Sundaram - Clayton Limited
RE 6 RELAY EMERGENCY VALVE
FUNCTION
The Relay Emergency Valve is normally used in trailer braking systems. It is a dual function valve, combining
the functions of a relay valve and an emergency valve.
The relay function is identical to that of a relay valve serving the air brake system as a remote controller brake
valve. Control (service) pressure from the vehicle is routed through the trailer service line and on to the relay
portion of the valve. The emergency function of the valve automatically applies full trailer reservoir air pressure
to the trailer chambers when the trailer supply pressure falls below a predetermined minimum.
For ease of service, the valve features an insert cartridge consisting of the inlet/exhaust valve and emergency
piston. Removal of the insert can usually be accomplished without line removal.
The RE-6 Relay Emergency Valve is provided with identified, convenient porting locations of delivery, service,
emergency (supply) and reservoir ports.
OPERATION
Initial Charging
When the tractor is connected to a trailer and the service and emergency lines are opened (via the tractor
protection system) the valve permits charging the trailer reservoir to approximately the same air pressure as
that of the tractor reservoirs. Under initial charge conditions, the valve applies trailer service air chambers as
the trailer emergency line is charged. The application is continued until the trailer supply (emergency) line is
charged to 3.7 - 4.5 bar, at which time the application is automatically released. The trailer reservoir continues
to be charged to full operating pressure.
Service Application
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Sundaram - Clayton Limited
During normal, service braking operation, the valve serves as a relay valve, synchronizing tractor service
(application) air pressure with trailer service (application) air pressure as the service foot brake valve on the
tractor is operated. If the tractor is equipped with a trailer hand control (TC) valve, the trailer brakes can also
be applied independently of the tractor brakes.
Emergency Application (Trailer Air System charged to normal operating pressure)
Venting the trailer supply (emergency) line to atmosphere, will cause the emergency portion of the Relay
Emergency Valve to apply full trailer reservoir pressure to the trailer air chambers. If the trailer supply line
pressure is reduced to approximately 1.4 bar due to leakage or conditions other than the above, a graduated
trailer air chamber application will occur. The rate of this brake application will depend upon the rate of
pressure loss in the supply line.
If the trailer is not equipped with parking actuators (such as spring brakes), the trailer wheels should be
blocked to prevent trailer movement, in the event reservoir pressure would be depleted.
To Release an Emergency Application
Recharge trailer air system
 For trailers equipped with standard brake chambers, block wheels and drain trailer reservoir.

For trailers equipped with spring brake chambers, block wheels and mechanically release spring brake
chambers via the mechanical release mechanism.
PREVENTIVE MAINTENANCE
Quarterly or 25000 kms or 250 hmr
 Check the mounting bolts, nuts, etc. For
slackness and tighten if required.
 Check the pipes for cracking, nick marks or
corrosive surface and replace if necessary.
Yearly or 1,00,000 kms or 1000 hmr
 Overhaul the unit using genuine SCL Repair kit
REMOVING




Block trailer wheels
Drain trailer system air reservoirs.
Identify and disconnect airlines from valve.
(Note: the emergency piston and valve assembly, generally referred to as the “insert” can be removed
without line removal. To remove the insert, remove the exhaust cover and pull insert out)
Remove mounting bolts or unscrew from pipe nipple mount.
INSTALLING
If the valve will be flange mounted directly to steel, it is recommended that a flange gasket be utilised to
prevent electrolytic action between the unlike metals.
If the valve is adaptor or nipple mounted directly to a reservoir, it is recommended that a suitable lubricant
be applied to the threads before installation. This will prevent rust formation of the threads and make removal
easier.
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Sundaram - Clayton Limited



Clean and inspect all connecting line and hoses for cracks, deterioration or damage.
necessary.
Mount valve securely
Connect all lines and hoses to valve.
Replace as
Disassembly
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Mark cover (30) and body (23) to assure proper positioning when assembling.
Remove cap screws (4), lock washers (5) and exhaust cover (6).
Remove check valve (18) and check valve spring (19) and ‘O’ Rings (20 & 8). Remove spring (7).
Remove exhaust diaphragm screw (1), diaphragm (3), and washer (2) from exhaust cover.
