6 Ways to Ensure You Have a Tight Seal in Your Gasketed Joint

The lack of a tight seal in a gasketed joint is a ticking time bomb. The timing of the issue presenting itself may vary, but unfortunately, you will have issues. The good news (for those of you that love troubleshooting) is that there are a variety of things that can contribute to the problem. In a perfect world, all of these things would be addressed during the design phase. Hopefully we can help some of you start to recognize these things sooner rather than later to get you out of the troubleshooting group!

We put together a short list of things that you should consider when it comes time to design or troubleshoot your gasketed joint.

Ways to Ensure a Tight Seal

1. Is the proper load applied?

Bolts not tightened to the proper torque values spell trouble for your application. If the load values defined in the development stages are not adhered to, you will most likely find a leaking gasket (and possibly further damage if it goes on for too long). What if you don’t know what the load should be? Start with the specified gasket material. You may be able to reverse engineer the values based on the recommended loads that the gasket material is designed for (you may need to talk with the materials supplier). You might also gather input from service instructions for similar applications. It will take some trial and error, but you can probably figure it out.

2. Can the gasket withstand the conditions it is under?

Sometimes conditions in the application are underestimated, and sometimes the robustness of a certain gasket material is overestimated. Whichever way it happens to go, there will most likely be problems. Is your gasket material designed to resist the effects of the fluid, pressure, and temperature of the joint? If it isn’t, you can count on having trouble maintaining a tight seal. However, this is generally an easy fix if you do a little research into materials that can withstand the specific conditions in your application and choose properly.

3. Is the bolt design sufficient?

This is probably the most expensive problem on this list. A redesign due to an incorrect bolt design can cost a lot of money, especially if you are too far down the design path. If your answer to this question is “no”, and you do have an insufficient bolt design, we can offer some advice on where to go from here. If there is any hopeful news in this scenario, it is that there are materials out there that are more forgiving than others that can help mask questionable design choices. Talk to your trusted gasket material supplier about some of the composite materials on the market. Three layer composites (or metal reinforced materials) can be manufactured to a specific thickness and they conform very well to flange surfaces – both of which can help compensate for bolt design issues. It isn’t always a magic bullet, but it’ll do the job in a lot of situations where nothing else will work.

4. Are the flanges appropriate for the gasket technology chosen?

Flange surface finish plays a huge role in the ability for certain gasket materials to adequately hold a tight seal. Gaskets made of stainless steel (MLS/SLS) require mirror-smooth surfaces, while metal reinforced graphite and certain fiber gaskets are more forgiving. If the flanges are not machined properly, or they wear over time, you will start to have sealing issues with MLS/SLS.

5. Are the leakage requirements met?

It is a common misconception that a gasket is expected to never leak. Leakage requirements are set during the design phase (you’ll commonly see mL/minute or mL/hour) and the load on the joint has a direct effect on whether or not these numbers are achieved. If you are exceeding your leakage requirements, that is a clear indication that your seal is not as tight as it needs to be.

6. Is a re-torque necessary?

What if you’re feeling pretty confident in everything above, and you’re still having issues with maintaining a tight seal? Maybe the solution is something as simple as a re-torque. If you have gaskets installed that are going through their first heat cycles, bolts loosen and a re-torque is often necessary. Without it, the tight seal you thought you had prior to running your application is long gone.

Maintaining the Seal

As you can see, there are definitely some things to consider if you are having trouble maintaining a tight seal. Some are always quick to blame the gasket, but a gasket is only as good as the conditions that it is designed for and the type of conditions it is placed under. It is important to have a full understanding of all of the things that can lead to the demise of a tight seal.

What is the most common issue you find with your seals remaining tight?Armor product comparison

What Is Bolt Load, and Why Do I Care?

Here is the second installment of our “Why Do I Care” series. Every so often, we’ll blog about some of the questions people new to the gasket industry may be looking for more information on. The last installment was “What Is Compressibility & Recovery, and Why Do I Care?”.

This week, we’re going to talk about bolt load. You may also have heard the terms: torque load, flange load, or compressive force, which all refer to the same thing. Bolt load is something to keep in mind when you are designing your joint and selecting your gasket material. Without knowing or paying attention to it, you may be setting yourself up for an insufficient load situation…and a problem.

Bolt Load

Putting it simply, bolt load is the key to the joint. Sufficient load must be available to achieve the initial seal, and then maintain that seal long-term over the life of the joint. The load must be comfortably more than needed, to overcome obstacles so a sufficient safety factor is present.

Achieving the proper load isn’t something that simply happens by grabbing a wrench and tightening the bolts until they feel snug. There is a lot that goes into the calculation and subsequently, the assembly, to ensure that the joint will stay properly sealed.

Bolt loading is not only the sum of the force from all of the fasteners, but also how it is applied and the geometry of how it is applied. Generally, the bolts should be placed such that they distribute the load evenly throughout the sealing surface and in line with it as best as possible (bolt circle).

Load is divided by sealing area to determine average flange load and thus target loading. This can be correlated to material studies so the engineer can make a determination of how much load is needed, and thus, how many bolts, what size bolts, and the torque to apply. Manufacturers will tell you that fasteners should be sized and loaded just before, at, or just after yield strength to apply the most load properly. This is also the reason they should not be reused, such as in a head gasket application.

Loading issues such as these are a key component in FEA (finite element analysis) and should be as accurate as possible to make a good model. Engineering evaluations such as this are often very helpful in establishing a successful design.

Gasket Material Makes A Difference

Bolt load is only as good as the compressibility and recovery your particular gasket material can achieve. One can figure out the perfect design and exactly what bolt load is needed in your application. But, if you don’t have the right gasket material (either because a poor selection was made, or there isn’t really a “right” material for your application because of how it was designed…oops), you aren’t going to achieve the seal that you need. Selecting the proper gasket material to meet your requirements is probably one of the more important pieces of the design, and the sooner in the design process you do this, the better off you’ll be.

Now That You Know

As you can see, bolt load is something that generally falls within the scope of a design engineer, but a good gasket material supplier can be a great resource. If you are unable to achieve the proper load, or you want to ensure that there a material to meet your loading requirements, talk with your supplier. They should be able to give you some insight, and maybe even a different material to consider.

What are some of the main reasons for your insufficient load problems?Request a Call