Cold flow is a significant problem in hose systems that can cause leaks and performance failures over time. This problem occurs when the hose material gradually relaxes or compresses, which reduces the stability of the clamp. So how can we solve it? Constant tension hose clamps, which are adjusted primarily to the application material, maintain a tight, secure seal even when the hose expands or contracts.
In this article, we’ll take a deep dive into how cold flow occurs, the effects it has on hoses, and how constant tension hose clamps are the solution to this problem.
Constant tension hose clamps work by maintaining a constant clamping force, which compensates for the natural expansion and contraction of the hose material due to temperature changes. These clamps have a spring mechanism that automatically adjusts to ensure that the hose always has the same pressure. This prevents leaks and keeps the system reliable, even if the temperature or pressure changes.
To understand how constant tension hose clamps work, you need to understand how cold flow affects hose systems. So let’s talk about cold flow and how these clamps can help prevent it.
Cold flow is the gradual deformation of a material (usually rubber or elastomer) under sustained pressure. In a hose connection, this deformation can lead to reduced clamping force, which can cause leaks or failures. As the temperature decreases, hose materials such as rubber shrink, lose their original shape, and create gaps in the seal of the hose clamp. This reduced seal integrity can lead to leaks, pressure loss,s and system inefficiencies.
Hose materials, especially rubber, soften and deform over time when subjected to constant pressure. When this happens, the ability of the hose clamp to hold the hose in place is compromised. The material shrinks in the cold and expands when heated. This problem becomes more pronounced in applications with large temperature changes.
Cold flow can have serious consequences for a hose system. When the hose is loose, the seal formed by the hose clamp becomes weaker. This can lead to the following issues:
The key to constant tension hose clamps preventing cold flow lies in their design and function. These clamps feature a Belleville washer, a spring that compensates for temperature-induced hose contraction. When the temperature drops, the rubber hose contracts, and the Belleville washer compresses, automatically tightening the clamp to compensate for the change in hose size. This ensures that the hose remains tightly secured and prevents cold flow.
Constant tension hose clamps can be adjusted by oneself. Meaning they require little to no human intervention, this feature is critical to preventing cold flow because it ensures the clamp maintains consistent pressure on the hose, even if the material contracts or expands due to temperature changes. In turn, this prevents the seal from loosening, eliminating the risks associated with cold flow.
Constant tension hose clamps are typically made of high-quality materials, such as stainless steel, which are corrosion-resistant and abrasion-resistant. This durability allows the clamp to perform reliably over the long term.
Constant tension hose clamps are made of strong materials, such as stainless steel and high-strength alloys, so they can survive harsh environments. The most commonly used technology is a disc spring mechanism, which allows the clamp to automatically adjust its size. The spring compensates for the expansion or contraction of the hose material, allowing the clamp to maintain the proper tension and prevent cold flow. Some clamps also have an anti-corrosion coating, so they can last a long time under harsh conditions.
There are several benefits to using constant tension hose clamps to prevent cold flow:
Constant tension spring clamps offer an advantage over traditional hose clamps on radiator hoses, as temperature changes are more pronounced in radiator or coolant hoses, and constant tension spring clamps also maintain consistent pressure during hose expansion and contraction. Because these clamps adjust automatically, they prevent leaks and ensure the hose remains securely in place.
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Constant tension hose clamps provide a reliable solution for cold flow, preventing leaks and maintaining the performance of your hose system. These clamps use a Belleville washer to automatically adjust, helping to prevent cold flow and ensure a tight seal, making them ideal for applications where hoses need to be securely connected at varying temperatures.
If you’ve ever clamped a hose or pipe, you know it’s not as simple as set it and forget it. You want the clamp to compress the hose around the fitting to ensure a tight seal, but that compression can deform the hose and lessen the effectiveness of the seal.
After you install a clamp, the material of the hose actually moves out from under the clamp to escape the pressure. This movement, known as cold flow, means that over time, the seal the clamp provides will not be as tight as it was when you installed it. This is so even if the hose isn’t in regular use and nothing in the environment changes.
But add in the expansions and contractions of the materials caused by temperature changes, plus the changes in pressure resulting from normal use, and the cold flow process accelerates. The endpoint of cold flow is the condition of the compression set, where the hose has permanently deformed to the size of the clamp.
Certain materials are more prone to cold flow issues. It’s seen more with thinner-walled, less rigid hose materials, most notably silicon. Materials engineers have made changes to the design of silicon hoses over the years, but cold flow still occurs, so it’s essential to choose the right clamp to address the potential problems.
You need a clamp that allows for expansion and contraction. Otherwise, you’ll have a situation in which the hose won’t give as the pressure and temperature change, leading to a bulging hose and a more extreme compression set. Your best bet is a constant tension clamp (also called a constant torque clamp), which has been designed to operate in cycles of expansion and contraction.
The two most common types are the constant tension band clamp and the constant tension spring clamp. These both tend to be robust clamps that allow you to generate high sealing force or band load. But tightening the clamp does only so much when the side inside of the clamp is smooth; it doesn’t bite down well on the equally smooth material of the hose.
Silicon hoses are common in automotive installations, and constant tension clamps are fine for many of these uses: Exhaust systems often use band clamps, for instance. But in high-performance installations, something more is needed.
Tight, reliable seals are essential for the safe operation of the family car, but they’re even more essential in the more demanding conditions of a race car. In turbo-powered engines, a clamp failure can cause loss of boost, or even hose blow-off, which could be extremely hazardous if the car is operating at a high speed.
To counteract that danger, the engineers at Murray Corporation have further refined the design of the constant tension band clamp. They have created a turbo seal constant tension clamp with a convoluted band, and a dual bead shield that bites down on the hose material even at lower temperatures. It, therefore, requires less tightening than a T-bolt clamp to generate a good seal. This unique Dual Bead Shield® design is proven to remain in place even under the high-stress engine conditions of a race car.
No clamp can just be installed and ignored – not even a constant-tension clamp. Once you’ve chosen the right clamp and installed it, you still need to check it regularly and tighten it as needed to make sure that it continues to provide the tight seal that will prevent problems.