PRESSCON HORTI Manual de usuario

User manual

Safety valves (Vacuum-overpressure safety valve and vacuum safety

valve)

Type

Manual safety valve

Datum

07-04-2021

Version / Revision

Version 3.0 Revision00

Status

Accepted

Company

PRESSCON

Location

Honselersdijk

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 Page 3 of 18 
 
 
 
Table of contents 
Introduction........................................................................................................................................................ 4 
Precautions and safety instructions........................................................................................................... 4 
Application ................................................................................................................................................. 5 
Construction............................................................................................................................................... 6 
1 Vacuum-overpressure safety valve ................................................................................................... 6 
2 Vacuum safety valve.......................................................................................................................... 7 
Functioning of the safety valves ................................................................................................................ 8 
1 Operation of a vacuum-overpressure safety valve............................................................................ 8 
2 Operation of a vacuum safety valve .................................................................................................. 8 
Construction............................................................................................................................................... 8 
Mounting.................................................................................................................................................... 9 
Test.......................................................................................................................................................... 10 
Maintenance ............................................................................................................................................ 10 
1 Maintenance for vacuum-overpressure safety valves..................................................................... 10 
1.1 Annual check-up of the vacuum-overpressure safety valve........................................................ 10 
1.2 Criteria for the replacing of the vacuum and overpressure pallets.............................................. 11 
1.3 Methods for the revision of the vacuum-overpressure safety valve............................................ 12 
2 Maintenance for vacuum safety valves ........................................................................................... 13 
2.1 Annual check-up of the vacuum safety valve .............................................................................. 13 
2.2 Revision of the vacuum safety valve ........................................................................................... 13 
Technical data ......................................................................................................................................... 14 
1 Technical data vacuum-overpressure safety valves ........................................................................... 14 
1.1 Technical data PV 200/25/20-2 ................................................................................................... 14 
1.2 Technical data PV 150/25/20-2 ................................................................................................... 14 
1.3 Technical data PV 80/25/20-2 ..................................................................................................... 14 
2 Technical data vacuum safety valves.............................................................................................. 15 
2.1 Technical data PV100-2-F........................................................................................................... 15 
2.2 Technical data PV80-2-F............................................................................................................. 15 
2.3 Technical data PV50-2-F............................................................................................................. 15 
Warranty .............................................................................................................................................. 16 
Appendix.............................................................................................................................................. 17 
Document history................................................................................................................................. 17 
To Conclude ........................................................................................................................................ 18 
 
 

Page 4 of 18

Introduction

Before anything else, we’d like to congratulate you with the purchase of a PRESSCON vacuum-

overpressure safety valve or a vacuum safety valve. The vacuum-overpressure safety valve and vacuum

safety valve will provide safety against overpressure and a vacuum for your buffer tank. To clarify the usage

and functioning of your vacuum-overpressure safety valve and vacuum safety valve we offer you this

manual.

1. Precautions and safety instructions

During working with the vacuum-overpressure safety valve and the vacuum safety valve there are several

safety hazards that need to be taken into account. These are important both while working and installing the

safety valves. We highly recommend taking these safety hazards into account before proceeding to work

with the vacuum-overpressure safety valve and the vacuum safety valve.

Symbol

Description

Applies to

WORKING WITH HEIGHTS,

Vacuum-overpressure safety valves and vacuum safety

valves that are mounted on a vertical or horizontal buffer

tank are usually placed a couple of metres from the

ground. In most cases while working on the safety

valves, the height exceeds 2,5 metres. This is why

working on the safety valves is considered working with

heights. It automatically means that a safety harness or

other adequate fall protection is mandatory.

-Vacuum-overpressure safety

valve on a vertical buffer tank;

-Vacuum safety valve on a

horizontal buffer tank.

