Category Archives: Overseas Customers

Offshore oil rig showing chiller service being carried out in marine environment

Offshore & Marine Chiller Service

North Sea Offshore & Marine Chiller Service

On a previous visit for offshore & marine chiller service on an oil rig, our customer had shown us to a large air cooled chiller. His complaint was that it was tripping out all the time when there was nothing wrong it. Complicated ‘in house’ controls, where a string of PCBs, plugged into each other were found in the panel. We recommended a controls retrofit and received the order to carry out work…

Finicky Controls

All of the finicky control PCBs were removed from the panel and placed in the electrical recycling skip.

Offshore & Marine Chiller Service to Control Wiring 

The control wiring was removed and grouped together according to colour. This was because the same wiring was going to be re used to re wire chiller.

Inverters

Two Danfoss inverters were installed into the panel. These were to provide a VSD (variable speed drive) for two large screw compressors.

Electronic Expansion Valves

Danfoss EEVs were easily brazed into place as both systems could be pumped down and valved off. This part of the fridge system was then nitrogen pressure tested then vacuumed according to standard industry guidelines.

Fan Speed Controllers

Both systems had a Danfoss fan speed controller fitted to the chiller frame to control the condenser fans. Then, the control transducers were wired in to the FSCs. This made them stand alone and capable of independently controlling the head pressure of each system.

Danfoss Chiller Controller

The controller in the photo is capable of running the inverter drives for the compressors and the electronic expansion valves. It was wired in, one wire at a time: first the Inputs, then the Outputs and finally the power supply.

Offshore & Marine Chiller Commissioning Service

We always carry out commissioning in the morning as this is the best time of the day to solve problems. It was time for a cup of coffee and a deep breath. Our engineer had only re wired one panel previously and he was also a long way from the office.

Switch On

When he switched the power supply on, there were no immediate problems, so he waited for the for the timer to count down. System 1 started and after a while System 2 started too. There were a few teething problems with the settings, but then the chiller settled down. No more spurious trip outs.

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Controller used in offshore chiller service
Cheap and very reliable

Offshore & Marine Chiller Service in Liverpool

A bulker had got into difficulties in the Irish Sea and been towed to Liverpool for service. It was discovered that a rope had got wrapped around the propeller. Aside from this, one of two chillers which are used for the cooling of the living quarters had tripped out. The Chief Engineer had therefore decided to kill two birds with one stone. Most of the crew were from around Tanger Med in Morocco and so spoke only a little English. They also have limits as to how far they will go with a fridge system. Not to worry though: all we need is to see the plant and we can take it from there...

Seawater Cooled

The plant had a sea water cooled condenser which was fed via a pump set in an adjoining plant room.

Offshore & Marine Chiller Service to Controller

The controller alarm message stated that there was a low pressure condition in the evaporator. On interrogation of the menu, however, the pressure of the evaporator was found to be 7 bar which was the same as in the condenser.

Reset

Our engineer therefore decided to follow through the reset procedure. The alarm cleared and the machine started up. Then, it pumped down to 1 bar and tripped out on the same fault.

Liquid Line Solenoid Valve

While this was happening, our engineer was quick to notice that the liquid line solenoid valve had not activated. He decided to manually jack it open with his test equipment and the refrigerant rushed through okay.

Liquid Line Solenoid Coil

Having decided that the valve was okay, he then investigated the coil. The connection box and the wiring was found to be in poor condition.

Isolate

He then isolated the power supply and checked that it was dead.

Rewire

The wiring was cut back and he re made the connections onto the solenoid coil without using the connection box. Then, he insulated the area with a special compound.

Test Operation

Now to see if he had got the diagnosis correct. He powered up the chiller and carried out a run test- all readings were found to be nominal and the machine went back into service.

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Planning for Offshore & Marine Chiller Service

The main part of the planning for an offshore visit is done on the previous job. A detailed list of the required parts, materials, refrigerant, tools and equipment is composed on our Offshore Manifest Sheet. The questions and headings have been designed to prompt an engineer into thinking about all aspects of the job in detail.

Preparation for Offshore & Marine Chiller Service 

Having emailed the above mentioned sheet to Head Office, we cross reference the information with the engineer while he is still offshore. All this preparation is to ensure that the upcoming job goes as planned. There would be nothing worse than to have to postpone the job due to a lack of preparation.

Steel Chests

We have several steel chests that we use for shipping to oil rigs. After the parts and materials arrive at Head Office, they are checked off, one at a time into the shipping chests. Then, the necessary tools and equipment is checked off too.

Offshore Stores

Our customers also have their own equipment in their stores. They have things like fittings and fuses too. This is a good backup for when something is unforeseen, or if something breaks.

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Man commissioning a chiller in Saudi wareing head gear

Saudi Chiller Commissioning

We arranged the trip to carry out Saudi chiller commissioning for our Company Director and overseas engineer Dave Thompson. 2x 500kw air cooled chillers had been positioned at high level on a gantry. These were at the back of a newly constructed building at a factory in Jeddah. The factory produces plastic water pipes used for buildings and industry. Their own pipework, produced onsite, was used for the water systems of the plant in this article.

Water System Check Valves

There are two underground water system reservoirs for the plant. A check valve is fitted below the water line on the inlet pipe feeding all of the pumps. This ensures that water is available to the pumps on start up, despite the reservoirs being below the pumps.

Saudi Chiller Commissioning of Chiller Pump Set

The chiller pump set sucks water from the underground chiller reservoir. It then discharges the water through a plate heat exchanger, then it flows up to the chillers. The chilled water then returns 5°C cooler back to the underground chiller reservoir.

