Dresser Style 38 vs Style 40 Coupling

Dresser Style 38 vs Style 40 Coupling

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Watermain Supply Technical Guide

Dresser Style 38 vs Style 40
When to Use Which Coupling

A practical decision guide for contractors and engineers specifying Dresser bolted couplings — including installation procedure, torque specifications, and the one detail that determines which style your job needs.

Dresser Style 38 and Style 40 are the two workhorse bolted couplings in the Dresser pipeline product family. They share the same construction principles, materials, gasket compounds, and pressure capabilities. They differ in one practical detail that determines which one your job actually needs: the length of the middle ring.

This guide walks through the spec differences, when each is the right choice, and the official Dresser installation procedure including torque values. Written for waterworks contractors, utility crews, and engineers specifying Dresser bolted couplings on steel, cast iron, ductile iron, or transition pipe work.

TL;DR — The 30-Second Answer

Both couplings do the same thing: create a flexible, bolted, gasket-sealed joint between two pipe ends without welding or threading. The difference is middle ring length.

  • Style 38 — standard 5 in or 7 in middle ring. Use when pipe ends are normally spaced. The default choice for new installations.
  • Style 40 — long body (12 in, 16 in, or 24 in middle ring). Use when pipe ends are widely separated — repair work, dropped sections, alignment recovery, or where you need extra coverage over a damaged pipe area.
  • Same pressure ratings, same gaskets, same materials. Both absorb up to 3/8 in expansion/contraction per joint on 10.75 in OD and larger.
  • Same installation procedure and torque values.

Construction — Identical Working Principle

Both Style 38 and Style 40 use the same core construction: a cylindrical steel middle ring with conical flares at each end, two follower rings, two resilient rubber gaskets, and trackhead bolts. As the nuts are tightened, the bolts draw the followers toward each other, compressing the gaskets into the wedge-shaped space formed by the follower ring, middle ring flare, and pipe surface. The result is a flexible, leak-proof seal that accommodates pipe movement, vibration, expansion, and minor angular deflection.

Materials of Construction (Both Styles)

Component Specification
Followers AISI C1012 or ASME SA36 carbon steel (ductile or malleable iron for 1/2 in thru 1-1/2 in pipe sizes)
Middle Ring ASTM A513, ASTM A635, or ASME SA675 GR60 carbon steel
Bolts AWWA C111 / ANSI A21.11, trackhead design, E-coated as standard
Coating Fusion-bonded epoxy (Dresser ALCLAD)
Standard Gasket Grade 27 Buna-S (SBR)
NSF Certification NSF 61 and NSF 372 certified (Grade 27 and EPDM)

The Real Difference — Middle Ring Length

Style 38

Standard Length Middle Ring

Middle ring lengths of 5 in or 7 in are the working standard. The 5 in body is the most common general-purpose coupling. The 7 in version provides more bearing surface on the pipe and is preferred for higher-pressure or larger-diameter service.

Use Style 38 When
  • New construction with normal pipe end spacing
  • Standard joint connections between cut pipe sections
  • Routine watermain extensions or branch tie-ins
  • Replacement of an existing coupling on undisturbed pipe

Style 40

Long Body Middle Ring

Middle ring lengths of 12 in, 16 in, or 24 in with a larger belly diameter. Provides significant coverage over the pipe ends — useful when pipe ends are not cleanly aligned or when extra coverage is needed over a damaged or irregular pipe section.

Use Style 40 When
  • Pipe ends are widely separated (broken pipe, dropped section, settlement gap)
  • Emergency repair where cut pipe lengths can't be precisely matched
  • Covering a damaged pipe section without replacing the run
  • Lining up to existing infrastructure with imperfect spacing
  • Bridging across a corroded or eroded length of pipe
Critical point on expansion/contraction

The Style 40's longer middle ring does NOT increase movement capability. Both styles accommodate the same 3/8 in of axial pipe movement on 10.75 in OD and larger (1/8 in for 3/4 in thru 2 in OD; 1/4 in for 2-1/2 in thru 10 in OD). If your application needs more movement, specify a Dresser Style 63 expansion joint instead.

Pressure & Sizing Reference

Working pressures are calculated by Barlow's formula using a working stress equal to one-half the minimum yield of the middle ring material. Below is a working reference covering the most-installed sizes on steel pipe. The full Dresser catalog covers 1/2 in ID through 400 in+ OD.

