From steam boilers and steam systems through compressed air systems to pressurised heating systems and other pressurised systems.
The Pressure Systems Safety Regulations 2000 (PSSR) call for a Written Scheme of Examination to be drawn up for the majority of pressure systems (some exemptions apply), including compressed air and steam systems, and for thorough examinations to be carried out accordingly. Our engineers will draw up the written schemes for you (schemes for simple systems are provided free of charge) and examine the plant accordingly. To minimise disruption, we aim to fit in with maintenance/shut down periods keeping downtime to a minimum while ensuring you comply with all current legislation.
Furthermore, the Thurra team will advise on exactly what needs to be inspected and when and will keep track of everything to ensure you are reminded when inspections are due.
The Thurra team is a good source of reference and guidance on these requirements; more detailed information is available in the HSE guide to the safe operation and maintenance of pressure systems: www.hse.gov.uk/pubns/indg261.pdf
Pressure systems that normally need to be inspected include:
- Compressed air systems (fixed and portable)
- Steam boilers and steam heating systems
- Steam autoclaves, vessels, retorts, drying cylinders etc.
- Heat exchangers and refrigeration plant
Common defects of Pressure Systems
Our Engineers are out in the field inspecting plant and equipment day in, day out. From this experience, we have compiled a series of reports of the most common defects they find, some tips on what you can do to stay safe in between inspections and simple preventative measures. Remember, some of these defects are not only inconvenient but may in some cases be fatal to operators or those in the vicinity.
- Defective safety valve – Air receivers are designed to operate within specific parameters. A defective safety valve can result in the over-pressurisation and the potential for significant damage to the air receiver and injury to those in its vicinity.
- High levels of condensate inside air receivers – Air receivers should be drained of water daily. Any build-up of water could cause condensate to travel down the air lines and damage technicians air tools. The compressor will operate more frequently causing the compressor and motor to overheat. All of which are expensive situations that can be easily avoided.
- Blocked blow down / drain valve – This will prevent the air receiver from being blown down daily as required. The results could be a build-up of water causing condensate to travel down the air lines and damage technicians air tools and overheating of the compressor and motor. Again, expensive situations that can be easily avoided
- High levels of emulsified oil inside the air receiver – As with high levels of condensate this potentially could be very expensive. The emulsified oil build up could also be identifying that there is excessive wear taking place within the compressor. Easily remedied if caught early.
- No clear indication of the safe working pressure marked on the air receiver – This has to be marked on the air receiver to aid the operators, service technicians and inspection engineer during the course of their duties.
The Thurra Engineer Surveyors share their findings of the most common faults they find when inspecting expansion vessels.
Top 5 Defects – Expansion vessels.
1 Expansion vessel low pressure – A common occurrence which can cause the heating system to operate inefficiently and in some circumstances cause air to be drawn into the heating system which may bring on the internal corrosion of susceptible components. Although the low pressure may seem to be more of an inconvenience than a dangerous situation, its resulting problems can be very expensive to put right and time consuming. The majority of expansion vessels do not have a local pressure indicator connected to the expansion vessel. However, a good indication of the pressure can be ascertained from other parts of the system.
Thurra’s experienced engineers at every inspection will carryout a full check on the expansion vessel to ensure that the system is operating at the desired pressure. On completion any defects are identified to the customer highlighting their significance.
2 Expansion vessel high pressure – Excessive pressure may cause the heating system to operate at the upper limits of its design capability and in certain circumstances cause the safety valve to lift as the heating system warms up. The over pressurisation of the expansion system and heating system can in some circumstances have a disastrous effect. Leading to failure of the system and the uncontrolled release of hot water. The over pressurisation can occur due to a number of reasons including the loss of the expansion vessels pre-charge pressure.
Checks on the expansion vessel to determine the state of the air pressure are conducted at every visit. If Thurra’s engineer concludes that the pre-charge pressure has been lost he will inform the customer who can then make arrangements to get the system returned to its original design specification.
3 Damaged Schrader valve – A damaged Schrader valve would not allow the expansion vessel to be recharged but could potentially cause the release of any pre-charge pressure to escape. Any damage to the Schrader valve would compromise the ability to set the pre-charge pressure and act as an integral part of the expansion vessels secure structure. The replacement of the valve is quite straight forward but would mean that the heating system is shut down.
Thurra’s engineer will check the integrity of the Schrader valve and advise the customer if the valve was no longer operating as designed
4 No clear indication of the safe working pressure – The safe working pressure has to be marked on the expansion vessel to aid the system operator, service technicians and inspection engineer during the course of their duties.
Most manufacturers display the safe working pressure on the manufacturers’ name plate, as well as stamping the details on the vessel. Thurra’s engineer will look to identify these and advise the customer if they should be clearly marked
5 Damaged internal bladder – A damaged internal bladder would mean that the heating system had potentially lost its thermal expansion capability. In this situation excessive pressures can be experienced and in turn cause the safety valve(s) to lift discharging hot water. The replacement of the bladder is time consuming and potentially expensive and would mean that the heating system is shut down.
