Dresser · Line Cap
Style 31 Line Cap for Cast and Ductile Iron Pipe
Style 38 coupling parts with a dished steel head welded into the middle ring; one gasket, 1 in NPT vent.
150 PSI MAOP, All Sizes
Grade 27 Buna-S Gasket
Carbon Steel Middle Ring and Follower
AWWA C111 Bolts
Fusion-Bonded Epoxy Coating
1 in NPT Vent Standard
2.50-25.80 in Pipe OD
12-230 lb Weight
Overview
Dresser Style 31 line caps close off sections of a line during construction and testing, and cap dead ends left for future branch connections. Each cap is made from Style 38 coupling parts: a convex dished steel head is welded into one end of the middle ring, one follower is welded to the cap, and only one gasket is needed.
Application: Closing, testing and capping plain-end cast and ductile iron pipe.
- One gasket, one bolted follower
- 1 in NPT vent: centered on 2 and 3 in, off-center on 4 in and larger
- Caps without vents or with lock pins available to order
- Insulating design available to order
What Ships and What It Needs to Run
Included: the cap body with welded head and follower, one loose follower, one gasket, bolts and nuts, and the 1 in vent plug.
Pipe prepared before install: a clean, round plain pipe end where the gasket seats.
Thrust blocking, by others: Dresser requires anchorage or blocking that holds the full end thrust of the line pressure before the cap is pressurized.
Genuine Dresser equipment, factory-new in original packaging — sold and supported by Watermain Supply, an independent industrial supplier.
12-Month Dresser Warranty
Covered for 12 months from the date of purchase under Dresser’s published warranty terms.
Working Pressure
150 PSI MAOP in every size; Dresser builds higher ratings per application. The allowable pressure on a job also depends on the pipe, its condition, the service and the workmanship.
Materials Specifications
| Followers |
AISI C1012 or ASME SA36 |
| Middle ring |
ASTM A513, ASTM A635 or ASME SA675 GR60 |
| Bolts |
AWWA C111 / ANSI A21.11 |
| Gasket |
Grade 27 Buna-S standard |
| Coating |
Fusion-bonded epoxy; RED-D shopcoat optional |
Source: Dresser Style 31 submittal, 2021.
Sizes
Sizes (19)
| Nominal |
Pipe OD (in) |
Middle ring (in) |
| 2 |
2.500 |
.187 x 5 |
| 3 |
3.800 |
.188 x 5 |
| 3 |
3.960 |
.203 x 5 |
| 4 |
4.800 |
.229 x 5 |
| 4 |
5.000 |
.229 x 5 |
| 6 |
6.900 |
1/4 x 5 |
| 6 |
7.100 |
1/4 x 5 |
| 8 |
9.050 |
1/4 x 5 |
| 8 |
9.300 |
1/4 x 5 |
| 10 |
11.100 |
3/8 x 7 |
| 10 |
11.400 |
3/8 x 7 |
| 12 |
13.200 |
3/8 x 7 |
| 12 |
13.500 |
3/8 x 7 |
| 14 |
15.300 |
3/8 x 7 |
| 16 |
17.400 |
3/8 x 7 |
| 18 |
19.920 |
3/8 x 7 |
| 20 |
21.600 |
3/8 x 7 |
| 20 |
22.060 |
3/8 x 7 |
| 24 |
25.800 |
3/8 x 7 |
Dresser Style 31 data sheet and 2021 submittal.
Installation Notes
- Never pressurize a Style 31 line cap without anchorage or blocking that withstands the full longitudinal thrust.
- Read the Dresser installation instructions and warnings before installing.
Source: Dresser Gas Product Selection Guide (NGS-DPS-015), product warnings.
Before You Order. Anchor or block the cap for the full thrust of the line pressure before pressurizing: an unanchored cap can blow off the line (Dresser warning). Non-stock Dresser parts are not returnable without Dresser’s authorization, and ship time is confirmed when you order. Custom builds (other sizes, widths, gaskets or materials) are available: email
sales@watermainsupply.com with the pipe OD, material and line content.
