How to choose a Dresser Coupling?

How to choose a Dresser Coupling

Dresser Pipeline products have many coupling options to choose from. While one coupling type may work in place of other, it may not be the best use of money and space while repairing a pipe or working on a new construction. Dresser also offers several clamps that can achieve somewhat similar results but we will keep that discussion for another blog to keep this topic focused on couplings. Let’s assume a coupling is a best option and we need to make sure we select the right one.

Dresser coupling offers a fast and convenient way of joining two sections of pipe when you are able to slide the coupling onto the pipe. If the space does not warrant a cutout and repair with a coupling, a clamp may be a better option. However we will not discuss clamps in this blog.

Dresser couplings can be divided into two main categories;

1. Bolted Coupling
2. Compression Coupling

Dresser bolted line of coupling includes;

1. Style 38 Coupling
2. Style 40 Coupling
3. Style 39 Coupling
4. Style 62 Coupling
5. Style 138 Coupling
6. Style 128 Flange Adapter Coupling

Dresser compression line of coupling includes;

1. Style 65 coupling
2. Style 88 coupling
3. Style 90 coupling

Dresser couplings should be selected based on the intended applications. Factors that can affect coupling performance includes;

• Line content
• Pressure
• Temperature

Other factors that can affect the selection includes;

1. Location (at a plant, on a vessel etc.)
2. Application (pipe, pump, compressor, process line etc.)
3. Space available
4. Risk tolerance

Line Content

Dresser couplings are widely used in water, waste water, gas and many other downstream fluid applications.

All dresser couplings are made of carbon steel middle ring and follower. Bolts are also made of carbon steel. All stainless steel Dresser couplings are available on request. Gasket is either Buna S, Buna N, Viton, EPDM or Graphite Fiber hybrid. 27 Buna S is the most common gasket used. All gaskets are available in the armored version also that adds addition rigidity to the seal and also provide means of electrical contact to the pipe. Click here to learn more about Dresser Gaskets. You can buy these gaskets online here.

 Pressure Rating

Other consideration is pressure rating. Dresser couplings are rated from 150 psi to 2250 psi maximum working pressure. Dresser light pattern couplings are rated up to 150 psi. Dresser style 65 and style 90 couplings are considered 150# and 300# couplings respectively. Refer the size and dimension table to look up the pressure rating of a bolted coupling. Generally, as the size goes up, the pressure rating goes down. Any coupling with 150 psi working pressure is a light pattern coupling.

 Temperature Rating

Temperature mainly affects the gasket and pressure rating of the coupling. Higher the temperature, lower the pressure rating. Different gaskets are rated for different temperatures. Dresser makes lifetime® gaskets but factors that can affect the performance of gasket are temperature “cycle” that can result in compression set, abrasive line content that can damage the lip of seal and combination of chemical compatibility, temperature and pressure. Generally speaking, anytime the temperature is above 200 deg F, you should pay close attention to your selection of gasket, gasket chemical compatibility and pressure.

 Location

Location can affect your selection criteria if you have specific restrictions such as ABS approved coupling for vessels, stainless steel body due to corrosive environment, maintenance concerns and any other area-specific requirements. Generally the hot work permit is not an issue for Dresser Coupling as there is no welding needed. In hazardous locations, non-sparking hand tools can be used to tighten the bolts or the nut of the coupling, which is the only assembly step required on the coupling.

 Application

This is the most important factor of all. What are you trying to achieve? Some of the reasons customers use Dresser couplings are;

1. Repair a pipeline
2. Connect a pump or compressor with Dresser style 128 flange adapter for ease of access to the equipment in future
3. Repair a pipe that will be buried
4. Allow for thermal expansion and contraction and avoid pipe bends & cracks
5. Minimize vibration damage. The seal in the coupling acts as a cushion
6. Straddle two couplings and repair a longer than normal section of pipe
7. Repair pin hole leak that cannot be repaired with a clamp

 Space Available

This is also very important. If you are repairing a pipe that is under 2 inch nominal dimension and you do not need more than 300 psi pressure, style 65 or style 90 may be your best choice. If you are repairing a gas line, style 90 universal coupling is very popular to repair gas lines. If you are repairing a PVC or PE pipe or any combination of steel and PVC/PE pipe, style 90 universal coupling has a lock ring to prevent from pipe pull out.

If space is not an issue, light pattern should be your next choice as along as pressure requirement is no more than 150 psi. You will save money and space as long as light pattern can work in your application. Your next choice could be style 38, style 40, style 39, style 138 or style 62, all depends on the specific application.

 Risk Tolerance

How important is the application of coupling? Have you done any risk assessment if anything goes wrong? How difficult it will be to access the equipment or the pipeline. Can you afford downtime while an equipment is being repaired? In most situations, Dresser Coupling offers fast and convenient way to join pipe connections & equipment. If selected correctly, Dresser coupling provides years of service without needing any maintenance.

So which coupling I should use?

Below is a rough guideline of where each coupling should be used;

Style 38 Dresser Coupling: We sell more style 38 couplings that any other coupling combined. Style 38 coupling is available in a wide range of size, wall thickness and lengths. While choosing style 38, you should consider following;

1. Would light pattern work for me?
2. If under 2 inch nominal pipe, can I use style 65 or style 90
3. Is pipe pull out a concern?

