with a screwed-in seat ring, with lugs protruding into the bore. When in doubt, insist the valves be examined by a reputable valve service facility - this precaution up front will save a lot of headaches later.