For stainless steel distributors, understanding pad flanges means being better prepared when customers need something outside the ordinary.
A pad flange is a specialized flange designed to be welded directly to a tank or vessel. Its primary purpose is to provide a secure connection for immediate or future pipeline connection directly from the tank. This flange is typically about 1-1/2” to 2” thick with tapped boltholes. Flanges can be furnished thicker for instances of welding to smaller tanks that have a smaller diameter that would require the weld side of the pad flange to match the contour of the flange they are welding to.
A special type of pad flange is a transmitter flange. These are commonly applied to tanks that require monitoring of the depth of a bulk tank. Measuring instruments, particularly level transmitters are mounted to these. A common application would be stock tanks for paper mills. The transmitter measures head pressure and displays it without someone climbing a 30 foot ladder. When mounted to a stock tank, the flange has a beveled inside diameter on the backside that prevents stock fibers from lodging in the port of the flange. They also have an offset bolt pattern that accommodates a transmitter isolation valve or allows a level transmitter to be mounted directly.
These flanges are frequently used in applications where accurate liquid-level measurement is important.
- Stainless steel storage tanks
- Chemical processing equipment
- Food and beverage processing
- Pharmaceutical manufacturing
- Industrial liquid storage systems
- Water treatment facilities
In many cases, a pad flange is a relatively small part of a much larger tank fabrication project. However, getting the correct dimensions and configuration is essential.
As illustrated on our website, a transmitter flange can incorporate an offset bolt pattern, with certain mounting holes positioned at a 20-degree offset. This arrangement helps accommodate the equipment being installed. Download the Pad Flange PDF.
Unlike standard pipe flanges, where dimensions and bolt patterns are often established by common industry standards, pad flanges may require special configurations.
This is where having a manufacturer capable of producing custom stainless steel fittings and flanges becomes valuable.
You may receive a request for a pad flange with unusual dimensions, a specific bolt pattern, or a particular material grade. Rather than turning away the request, there may be an opportunity to provide a custom-manufactured solution.
Material Options and Custom Manufacturing
Pad flanges can be manufactured from several materials depending on the application.
Common options include:
- 304L Stainless Steel
- 316L Stainless Steel
- 317L Stainless Steel
Tank manufacturers frequently encounter situations where standard dimensions simply will not work. A particular tank design may require a different outside diameter, inside diameter, thickness, or mounting configuration. Some applications may also require the flange to be contoured to match the curvature of the tank wall.
Gathering information from your customer upfront can help avoid unnecessary delays:
- What material grade is required?
- Does the flange need to match the tank curvature?
- Are there specific bolt-hole locations or dimensions?
- Is the flange intended for a particular transmitter or isolation valve?
But what happens when a customer calls looking for a transmitter flange with an unusual bolt pattern or custom dimensions?
That’s where a manufacturer specializing in fabricated and custom stainless steel products can help. Instead of searching endlessly for an exact match, a custom pad flange may be manufactured to the customer’s specifications.
At Appleton Stainless, we understand that not every customer request fits into a standard catalog.
The Bottom Line
Pad flanges may not be an everyday item for most stainless steel distributors, but they serve an important purpose in tank fabrication and industrial instrumentation.
Understanding what they are, how they’re used, and why they sometimes require custom manufacturing can help distributors better serve their customers.
The next time a customer asks for a pad flange or transmitter flange, don’t assume it’s something you can’t supply. Whether you have a drawing, a sample, or simply a set of specifications, Appleton Stainless may be able to help. Standard or custom—send us your requirements.
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