Marshall Excelsior MEGR-198H User manual

The contents of this publication are for informational purposes only. While every effort has been made to ensure accuracy, these
contents are not to be construed as warranties or guarantees, expressed or implied, regarding the products or services described herein or
for their use or applicability. Marshall Excelsior Co. reserves the right to modify or improve the designs or specifications of such
products at any time without notice. The MEC™ logo is the trademark of Marshall Excelsior Co.
Form #904 Rev A
MEGR-198H BACKPRESSURE REGULATOR/RELIEF VALVE
Instruction Manual- Look Inside For:
Description
Installation
Start-Up
Maintenance
Parts Ordering
Parts List
Marshall Excelsior Company
Marshall, MI 49068
269-789-6700
FAX [phone]
www.marshallexcelsior.com
MEGR-198H Instruction Manual

Form #904 Rev A
Applications
Superheated Steam
Steam Tracing
Nitrogen Purging
Boiler Feed Water
Process Chemicals
Cooling Water
Test Fixtures
Wash Tanks
Sterilizers/Autoclaves
Fuel and Oil Lines
Pneumatic Supply
Introduction
The MEGR-198H backpressure regulator is a manual, direct
acting, self-operating, spring loaded, large capacity adjustable
relief valve. It monitors upstream pressure and opens to
relieve excess pressure when the upstream pressure increases
above a set point. As a backpressure regulator, the upstream
pressure is monitored and released downstream when the set
point is exceeded. Relief pressure ranges are 15 to 200 PSIG
for the MEGR-198H.
How It Works
The force of the range spring acting against the diaphragm is
opposed by the force of the relief pressure acting against the
opposite side of the diaphragm. Until the force of the relief
pressure overcomes the force of the range spring acting
against the diaphragm, the MEGR-198H main valve will
remain closed. After the relief pressure force overcomes the
force of the range spring acting on the main valve, the main
valve will open pressure from the inlet port and allow it to
flow into the outlet port. Once this pressure decreases beneath
the set point of the range spring, the main valve closes again.
Materials of Construction
Body Iron
Bonnet Iron
Diaphragm Stainless Steel
Valve Plug Stainless Steel with Nitrile
Specifications
Maximum Inlet 300 PSIG
Pressure Ranges SEE TABLE 1
Port Sizes 3/4" NPT
1" NPT
Orifice Sizes 3/4" NPT-9/16"
1" NPT-9/16"
End Connections NPT
Temperature Range - Nitrile -20°F TO 200° F
-29°C TO 93° C
Approximate Weight
20 lbs (9.1 kg) for 3/4"
NPT
20 lbs (9.1 kg) for 1" NPT
Shutoff Classification Class VI
Installation
Qualified personnel should perform installation, operation and
maintenance in accordance with NFPA 54 & 58 and other
local, State and Federal Regulations. The regulator can be
mounted in any position, however the flow through the body
must be in the direction from inlet to outlet (as marked by the
arrow on the body). It is important that the drilled bonnet vent
remain unobstructed at all times. Also make sure to position
the regulator to prevent any contamination, rain and debris
from entering the drilled bonnet vent. Prior to installation,
inspect the regulator and the piping lines for any debris or
contamination. Apply pipe compound to the male pipe
threads prior to installation. After installation, periodically
inspect the regulator for damage, especially after any
overpressure condition.
Warning!
If the MEGR-198H operates beyond the listed
specifications, it may cause damage to the internal parts,
up to and including blowing a hole in the diaphragm.
Please periodically check the drilled bonnet vent to see if
any sort of leakage is occurring. If so, safely remove the
regulator from the line and inspect for damage.
Start-Up and Adjustment
Warning!
The use of pressure gauges to prevent overpressure
conditions, which might cause personal injury or
equipment damage, is highly recommended. Before
starting up the regulator, relieve the downstream pressure
on the diaphragm. Failure to do so may result in personal
injury or equipment damage.