Saudi Chiller Commissioning of PHE Pump Set

Another pump set sucks from the separate underground process reservoir and discharges through the other side of the above mentioned plate heat exchanger. The water is chilled by around 5°C which can be adjusted with a pressure regulating valve on the outlet of the PHE. This chilled water then returns to the underground process reservoir.

Saudi Chiller Commissioning of Process Pump Set

A third pump set also sucks from the above mentioned underground process reservoir. It then discharges up to a ring main which goes along the top of 6 lines. Then, it drains down into plastic extrusion moulding machines to cool the newly formed plastic pipe. It does this at just the right rate to prevent bending and distortion. After this, the chilled water drains at gravity pressure back into the underground process reservoir.

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Control Panels for Pump Inverters

All of the pumps run on inverter drives which saves a significant amount of electricity. These drives are located in three panels- one for each pump set. A spare inverter is available in each panel for easy switch over in the event of failure. A touch screen pump control display is fitted to each panel. Each display is wired into a PLC.

Touch Screen Central Control

The PLCs in each panel are in turn wired into a Schneider Electric touch screen central control interface. This is located on the front of the middle panel. All of the analogue sensor and transducer inputs are wired into this interface from around the plant. The underground process reservoir temperature sensor was found to be reading 4°C high, so an offset was put into the program. The digital outputs go from here to the various components around the plant.

3 Way Valve

One of these components is a 3 way valve on the plate heat exchanger. This valve regulates the percentage flow of water through the PHE, relative to the percentage of bypass to the chillers. In high load conditions, 100% of water is pumped through the PHE. With no load, 0% of water goes through the PHE with full bypass to the chillers. In a low load condition, the valve modulates at between 0% and 100%. All of these scenarios achieve a close control of 20°C in the underground process reservoir.

Saudi Chiller Commissioning of Filtration Systems

Chiller Evaporators

The chiller evaporators are protected by a ‘y’ strainer on each inlet.

PHE Chiller Side

The plate heat exchanger also keeps contaminants from the process reaching the evaporators of the chillers. This prevents the premature failure of the evaporators and also prevents heat exchange issues due to thermal insulation.

PHE and Process Bollfilter

Both of these water systems go through a Bollfilter back flush system. As the difference in pressure between filter inlet and outlet reaches a predetermined level, the back flushing operation is initiated with a green light being illuminated. This feature prevents the need to manually clean the filter at scheduled intervals. During the visit, however, these filters were overwhelmed by the residue left in the pipes and a narrow 100 micron filter size. The maximum difference in pressure was exceeded and the filtration system yellow warning light became illuminated. The filters were stripped down, cleaned and reassembled.

‘Y’ Strainer in Parallel

The factory engineer who had designed the system had the foresight to build a second filter into the water system. This ‘y’ strainer runs in parallel to the above Bollfilter and ensures seamless operation of the factory in the event of a blocked Bollfilter.

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Start Up during Saudi Chiller Commissioning

On first start up of the chillers, they were both found to be tripping on high pressure and not loading up. The chillers run on R134a which is a low pressure refrigerant in the UK. In Saudi Arabia, however, the ambient is around 40°C. This translates to an operating pressure of between 15 bar and 18 bar depending on loading and water temperature.

Loading Solenoids

Unloader switches are available on each system. These feed back to the PLC, from here the program energises the loading solenoids. They had been set to 14 bar which was the cause of the unloading issue. Our overseas engineer set the switches to 19 bar.

High Pressure Switches

He then changed the high pressure cut outs from 15 bar to 20 bar.

PRVs Checked during Saudi Chiller Commissioning

The pressure relief valves vent at 23 bar which is enough of a difference in pressure from the high pressure cut out.

Low Load Trips

Because only one line was running at the time of commissioning, one of the chillers was found to have tripped on a low temperature related trip. This fault had occurred the following morning when the water temperature had become too low due to the minimum run time of the compressors. The freeze up set point was also found to be too high at 7°C. Our overseas engineer entered a password into the front end of each chiller and modified the parameters to prevent this fault re occurring.

Full Load Testing

The water system temperature was allowed to build up to 30°C when production in the factory was offline. Then, the chillers were ran in anger until set point was achieved. An efficient superheat value of 3°C was recorded on all of the systems. This is due to electronic expansion valves being fitted. When the factory came back online, the systems were found to be off cycling or unloading to match the load.

Chiller Redundancy

Redundancy has been considered in the capacity of the chillers to allow for future factory expansion and systems being offline during repairs.

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Global chilled water system service near Saint Basil's Cathedral

Global Chilled Water System Service

Moscow Visit

Always good for our engineers to get out of the country to carry out global chilled water system service. He just had a little free time this visit to see Red Square and Saint Basil's Cathedral. Most of the visit was bogged down resolving issues.

Electrical Problems

One of the chillers was pumping down due to electrical problems. One of the solenoids for the evaporator was not opening. All checked out okay with the solenoid coil and valve. Following the wiring diagram led to the relay board. The relay board is responsible to run various components around the compressor. It was not obviously blown and there were no dry soldered joints on the back. Our engineer decided to tighten up the wiring and unplug, then plug all the connectors back in. When he ran the chiller again the problem went away.

Chilled Water System Global Service

As we provide a global service: we cannot get back the day after leaving site. Therefore, after resolving the above issue, our engineer ran the system in local with some of the other systems off to prove it. All was okay. After completing the rest of the service on the chillers, he put the whole of the plant back in Auto to prove it all together.

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Flow Switch Failure during Global Chilled Water System Service

Due to security issues, this one of the most remote plant rooms for a flow switch to fail. The chiller did not stop when a test was carried out. Our engineer did not want to valve off the water system as the air handlers are old and 'dead heading' could cause failure. Instead, he decided to use the Hand/ Off/ Auto switch for the pump. After several attempts of trimming, he got the switch to settle down, then carried out tests to make sure it would not happen again.

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