Repairing Pipeline Slab Gate Valves: A Solution for Aging Facilities

U.S. oil production has ramped up to a level not seen in decades. Last November, production hit 10 million barrels a day for the first time since 1948, and according to some estimates it could reach 12 million barrels a day by the end of 2019.

While this growth brings many benefits for oil and pipeline companies, it also poses challenges. In particular, many of the pumping stations along pipelines haven’t been used in a while, and some of their components have become faulty.

For example, slab gate valves with nickel-plated stems and gates are commonly found at pump stations as well as up and down pipelines. The majority of these valves were installed 30+ years ago, and as companies start bringing facilities back online, they’re discovering that the nickel plating has come off the stem and punctured the seal, causing the valves to leak.

That’s exactly the problem an industry giant recently called on Allied Valve to fix. Mark Zinger, the shop supervisor for Allied’s Iowa facility, and his team came up with an innovative solution that not only solved the problem but also saved the client more than 60% on repair costs.

An overview of slab gate valves

Slab gate valves are full-port valves, which means the hole in the gate is exactly the same size as the pipe. This full port design provides full flow through the valve and low pressure drop, and it allows for pigging the line when needed.

Slab gate valves are used mostly for petroleum products, including crude oil, gasoline, and diesel. Some are also used for gas service. They can be found at pump stations and along the lengths of pipelines, either buried or above ground. In short, these valves are everywhere.

The problem: Nickel plating had damaged the seals and caused the valves to leak

About 90% of slab gate valves in service today have nickel plating. This is because 30 or so years ago when many of these valves were put into service, it was commonly assumed that nickel plating would last forever.

Unfortunately, time has proven this assumption false. After years of service, the nickel plating on the stem starts to chip off, causing the stem seals in the top plate and the bonnet to start leaking.

On the project Allied service technicians recently completed, the valve body, slab, and seat were all in good condition and the valve was functioning properly for shut-off. But the nickel plating on the stem had damaged the seals in the top plate and bonnet, which meant that the stem and seals had to be replaced. In addition, the valves were buried underground, and the customer wanted the repairs to be completed on-site, without having to dig them up.

The solution: Allied redesigned the top plate to be leak-proof

The Allied service team approached the problem with an innovation mindset. They didn’t just want to replace the nickel plating — they wanted to ensure that the valve would be leak-proof for decades to come. So, they revamped the top plate using a more robust material and a new design.

Here’s what they did:

  • Replaced the nickel-plated valve stem with stems made from 17-4 Stainless Steel. 17-4 Stainless Steel is a strong, corrosion-resistant material. It’s hard and smooth enough that it doesn’t require plating.
  • Counterbored the top plate and added energized seals to the bonnets. Any debris that gets into a seal can cause damage — and crude oil contains a lot of debris (dirt, sand, gravel, etc.). With four seals, if one starts leaking, there are three backups to prevent product loss and environmental damage.
  • Drilled and tapped new grease fittings. Typically, a valve bonnet has one hole for a grease fitting. If the valve starts to leak, a technician can inject fluid grease into the fitting to stop it. Allied drilled a hole in the opposite side of the bonnet as well so the grease can flow in one hole and out the other. This ensures full coverage and will be crucial down the road to extend the life of the equipment.

To verify that the redesign worked, an Allied technician performed an API 6D test on the new plate, actuating the stem up and down for four hours. After a successful test, he installed the new top plate on the still-buried valve.

The result was a like-new valve with an improved design for roughly one-third what it would cost to repair the entire valve.

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As the U.S. oil infrastructure ages, we expect to see more problems of this kind — problems require creative, cost-effective solutions. Whatever your challenges, we’re here to help! Contact us to learn more about our valve repair services.

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