Spirax Sarco LP20 User manual

IM-P402-37 AB Issue 9 1
LP20
Capacitance Level Probe
Installation and Maintenance Instructions
IM-P402-37
AB Issue 9
Printed in the UK © Copyright 2012
1.Safetyinformation
2.Generalproduct
 information
3.HowtheLP20
 probeworks
4.Installation
5.Wiring
6.Maintenance
4024650/9

2IM-P402-37 AB Issue 9
1. Safety information
Safe operation of the product depends on it being properly installed, commissioned
and maintained by a qualified person (see Section 1.11) in compliance with the
operating instructions.
It is essential to comply with general installation and safety instructions for
pipeline and plant construction, as well as to make proper use of tools and safety
equipment.
The product is designed and constructed to withstand the forces encountered
during normal use. Use of the product for any other purpose, or failure to install
the product in accordance with these Installation and Maintenance Instructions,
could cause damage to the product, will invalidate the marking, and may cause
injury or fatality to personnel.
Additional Safety Notes
Level control and level limiting / alarm products in steam boilers
Products / systems must be selected, installed, operated, and tested in accordance with:
- Local or National standards and regulations.
- Guidance Notes, (Health and Safety Executive BG01 and INDG436 in the UK).
- The requirements of Approvals Authorities.
- Boiler inspection bodies.
- Boiler manufacturer’s specifications.
Two independent low water limiting / alarm systems must be installed on steam
boilers. Level probes must be installed in separate protection tubes / chambers,
with sufficient clearance between the tips, and earth.
Each probe must be connected to an independent controller. The alarm relays
must isolate the boiler heat supply at low alarm status.
A high water alarm may be part of the water level control, or a separate system.
An independent high water alarm system must be fitted if it is considered a
safety requirement. In this case, the relays must simultaneously isolate the
feedwater supply and the boiler heat supply at high alarm status. All boiler water
limiters / alarms require regular functional testing.
A suitable water treatment regime must be used to ensure continuous safe and
correct operation of the control and limiter / alarm systems. Consult the above
authorities and a competent water treatment company.

IM-P402-37 AB Issue 9 3
Warning
Isolate the mains supply before unplugging the controller since hazardous
voltages will be exposed on the controller base. This product complies with
the requirements of Electromagnetic Compatibility Directive 89 / 336 / EEC and
93 / 68 / EEC by meeting the standards of:
- EN 61326 : 1997 A1 + A2 Emissions Class B equipment Table 4.
- EN 61326 : 1997 A1 + A2 Immunity for Industrial Locations Annex A.
The following conditions should be avoided as they may create interference above
the limits specified in EN 61326 (Immunity) if:
- The product or its wiring is located near a radio transmitter.
- Excessive electrical noise occurs on the mains supply. Power line protectors
(ac) should be installed if mains supply noise is likely. Protectors can combine
filtering, suppression, surge and spike arrestors.
- Cellular telephones and mobile radios may cause interference if used within
approximately 1 metre (39") of the vary according to the surroundings of the
installation and the power of the transmitter.
If this product is not used in the manner specified by this IMI, then the protection
provided may be impaired.
1.1 Intended use
i) Check that the product is suitable for use with the intended fluid.
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.
Safe operation of this product can only be guaranteed if it is 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.

4IM-P402-37 AB Issue 9
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.
1.3 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 the danger of burns.
For personal protection wear protective clothing, especially heavy duty gloves and
safety glasses.
PTFE:
If parts made from PTFE have been subjected to a temperature approaching
260°C (500°F) or higher, they will give off toxic fumes, which if inhaled are likely to
cause temporary discomfort. It is essential for a no smoking rule to be enforced
in all areas where PTFE is stored, handled, or processed as persons inhaling
the fumes from burning tobacco contaminated with PTFE particles can develop
'polymer fume fever'.
1.9 Tools and consumables
Before starting work ensure that suitable tools and / or consumables are 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.

IM-P402-37 AB Issue 9 5
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.
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.
Many products are not self-draining. Take due care when dismantling or removing
the product from an installation.
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
The product is recyclable. No ecological hazard is anticipated with the disposal of
this product providing due care is taken, EXCEPT;
PTFE:
- Can only be disposed of by approved methods, not incineration.
- Keep PTFE waste in a separate container, do not mix it with other rubbish, and
consign it to a landfill site.
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.