Remove cap screws and lock washers from cover (30).
Remove cover (30), relay piston (28) and piston return spring (27) (if so equipped). Remove piston O Ring
(29). Remove O Ring (25) from body bore.
Remove exhaust valve seat (26) from piston
Remove sealing (24) from body.
Remove filter assembly (17) from emergency (supply) port. (Note: if new insert is to be installed, omit
steps 10 - 15).
Apply downward pressure on emergency piston (21) and remove emergency piston and inlet/exhaust
valve assembly.
Remove the large valve retainer with suitable pliers, from the bottom of emergency piston assembly.
Push through small end of emergency piston (21) with finger and remove inlet/exhaust valve assembly.
Remove emergency piston O Ring (22) and O Ring (13) from inlet/exhaust valve assembly.
Remove retaining ring (10) from inlet/exhaust valve assembly.
Remove valve guide (11), spring (14), retainer (15) and valve guide O Ring (12).
CLEANING AND INSPECTION




Clean all the metallic parts in cleaning solvent and blow dry with compressed air. Ensure that no trace of
solvent is present during reassembly.
Check top cover, valve body, base cover and relay piston for excessive wear, nick / score marks, cracks
and damages.
Check the spring for distortion, corrosion and permanent set.
Scrap all the old parts found to be unserviceable.
ASSEMBLY
Note: All torques specified are assembly torques and can be expected to fall off after assembly.
Do not re-torque after initial assembly torques fall. For assembly, hand wrenches are recommended.
Prior to assembly, lubricate all O Rings and mating surfaces with pneumatic grease.
If new insert is installed, omit steps 1-6.
1. Install O Ring (12) in valve guide (11).
2. Install valve retainer (15), spring (14) and valve guide (11) to inlet/exhaust valve.
3. Compress spring by holding valve guide and install retaining ring (10). Make certain the ring is properly
installed in groove.
4. Install O Ring (13) on valve guide.
5. Install inlet/exhaust valve assembly into emergency piston. With suitable pliers, install valve retainer (9)
making certain that it is in groove.
6. Install emergency piston O Ring (22)
7. Install filter assembly (17) in emergency (supply) port.
8. Install seat (26) on piston.
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Sundaram - Clayton Limited
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Install O Ring (29) on piston.
Install O Ring (25) in upper bore of body
Install sealing ring (24) in groove of body
Install relay piston (28) in cover. (Boss on cover will fit bore in piston)
If so equipped, install piston return spring (27).
Install cover to body, make certain cover is in previously marked position. Torque cap screws to
approximately 15 Nm.
Install emergency piston and inlet/exhaust valve insert in body.
Install O Ring (8) in body.
Install spring (7) in body
Install exhaust diaphragm (3), washer (2) and screw (1).
Install small O Ring (20) in exhaust cover.
Install check valve (18) and spring (19). Spring will fit in groove in cover.
Install exhaust cover (6). Install cap screws and lock washers, torque to approximately 15 Nm.
Check valve as outlined in “Operating and Leakage” check sections before placing vehicle in service.
OPERATING AND LEAKAGE TEST
1. Start these tests with no air pressure in the tractor or trailer system. Make certain trailer connection shutoff cocks are open if present. Build tractor air system to at least 3.5 bar Move tractor protection control
valve to normal position. As trailer brakes should apply and then completely release as trailer supply line
pressure reaches 4 – 4.5 bar.
2. Fully charge tractor and trailer air brake system. Make several service brake applications and check for
prompt braking response at trailer wheels. With brakes released and system reservoir pressure stabilised
at 6.9 –8.27 bar with engine stopped, a two minute check should result in no more than a six pound
pressure drop for the combination vehicle system. If this check indicates possible excessive leakage of
valve, soap solution should be applied to the exhaust port to detect possible leakage of inlet valve and
emergency piston O ring leakage. Leakage of a one inch soap bubble in not less than five seconds is
permissible at pipe plugs or fittings.
