Description
Note: Many products are not yet listed. Please contact us for more product information. Our supply channels are constantly expanding, and we currently have 20 stable shared supply channels. Please confirm the model, product, price, and all other necessary information with customer service before placing an order. We offer new, refurbished, and used products, and prices are adjusted according to the year of the item you require.
3. Key Technical Specifications
Confirm each line against the OEM datasheet and the label on your existing module before ordering. Relay contact ratings and terminal block part numbers must be verified for your specific build.
| Parameter | Value |
|---|---|
| Model | 3500/33 |
| Brand | Bently Nevada |
| Product Family | 3500 Machinery Protection System |
| Module Type | 16-Channel Relay Module |
| Relay Channels | 16 (individually configurable) |
| Relay Contact Type | SPDT (Form C) — normally open and normally closed available per channel |
| Contact Rating | Verify with OEM datasheet — confirm AC and DC ratings for your load type |
| Contact Life | Verify — relay contacts are a wear item under high-cycle alarm conditions |
| Isolation | Field side to logic side — verify isolation voltage |
| Configuration | 3500 Rack Configuration Software — verify supported version |
| Alarm Logic | Each channel configurable for alarm, trip, or combined logic — verify voting options |
| Voting | Configurable AND/OR voting across monitor channels — verify in the software |
| Backplane Interface | 3500 rack backplane — verify slot assignment and chassis compatibility |
| Terminal Block | External terminal block required — verify the correct part number for your module and rack |
| Status Indicators | Module OK and per-channel status LEDs — verify arrangement |
| Operating Temperature | 0 °C to +60 °C (typical — verify) |
| Storage Temperature | –40 °C to +85 °C (typical — verify) |
| Humidity | 5% – 95% RH, non-condensing |
| Weight | Verify with OEM datasheet |
| Certifications | CE, UL, CSA — verify on the specific unit’s label |
4. Product Introduction
The Bently Nevada 3500/33 is a sixteen-channel relay module for the 3500 machinery protection system. It takes the alarm and trip decisions from the rack’s monitor channels and converts them into dry contact outputs that drive annunciators, shutdown relays, PLC inputs, and interlock circuits. It is the module that turns a vibration or temperature reading into a physical action.
The engineering value is the configurable voting logic. Each relay channel can be programmed to respond to a specific monitor channel, to a combination of channels, or to a voted condition across redundant monitors. In my experience, that is what lets a plant tailor the trip matrix to the machine — a high-vibration trip on one bearing does not have to shut down the whole train if the process can tolerate it. The module handles the logic so the field wiring stays simple.
Two things decide whether a swap works. First, the terminal block. The 3500/33 does not land field wiring directly — it mates with an external terminal block that carries the marshalling. If the block is wired for a different module or a different channel assignment, the replacement will not work. Second, the configuration. The relay logic is stored in the rack configuration, not in the module. Verify the configuration file is current before you swap the module.
5. Application Scenarios & Field Experience
Part 1 – Narrative Paragraph
The failure that hurts most on a relay module is a contact that sticks closed. The alarm clears, the monitor channel returns to normal, and the relay stays energized. The operator sees a trip condition that will not reset, and the maintenance team chases the monitor channel instead of the relay. I have seen that on a compressor where a high-vibration trip latched and would not clear even after the vibration returned to normal. The monitor was fine — the relay contact had welded closed. On a machinery protection system, that is the failure mode that keeps a machine offline. When you replace a 3500/33, verify the relay contact releases before you return the machine to service. Do not assume that because the LED went out, the contact opened.
Part 2 – Numbered List (Application Scenarios)
- Power Generation – Steam Turbine Trip Circuits – The module drives the turbine trip relay from the vibration, thrust, and eccentricity monitor channels. The configurable voting lets the plant require two-out-of-three monitor agreement before tripping, which reduces false trips.
- Oil & Gas – Centrifugal Compressor Shutdown – Used to command the compressor shutdown circuit from the radial vibration and axial position monitors. The Form C contacts drive both the shutdown relay and the annunciator panel.
