---
title: High Level Alarms or Low Level Alarms (Transmitter) – Initial Troubleshooting
description: Initial troubleshooting guide for analog level alarms on LiqTech Crossflow systems. Covers level transmitter scaling, setpoints, alarm limits, BW interaction, and common process-related causes of high and low level alarms.
---
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# High Level Alarms or Low Level Alarms (Transmitter) – Initial Troubleshooting
## This guide describes a practical, field-proven approach for troubleshooting analog level alarms based on level transmitters on LiqTech Crossflow (CF) systems. It focuses on process behavior, setpoints, scaling, and alarm configuration rather than signal or hardware faults.
#### When to use this guide
Use this guide when:
- A **High level** or **Low level** alarm based on a **level transmitter** is active
- The tank level appears implausible compared to expected operation
- Level alarms occur repeatedly during normal operation, BW, or refilling
- The alarm severity does not seem appropriate for the situation
- A customer refers to a **specific alarm ID** together with high or low tank level
---
#### Scope and boundaries
This guide applies to **levels measured by analog transmitters**.
It focuses on:
- process behavior
- setpoints
- scaling
- alarm limits and severity
It does **not** cover:
- digital level switches
- discrete level alarms used in CIP or chemical modules
- transmitter signal faults (wiring, IO, 4–20 mA loss)
---
#### Preconditions and safety
Before starting troubleshooting:
- The system should normally be in **STOP state** for checks and adjustments
- Observation of level behavior may be done during live operation
- Electrical troubleshooting shall only be performed by personnel with relevant competence
- Always follow site-specific safety procedures
---
#### Important concept (read first)
On the majority of CF systems, the **Permeate / BW tank** is an **actively controlled tank**.
- The HMI setpoint **“Permeate tank level \[%\]”** is used as a **control reference**
- It regulates the **pump discharging permeate downstream**
- The level is **PID-controlled**, not static
This means:
- The tank level will naturally **move around the setpoint**
- Small oscillations, overshoot, or undershoot are **expected behavior**
- Level alarms must always be interpreted in the context of:
- current operating mode
- production settings (feed, recovery)
- BW activity
A level alarm does **not automatically indicate a fault**.
---
#### Step-by-step troubleshooting procedure
### 1. Understand which alarm you are dealing with
Confirm whether the alarm is:
- **High level (transmitter)**
- **Low level (transmitter)**
Both are **process alarms**, not safety switches.
As a general guideline:
- **Low level** is typically **critical**, as it protects pumps and operation
- 70-85% is a normal level setpoint to aim for.
- **High level** is often **non-critical**, especially if a physical high-level switch exists in the same tank
Always verify the configured alarm severity on the HMI.
---
### 2. Check whether the alarm fits the current operation
Before adjusting anything, ask:
- Did the alarm occur:
- after BW?
- during extensive BW?
- after a change in feed setpoint or recovery?
- Is the tank currently being:
- actively filled?
- actively drained?
- regulated around a setpoint?
Many level alarms occur during **transient but expected conditions**.
---
### 3. Verify level transmitter scaling (always relevant)
Scaling must be considered **regardless of whether the alarm is high or low**.
A level reading can be:
- perfectly scaled
- functionally acceptable
- or clearly non-functional
The goal here is **plausibility**, not perfection.
#### Practical scaling plausibility check
A simple and effective method:
1. Set the permeate tank level setpoint to approx. **50 %**
2. Stop the system
3. Verify that the liquid level is roughly:
- half the effective tank height
- measured from the bottom of the transmitter
4. Let the tank fill to approx. **75 %** and verify plausibility again
5. Finally, let the tank approach **100 %** (or the physical upper limit being the high level switch) and verify that the reading still makes sense relative to the tank geometry
The transmitter should behave **monotonically and reasonably** across the range.
Also inspect the physical condition of the transmitter:
- buildup
- damage
- abnormal response
- placement - if submergable it needs to be close to the bottom of the tank.
