Is your C Series Type D Seal Squealing? Here’s what to do.

One of the most common C series pump troubleshooting questions we get every day is from a customer who’s C Series type D seal is “squealing”. While this noise is rather unpleasant, there’s not too much to worry about and you have a few options to resolve it. Read on to find you.

First, let’s start by taking a look at what’s causing the noise. The C series pump a very simple pump common in all sorts of sanitary applications, but probably most common in breweries. We love the C series because it’s simple, cheap, and easy to service. The C series pump has essentially 6 parts- the adapter, casing, the impeller, backplate, seal, and stub shaft. We’ll spend the rest of this post focusing on the culprits here- the seal and the backplate.

C Series Type D Seal

The most common seal in a C series pump is the Type D seal. We like it for similar reasons we like the C series in general- its simple, easy to service and cheap to replace. The Type D seal features a black carbon seal that rides on a stainless steel backplate. This is a great seal for cool, clean fluids.

Unfortunately, the carbon vs. stainless combination doesn’t do great with high temperatures or abrasive fluids. This is when we start to get the “squealing” sound. While it’s unpleasant to hear, no it does not mean your pump is going to explode, it just means you’re putting stress on that carbon seal. If you can tolerate it or if the high temps are only intermittent, don’t fret- a replacement carbon is only about $15-$25.

If you can’t tolerate it (and really, you shouldn’t), there are a few things we can do to fix the issue.

C Series Seal w/ Flush

The first thing we can try is a seal flush. Have you ever wondered why there’s a threaded connection on your adapter? That’s there so you can thread in a flush hose to bring fluid to the seal. As we mentioned in our prior post on seal flush, the flush is going to do a few things for us here. First, it’s going to flush or clean the seal faces. More importantly, it’s going to lubricate and cool the seal, which will almost certainly reduce our noise problem.

The drawback to the flush is the cost and mess it can create. Water isn’t free and no one wants it on the floor. So if we want to avoid a flush, we have two different seal options- the DG and the CB+ internal seal.

C Series Type DG Seal

Let’s look first at the DG seal. This is the older of our two options and like the Type D seal is an external seal option. To install a DG seal, we replace our existing backplate with a new “modified” backplate designed to have a ceramic or silicon carbide stationary seal bolted into it. We still use the same carbon rotating seal we do in the Type D seal, but because carbon vs. ceramic creates much less heat than carbon vs. stainless, we get longer, quieter operation with high temperature or abrasive products.

C Series CB+ Seal

The second seal option we have is the Type CB+ seal option. Originally developed by Q pump and Ampco for industrial applications and modified for sanitary and craft brew applications, the CB+ seal is an internal seal that uses a modified backplate to accommodate a silicon carbide stationary in the backplate and rotating silicon carbide seal element. The internal seal configuration not only features superior sealing materials similar to the DG, but also allows us to use the product itself as a seal flush. The primary drawback is having the seal in the product zone and what happens if and when the seal fails. For that reason, we recommend having strainers downline of the pump and avoid using it to feed filling machines or other sensitive equipment.

So whether you’re running a hot CIP or pumping out of your brew kettle and you hear your C series start to squeal, don’t panic. The pump is fine. If this continues to happen, consider our three tips above. Start with a seal flush. If that’s not an option, we can try either a Type DG or Type CB+ seal. And as always, if you have any questions about any of your C series pumps, contact a Triplex Sales Engineer today.

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