PGEV and PGE Locomotive Governors. Manual - part 6

Manual 36703

PGEV and PGE Locomotive Governors

Woodward

Oils For Hydraulic Controls

This is a guide in the selection of a suitable lubricating hydraulic oil for governor
use. Oil-grade selection is based on viscosity change over the operating
temperature range of the governor.

This is NOT intended to be used in the selection of the engine, turbine, or other
type of prime mover lubricating oil.

Governor oil is both a lubricating oil and a hydraulic oil. It must have a viscosity
index that allows it to perform over the operating temperature range and it must
have the proper blending of additives that cause it to remain stable and
predictable over this range. Governor fluid must be compatible with seal
materials (nitrile, polyacrylic, and fluorocarbon). Many automotive and gas engine
oils, industrial lubricating oils, and other oils of mineral or synthetic origin meet
these requirements. Woodward governors are designed to give stable operation
with most oils, if the fluid viscosity at the operating temperature span is within a
50 to 3000 SUS (Saybolt Universal Seconds) range. Ideally, at the normal
operating temperature the viscosity should be between 100 to 300 SUS. Poor
governor response or instability usually is an indication that the oil is too thick or
too thin.

Excessive component wear or seizure in a governor indicates the possibility of:

1. Insufficient lubrication caused by:

a. An oil that flows slowly either when it is cold or during start-up.

b. No oil in the governor.

2. Contaminated oil caused by:

a. Dirty oil containers.

b. A governor exposed to heating-up and cooling-down cycles, which

create condensation of water in the oil.

3. Oil not suitable for the operating conditions caused by:

a. Changes in ambient temperature.

b. An improper oil level which creates foamy, aerated oil.

ZDP Additives

ZDP is corrosive to silver and tends to attack it. Oils with a ZDP antiwear additive
are not recommended for use in the PGEV governor with an oil-filled side plate.
The PGEV governor contains a load-control resistor with silver contacts.
Increased silver contamination of the oil and wear of the load control resistor
contacts may result from using an oil with a ZDP antiwear additive. PGE
governors and PGEV governors without an oil-filled side plate may continue to
use oils with a ZDP antiwear additive, as the oil does not come into contact with
the silver contacts.

Zinc Dialkyldithiophosphates (ZDPs) are often used as antiwear additives and
are found in many common hydraulic and engine oils. Governors do not normally
require antiwear additives, but under certain marginal lubrication conditions may
benefit from their use.

Operating a governor continuously beyond the high limit temperature of the oil
will result in oil oxidation. This is identified by varnish or sludge deposits on the
governor parts. To reduce oil oxidation, lower the governor operating
temperature with a heat exchanger or other means, or change to an oil more
resistant to oxidation at the operating temperature.

PGEV and PGE Locomotive Governors

Manual 36703

Woodward

A loss of stable governor control and possible Prime Mover
overspeed may result if the viscosity exceeds the 50 to 3000 SUS
range.

Specific oil viscosity recommendations are given on the chart. Select a readily
available good brand of oil, either mineral or synthetic, and continue using it. Do
not mix the different classes of oils. Oil that meets the API (American Petroleum
Institute) engine service classification in either the "S" group or the "C" group,
starting with "SA" and "CA" through "SF" and "CD" is suitable for governor
service. Oils meeting performance requirements of the following specifications
are also suitable. MIL-L-21O4A, MIL-L-21O4B, MIL-L-2104C,
MIL-L-46152, MIL-L-46152A, MIL-L-46152B, MIL-L-45199B.

Replace the governor oil if it is contaminated. Also change it if it is suspected of
contributing to governor instability. Drain the oil while it is still hot and agitated;
flush the governor with a clean solvent having some lubricity before refilling with
new oil.

Be sure the solvent is compatible with seals. If in doubt contact
Woodward.

If drain time is insufficient for the solvent to completely drain or evaporate, flush
governor with the same oil it is being refilled with to avoid dilution and possible
contamination of the new oil,

To avoid recontamination, the replacement oil should be free of dirt, water, and
other foreign material. Use clean containers to store and transfer oil.

Oil that has been carefully selected to match the operating conditions and is
compatible with governor components should give long service between oil
changes. For governors operating under ideal conditions, i.e., minimum exposure
to dust and water and within the temperature limits of the oil, oil changes can be
extended to two or more years. If available, a regularly scheduled oil analysis is
helpful in determining the frequency of oil changes.

Any persistent or reoccurring oil problems should be referred to a qualified oil
specialist for solution.

The recommended oil temperature for continuous governor operation is 140F
(60C) to 200F (93C). Measure the temperature of the governor or actuator on the
outside lower part of the case. The actual oil temperature will be slightly warmer,
approximately 10F (6C). The ambient temperature range is -20F (-29C) to 200F
(93C).

The primary concern is for the hydraulic fluid properties in the
governor.

Oil Level

Fill the governor with oil to the mark on the sight gauge, recheck with the engine
idling. Oil must be visible in the glass on the gauge during all other conditions.

If additional information for oil properties is required, see manual 25071, Oils for
Hydraulic Controls

Manual 36703

PGEV and PGE Locomotive Governors

Woodward

Figure 2-1. Viscosity Comparison Chart

Figure 2-2. Oil Comparison Chart

PGEV and PGE Locomotive Governors

Manual 36703

Woodward

Chapter 3.

Principles of Operation

Introduction

For purposes of description, the PGE and PGEV governors are considered to
consist of three major functional sections: a basic governor section, a speed
setting section, and a load control section.

Basic Governing Section

(Figure 3-1)

This section consists of an oil pump, two accumulators, a speeder spring, a
flyweight head assembly, a thrust bearing, a pilot valve plunger, a rotating
bushing, a buffer compensation system, and a power cylinder.

The governor drive shaft passes through the governor base and engages the
rotating bushing. The pump supplies pressure oil for operation of the basic
governor section, the speed setting section, the load control system (except
applications using a remote vane servo, or where engine oil is supplied to the
control system), and all other auxiliary features or devices.

A spring loaded accumulator and relief valve system maintains governor oil
operating pressure. When operating pressure is reached the spring pressure is
overcome and the oil is released to sump.

Direction of rotation is normally determined by the engine manufacturer or
Woodward Governor Company. Governor rotation is either fixed cw, fixed ccw, or
reversible. Figure 3-1 shows the arrangement for reversible rotation with four
check valves in the oil pump passages. For fixed rotation the four check valves
are removed and two plugs are placed in two of the passages to allow only one
direction of flow.

Governors for locomotives are built for one direction of rotation.

The governor drive rotates the oil pump and pilot valve bushing. The flyweight
head assembly is driven by the rotating pilot valve bushing. A thrust bearing rides
on top of the flyweight-head toes permitting the rotational motion between the
downward force of the speeder spring and the upward force of the flyweights.

The relative motion between the bushing and plunger minimizes static friction.
There are several styles of flyweight head assemblies available. The exact style
used depends upon the engine drive train to the governor. A solid head is used
where the drive is relatively free of torsional vibrations. "Spring driven" and
"spring driven oil damped" head assemblies are used to attenuate objectionable
levels of torsional vibration which may be imparted to the governor from the
engine. These vibrations may originate from a source other than the drive itself
but reach the governor through the drive connection. Unless minimized or
eliminated, these vibrations are sensed as speed changes and the governor will
continually adjust the fuel rack in an attempt to maintain a constant speed.

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