---
### 4. Platform-specific note on scaling
- **MK8 and newer CF systems**
- Level transmitter scaling can be adjusted from the **HMI**
- Scaling errors may therefore originate from previous adjustments
- **MK6 systems**
- Scaling **cannot be adjusted from the HMI**
- If scaling is clearly off (non-functional or implausible), **LiqTech must be contacted**
- Provide:
- observed level values
- approximate physical level
- tank geometry
- when the alarm occurs
There is an important difference between:
- perfectly calibrated
- functionally acceptable
- non-functional scaling
Only the last requires immediate escalation.
---
### 5. Review alarm limits and setpoints together
Level behavior is defined by **three interacting elements**:
- the **PID setpoint** (e.g. permeate tank level \[%\])
- the **level transmitter alarm limits**
- the **physical tank volume**
Verify that:
- High and low alarm limits are **not too close** to the normal operating range
- Normal refilling after BW does **not unintentionally trigger high level alarms**
- Extensive BW does **not unintentionally trigger low level alarms**
---
### 6. Handling repeated high level alarms
If repeated **high level transmitter alarms** are observed:
- A **small reduction** of the permeate tank level setpoint may be considered
- This is often sufficient when:
- production parameters are changed rapidly
- feed setpoint or recovery is increased
- the system is installed in a marine environment with significant motion
This is a **drift optimization**, not a fault correction.
---
### 7. Handling repeated low level alarms
If repeated **low level transmitter alarms** are observed:
- Consider whether BW volume or BW duration is excessive
- Verify whether permeate production is sufficient to refill the tank
- If practice allows, the tank level setpoint may be increased slightly
The most common root cause is:
- long or heavy BW cycles
- sometimes combined with insufficient permeate production
---
### Example – Permeate tank level alarms and operating setpoints
High and low level alarms on the permeate tank are often a result of **normal operating behavior**, not incorrect alarm configuration.
In typical operation:
- The **Permeate tank level \[%\]** defines the normal operating level (Setpoint)
- **Minimum level to start BW \[%\]** is set lower than the normal operating level (Setpoint)
- A **Low level alarm** is set to trigger before the tank becomes empty (Alarm Setting)
- A **High level alarm** is set above the normal operating level (Alarm Setting)
- A **High level switch** acts as the final safety layer
If the operating setpoints are poorly aligned, level alarms may occur even though the system is functioning as intended.
#### Common root causes
**Most common**
- Operation setpoint level set to close to Alarm limits or vice versa.
- Incorrect or poorly aligned level transmitter scaling
**Also common**
- Production changes (feed, recovery)
- Extensive BW consuming more volume than expected
- Setpoint not adapted to actual operating conditions (e.g. high seas on marine systems)
These are **process configuration topics**, not hardware failures.
---
#### When to contact LiqTech
Contact LiqTech if:
- Level transmitter scaling on an MK6 system appears non-functional
- Level readings are implausible across the entire range
- Repeated alarms cannot be rationalized by operation, BW, or setpoints
When contacting LiqTech, clearly describe:
- what level is shown
- what physical level is observed
- when alarms occur
- what has already been verified
---
#### Alarm ID references (examples)
The following alarm IDs are **examples** of **analog level alarms** this guide applies to.
They are provided as **recognition aids** for support agents.
Other alarm IDs with similar texts may exist.
### **MK6 – Level Transmitters**
- Alarm ID **34** – Level transmitter (permeate / tank related)
- Alarm ID **131** – Level transmitter (permeate tank variant)
- Alarm ID **197** – Level transmitter (concentrate tank)
- Alarm ID **204** – Level transmitter (reject tank)
- Alarm ID **223** – Level transmitter (precipitation tank)
These alarms may represent **high or low level conditions**, depending on configuration.
---
### **MK8 / newer systems**
Level alarms are typically referenced as:
- *Permeate tank high level*
- *Permeate tank low level*
- *Tank level high / low*
Alarm numbering and naming may vary by project and configuration.
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