GE mn-28000_series Service Manual download pdf (Page 20)

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5.8 CONVERTING A 7700P POSITIONER (PNEUMATIC)

INTO A 7700E POSITIONER (ELECTROPNEUMATIC)

A kit comprising the manifold block (144) and the I/P

module (20) is available from your local Masoneilan

representative or the Spare Parts Department.

REFER TO ATEX INSTRUCTION MANUAL

No. 185977 FOR ALL MAINTENANCE ON

THE ELECTRICAL PARTS OF THE 7700E

POSITIONER.

Shut off the signal and supply pressure. Isolate and

depressurize the valve body.

A. Disconnect the two pressure connection nuts (138a)

and pull the tubing (140) out.

B. Loosen the two cap screws (141a) and remove

manifold block (144). The spring (158), gasket (146)

and the three O-rings, the pilot valve assembly (155

to 157), shims (145), and O-ring (153) do not need to

be removed unless you have new parts. Otherwise,

simply check that parts are in perfect condition

before reﬁtting.

Caution: Handle the shims carefully (145).

C. If the parts mentioned above have been removed,

proceed as follows:

Fit the O-ring (153), shims (145), pilot valve assembly (155

to 157), gasket (146) and the three O-rings, the spring

(158) and manifold block (144) - I/P module (20). Tighten

screws (141a), reﬁt tubing (140) and tighten pressure

connection nuts (138a).

Note: The ports in gasket (146) must be aligned with

those in positioner block (147).

To ensure correct positioner performance, check that all

gaskets are perfectly leaktight.

D. Hook spring clamp (115) to lever (22) (VariPak 28002)

or (113) (VariPak 28001). In the case of VariPack

28001 valve, see ﬁgure 6 to position the spring clamp

(115) according to the actuator required action.

Admit the supply pressure and enable the electrical

signal. Adjust the start-up pressure following the

instructions under "Calibration". Put back into service.

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GE mn-28000_series Service Manual Page 20