Fittings and Valves


The Cost of Tube Fittings: Are Swagelok fittings still worth the high price?

When it comes to Double Ferrule tube fittings and valves, we all think of the Swagelok brand as the industry leader, and they certainly are. It’s been about 40 years since Swagelok’s first patent blocked other manufacturers from producing an equivalent, double-ferrule fitting. Once they expired, it invited other manufacturers into the market and created competition for the product category.

DK-LOK Fittings & Valves is one of those manufacturers that entered the marketplace, and over time with their quality, service and competitive pricing; DK-LOK has become a best-in-class manufacturer for the industry.

What separates DK-LOK from the other manufacturers?

We would say its their willingness to prove their products are equal in quality to the Swagelok brand by testing them in a 3rd party environment. DK-LOK recently conducted a complete ASTM F-1387 intermix test through TUV Rheinland; a global leader in independent inspection services. The purpose of the test was to establish that any intermixed combination of individual components of DK-LOK with Swagelok would provide a leak-free performance.

Based upon performance results, it is confirmed DK-LOK tube fittings are interchangeable with Swagelok in threads, make-up distance, bore, sealing integrity, surface finish, design and pressure ratings and even offers an intermix guarantee publicly to the marketplace.

So…we ask the question… Why do customers continue to pay high prices for the Swagelok brand when it’s proven that DK-LOK manufactures an equal product for a fraction of the price?


We live in a world of options now, where you can cut costs but not the quality, and DK-LOK is one of those options. How often do people go shopping and purchase a product that is not the “name brand” but end up completely satisfied with the product they chose? The proof is in the tube fitting…see how much you’d be saving by switching brand names.

If you have any questions, feel free to send us an inquiry online or call us at 1-800-234-3033 and we will make sure to get back to you as soon as possible.

Traditional vs New DBB

5 Benefits of Using the New Method to Achieve Double Block & Bleed

True Double Block & Bleed can be accomplished in different ways; while specific sets of operating criteria and unique piping arrangements may point to one method over another.

Here is a list of some benefits that would reasonably be expected to achieve while using a single-body, forged valve (with 2 separate isolates & 1 vent), versus the “traditional” Double Block & Bleed method, using multiple valves and piping.

1.  Reduced Leak Paths

In looking at the “traditional” portion of the drawing above — which is no doubt a depiction of worst case scenario — there are multiple connections between valves, fittings & piping. The single valve shown to the right (“new”) is accomplishing all those same Double Block and Bleed (DBB) characteristics with far fewer connections / leak paths.

2.  Reduced Space & Weight

In many cases, these may not be a factor, but there are some applications where this is more important than others. Owners and operators of Offshore Platforms continue to rely on the single-body DBB design, where it is both highly approved and widely specified. Also, custom-build skidded equipment manufacturers are often tasked with turning broadly-defined specifications into a product solution that can be delivered in a very tightly-defined footprint. Actual weight & space savings vary greatly, depending on the size and pressure class of valves.

3. Reduced Labor

Pipefitters and welders are most valuable to the organization when their direct labor is allocated to the highest-value activities. Is some arrangements, labor spent on cutting and welding support brackets can take this skilled team off course.

4. Cost Reduction

Here, specific savings will not only vary greatly based on size and pressure class, but materials of construction will play a significant role in this area.  As customer requirements move into Duplex, Super Duplex and High-Nickel Alloys, tremendous savings can be realized when a single valve can take the place of 3 valves and the associated piping and fittings.

5. Safety A

This type of valve was initially born out of a tragic accident that occurred in the North Sea in 1988 on a platform known as Piper Alpha. A horrible explosion occurred and as the fire continued to burn, bolting & gaskets began to fail under extreme heat. The resulting breaches quite literally fueled the fire killing 167 workers and resulted in a total loss of the platform. 

Among the many lessons learned was a need to reduce leak paths within the piping systems.  Within months of the findings, Occidental Petroleum worked in concert with valve manufacturers in the UK to develop this new, better way.  There is also another version called Safety B,  which features fewer hours spent on cutting, grinding and welding activities can further reduce risk of injuries in the workplace.


