• Cost Effective—Single trip valve construction reduces costs and spare part requirements of those systems using three separate switching valves to perform the failure functions. A single trip valve greatly simplifies piping requirements.
• Ease of Mode Conversion—Conversion to any of the fail modes requires only minor hookup changes.
• Adjustable Trip Valve—The trip point is adjustable for specific supply pressure requirements.
• Reliable Operation—The trip valve design includes large diaphragm areas and few moving parts for efficient performance, minimum maintenance, and long service life.

Available Configurations

When supply pressure falls below the trip point,
Type 377D Trip Valve: Fails actuator piston down. Includes check valve and volume tank
Type 377L Trip Valve: Locks actuator piston in the last position
Type 377U Trip Valve: Fails actuator piston up. Includes check valve and volume tank.
Type 377CW Trip Valve: Fails fully clockwise to close the valve. Requires check valve and volume tank. Trip valve moves piston to either up/down position and requires actuator configuration for actual clockwise movement.
Type 377CCW Trip Valve: Fails fully counterclockwise to close the valve. Requires check valve and volume tank. Trip valve moves piston to either up/down position and requires actuator configuration for actual counterclockwise movement.
All 377 Series Trip Valves can be converted to any of the above fail modes with minor hookup changes

Allowable Supply Pressure for Trip Valve(1)

Maximum: 10.3 bar (150 psig)
Minimum: 3.8 bar (55 psig)

Outlet Pressure(1)

Normal Operation: Pressure from control device
Fail-Up or Fail-Down Mode: Maximum volume tank pressure
Lock-In-Last-Position: Respective cylinder pressure

Trip Point(2)

Adjustable from a minimum of 2.8 bar (40 psig) to a maximum of 72 percent of supply pressure; see figure 3.
Reset: 12.5 to 33 percent above adjusted trip point

Flow Coefficients (Cv)(3)

Depends on flow path (shown in figure 4) as follows:
Port A to Port B: 0.47
Port B to Port C: 0.56
Port D to Port E: 0.48
Port E to Port F: 0.64

Body Connections

1/4-inch NPT female

Temperature Capabilities(1)

Nitrile Diaphragms and O-Rings: -40 to 82°C (-40 to 180°F)
Fluoroelastomer Diaphragms and O-Rings: -18 to 104°C (0 to 220°F)

Volume Tank Maximum Internal Working Pressure (for Type 377D, 377U, 377CW and 377CCW trip valves)

Standard: 10.3 bar (150 psig) for non-ASME approved applications(4) .
ASME Approved Applications: Rated 10.3 bar (150 psig), maximum; 9.3 bar (135 psig), recommended

Volume Tank Sizing

See sizing section

Hazardous Area Classification

Complies with the requirements of ATEX Group II Category 2 Gas and Dust

Mounting

Top-Mounted: Manifold-mounted between a 3570 Series positioner and 480 Series actuator (manifolds cannot be supplied with 585C, 1061, 1066, and 1069 Series piston actuators)
Side-Mounted: Yoke-mounted or bracket-mounted for use with a FIELDVUE® DVC6000 or DVC6000f Series digital valve controller

Approximate Weight

Trip Valve: 2.0 kg (4.5 pounds)
Mounting Manifold: 0.5 kg (1.2 pounds)
Volume Tank: Varies between 5.4 and 21 kg (12 and 47 pounds) depending on size

Construction Materials

Body, Spring Case, and Manifold—Aluminum
Cover—25% mineral-filled thermoplastic polyester
O-Rings—nitrile or fluoroelastomer
Diaphragms—nitrile or fluoroelastomer
Interior parts—brass, aluminum, steel, and stainless steel

Note
Neither Emerson ® , Emerson Process Management TM , Fisher ® , nor any of their affiliated entities assumes responsibility for the selection, use, and maintenance of any product. Responsibility for the selection, use, and maintenance of any product remains with the purchaser and end-user.

Type 377D Trip Valve

In normal operation, supply pressure loads the upper diaphragm (see figure 4) of the unit. The valve plug spring keeps the exhaust port closed. Supply pressure also loads the lower diaphragm through the
restriction, causing the plug assemblies to move down and isolate ports C and F while connecting port A to B and port D to E. Normal actuator control pressure flows from the control device to the top of the cylinder through ports A and B and to the bottom of the cylinder through ports D and E. A volume tank is charged to maximum supply pressure through a check valve in order to retain maximum supply pressure in the volume tank if supply pressure drops.
When supply pressure falls below the trip point pressure in the fail-down mode (see figure 5), the exhaust port opens, venting the supply pressure that is loading the lower diaphragm. This causes the upper ports of the plug assemblies to close and shut off normal pressure flow from the control device to the actuator.
Volume tank pressure then flows through ports C and B to the top of the actuator cylinder, while pressure in the bottom of the actuator cylinder is vented through ports E and F. The pressure imbalance created forces the actuator piston down.
When supply pressure is restored, it loads the upper and lower diaphragms, causing the trip valve to reset. The exhaust port closes. The upper ports of the plug assemblies open, and the lower ports close. Normal actuator control pressure flow from the control device is restored through ports A and B and ports D and E. The check valve opens and recharges the volume tank to the maximum supply pressure.

Type 377L Trip Valve

When supply pressure falls below the trip point in the lock-in-last-position mode (see figure 6), the
exhaust port opens, venting supply pressure from the lower diaphragm. This causes the upper ports of the plug assemblies to close and the lower ports to open. Since ports C and F are plugged, no pressure change occurs on either side of the actuator piston, and the piston is pressure-locked in position upon loss of supply pressure. No volume tank is necessary in this mode. When supply pressure is restored, the plug assemblies move back into the normal operating position, and supply pressure flows from the control device through ports A and B to the actuator.

Type 377U Trip Valve

The fail-up mode of operation (figure 7) is similar to the fail-down mode of operation except that connections to port C and F are reversed. When
supply pressure falls below the trip point, the top of the actuator cylinder vents, and volume tank pressure loads the bottom of the actuator cylinder. The pressure imbalance created forces the actuator piston up.

Type 377CW and 377 CCW Trip Valves

Makes use of the 377D or 377U trip valve configurations, a piston actuator, and volume tank with check valve to move the piston actuator to either the up or down position. Requires the actuator and valve configuration for actual clockwise or counterclockwise movement.

Note
State and local regulations may require the use of ASME-approved volume tanks. It is the user's responsibility to determine requirements and applicable regulations for proper volume tank selection.

Seven different tanks of varying capacities are available. The volume tank must be selected so that its pressure at any time is greater than the minimum percentage of maximum supply pressure required to stroke the actuator (see figure 8).
1. Size the volume tank as indicated below:

Application

1. Available supply pressure
2. Actuator type number and size
3. Input signal range
4. Operating ambient temperature
5. Trip point (If the trip point is not specified, the unit is factory-set to trip at 72 percent of supply pressure or 2.8 bar (40 psig), whichever is higher.)
6. Volume tank size

Trip Valve

Refer to the specifications. Review the information under each specification and in the referenced figures. Specify the desired choice wherever there is a selection to be made. Be sure to specify the type number as described in the Available Configurations specification.
Refer to table 1 for guidelines on specifying the correct trip valve.