Style 38 — Steel Pipe Sizes (5 in & 7 in Ring)

Pipe Size Pipe OD (in) Ring Length Bolts (Qty x Dia x Length) Working Pressure (psi) Weight (lbs)
2 in 2.375 5 in 3 x 5/8 in x 8-1/4 in 1,500 10
3 in 3.500 5 in 4 x 5/8 in x 6 in 982 13.5
4 in 4.500 5 in 4 x 5/8 in x 6 in 931 16.5
6 in 6.625 5 in 6 x 5/8 in x 6 in 1,029 25.5
6 in 6.625 7 in 6 x 5/8 in x 8-1/4 in 1,029 31
8 in 8.625 7 in 6 x 5/8 in x 8-1/4 in 807 38
10 in 10.750 7 in 8 x 5/8 in x 8-1/4 in 657 49
12 in 12.750 7 in 8 x 5/8 in x 8-1/4 in 558 56
16 in 16.000 7 in 10 x 5/8 in x 10-3/4 in 449 70
20 in 20.000 7 in 12 x 5/8 in x 10-3/4 in 362 83
24 in 24.000 7 in 14 x 5/8 in x 10-3/4 in 304 105

Style 40 — Steel Pipe Sizes (12 in, 16 in & 24 in Ring)

Pipe Size Pipe OD (in) Ring Length Bolts (Qty x Dia x Length) Working Pressure (psi) Weight (lbs)
4 in 4.500 12 in 4 x 5/8 in x 15 in 1,063 28
6 in 6.625 16 in 6 x 5/8 in x 19-1/2 in 968 51
8 in 8.625 16 in 6 x 5/8 in x 19-1/2 in 769 63
10 in 10.750 16 in 8 x 5/8 in x 19-1/2 in 632 109
12 in 12.750 16 in 8 x 5/8 in x 19-1/2 in 520 119
16 in 16.000 16 in 10 x 5/8 in x 19-1/2 in 449 148
20 in 20.000 16 in 12 x 5/8 in x 19-1/2 in 362 201
24 in 24.000 16 in 14 x 5/8 in x 19-1/2 in 304 240
30 in 30.000 16 in 16 x 5/8 in x 19-1/2 in 282 290
36 in 36.000 16 in 18 x 5/8 in x 19-1/2 in 262 345

Light Pattern Couplings carry a standard 150 psi rating; consult factory or Watermain Supply for special pressure conditions. Sizes shown are most-installed; full Dresser catalog covers any custom OD.

Installation — Official Dresser Procedure

The installation procedure is identical for Style 38, Style 40, Style 56, 62, 69, 71, 72, 76, 89, 128, and 168 couplings per Dresser Tag No. 0001-0737-999. Eight steps from clean pipe to torqued joint.

1

Clean Pipe End

Remove all dirt, rust, oil, or loose scale from the pipe end. Inspect the gasket contact surface for gouges, grooves, or imperfections that would impair the seal. A clean, smooth pipe surface is the foundation of a leak-free joint.

2

Mark Centering Reference

For couplings, measure back on each pipe end one-half of the middle ring length plus 2 in. Place a chalk mark at this point. These marks let you center the coupling over the joint correctly. Example: a 7 in middle ring needs marks at 3-1/2 in + 2 in = 5-1/2 in from each pipe end.

3

Slide Followers onto Pipe

Slide the follower ring(s) over each pipe end. Make sure the followers face the correct direction — flat side toward the gasket. Push them back far enough to clear the gasket installation area.

4

Lubricate Gaskets

Wipe each gasket clean. Lubricate the gasket, the pipe OD, and the middle ring flares with soapy water or a non-petroleum-base lubricant. Petroleum products degrade rubber and must not be used. In freezing weather, add antifreeze to the lubricant.

5

Install Gaskets and Position Middle Ring

Slide a gasket over each pipe end. Assemble the middle ring onto one pipe end first — push it past the gasket area on that side.

6

Stab and Center

Push the second pipe end into the middle ring. Center the coupling between the two chalk marks. The pipe end must extend past the gasket a minimum of 1 in after any angular deflection — this margin prevents pullout under pressure or movement.

7

Hand-Tighten Bolts

Install the trackhead bolts through both followers. Thread on the hex nuts. Draw them up finger-tight. Don't power-tool at this stage — the goal is to seat the gaskets evenly before applying torque.

8

Torque to Spec (Cross-Pattern)

Tighten the nuts on opposite sides of the coupling in a cross-pattern sequence, drawing the followers down evenly. Tighten progressively in stages until all nuts reach the recommended torque (see torque table below). Re-check torque on all nuts before backfilling — gaskets settle and bolts can lose torque after initial seating.