HOT PARTS AND STEAM,

The nitrogen above the water in the vertical buffer tank

has a humidity of 100% and is able to reach a

temperature of 90°C. So the housing of a safety valve

and the steam that is released can be hot. During

disassembling a safety valve or the safety pallets there

is an increased risk of injury caused by combustion.

Take appropriate measures for this. Use fitting safety

apparel and consider for example the direction of the

wind.

-Housing of the vacuum-

overpressure safety valve on a

vertical buffer tank;

-The releasing of nitrogen by the

vacuum-overpressure safety

valve;

-Housing of the vacuum safety

valve on a horizontal buffer

tank.

ADDITIONAL EXPOSURE TO HOT STEAM,

In some cases the safety valve as an extra cover of

insulation material. Keep in mind that this enables the

hot steam to rise higher when the nitrogen is being

released.

-The releasing of nitrogen by the

vacuum-overpressure safety

valve which is covered with

additional insulation material.

Page 5 of 18

2. Application

Application vacuum-overpressure safety valve

The application of the PRESSCON vacuum-overpressure safety valve is the following:

The vacuum-overpressure safety valve is placed near the caged ladder on 0,5 m. out the cylindrical side of

the vertical buffer tank on the roof. The vacuum-overpressure safety valve then provides the vertical buffer

tank with protection against vacuum and overpressure.

Application vacuum safety valve

The application of the PRESSCON vacuum safety valve is the following:

Two vertical pieces of tube with welding flanges are welded on the two highest ends of a horizontal buffer

tank. The tubes have a diameter of 2” . On each of the flanges a PRESSCON vacuum safety valve is

mounted. The vacuum safety valve provides protection for the horizontal buffer tank against vacuum.

Page 6 of 18

3. Construction

3.1Vacuum-overpressure safety valve

The image below is a schematically drawn image of the vacuum-overpressure safety valve.

1. Overpressure valve

2. Overpressure lead

3. Overpressure pallet

4. Operating pressure valve

5. Operating pressure lead

6. Operating pressure pallet

7. Cover plate

8. Silicon gasket

9. Vacuum pallet

10. Safety valve housing

10.

Figure 1. Vacuum-overpressure safety valve

Page 7 of 18

3.2Vacuum safety valve

The image below is a schematically drawn image of the construction of a vacuum safety valve.

1. Cover plate

2. Vacuum pallet

3. Gasket

4. Safety valve housing

5. Gasket

6. Adjustment bolt

7. Vacuum pallet flange

8. Gauze

9. Assembly

10. M8 RVS nut

11. M8 RVS ring

12. RVS stud bolt M6x10

10.

12.

11.

10.

11.

Figure 2. Vacuum safety valve

Page 8 of 18

4. Functioning of the safety valves

4.1Operation of a vacuum-overpressure safety valve

If the pressure of the nitrogen above the water rises above the maximum operating pressure for any reason,

the operating pressure side of the vacuum pressure relief valve opens. This creates an open connection to

the outside air. The excess nitrogen can flow away through the opening. The working pressure valve

remains open until the pressure equals the operating pressure.

If the pressure keeps rising and reaches the maximum overpressure, the overpressure safety valve will also

open. The vacuum relief valve remains open until the pressure falls below the maximum overpressure.

When the pressure drops and a vacuum is created between -2 and -4 mbar, the vacuum relief valve on the

vacuum side opens. Due to the pressure difference between the outside and inside air, outside air flows in.

The pallet is lifted until the pressure difference is equalised.

By using a PRESSCON vacuum-overpressure safety valve the possibility of an unacceptable over- or under

pressure altering the lasting shape of the tank is prevented. To guarantee a correct operation of the vacuum-

overpressure safety valve it is prohibited to change the lead weights in the safety valve in any way.

