Seals are subject to toxic and aggressive a substance that needs to be prevented from the rest of the system. This liquid is sometimes acid or other aggressive substance that can affect the quality of the seal. You can identify a seal having poor health from the blemishes on it. A bad seal must be replaced immediately before it collapses completely, bringing down the whole system. In this article, we have discussed five problems of mechanical seals and their causes. With the help of this article, you can troubleshoot these problems easily.
1. Heat Checking
These are circular cracks that originate from the metallic center of the seal ring and act as cutting edges on the seal face. They wear out due to the scraping action. Heat checking results as seals are put on containers, with liquids having low specific gravity. The high speeds and pressures are other factors that cause heat checking. Regardless of the movement of the shaft, one might notice the steady dripping of the seal when it is in operation.
Inadequate cooling, insufficient lubrication, or vaporization at the seal face can cause heat checking in seals.
Taking care of the causes can prevent the problem itself. That means you can protect the seal by lubricating the seal or ensuring sufficient coolant flow at the seal face for the removal of excessive heat.
You can also avoid this problem by ensuring a sufficient vapor pressure margin in the seal chamber. If that seems to be fine, make sure that the seal is adjusted at the right height, and increase the flush flow rate after reviewing the system design. Also, you might want to check out the mating ring distortion to ensure heat checking does not occur.
2. High Wear and Grooving
This symptom typically appears on the mating ring which exhibits a 360-degree wear pattern by the primary ring. This symptom can be noticed during seal dripping, regardless of the motion of the shaft. Poor lubrication can cause grooving especially if both the faces are made of rigid materials. If the primary ring is made of softer material, then this pattern is more prominent because of the abrasives embedded in the ring.
You can prevent this issue by cooling seal faces and by avoiding abrasives for coating hard mating rings.
A black residue accumulates on the atmospheric side of the seal. This speeds up the wearing of seal faces because of oxidation. Coking happens because of an over-heated surrounding environment or due to the presence of contamination in the flush.
Coking can be prevented by replacing the seal face with a hard material that can withstand oxidation. In case the signs appear, you can remove the residue using steam.
4. Pitting and Corrosion
The seal can often develop corrosion as a result of a chemical attack. This is clearly a sign that you are using the wrong material seal. Likewise, due to dryness seal can develop pitting, making it weak and feeble so much that sealed gases can escape.
You can avoid this by considering the fluid’s chemical breakdown, and choosing an appropriate seal for this material. While picking the seal, select the material that performs well in normal conditions i-e non-process activities. Don’t consider aggressive activities such as cleaning, steaming, acid, and caustic flushes when you are picking the seal material.
5. Blistering On Seal Face
Due to heat or thermal attacks, small round sections can precipitate on some seals. It often leads to seal causes seal leakage because seals have to be super flat and any kind of blister can separate seal faces while operating, misaligning it eventually. Seals that shift from state On to state off, tend to develop more blisters.
Typically, fluids with high viscosity tend to cause more blisters. A rise in temperature drives out the oil from high-viscosity fluids, towards the seal face. Followed by abrupt cooling, there are higher chances of blistering on the seal face.
Blistering can be prevented by reducing frequent starts and stops and using a non-porous seal face material that does not allow oil to penetrate from the seal face.