Spirax Sarco 25BP Manuale utente

IM-P717-03-US Issue 1 1

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

Printed in US

Type 25BP and 26BP

Back Pressure Control Valve

Type 25P-BP, 25T-BP, 26P-BP and 26T-BP

Combination Regulators

Installation and Maintenance Instructions

IM-P717- 03-US

Issue 1

Safe operation of these products can only be guaranteed if they are properly installed,

commissioned, used and maintained by qualified personnel (see Section 1.11) in compliance

with the operating instructions. General installation and safety instructions for pipeline and

plant construction, as well as the proper use of tools and safety equipment must also be

complied with.

1.1 Intended use

Referring to the Installation and Maintenance Instructions, name-plate and Technical

Information Sheet, check that the product is suitable for the intended use / application.

i) The products have been specifically designed for use on steam, air or water/condensate.

The products’ use on other fluids may be possible but, if this is contemplated, Spirax

Sarco should be contacted to confirm the suitability of the product for the application

being considered.

ii) Check material suitability, pressure and temperature and their maximum and minimum

values. If the maximum operating limits of the product are lower than those of the

system in which it is being fitted, or if malfunction of the product could result in a

dangerous overpressure or overtemperature occurrence, ensure a safety device is

included in the system to prevent such over-limit situations.

iii) Determine the correct installation situation and direction of fluid flow.

iv) Spirax Sarco products are not intended to withstand external stresses that may be

induced by any system to which they are fitted. It is the responsibility of the installer

to consider these stresses and take adequate precautions to minimise them.

v) Remove protection covers from all connections and protective film from all name-plates,

where appropriate, before installation on steam or other high temperature applications.

1.2 Access

Ensure safe access and if necessary a safe working platform (suitably guarded) before

attempting to work on the product. Arrange suitable lifting gear if required.

1. Safety information

IM-P717- 03-US Issue 1

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

1.3 Lighting

Ensure adequate lighting, particularly where detailed or intricate work is required.

1.4 Hazardous liquids or gases in the pipeline

Consider what is in the pipeline or what may have been in the pipeline at some previous time.

Consider: flammable materials, substances hazardous to health, extremes of temperature.

1.5 Hazardous environment around the product

Consider: explosion risk areas, lack of oxygen (e.g. tanks, pits), dangerous gases, extremes

of temperature, hot surfaces, fire hazard (e.g. during welding), excessive noise, moving

machinery.

1.6 The system

Consider the effect on the complete system of the work proposed. Will any proposed action

(e.g. closing isolation valves, electrical isolation) put any other part of the system or any

personnel at risk?

Dangers might include isolation of vents or protective devices or the rendering ineffective

of controls or alarms. Ensure isolation valves are turned on and off in a gradual way to avoid

system shocks.

1.7 Pressure systems

Ensure that any pressure is isolated and safely vented to atmospheric pressure. Consider

double isolation (double block and bleed) and the locking or labelling of closed valves. Do

not assume that the system has depressurised even when the pressure gauge indicates zero.

1.8 Temperature

Allow time for temperature to normalise after isolation to avoid danger of burns.

1.9 Tools and consumables

Before starting work ensure that you have suitable tools and / or consumables available.

Use only genuine Spirax Sarco replacement parts.

1.10 Protective clothing

Consider whether you and / or others in the vicinity require any protective clothing to protect

against the hazards of, for example, chemicals, high / low temperature, radiation, noise,

falling objects, and dangers to eyes and face.

1.11 Permits to work

All work must be carried out or be supervised by a suitably competent person. Installation

and operating personnel should be trained in the correct use of the product according to

the Installation and Maintenance Instructions.

Where a formal ‘permit to work’ system is in force it must be complied with. Where there is

no such system, it is recommended that a responsible person should know what work is

going on and, where necessary, arrange to have an assistant whose primary responsibility

is safety.

Post ‘warning notices’ if necessary.

IM-P717- 03-US Issue 1 3

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

1.12 Handling

Manual handling of large and/or heavy products may present a risk of injury. Lifting, pushing,

pulling, carrying or supporting a load by bodily force can cause injury particularly to the

back. You are advised to assess the risks taking into account the task, the individual, the

load and the working environment and use the appropriate handling method depending on

the circumstances of the work being done.

1.13 Residual hazards

In normal use the external surface of the product may be very hot. If used at the maximum

permitted operating conditions the surface temperature of some products may reach

temperatures in excess of 300 °C (572 °F).

Many products are not self-draining. Take due care when dismantling or removing the product

from an installation (refer to 'Maintenance instructions').