Recommended Bolt Torque (Per Dresser)

Bolt Size Torque (ft-lbs) Notes
3/8 in 35 Smaller pipe sizes (typically 1/2 in - 2 in)
1/2 in 35 Common on smaller couplings
5/8 in 75 Most-used bolt size across the catalog
3/4 in 90 Larger diameters and high-pressure service
Single-Gasket Products

For products using one gasket (some specialty styles), reduce torque values by half. Always check the product-specific instructions before applying torque.

Maximum Laying Deflection Per Coupling

Pipe Size Range 5 in Ring 7 in Ring 10 in Ring
1/2 in thru 2 in OD 6° 6° —
Above 2 in thru 14 in OD 4° 4° 4°
Above 14 in thru 30 in OD 2° 4° 4°
Above 30 in thru 37 in OD 1-1/2° 3° 3-1/2°
Above 37 in thru 42 in OD — 2-1/2° 3-1/2°
Above 42 in thru 54 in OD — 2° 3°
Above 54 in thru 66 in OD — — 2-1/2°
Above 66 in thru 72 in OD — — 2°

Gasket Selection

Both Style 38 and Style 40 are available with the full Dresser gasket compound range. Grade 27 Buna-S (SBR) ships as standard and covers most water and general service. Specify alternative compounds when the fluid chemistry, temperature, or application requires.

Compound Designation Service
Buna-S Grade 27 (SBR) Standard for water, sewer, general service. NSF 61/372 certified.
Buna-N Grade 42 (NBR) Oil, fuel, hydrocarbon resistance. Refined petroleum service.
EPDM Grade 31 Higher temperature water, dilute acids/alkalis, NSF 61/372 certified.
Viton Fluorocarbon Aggressive chemicals, aromatic hydrocarbons, high temperature.
Butyl Specialty Specific chemical service per application.
High-Temp Specialty Service up to 1,200°F.

Frequently Asked Questions

Can I substitute a Style 40 wherever a Style 38 is specified?

Generally yes — Style 40 will perform every function Style 38 does, with the same pressure rating and gasket. However Style 40 is heavier, more expensive, and the additional ring length serves no purpose on clean new pipe with normal spacing. Use Style 38 unless the gap or pipe-end condition calls for the longer body.

Does the longer Style 40 ring give me more expansion capability?

No. Both styles accept the same 3/8 in of axial movement per joint on 10.75 in OD and larger. The longer middle ring lets you bridge wider physical gaps between pipe ends — but the movement budget after installation is identical. For repeated thermal cycling or movement greater than 3/8 in, specify a Style 63 expansion joint.

What about stainless steel versions?

Both Style 38 and Style 40 are available in Type 304 or Type 316 stainless steel for corrosive service. Stainless versions meet AWWA C219. You can specify all-stainless, stainless middle ring only, or stainless bolts and nuts only depending on the corrosion environment.

Are these couplings restrained?

Standard Style 38 and Style 40 couplings are not restrained — they accommodate flexibility but rely on pipe restraint (thrust blocks, harnesses, or Dresser Style 440 joint harnesses) to resist axial thrust. For restrained service in pressure pipe, add a Style 440 joint harness.

What's the difference between Buna-S and Buna-N gaskets?

Buna-S (Grade 27 SBR) is the standard for water and sewer service and is NSF 61/372 certified. Buna-N (Grade 42 NBR) is specified when the line carries hydrocarbons, fuels, or oils that would degrade SBR. Don't mix them — specify based on the actual service fluid.

Can these couplings join dissimilar pipe materials?

Yes, as long as the pipe outside diameters are compatible. If the two pipes have different ODs (such as cast iron to steel of the same nominal size), use a Dresser Style 62 Reducing/Transition coupling instead. For dissimilar metals requiring cathodic protection, use a Style 39-62 Insulating-Reducing coupling.

Specifying Style 38 or Style 40 for Your Job?

Send us the pipe material, OD, working pressure, service fluid, and quantity. We'll confirm the right style, ring length, gasket compound, and lead time. Same-day shipment on common sizes from our Houston stock.

281.664.8000 Email sales@watermainsupply.com Request a Quote
Dresser and ALCLAD are trademarks of Dresser Utility Solutions. Viton is a registered trademark of DuPont Corporation. Watermain Supply (a DBA of E4 Industrial LLC) is a Houston, TX-based authorized Dresser distributor.