4.2Operation of a vacuum safety valve

If water flows from the buffer tank and causes a decrease in the water level, then the water level will

foremost decrease in the vacuum safety valve. If the water in the housing of the vacuum safety valve drops

more, a vacuum will be created. When a vacuum exists between -2 and -2 mbar, the pallet of the seating will

be lifted. This causes an open connection with the outside air. Because of the differential pressure between

outside and inside, outside air will flow into the buffer tank. The differential pressure is settled. By applying a

PRESSCON vacuum-overpressure safety valve the possibility of an unacceptable over- or under pressure

altering the lasting shape of the tank is prevented. To guarantee a correct operation of the vacuum safety

valve it is absolutely prohibited to turn the adjusting screw on the downside of the valve. The adjusting screw

is adjusted and secured in the factory.

5. Construction

PRESSCON has aimed to make the construction of the vacuum-overpressure safety valve as simple as

possible. Except for the flange for the mounting on the tank, only the gasket under the pallets is capable of

leaking. A very durable rubber is chosen as the material for the gasket. As a seal between the inside and the

outside, a combination of a stainless steel seating with a special rubber has been chosen. An important

feature of this special rubber is its lack of permit for dirt to attach itself to the rubber. The rubber is also very

heat resistant. The vacuum-overpressure and vacuum safety valve are constructed in such a way that after

assembly they are completely resistant to a plurality of pressures that can occur at a vertical or horizontal

buffer tank.

Page 9 of 18

6. Mounting

Mounting the vacuum-overpressure safety valve

The mounting of the vacuum-overpressure safety valve is as follows:

Make sure there are no irregularities on the flange of the vacuum-overpressure safety valve other than the

placed components of the manufacturer. Loosen all the RVS nuts on the threaded ends. Place a rubber

gasket of the correct dimensions on de welding flange. Place the vacuum-overpressure safety valve on the

flange with the threaded ends through the holes in the welded flange. Tighten the nuts on the threaded ends.

Make sure that all the nuts are all tightened even. Make sure that the connection between the welded flange

and the valve is leak-proof. The valve is now company ready.

Mounting the vacuum safety valve

The mounting of the vacuum safety valve is as follows:

Make sure there are no irregularities on the flange of the vacuum safety valve other than the placed

components of the manufacturer. Place a rubber gasket on the welded flange. Place the vacuum safety

valve on the four holes on the welded flange. Place 4 M16 bolts through the holes and place 4 M16 nuts on

the bottom side. Make sure all the nuts are tightened even. Make sure that the connection between the

welded flange and the valve is leak-proof. The valve is now company ready.

Page 10 of 18

7. Test

Each PRESSCON produced vacuum-overpressure safety valve and vacuum safety valve is adjusted and

tested according to the regulations. Every vacuum-overpressure safety valve or vacuum safety valve is

provided with a unique serial number. The serial number is also mentioned on the test certificate. The test

certificate is added to the manual.

8. Maintenance

Every vacuum-overpressure safety valve and vacuum safety valve has to be checked yearly to guarantee a

correct operation. It is advised to let the vacuum-overpressure safety valve and the vacuum safety valve be

checked once a year and revised once every two years. The vacuum-overpressure safety valve can be

revised on the site by a mechanic of PRESSCON or an instructed technician. The vacuum safety valve can

only be revised in the factory of PRESSCON. There is an exchange program available with revised vacuum

safety valves in stock.

8.1Maintenance for vacuum-overpressure safety valves

8.1.1 Annual check-up of the vacuum-overpressure safety valve

To check if the vacuum-overpressure safety valve is working satisfactorily, the annual inspection should be

performed according to the following work instruction.

1. Start by checking the pressure of the nitrogen blanket. This can be seen on the display of the

nitrogen generator.

2. Then climb the buffer tank and check whether the safety device is blowing or not. The type plate of

the safety valve indicates the operating pressure and the maximum pressure. Decide on the basis of

this information if the safety valve should be blowing off or if this should be closed.

Caution! When opening the vacuum overpressure safety device, steam is released with

a temperature of 90°C. It is recommended to wear protective gloves and additional

protective clothing.

Figure 3. Vacuum-overpressure safety valve

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