3. Make and hold a full service brake application with system reservoir pressure stabilised at 6.9-8.27 bar with
engine stopped. A two-minute check should result in no more than
0.5 bar drop for the combination vehicle system. If this check indicates possible excessive leakage of
valve, soap solution should be applied to cover to detect body O Ring leakage and to exhaust port to detect
valve and O ring leakage. A combined leakage as indicated by a one-inch bubble in not less than three
seconds is permissible. Release the service brake application.
4. With tractor and trailer air brake system fully charged, place the tractor protection control valve in the
“emergency” position or close the emergency line shut-off cock on the tractor and uncouple the trailer
emergency line coupling. Note that trailer brakes apply promptly. Check at the supply (emergency) line
coupling at the front of the trailer for leakage. No leakage permitted. A leak detected at the supply
(emergency) line coupling would indicate leaking non-return valve or piston O Ring in the valve. Check at
service line coupling at the front of the trailer. A leak at the service line coupling would indicate leaking
relay piston O Ring. Reconnect service and emergency lines and recharge tractor and trailer air brake
system, noting that trailer brakes release at a maximum of 4.5 bar trailer supply (emergency) line pressure
as the trailer air brake system is recharged to full operating pressure.
5. With tractor and trailer air brake systems fully charged, stop engine. Reduce pressure by making a series
of foot valve applications, and note that trailer brakes apply automatically at approximately 1.4 bar, tractor
reservoir pressure or at the automatic emergency setting of the tractor protection equipment, if installed.
6.
Apply brakes and hold. Apply soap solution at all joints, pipe connectors and RE-6 exhaust diaphragm.
No leak is permissible.
7. Deplete the air pressure from the emergency line. Check if the brakes are getting applied when the system
pressure is approximately 2.0 bar.
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Sundaram - Clayton Limited
IMPORTANT! PLEASE READ
When working on or around brake system and components, the following precautions, should be observed: 1. Always block vehicle wheels. Stop engine
4. Never attempt to disassemble a component
when working under a vehicle. Keep hands
until you have read and understand
away from chamber push rods and slack
recommended procedures. Some components
adjusters’ they may apply as system pressure
contain powerful springs and injury can result if
drops.
not properly disassembled. Use only proper
2. Never connect or disconnect a hose or line
tools and observe all precautions pertaining to
containing pressure; it may whip.
Never
use of those tools.
remove a component or pipe plug unless you
5. Use only genuine CD-TVS replacement parts
are certain all system pressure has been
and components.
depleted.
6. Devices with stripped threads or damaged
3. Never exceed recommended pressure and
parts should be replaced. Repairs requiring
always wear safely glasses when working.
machining should not be attempted.
TROUBLESHOOTING
Problem 1: Leak through exhaust when brakes
are not applied (off leak)
Possible Causes
1. The following sealing rings or mating parts
damaged. 12, 13, 22 & 25.
2. Valve retainer (11) damaged.
3. Rubber valve or the guide portion of the
Inlet/Exhaust valve (16) damaged.
4. Inlet valve seat or the top stem of the
Emergency piston (21) damaged.
Problem 2: Leak through exhaust when brakes
are applied (on leak)
Possible Causes
1. Rubber valve of the Inlet/Exhaust valve (16)
damaged
2. Valve seat (26) damaged or is out of scariness.
3. Sealing ring (24) or mating parts damaged.
Problem 5: Emergency brakes automatically
getting released when emergency line pressure
is 0 bar.
Possible Causes
1. Check Valve or Non return valve (19) or valve
seat damaged
2. Heavy air leak in reservoir line.
3. Heavy leak in delivery circuit.
Problem 6: Joint Leak
 Leak through the joint between Base cover (6)
and Body (23).
1. Sealing rings (8 and 20) or mating parts
damaged.
 Leak through the joint between Top cover (30)
and Body (23) in brakes applied condition.
2. Sealing ring (29) or mating parts damaged.
Problem 3: Emergency brakes are not released
within the specified pressure limits (3.7 - 4.5
bar at emergency line)
Possible Causes
1. Excess spring load of the spring (7)
2. Sluggish movement of the emergency piston
(21).
Problem: 4 Emergency brakes are not applied
at the specified pressure (2.0 bar at emergency
line)
Possible Causes
1. Insufficient spring load of the spring (7).
2. Sluggish movement of the emergency piston
(21).
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