Masoneilan Type 37/38 Pneumatic Spring-Diaphragm Actuator, Sizes 11 to 24

Overview

The Masoneilan Type 37/38 pneumatic spring-diaphragm actuator is a simple, powerful, mechanical actuator from Baker Hughes with two action types and seven standard sizes. Type 37 is direct acting (air to close, extending the stem) and Type 38 is reverse acting (air to open, retracting the stem). The technical specification (Rev. C, 09/2023) lists sizes 11, 13, 15, 18, 18 (16 in.), 18 (20 in.) and 24, with nominal diaphragm areas from 71 to 330 sq. in., maximum travel from 1.0 to 4.0 in. and a maximum supply of 60 psi (55 psi on size 24).

In Oman and the GCC, Seven Star LLC supplies the Masoneilan Type 37/38 range to operators in Oman and the GCC. The design is found on many older Masoneilan globe valves, so most RFQs concern repair of installed units and matching diaphragms and kits rather than new installations.

Masoneilan Type 37/38 Sizes, Area, Travel and Weight

Standard bench ranges are 3-15 and 6-30 psi (6-30 only on the 20 in. size); other travels and spring ranges are available. The manual also lists size 9 (45 sq. in., 3/4 in. travel). Temperature range is −30°C to +80°C (−22°F to +176°F).

Design Features of the Masoneilan Type 37/38

Baker Hughes names four design features: a heavy one-piece yoke; pressed-steel diaphragm cases that combine lightness with strength; a molded elastomer diaphragm with a fabric insert; and deep cases that minimise area change and give a linear relationship between travel and air pressure. In an air-to-extend actuator the molded diaphragm acts as a flexible upper stem guide and an oil-impregnated bronze bushing is the lower guide. In an air-to-retract actuator the spring sits above an inverted diaphragm and a packing box is the lower guide. Air connections are 1/4 in. NPT, in the upper case for air-to-extend and in the yoke for air-to-retract.

Travel Time of the Masoneilan Type 37/38 on the Bench

For a 3-15 psi range and 20 psi supply the specification gives bench travel times with an 8012 electro-pneumatic or 7400 pneumatic positioner. Size 11 at 1.0 in. takes 3.3 s and 7 s; size 15 at 2.0 in. takes 11.4 s and 20 s; size 18 at 2.5 in. takes 21 s and 34 s; the 18 (16 in.) at 4.0 in. takes 32 s and 48 s. For 6-30 psi add 15 percent. These figures let a designer compare the larger Masoneilan Type 37/38 sizes before specifying them on a fast loop.

Dimensions and Installation Clearance of the Masoneilan Type 37/38

The spud diameter must match the valve bonnet when a replacement actuator is ordered for an installed valve.

Handwheel Options for the Masoneilan Type 37/38

Side-mounted handwheels are the 6A series (6A1 for size 11, 6A2 for size 13, 6A3 for sizes 15 and 18) and the 8A series (sizes 18, 18 (16 in.), 18 (20 in.) and 24). The 6A3 on a size 18 is limited to 40 psi supply at 2.0 in. travel and 35 psi at 2.5 in., while the 8A allows 60 psi (55 psi on size 24). Case-mounted handwheels are 2-11, 2-13, 3-15, 4-18, 6-18 and 7-24 for direct actuators and 9-11 and 9-13 for reverse ones, with 14 to 32 turns for rated travel. Confirm the type before ordering any handwheel spare.

Spares, Packing and Maintenance of the Masoneilan Type 37/38

The Parts Reference marks the packing-box gasket (15), the gasket between lower case and yoke (19), the packing (32) and the diaphragm (39) as recommended spares. Diaphragm renewal needs the spring compression relieved with the adjuster first, and the spring is then set so the stem just begins to move at the minimum pressure on the serial plate. Packing is square-section carbon core with a braided PTFE jacket and can be replaced without dismantling the actuator.

Key Features

• Masoneilan Type 37/38 in seven sizes from 11 to 24
• Direct acting (Type 37) or reverse acting (Type 38)
• Diaphragm areas from 71 to 330 sq. in. and travel to 4.0 in.
• 3-15 and 6-30 psi bench ranges with 6A, 8A and case-mounted handwheels
• Standard range of −30°C to +80°C

Industrial Applications

Type 37/38 actuators operate globe valves in refineries, gas plants, power stations and water treatment works across Oman and the GCC. Seven Star LLC supports the installed base of the Masoneilan Type 37/38 with diaphragms and kits: diaphragm-only items are listed on the 010271-016-686 size 9 diaphragm page, and the larger 87/88 family is on the Type 87/88 actuator page.

The complete rebuild kit list is described on the Masoneilan 37/38 soft goods kits.

Related published Masoneilan pages: Masoneilan 10000 Series double-port valve.

Technical Specifications

The table lists the data Baker Hughes publishes for the Masoneilan Type 37/38 actuator.

Request a Quote for Masoneilan Type 37/38

Send Seven Star LLC an RFQ for Masoneilan Type 37/38 actuators, diaphragms or handwheel parts with the case size, type (37 or 38), serial number and travel. In Oman and the GCC, we check the configuration against the Baker Hughes documents linked on this page and arrange delivery from Muscat.