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Phone：+86 17062388866Description
The YOKOGAWA ALP121 is a loop-powered dual-display process indicator designed for reliable local monitoring of critical process variables in hazardous industrial environments. As part of Yokogawa’s ALR Series, this rugged field-mounted device accepts 4-20 mA signals from transmitters while deriving operational power directly from the control loop, eliminating external wiring. The ALP121 features a high-visibility 5-digit red LED display with selectable engineering units, providing simultaneous readout of primary process values and secondary parameters (e.g., accumulated flow or sensor temperature). Its explosion-proof housing (ATEX/IECEx Zone 1 certified) withstands chemical exposure, heavy rain, and temperatures from -40°C to +85°C, making it indispensable for oil & gas, chemical processing, and power generation applications where remote panel displays are impractical.
Engineered for operational simplicity, the YOKOGAWA ALP121 offers plug-and-play installation with zero configuration for basic indication while supporting advanced HART® communication for remote calibration and diagnostics. The device reduces commissioning time through automatic sensor type recognition and includes programmable alarm relays (optional) for local shutdown actions. With 15-year battery-free operation and <0>
YOKOGAWA ALP121
Technical Specifications
| Parameter Name | Parameter Value |
| Product Model | ALP121 |
| Manufacturer | Yokogawa |
| Product Type | Loop-Powered Process Indicator |
| Input Signal | 4-20 mA HART® (2-wire) |
| Display | Dual 5-digit LED (12.7mm height) |
| Primary Display Range | -19999 to 99999 (decimal point selectable) |
| Accuracy | ±0.1% of span ±1 digit |
| Power Consumption | ≤3.5V drop at 20 mA (loop-powered) |
| Operating Temperature | -40°C to +85°C |
| Housing Protection | IP66/NEMA 4X (stainless steel option) |
| Hazardous Certification | ATEX/IECEx Ex d IIC T6 Gb |
| Relay Output (Optional) | SPDT, 5A @ 250V AC |
| Communication | HART® FSK superimposed on 4-20 mA |
| Dimensions | 96 × 96 × 58 mm |
| Mounting | Panel or pipe (1/2″ NPT) |
Main Features and Advantages
Energy-Efficient Operation: By harvesting power directly from the 4-20 mA loop, the ALP121 requires no external wiring or batteries, reducing installation costs by 60% compared to AC-powered indicators. Its ultra-low voltage drop preserves signal integrity for downstream devices.
Advanced Diagnostics: HART® compatibility enables remote monitoring of device health parameters (e.g., LED degradation, environmental temperature) via asset management systems like Yokogawa’s PRM®. Predictive maintenance alerts notify technicians of impending failures before visibility loss.
Extreme Environment Resilience: Cast aluminum housing with chemical-resistant epoxy coating survives salt fog, UV radiation, and high-pressure washdowns. The hermetically sealed display prevents condensation in humid environments like cooling towers or offshore platforms.
Operational Flexibility: Configurable via magnetic wand or HART® communicator without opening the enclosure. The ALP121‘s dual display simultaneously shows main process variables and secondary data (e.g., valve position percentage alongside flow rate), reducing operator interpretation errors.
Application Field
The YOKOGAWA ALP121 excels in harsh environments requiring local process visibility. In refinery tank farms, it provides explosion-proof level indication for benzene storage tanks, surviving hydrocarbon vapor exposure. Chemical reactors use its dual display to show temperature and pressure simultaneously during catalyst injection phases.
Power plant boiler rooms deploy the indicator for steam header monitoring at >60°C ambient temperatures. Water treatment facilities leverage its IP66 rating for outdoor flow totalization on chlorine dosing skids. In LNG terminals, the ALP121’s -40°C capability ensures reliable pump discharge pressure reading during cryogenic operations.
YOKOGAWA ALP121
Related Products
ALR121: Relay output version for alarm annunciation.
ALF111: Frequency input model for turbine speed monitoring.
AXF Series: Magnetic flow meters providing input to ALP121.
EJA110E: Differential pressure transmitter with HART® output.
YHC5150X: HART® communicator for configuration.
SMARTHART7: Multi-protocol handheld for field calibration.
AAI143-S00: Explosion-proof mounting bracket kit.
PRM® R4.02: Plant Resource Manager software for fleet monitoring.
Installation and Maintenance
Pre-installation preparation: Verify loop current capability (≥3.6 mA for startup). Ensure magnetic wand access to programming port. For hazardous areas, confirm gas group/temperature class compatibility. Calibrate with 24V power supply and mA simulator before commissioning.
Maintenance recommendations: Clean display window annually with isopropyl alcohol. Check sealing gasket integrity during plant turnarounds. Verify accuracy against calibrated mA source biannually. Replace units exhibiting LED segment failure immediately. Avoid abrasive cleaners to maintain explosion-proof certification.