1.14 Freezing

Provision must be made to protect products which are not self- draining against frost damage

in environments where they may be exposed to temperatures below freezing point.

1.15 Disposal

Unless otherwise stated in the Installation and Maintenance Instructions, this product is recyclable

and no ecological hazard is anticipated with its disposal providing due care is taken.

1.16 Returning products

Customers and stockists are reminded that under EC Health, Safety and Environment Law,

when returning products to Spirax Sarco they must provide information on any hazards and

the precautions to be taken due to contamination residues or mechanical damage which

may present a health, safety or environmental risk. This information must be provided in

writing including Health and Safety data sheets relating to any substances identified as

hazardous or potentially hazardous.

1.17 Working safely with cast iron products on steam

Cast iron products are commonly found on steam and condensate systems. If installed

correctly using good steam engineering practices, it is perfectly safe. However, because of

its mechanical properties, it is less forgiving compared to other materials such as SG iron

or carbon steel. The following are the good engineering practices required to prevent

waterhammer and ensure safe working conditions on a steam system.

Safe Handling

Cast Iron is a brittle material. If the product is dropped

during installation and there is any risk of damage the

product should not be used unless it

IM-P717- 03-US Issue 1

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

Prevention of waterhammer

Steam trapping on steam mains:

Steam Mains - Do's and Don'ts:

30 - 50 metre intervals

Gradient 1:100

Trap set

Condensate

Steam

Flow Flow

Steam Steam

IM-P717- 03-US Issue 1 5

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

Prevention of tensile stressing

Pipe misalignment:

Installing products or re-assembling after maintenance:

Do not over tighten.

Use correct torque gures.

Flange bolts should be gradually tightened across diameters to ensure even load and alignment.

4 2

Prevention of tensile stressing continued on next page

IM-P717- 03-US Issue 1

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

Thermal expansion:

Limit

rods

Limit rods

Fixing point

Medium

distance

Small lateral

movement

Small lateral

movement

Short

distance Fixing point

Axial

movement

Axial

movement

Guides

Guides Guides

Guides

Large

lateral

movement

Large lateral

movement

Guides

IM-P717- 03-US Issue 1 7

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

The Type 25BP is a back pressure regulator for steam service. The control consists of a pilot with

reverse-acting valve trim that positions a main valve in response to pressure fluctuations at the inlet.

Normal operation of the main valve will depend on the application type:

Type A. As a back pressure surplussing valve

The normally closed main valve is opened by the pilot when the inlet pressure increases

above its setting. (Figure 2)

Type B. For automatic shedding of non-essential steam loads when peak demand causes

line pressure to fall.

The main valve is normally open and is closed by the pilot when inlet pressure drops below

the set point. (Figure 3)

Type C. Using a combination of back pressure pilot with either temperature or pressure

control to automatically shed non-essential steam loads when peak demand causes

line pressure to fall.

The valve will shut steam off to a piece of steam-consuming equipment that is under either

pressure or temperature control when inlet presure drops below set- ting of back pressure

pilot. (Figure 4)

How the 25BP operates

Normal positions before start-up are with the main valve closed and the pilot valve held closed by

spring force. The pressure on the inlet side of the valve acts on the bottom of the pilot valve diaphragm

through the sensing line to oppose the force of the pilot valve spring. As this force increases beyond

the thrust of the spring, the pilot valve is opened. This sends pressure from the inlet side of the valve

to the bottom of the main valve diaphragm thereby forcing the main valve head open. Simultaneously,

the pressure in the main valve diaphragm is controlled by the opening of the pilot valve head and

by the bleed orifice. The net result is that the pilot valve positions itself to maintain a predetermined

main valve opening to insure a constant pressure on the inlet side of the valve. Any increase in the

inlet pressure opens the valve further and any decrease in pressure tends to close the valve. When

the inlet pressure to the valve falls below the setting of the pilot valve, the main valve closes tight to

provide a dead- end shutoff. Adjustment of the spring above the pilot dia- phragm changes the inlet

pressure set point. This valve, in effect, operates as a safety valve. The difference is that the back

pressure regulator throttles flow whereas the safety valve pops full open.

2. General product information

Pressure

diaphragm

Pressure adjustment

Pressure sensing line

Main

valve

Orifice

Main

diaphragm

Control pressure

Fig. 1

Type 25BP Back Pressure Regulator

IM-P717- 03-US Issue 1

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

Installing the valve

Unpack carefully

Do not lift the regulator by the tubing. Grasp the body of the valve firmly when lifting.