6IM-P402-37 AB Issue 9
2. General product information
2.1 Description
The Spirax Sarco LP20 is a capacitance probe
designed for modulating level control in conductive
liquids, in conjunction with a PA20 preamplifier,
which is supplied separately. It can also be used for
adjustable on / off control.
The LP20 may be used with one or more controllers
or transmitters to provide level control, level alarms,
and / or outputs to a building management system.
The probe is normally installed in a steam boiler or
metal tank where it is earthed through the ½" BSP
screwed connection, the boiler or tank forming the
earth return path.
It may be used in a non-conductive tank (e.g. plastic
or concrete) if an earth rod is provided.
The PA20 preamplifier (described in separate
literature), is screwed to the top of the probe and
hand tightened, enabling easy removal without the
need to disturb the probe.
The LP20 probe is compatible with the Spirax Sarco
range of controllers and transmitters, which are
described in separate literature.
Approvals
The LP20 is also available with a ½" NPT screwed
connection, approved to UL61010. Please note
that this version will not be CE marked and is not
suitable for Europe.
Caution:
The probe is not suitable for outside installation
without additional environmental protection.
Note:
For additional product data see the following Technical
Information sheet TI-P402-39
2.2 Available probe lengths
(approximate) in mm
370, 470, 550, 600, 650, 750, 800, 900, 950, 1 050, 1 200,
1 350 or 1 500.
Note: Probe length includes the 25 mm 'dead' length at
its tip. The probe must not be cut to length.
2.3 Pressure / temperature limits
Nominal pressure rating PN40
Maximum pressure 32 bar g
Maximum temperature 239°C
Maximum 70°C
Ambient temperature Minimum 5°C
Designed for a maximum cold hydraulic test pressure of: 60 bar g
2.4 Technical data
Sensing depth Probe length minus 25 mm
Minimum conductivity 5 µS / cm or 5 ppm
Fig. 1
Capacitance level probe
'O'
ring
LP20
connector
Vent
holes
Body
Probe
½" BSP
taper
thread.
The UL
probe has
a ½" NPT
thread and
UL label
Drain
holes
27 A / F
PTFE
sheathing
25 mm
(1")
'dead'
length

IM-P402-37 AB Issue 9 7
4. Installation
The probe consists of a metal rod
completely insulated from the liquid by
PTFE sheathing. It works by sensing the
variation in capacitance caused by a
change in water level, an increasing level
giving a proportionally increasing output.
The capacitance is measured by the
preamplifier and transmitted as a dc signal
to the controller or transmitter. Control and
switching levels are set in the controller.
The preamplifier sensitivity is selected
according to the immersed length of
the probe, and the wiring variations
that achieve this are described in the
preamplifier Installation and Maintenance
Instructions (IMI).
CAUTION: Over-tightening by hand or
use of a wrench will cause damage
to the 'O' ring and may damage the
preamplifier.
PA20
'O' ring
LP20
Capacitance
level probe
Fig. 2
WARNING: The LP20 probe must not be cut to length. Do not install the probe
outdoors without additional weather protection. Do not block the drain or the
vent holes.
A protection tube of 80 mm (3") nominal bore is required for boilers, or in tanks where
turbulence is likely. This should be as long as possible, and at least long enough to
cope with the expansion of the probe at maximum operating temperature (0 - 239°C,
32 - 462°F). Allow 20 mm (¾") clearance for probes up to 750 mm in length, and 38 mm
(1½" for longer probes).
4.1 Install the probs as follows
- Ensure both male and female threads are in good condition.
- Use up to three turns (no more) of PTFE thread sealing tape on the probe thread.
WARNINGS: Do not use excessive tape. Do not use paste type jointing compound.
- Fit and tighten the probe by hand initially - use a suitable spanner to tighten the probe.
Under no circumstances use a pipe wrench.
- Due to the nature of a taper / parallel joint it is not possible to recommend tightening
torque figures.
- Do not overtighten - there should always be visible thread on the probe.
- Note: The probe thread will not 'bottom out' (i.e. probe body hexagon contacts the
face of the female screwed connection), unless there is excessive wear or an
out-of-tolerance female thread, in which case it will be necessary to replace or re-work
the flange or connection. After installation ensure that resistance from the probe body
to the pipework / boiler shell is less than 1W.
3. How the LP20 probe works

8IM-P402-37 AB Issue 9
6. Maintenance
5. Wiring
4.2 Subsequent removal and refitting
Cabling should be installed in accordance with BS 6739 - Instrumentation in Process
Control Systems: Installation design and practice or local equivalent.
Warning: Ensure boiler or vessel is depressurised and vented to atmosphere
before attempting to unscrew or remove the probe.
- Always use the correct size spanner - not a pipe wrench.
- Inspect male and female threads for signs of damage, which may have occurred through
overtightening, leading to torn threads or even localised cold welding (galling / picking up).
- If damage has occurred replace the probe.
- Carry out an electrical continuity check to ensure that the resistance between the probe
body and the boiler or tank is less than 1W.
- An 'O' ring is supplied with both the LP20 and PA20. Ensure only one 'O' ring is fitted
between the probe and the PA20 preamplifier (see Figure 2).
The preamplifier must only be screwed on hand tight to avoid damage to the 'O' ring.
Refer to the preamplifier IMI for further information.
Refer to the preamplifier and controller / transmitter Installation and Maintenance
Instructions for wiring details and diagrams.
Note: Read the 'Safety information' in Section 1 before starting any maintenance.
No special servicing, preventative maintenance or inspection of the product is required.
Level controls
Boiler water level controls and level alarms, however, do require testing and
inspection. General guidance is given in Health and Safety Executive Guidance
Notes BG01 and INDG436.
For specific instructions for the Spirax Sarco system please see separate literature.
Cleaning instructions
Use a cloth dampened with tap / de-ionised water or isopropyl alcohol. Use of other
cleaning materials could damage the product and invalidate the warranty.