Xylem Bell & Gossett Hoffman Specialty 2000 Series Instruction Manual Download Page 2

Page: 2 / 24

PLANNING THE INSTALLATION

Planning for the Pilot Installation

1. The regulator main valve must be located in an

accessible straight run of horizontal piping.
NOTE: Main valve must be installed with diaphragm
located on bottom, as shown in Main Valve Installation
illustration, page 3.

2. Allow clearance on top of the main valve to remove

the cover plate to inspect and service the valve.

3. Allow clearance under the main valve diaphragm

cover to replace diaphragms and drop out the stem
for service.

4. Piping should be sized per good engineering practice.

HVAC applications generally use 6,000 FPM velocity.
Industrial applications generally use 8,000 to 10,000
FPM.

5. Blow out all piping with steam or compressed air before

installing the main valve to remove mill scale and dirt.

6. Use long radius elbows in the low pressure piping.

Avoid the use of bull-headed tees.

7. Provide a bypass line with a globe valve to allow

inspection without interrupting service.

8. Install pressure gauges on inlet and outlet sides of

regulator to indicate system performance.

9. Install drip traps to prevent:

• Accumulation of condensate that can cause water

hammer and destroy the main valve and pilot
diaphragms.

• Slow response times that cause temperature or

pressure fluctuations.

10. Install "Y" Strainers in steam lines with the dirt pocket

turned to the side to prevent collection of condensate
that can be carried into the regulator and cause water
hammer.

11. Install pressure relief valves in accordance with local

and national codes. The relief valve must be capable
of passing the full capacity of the regulator with its
largest seat trim.

Select the relief valve opening set point pressure
based on the downstream pressure from the regulator.
The actual relief valve set point pressure depends on
the relationship of the flow (load) to the main valve
rated capacity.

For systems with spring or air pilots:

Determine the relief pressure set point pressure for
systems as follows:

For systems with temperature pilots only:

The steam system relief valve opening set point
pressure is based on the supply steam inlet pressure
to the regulator and must be set as follows:

12. Locate temperature regulators close to the temperature

sensing location. The temperature pilot capillary tube
must allow the sensing bulb to be fully inserted into
the system fluid.

Downstream

Flow

Relief valve

System

(Load)

opening set

Pressure (DSP)

Condition

point pressure

< 35 psig

< 50% of capacity

DSP + 5 psig

< 35 psig

≥

51% of capacity

(1.1 x DSP) + 5 psig

≥

36 psig

< 50% of capacity

DSP + 10 psig

≥

36 psig

≥

51% of capacity (1.1 x DSP) + 10 psig

1. The pilot valves can be installed on either side of the

main valve. The main valve is shipped with the U-tubing
and the bleed orifice installed for left-hand side
mounting of the pilot valves. (U-tubing is mounted on
the right-hand side and the bleed orifice is installed
on the left-hand side.)
If right-hand side mounting of the pilot(s) is desired,
the U-tubing and the bleed orifice must be relocated
to the opposite sides of the main valve.

Note: Right-hand side and left-hand side positioning
is determined when the main valve inlet directly faces
the observer.

2. Determine which pilot(s) are to be used for the instal-

lation. Multiple pilots can be used in combination on
one main valve. Mount the pilot(s) as follows:
• SLD Solenoid Pilot

Always mount closest to the main valve.

• SPS Spring or AP Air Pressure Pilots

When used in combination with other pilots,

always mount spring or air pilots furthest from
the main valve.

• STPA Temperature Pilot

When used with pressure pilot

mount closest to

main valve.

When used with pressure and solenoid pilots –