Caution:

Installation and troubleshooting should be performed by qualified service personnel. Before breaking

any connection every effort should be made to assure that internal pressure has been relieved. When

breaking any connection, piping/bolts should be removed slowly so that if the line is under pressure,

this fact will be apparent before completely removing the pipe or component. Always relieve pressure

before breaking any joint.

Piping

1. Typical hookup sketches as shown in Figures 2, 3 and 4 will aid in planning a correct installation.

2. Piping on the dowstream side of the valve should be increased so as not to restrict flow.

3. Swage nipples are recommended for changes in pipe sizes and a Spirax Sarco ½" steam trap

fitted to drain any condensate from the valve inlet.

4. Before installing the valve, make sure the piping is free of foreign material, scale, etc. A pipeline

strainer is recommended before the valve and all steam traps.

5. Make certain the arrow cast on valve body is pointing in the direction of flow.

6. Valve should always be intalled in a horizontal position.

7. Pressure gauges must be installed on both sides of reducing valve.

Pilot pressure sensing line for back pressure pilot

1. Copper tubing (¼" OD) can be used for the sensing line with suitable compression fittings or as

an alternative, ¼" piping can be used.

2. Connect the sensing line to the upstream side of the main valve to a straight portion of the piping

10 pipe diameters from nearest fitting and approximately 1 foot from elbows, tees, valves and

other restrictions. (See Figures 2, 3 and 4).

3. Install a small gate valve in the sensing line so that this can be closed when servicing the regulator.

4. The sensing line must be pitched downward from the main valve to ensure proper drainage.

5. To permit accurate setting of the back pressure regulator, a pressure gauge should be installed

as close as possible to the pilot sensing line connection.

Note: Installation of sensing line for Presssure Reducing Pilot is identical, except that it is connected

to the down- stream steam line.

3. Installation

IM-P717- 03-US Issue 1 9

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

IM-P717- 03-US Issue 1

Type 25BP and 26BP Back Pressure Control Valve / Type 25P-BP, 25T-BP, 26P-BP and 26T-BP Combination Regulators

Type A application

Surplussing valve for upstream pressure controls

A typical flash recovery system hookup is shown in Figure 2. This application allows utilizing flash

steam whose pressure is limited by the 25BP (back pressure valve) for low pressure processing.

The 25BP acts as a surplussing valve venting only excess steam from the receiver to atmosphere.

Note:

The 25BP control setting (receiver maximum operating pressure) may be greater than that normally

desired in the Low Pressure main but must not exceed the pressure rating of the L.P. equipment

being supplied. Also, it is recommended that the setting should not exceed 50% of the high pressure

system steam traps. This is most important when H.P. equipment is supplied by modulating control

valves.

The Back Pressure control setting should also be at least 2 to 5 psi g below the Safety Relief Valve

pressure setting. These recommendations allow maximum recovery of flash steam and will prevent

excessive back pressure from interfering with operation of the H.P. system traps and equipment.

Pilot setting procedure:

1. On existing installations, make certain flash tank is isolated from low pressure steam and

condensate return piping.

2. Make certain that a safety valve, in good operating condition, is installed and is properly set to

protect the flash tank. A back pressure regulator is NOT a safety valve and should NEVER

be used for the purpose.

3. Provisions must be made for proper trapping of conden- sate from the flash tank.

4. After installing 25BP regulator with sensing line back to inlet, remove stainless steel cover from

pilot, exposing the adjusting spring.

5. To set the valve opening pressure: Turning the adjusting spring screw clockwise will increase

the pressure at which the 25BP control will open. Turning counterclockwise will reduce the set

pressure.

6. Turn 25BP pilot adjustment screw clockwise approximately 5 turns. This is to make sure that the

BP pilot is in a closed position.

7. The high pressure condensate system can now be put into operation; however, steam valve A to

low pressure system must be kept closed.

8. As steam pressure develops in flash vessel, observe pressure on Gauge B. When the desired

pressure is obtained, turn adjustment screw on 25BP pilot counterclockwise until main valve

just starts to open. This opening point can be determined by audible means or observing flow

at exit of vent pipe.

9. After setting has been established, Valve A to low pressure main can be opened. Replace cover

over pilot spring and tighten lock nut on adjustment stem to secure the setting. Valve is now in

operation.

4. Applications

Thermostatic air vent

Strainer

25 BP back pressure

control valve

Vent

Low pressure

steam supply

Safety relief valve with drip pan elbow

Flash

recovery

vessel

Valve A

Pilot operated

pressure

regulator

Separator

Float &

thermostatic

trap

Spira-tec

loss detector

Strainer

High pressure condensate

High

pressure

steam

supply

Strainer

Spira-tec

loss detector

Float &

thermostatic

trap

Gauge B

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