Flowserve GTS User Manual

GTS Series

Internally Mounted Steam Seal

Installation

Instructions

Experience In Motion

Introduction

The GTS steam turbine seal is especially designed for operation in steam turbine
applications. Successful operation relies on proper installation of the seal. These
installation guidelines will cover the basic steps required to install the seal as well
as additional factors to consider that will affect the installation. These steps are
based on a cross section of turbines seen in actual installations and will cover all

of the basics. There may be differences in your specic application.

A typical seal assembly is attached for reference purposes only. Refer to the
job drawing for details on the actual seal assembly dimensions, correct part

numbers, and the turbine conguration. The item numbers in the procedure refer

to the item numbers on this typical drawing. Item numbers may differ slightly on
the job assembly.

1 Tools

The GTS seal is designed around standard hardware with a minimum of tools
required for installation. These include:

Needle nose pliers
5/16 Open end wrench
7/64 and 5/32 “Allen” wrenches
Set of adjustable OD spanner wrenches

2 Inspection of Steam Turbine in Operation

If possible, observe the turbine operating with the carbon rings installed prior
to taking it out of service to install the GTS seals. Excessive steam leakage for
carbon rings could indicate a problem with the turbine that should be addressed
prior to seal installation

Investigate the following areas for excessive steam leakage:

2.1 Bad carbon rings or failed seal.

2.2 Cracked turbine case. Inspect the areas where steam leakage was present
for signs of erosion, corrosion, etc.

2.3 Split line of turbine case or cover. Check for warpage that prevents effective
sealing. Examine split line to see if steam leakage across the joint has
eroded the case and cover.

2.4 Shaft damage, especially in the area of the carbon rings. Check the
integrity of the overlay. It is possible for steam to leak beneath the overlay if
improperly applied.

The images of parts shown in these instructions may differ visually from the actual

2

parts due to manufacturing processes that do not affect the part function or quality.

2.5 Check the turbine alignment. The shaft runout and the perpendicularity
should meet normal pump standards. The concentricity may be much larger

than that typically seen in a pump. The ange for internally mounted seals

pilots on the turbine and requires a TIR < .020” for proper seal function.

Talk to the operations and maintenance personnel regarding the above
concerns. Find out if there are any other issues regarding turbine reliability and
performance.

3 Inspection of Steam Turbine Piping and Application
of Steam Traps

Water is a problem for turbines in general, but poses some unique challenges
for mechanical seals. Hot water under pressure at the OD of the seal faces will

ash to form steam as it crosses to the atmospheric pressure at the ID of the

faces. The expansion ratio when water is converted to steam is over 1600 to 1.
This generates a large force that causes the faces to separate, resulting in high
leakage. The GTS seal is robust and can recover from normal water slugs that
occur during start up. However, operation in water will result in high leakage that
is not generally acceptable for prolonged operation.

As a practical matter, altering the turbine piping to remove water and improve
performance of the turbine and mechanical seals is not an option for most
end users. However, inspecting the piping can yield useful information about
potential problems that may be reduced or eliminated through the application of

mechanical free oat actuated steam traps.

Check your piping system for the following:

3.1 Piping should slope downward 10 cm per 10 m (4 inches per 30 ft) in the

direction of steam ow to aid condensate drainage.

3.2 Piping should be straight and free from sags where condensate could
collect and create a slug of water.

3.3 Eccentric reducers should be used instead of concentric reducers, to
prevent condensate from pooling upstream of the reducer and creating a
slug of water.

3.4 Equipment supply lines should be connected to the top of steam mains, not
the bottom, so that dirty condensate running along the bottom of the mains

does not ow into the equipment.

3.5 Steam traps should be installed at regular intervals (every 30 to 50 m or
100 to 150 ft) in the steam main with correctly sized condensate pockets.

3.6 Steam traps should be installed upstream of isolation valves that are
regularly closed.

3

3.7 Insulation of sufcient thickness should be installed on the piping to prevent

excess radiation losses that result in condensate formation. Insulation
should be dry, weatherproofed, and undamaged.

If your steam piping system lacks one or more of these features you may
experience more problems with water slugs entering the turbine and with
condensate collecting in the turbine. These problems will be further worsened
if the steam main temperatures are near or at the saturation temperature of
the steam. Typically, turbines that are distant from the source of the steam
experience more problems because radiation losses have caused the steam
temperatures to drop and condensate formation to increase. Also, condensate

from upstream in the system will ow downstream if steam traps are not installed

and functioning properly at regular intervals along the steam main.

To reduce problems caused by water in the turbine, the case drain of the turbine
should be piped to a steam trap with the following features:

3.8 Mechanical free oat actuation. There are a wide variety of steam traps on

the market that fall into three basic categories: mechanical, thermostatic,

and thermodynamic. A mechanical free oat trap evacuates water

immediately, whereas other types of mechanical traps and the thermostatic
and thermodynamic traps operate intermittently. Intermittent operation can
allow condensate to back up into the turbine and possibly the seals, which
is undesirable.

3.9 Automatic air venting. This feature is necessary to prevent air present
during start-up from locking the trap and preventing it from evacuating
water.

3.10 Adequate size for condensate load. For instance, a turbine that is placed in
hot standby will experience a much higher condensate load than a turbine
that operates continuously or in slow roll. In hot standby, radiation losses
from the exhaust pipe will cause condensate to form and run down into the
turbine. If the exhaust line enters the bottom of the exhaust steam main,
condensate running along the bottom of the main will enter the turbine as

well. It will take a large trap to prevent condensate from ooding the turbine

and the seals.

In continuous operation or slow roll, hot inlet steam will enter the turbine

and ow out through the exhaust. This will usually keep the exhaust line
much warmer than in hot standby, reducing the ow of condensate into

the turbine. Of course, the steam trap must be sized for the worst case
condition. If a turbine experiences both hot standby and continuous
operation, the steam trap should be sized for hot standby.

3.11 Located as near the turbine as possible. Long piping distances between
a steam trap and a turbine can cause the trap to steam lock. This occurs

when the line to the trap is lled with superheated steam. Superheated

4