Masoneilan 77-80H and 00-80H High-Capacity Air Valve

Overview

The Masoneilan 77-80H is an air valve for pneumatic control systems: a high-capacity, set-pressure controlled three-way valve in which a pilot valve and a body are combined. Baker Hughes publishes it together with the 00-80H, the three-way valve obtained by removing the pilot valve, in one instruction manual. The pair is used where a pneumatic actuator or a group of actuators must change state when the air pressure at the signal connection falls below a defined value, for example when the instrument air supply is lost or when a trip signal is removed.

Seven Star LLC, a trusted supplier of Masoneilan products, supplies the Masoneilan 77-80H to industrial, energy and utility customers in Oman and the GCC. Replacement of these small air valves is a routine item during shutdowns, and our instrumentation division in Muscat checks the model code, set pressure and thread type against the nameplate so that the correct unit arrives in one shipment.

Set-Pressure Air Valve Principle

In the Masoneilan 77-80H the supply pressure is connected directly to the SIG IN connection. A range spring in the pilot section is compressed by an adjusting screw to give the set pressure. While the signal pressure exceeds the set pressure, the IN port is open to OUT. If the pressure drops below the set pressure, or disappears altogether, the valve operates to close IN and to connect OUT to EXH, so the actuator exhausts through the large EXH port. When the valve is used as a lock-up valve, both EXH ports are plugged so that the actuator pressure is held instead of vented.

The manual describes the setting as a factory adjustment, with a procedure for the field: relieve the range spring, connect the air supply to IN to check opening and closing, fit a gauge and a regulator to the signal connection, set the regulator to the required pressure, and turn the adjusting screw until air stops leaking from OUT. The adjusting screw locknut is then tightened and the valve returned to service. Because the capacity of the Masoneilan 77-80H is large, the signal pressure should not be taken from near the IN side of the body, which would change the signal air pressure and cause hunting.

Engineering Design of the Masoneilan 77-80H

The housing of the Masoneilan 77-80H is aluminium alloy. The main connections are Rc 1/2 (with 1/2 NPT as an option) for inlet, outlet and exhaust, and the signal connection is Rc 1/4 (1/4 NPT option). The valve has two EXH ports, of which the unused one is pipe plugged. The body contains a plug assembly, a piston, a rubber insert, a pilot valve and a diaphragm assembly, and the sealing is by O-rings, which the manual says to lubricate with silicone grease at reassembly, together with a new shim.

The standard operating temperature range is minus 30 to plus 70 degrees Celsius, and the manual lists two options: a high temperature version for minus 18 to plus 100 degrees Celsius, and a low temperature version for minus 49 to plus 80 degrees Celsius. The inlet pressure limit is 880 kPa (125 psig), and the specification table gives a set pressure range of 100 to 700 kPa. The marking shown on the dimension drawing reads 35 to 700 kPa (5 to 100 psig), so the exact set pressure of a given unit is taken from its nameplate. Storage guidance is to keep the unit protected from rain, vibration and impact at around 23 degrees Celsius and 65 percent humidity, with the caps left in the ports until immediately before installation so that no foreign body can enter.

Key Features

The following features, taken from the Baker Hughes instruction manual, show why the Masoneilan 77-80H is used on larger pneumatic actuators:

• A pilot valve and a three-way body are combined, and the pilotless 00-80H allows several bodies to follow one pilot.
• The Masoneilan 77-80H has a Cv of 4.56 from IN to OUT and 4.25 from OUT to EXH gives a fast response on large actuator chambers.
• The Masoneilan 77-80H has a specified set pressure range of 100 to 700 kPa, with hysteresis of 34 kPa or less.
• Two EXH ports let the installer pick the vent direction, and plugging both converts the valve into a lock-up valve.
• High-temperature (up to 100 degrees Celsius) and low-temperature (down to minus 49 degrees Celsius) options extend the standard minus 30 to plus 70 degrees Celsius range.
• Rc 1/2 main ports with 1/2 NPT alternatives, and an Rc 1/4 signal connection, fit most instrument air tubing standards.
• A single piping connection from the pilot to each 00-80H allows simultaneous changeover of several valves.
• The manual gives clear inspection points: the diaphragm, the pilot valve seat and the O-rings of both the pilot and the body.

Industrial Applications

The Masoneilan 77-80H is installed in the air lines of pneumatic actuators that must react to a change in signal or supply pressure, for example to exhaust a spring-return actuator on loss of air, or to lock a double-acting actuator in place. The Masoneilan 77-80H is built for industrial compressed air, and the manual stresses that the air must be clean and dry. In Oman it is relevant to refineries, gas processing plants and power stations, to pipeline stations with remote valve operators, and to water and desalination plants where instrument air is shared among many valves.

Seven Star LLC distributes the Masoneilan 77-80H together with its companions. Engineers can combine it with the Masoneilan BR200 volume booster relay, drive larger valves through the Masoneilan Type 51/52/53 piston actuators or the Masoneilan Type 87/88 spring-diaphragm actuators, and see the 77-6 air lock-up valve below for a simpler lock-up function.

Technical Specifications

The table sets out the data published for the Masoneilan 77-80H in the Baker Hughes instruction manual for the 77-80H and 00-80H air valves (Rev. A, 07/2021).

Request a Quote for Masoneilan 77-80H

A quotation request for the Masoneilan 77-80H should include the nameplate model code, the set pressure, the connection thread type and the ambient temperature range. Seven Star LLC then confirms the configuration, checks regional stock and provides the Baker Hughes instruction manual for download from this page. As trusted supplier for Masoneilan in Oman and the GCC, we deliver genuine products with manufacturer documentation and local support.