Also make sure you always select the right combination of middle ring wall thickness, number of bolts and length.

Fig 1 - Dresser Style 38 & 40 Coupling

Style 40 Dresser Coupling: Style 40 is a TALLER brother of style 38. The only reason you will NOT use style 38 is if you need 12 inch or longer coupling. Style 40 couplings are available up to 24 inch length.

 REMEMBER: You can always straddle a piece of pipe with two style 38 or style 40 couplings to repair a much longer section.

 Style 39 Insulating Coupling: Style 39 Insulating Dresser Coupling follow the same basic design as the Style 38, but have insulating properties. Style 39 is ideal for industrial applications for water lines where electrical isolation is needed. Besides being used for tank hook-ups, intake or discharge lines and pumping stations, Style 39 Dresser Coupling are also widely used on gas service lines.

Style 39 also comes in insulating and reducing style. Regardless if you need insulating feature, the reducing feature can be used to connect steel pipe to cast iron pipe.

Fig 2 – Dresser Style 39 Coupling

Style 138 Coupling: Style 138 Dresser Coupling for Cast & Ductile Iron Pipe provide flexible, leak-proof connections whether the cast iron pipe was made in 1890 or from your latest shipment. The unique feature of this product is one middle ring can be used with up to six different gaskets and three followers to cover a wide range of pipes.

Fig 3 – Dresser Style 138 coupling

 Dresser Style 128 Flange Adapter: Style 128 Flange adapter should be used where you have a regular flange connection (150#, 300#) on one end and want Dresser Coupling-Style connection on the other end. This type of connection is very popular on pumps and compressors, with flanged ends. This provides an easy access for maintenance in future.

One common misconception people have is that the coupling follower ring bolt pattern will match a flange bolt pattern. The follower ring (2 ea. end plates) has bellowed shape. It used to be flat face and looked very similar to flange fitting. Since Dresser Coupling is available in many configurations with multiple bolts, many customer tried to connect it to a flange with no success. Dresser style 128 is the ONLY way you can connect to a flange on one end.

Fig 4 – Style 128 Flange Adapter

Style 62 Coupling: Style 62 coupling should be used where you want to connect two pipes of different sizes or steel pipe to a cast iron pipe. Choices are limited to what reduction you can have so it is important that you check the diameter range of reducing end while selecting the coupling.

Fig 5 – Style 62 reducing coupling

 Style 65 Compression Coupling: Style 65 is a 150# galvanized compression fitting intended for plumbing and light industrial use. It is available in sizes from ½” to 2” nominal. Style 65 is very popular in industrial installations and repair, especially for tight spaces where threading, bolting or welding is not a good option. Style 65 is also maintenance friendly and can be easily disassembled to access the pipe, change gasket in the coupling or perform line repairs. Dresser style 65 is available as;

• Regular coupling
• Long coupling
• 90 degree elbow
• Male adapter

Style 65 should NOT be used where pressures are greater than 150 psi. Refer to our video on style 65 to learn more.

Fig 6 – Dresser style 65 fittings

 Dresser Style 90 Coupling: Style 90 is also a compression-type fitting available in sizes from ½” to 2” nominal. Style 90 is a 300# coupling and provides an alternative to style 65 for heavier use. Style 90 also comes in a “universal” style with lock ring that prevents pipe pull out. Style 90 coupling is very popular on gas service lines due to armored gasket, ability to prevent pipe pull out and heaver grade. Refer to our video on style 90 to learn more about this style of dresser coupling.

Fig 7 – Dresser Style 90 couplings

Dresser Style 88 Coupling: Style 88 is made exclusively for copper tubing. Since copper tubing dimensions are different from steel pipe, the coupling has different IDs to match that of copper tubing. Style 88 coupling can also be used in tandem with style 65 coupling by using insulating adapter. Insulating adapter is a gasket adapter that fits over the copper tubing which in turn fits inside the style 65 compression coupling.

Fig 8 – Style 88 Dresser Fitting

Style 440 Joint Harness: Remember that with the exception of Style 90 universal coupling, Dresser Couplings will not prevent excessive axial forces. If pipe pull out a major concern, one should use Dresser Style 440 Joint Harnesses are steel tie-bolts, diametrically opposite, which extend across a coupled joint from lugs welded to the pipe on either side of the joint. Joint harnesses are particularly effective on unanchored bends subject to pulsating pressures of sharp intensity.

Fig 9 – Style 440 Joint Harness

 Conclusion

As you can see, Dresser offers a broad line of choices for couplings. Each of these couplings are made for specific application and offer unique advantages. Coupling should be selected based on the intended application, pressure & temperate requirement, space available and any regulatory requirement. When used properly, Dresser Couplings offers a long life that often exceed the life of equipment/pipe. Dresser couplings can be used on steel pipe, cast iron pipe, ductile iron pipe, PVC pipe & HDPE pipe.

Dresser couplings are being used for more than 100 years and are proudly Made in USA. Trupply is an authorized Dresser Coupling Distributor and we stock pretty much all the styles and sizes for immediate shipment. Call us at 281.516.8100 or email sales@trupply.com

Useful Links

Dresser Couplings

Dresser Compression Fittings

Dresser Gaskets

Dresser Knowledge Central

Fig 10 – Trupply’s warehouse