Form #904 Rev A
When starting up the MEGR-198H, slowly open the upstream
shutoff valve, and then slowly open the downstream shutoff
valve. Check all piping and connections for leaks before
making any final pressure adjustments. The nameplate
provides the range of allowable pressure settings. For
pressure settings outside the allowable range, change to the
appropriate range spring and remember to change the
nameplate accordingly. When changing the range spring,
make sure that the diaphragm is properly installed and not
damaged. Check the unit for external leakage after rebuilding.
Before applying pressure to the “In” port of the MEGR-198H,
make sure that some range spring force is established as the
adjusting screw is rotated. Clockwise rotation of the adjusting
screw will increase the relief pressure setpoint;
counterclockwise rotation of the adjusting screw will decrease
the relief pressure setpoint. Then, slowly apply pressure to the
“In” port of the MEGR-198H and rotate the adjusting screw
until the desired relief pressure set point it reached.
Note: The use of a pressure-measuring device is highly
recommended when making any pressure adjustments with the
regulator.
Maintenance
Severity of conditions and the requirement of both state and
federal laws determine the frequency to which the regulators
need to be inspected. Debris in the process line, exterior
damage, and normal wear could require the replacement of
parts such as the diaphragm. The procedures below will
provide assistance when attempting to replace these parts.
Warning!
When attempting any inspection or disassembly, relieve all
pressure from the MEGR-198H and its adjacent piping so
as to prevent personal injury or equipment damage as a
result of an explosion or sudden pressure release.
To Access the Range Spring:
1. Loosen the Jam Nut (Item #15) and turn the
Adjusting Screw (Item #10) until there is no spring
force being applied.
2. Unscrew the Build Screws (Item #19) and lift the
Bonnet (Item #2) off of the regulator.
3. Remove the Spring Guide (Item #12) and the Range
Spring (Item #7). If the output pressure range is
being changed, place new Range Spring on the Piston
(Item #17) and reassemble by reversing the above
steps and torque the Build Screws to the Torque Spec
on Table 2.
To Access the Diaphragm Assembly and Valve Plug:
1. If the Diaphragm Assembly and Valve Plug need to
be accessed, disassemble the top half of the regulator
by performing the steps above. Carefully remove the
Diaphragm Assembly and Valve Plug (Item #4) by
lifting the Diaphragm Assembly straight up out of the
Valve Plug Guide (Item #13) counterbore. Be careful
not to drop the Valve Plug and damage the outer
diameter.
2. Inspect the Diaphragm (Item #8) in the Diaphragm
Assembly. If it is a metal diaphragm unit, there
should be two diaphragms in the unit. If there is any
damage to the Diaphragm, disassemble the
Diaphragm Assembly and replace the Diaphragm.
For metal diaphragms, the Diaphragms must have
their concave part facing up. The Lock Nut (Item #
16) must be tightened according to the Torque Spec
provided in Table 2.
3. Inspect the Gasket (Item #11 – metal to metal units
only) for damage. If there is any visible damage,
replace the Gasket.
4. Inspect the Valve Plug. If the Valve Plug is metal at
the sealing surface and there are nicks on that
surface, replace the Valve Plug. If the Valve Plug
has an O-Ring (Item #9) at the sealing surface,
replace the O-Ring if it is cut or punctured. A
medium strength Threadlocker should be used to
reseal the Machine Screw (Item #21) into the Valve
Plug.
5. Reassemble the unit.
To Access the Orifice:
1. Remove the Valve Plug Guide (Item # 13) from the
Body (Item #1).
2. Inspect the sealing surface of the Orifice (Item #3)
inside the Body. If there is damage to the sealing
surface, remove the Orifice from the Body and
replace.
3. If no other maintenance is required, reassemble the
pieces in reverse order from the previous steps and
torque the Orifice, Valve Plug Guide and Build
Screws to the Torque Spec provided in Table 2.
Make sure to reapply Never-Seez® to the threads of
the Orifice and the Valve Plug Guide. Make sure to
apply Lubriplate to the threads of the Adjustment
Screw.
4. Before tightening the Build Screws down and
applying the torque in Table 2, make sure to drive the
Adjusting Screw down to engage the spring force and
pick up the slack of the Diaphragm Assembly.
Set the desired output pressure and tighten down Jam
Nut until it is snug with the Bonnet.

Form #904 Rev A
MEGR-198H Parts List
Item Description Qty
1 Iron Body, 3/4" NPT 1
Iron Body, 1" NPT
2 Iron Bonnet, drilled 1
3 Orifice, 416 Comp. 1
4 Valve Plug 1
5
Pusher Post
1
6 Diaphragm Assembly Gasket 1
7 Range Spring 1
8 Diaphragm, 302SS 2
9
O-Ring, Nitrile
1
10 Adjusting Screw 2
12 Spring Guide 1
13 Valve Plug Guide 1
14
Nameplate, not shown
1
15 Jam Nut 1
16 Lock Nut 1
17 Piston 1
18
O-Ring Retainer
1
19 Build Screw 8
20 Drive Screw, not shown 2
21 Machine Screw 1
22
Washer
1
23 Lockwasher 1
Table 1: MEGR-198H Range Springs
Port Size NPT
(inches) Spring Range Spring
Color
Wire
Diameter
PSI BAR in mm
3/4 and 1
15-35
1.03-2.07
Yellow
0.218
5.54
25-75
1.72-5.17
Green
0.235
5.97
70-140 4.83-10.34 Red 0.281 7.14
130-
200
8.96-13.79
Blue
0.468
11.89
Table 2: MEGR-198H Torque Specifications
Port Size
NPT
(inches)
Diaphragm
Nut ft-lbs
Build
Screws
ft-lbs
Orifice
ft-lbs
Valve Plug
Guide ft-lbs
3/4 and
1 10 to 15 24 to 30
33 to
42 90