Oliver Twinsafe Pipeline Valves

Oliver Twinsafe has been around for over 40 years, and manufactures precision quality Pipeline valves well equipped to deliver true reliability and performance under the most strenuous of environments.

Oliver’s established range of Double Block & Bleed (DBB) large bore pipeline valves save space and weight, reduce potential leak paths and minimise maintenance requirements on both new and existing pipelines. 

Oliver Twinsafe offers a range of valves from 1″ to 16″ in either full or reduced bore sizes, in ASME pressure Classes from 150 to 2500 and API ratings up to 10,000 API. Both soft and metal seated options are available. 

Rigorous In-House Testing Facilites

All valves are designed and tested within the requirements of API 6D, ASME B16.34, API 598 and ASME VIII.  Material certification to BS EN 10204 3.1 or 3.2 and a unique serial numbering system, ensure full traceability for all of their valves.

Oliver has custom state of the art test stations which allow larger valves to be tested easily, accurately and quickly on water, air and gas media.

They also perform fugitive emission testing to ISO 15848 and firesafe testing to ensure all valves are certified to API 607, API 6A and ISO 10497, and facilities for low and high temperature testing to meet customer requirements.


Intermixing vs. Interchanging?

Check out this video where we mix up DK-LOK and Swagelok compression fittings.

All DK-LOK products are developed, manufactured and tested to meet and exceed the requirements of various industry applications around the globe.

In fact, DK-LOK even offers an intermix guarantee publicly to the marketplace based upon TUV Rhineland witnessing of intermix test results between DK-LOK and Swagelok components in accordance with ASTM F1387.

Thinking about leaving Swagelok for another manufacturer?


Oliver Double Block & Bleed Valves

The Double Block & Bleed concept was pioneered by Oliver Valves in the early 1980’s and has since become a standard world wide. Each Double Block & Bleed (DBB) has a unique serial number which records it’s factory history and provides traceability.

Double Block & Bleed valves are used in critical applications where cost, weight and space savings are paramount for pressure instrument take-off points.

Oliver Valves has since grown to become one of the world’s leading manufacturers of instrumentation, subsea, and pipeline valves for the global energy sector and they’ve manufactured more than 300,000 of these units installed worldwide.

Operating in accordance with ISO 9001:2015 quality management system, Oliver’s high quality of standards ensure reliability is always delivered and that’s why we love working with them so much. It is their mission to provide all customers  outstanding technical customer service, on-time deliveries and continued engineering innovation.

Double Block & Bleed valves can be used for sampling systems where a pipeline probe is integral with the valve or in chemical injection systems where a check valve is part of the valve assembly.

They are also good for draining tanks and pipes where space is restricted and they can be used to reduce vibrational stresses. And they can be used for high pressure firesafe diverter valves or hydraulic power unit systems; and the cost savings with exotic material designs are huge.


Some key advantages include:

  • Eliminate a terrific amount of space when compared with welding three individual valves together
  • Reduce labor and site installation costs
  • A reduced amount of leakage points – a huge benefit as fugitive emissions are so important.
  • There’s only one component to be ordered, which saves on inventory and site confusion.
  • The pressure instrument is a lot closer to the point of pressure measurement, which saves space (most important on skid mounting applications).
  • Unique numbering system on each valve recording factory history.

Specializing primarily in the oil, gas and petrochemical industries, Oliver operates internationally across all regions and they have specialists located all over the world.

The Oliver Double Block & Bleed part machine program was set-up many years ago, in which all aspects of the DBB concept are machined. You simply specify the desired flange, which reduces lead time and results in quicker shipping. It’s pretty neat.

You can choose from a variety of different variations, including vent and injection, ball range, exotic materials, and all the options available from standard ball and needle valves.

So as you can see, there’s tremendous amount of value behind Oliver’s Double Block & Bleed valve, which is why we love them so much!