- Petrochemical – Reciprocating Compressor Alarm and Trip – The module provides separate alarm and trip contacts for rod drop, crosshead vibration, and bearing temperature. The alarm contacts drive the operator panel; the trip contacts drive the shutdown circuit.
- Hydroelectric – Hydro Turbine Bearing Protection – Used to trip the unit on high bearing temperature or vibration. The relay contacts interface with the plant DCS and the unit trip circuit.
Part 3 – Short Field Story
A gas plant had a compressor that would not restart after a high-vibration trip. The monitor channel showed normal, the alarm had cleared on the operator station, and the shutdown relay stayed energized. The maintenance team replaced the monitor card and the problem persisted. We asked them to check the relay module contact with a meter. The contact was stuck closed — the relay had welded during the trip event because the shutdown relay coil was an inductive load that exceeded the contact’s break rating. The plant replaced the 3500/33 with the correct contact rating, added a suppression diode across the coil, and the compressor restarted. The monitor card had been fine.
6. Standard Operating Procedure (SOP) for Quality Control
- Visual & Origin Inspection – We verify the Bently Nevada marking, the 3500/33 model string, and the date code. We inspect the backplane connector for bent pins and the module housing for cracks or moisture ingress. A module with a damaged connector or evidence of rework is rejected.
- Revision and Configuration Documentation – We read and photograph the full model string, the firmware revision, and the module revision letter. That record ships with the module so you can compare it against the unit you are replacing.
- Chassis Fit Verification – Each module is seated in a 3500 test rack to confirm the connector engages fully and the retention mechanism holds. A module that fits loosely will cause intermittent backplane faults in the field.
- Power-Up and Self-Test – The module is powered in a live rack and we verify it completes its boot sequence and that the rack controller recognizes the module type without a fault.
- Relay Channel Verification – We command each of the 16 relay channels to energize and de-energize, and we verify the contact state with a meter. We check both the normally open and normally closed contacts.
- Contact Resistance Check – We measure the closed-contact resistance on each channel. A reading above the OEM limit indicates a worn or pitted contact, and the module is rejected.
- Diagnostic Function Test – We verify the module reports a relay failure or a stuck contact to the rack controller. A module that switches correctly but does not report faults is not acceptable for machinery protection.
- ESD-Safe Packaging – The module is wrapped in anti-static film, seated in a conductive foam insert with the connectors protected by rigid shrouds, and packed in a double-wall carton with static warning labels.
7. Frequently Asked Questions (FAQ)
Q1: Does the 3500/33 include the terminal block?
A: No. The 3500/33 is the module only. Field wiring lands on an external terminal block that mates with the module through the rack. The terminal block is a separate part number, and you must verify it matches your module type and chassis. If you send us the terminal block part number and the rack model, we can confirm the match before you order.
Q2: Where is the relay logic stored — in the module or in the rack?
A: The relay configuration is stored in the rack configuration, not in the module itself. That means a replacement module will pick up the existing configuration when it is installed in the rack. But verify the configuration file is current and backed up before you swap the module. If the rack configuration is lost, the relay logic must be rebuilt.
Q3: What is the warranty on this module?
A: We offer a 12-month warranty from the ship date. It covers relay contact failure, backplane connector failure, and diagnostic circuit failure under normal operating conditions. It does not cover damage from hot-swapping the module outside the OEM procedure, bent pins from forced insertion, or field wiring faults that cause a contact to fail. We test every module in a live 3500 rack and verify each relay channel before it ships.
Q4: Do you have this in stock?
A: Bently Nevada 3500 inventory moves quickly, and stock varies by revision. Confirm availability before you plan an outage. If we are out of the revision you need, we will tell you what we actually have rather than quote a date we cannot hold.
Q5: Any installation pitfalls I should watch for?
A: Four. First, verify the terminal block part number matches the module and the rack before you install. Second, verify the field load current and the load type against the relay contact rating — an inductive load like a relay coil or solenoid has an inrush current that can weld an underrated contact. Third, back up the rack configuration before you swap the module. Fourth, after the swap, command each relay channel and verify the contact state at the field terminal before you return the machine to service. A module that powers up is not necessarily switching correctly.