Checks by Thurra’s experienced engineers would give early indication of a deterioration in the bladder’s operation. Thereby hopefully avoiding the catastrophic failure that would result in added expense and inconvenience.
If you require advice or help on any of the above, please get in touch or speak to your Insurance Broker who will be happy to arrange a call from Thurra for technical advice, or a visit by an experienced engineer.
- Expansion vessel low pressure– A common occurrence which can cause the heating system to operate inefficiently and in some circumstances cause air to be drawn into the heating system which may bring on the internal corrosion of susceptible components.
- Expansion vessel high pressure– Excessive pressure may cause the heating system to operate at the upper limits of its design capability and in certain circumstances cause the safety valve to lift as the heating system warms up.
- Damaged schrader valve– A damaged schrader valve would not allow the expansion vessel to be recharged. The replacement of the valve is quite straight forward but would mean that the heating system is shut down.
- No clear indication of the safe working pressure– The safe working pressure has to be marked on the expansion vessel to aid the system operator, service technicians and inspection engineer during the course of the duties.
- Damaged internal bladder– A damaged internal bladder would mean that the heating system had potentially lost its thermal expansion capability. In this situation excessive pressures can be experienced and in turn cause the safety valve(s) to lift discharging hot water. The replacement of the bladder is time consuming and potentially expensive and would mean that the heating system is shut down. Regular checks by Thurra’s experienced engineers would give early indication of a deterioration in the bladder operation.
Unpromulgated shutdowns can be very expensive and in some cases, dangerous.
Regular, thorough detailed examination regimes have the benefit of highlighting to the boiler owner the condition of the boiler and remedial actions that are required. These examinations, if carried out correctly, have the added benefit of keeping the boiler and its associated equipment safe. An industrial steam boiler or Industrial hot water boiler stores a vast amount of energy which if released uncontrollably could be a risk to personnel and equipment.
Steam boilers and hot water boilers are complex items of plant and as such, a significant amount of experience is required to be able to conduct a thorough and working examination of such high energy equipment. Thurra has a vast amount of experience in carrying out boiler examinations. We work extensively with the boiler service engineers and the Non-Destructive Test (NDT) engineers to ensure that high-energy equipment operates safely and within the confines of their design specification.
The 5 most common defects Steam Boilers and Associated Plant.
1 Poor Boiler Water Chemistry Management: Arguably the most common source of all boiler defects is poor boiler water chemistry management. This can result in a large build-up of ‘boiler water scale’ below and sometimes above the furnace tube. Any such build-up generally causes unequal heat removal from the furnace tube, resulting in excessive strain on certain areas. NDT engineers, as part of their 5-yearly test, specifically look for these areas and if found can result in a very expensive repair bill.
Annually, Thurra’s engineers review the chemistry log and assess the status of any chemical scale within the boiler. These examinations should give an early indication of the boiler water chemistry and remedial actions required.
2 Incorrect boiler water level indication: When the boiler water is too high, there is the possibility that water could be sent down the steam pipework causing extensive damage and potential failure of the downstream components. When the boiler water is too low there is the potential to uncover the furnace and boiler tubes thereby ultimately causing the boiler to overheat and fail.
During the course of the examination Thurra’s engineer will have the boiler water level control system stripped down, examined and when assembled, checked to be working on the operating boiler. In addition, our engineer will look at the operating log to see that the daily, weekly and monthly maintenance schedule is being completed.
3 Tube failure: Identifying and correcting the root cause of tube failures is essential to help lessen the chance of future problems. The tubes can fail for a number of reasons, including oxygen-pitting and flame impingement of the tube ends. In either case a partial retube or in some cases a full retube will be required, which is very costly and time consuming.
As part of the inspection programme, Thurra’s engineers inspect the condition of the tubes both internally and externally. Checking for any oxygen pitting which is generally caused by not having sufficient oxygen scavenger within the boiler water and flame impingement caused by the burner not being set up correctly. Early identification of these situations by Thurra will allow the boiler owner to make changes to his maintenance and operating settings that will prevent very costly and time-consuming repairs. Any defects identified with the boiler tubes will be explained to the boiler owner.
4 Passing Safety Valves: Safety valves are one of the features that give the boiler its ultimate safety mechanism. The devices will stop the boiler over-pressurising should one of the operating systems fail. If the safety valves are passing it will reduce the likelihood of the safety valves operating at the correct pressures and in some extreme cases cause the valves springs to rust which could prevent the safety valves from operating at all.
During the examination, the safety valves are stripped down, examined, reconditioned and reassembled. If required, Thurra’s engineer will ask for new valves to be fitted with all the supporting documentation. The final part of the examination is to see that the safety valves actually operate whilst the boiler is at operating temperature and design pressure. All results following the examination and test are communicated to the boiler owner.
5 Poor insulation: When the boiler is in operation it operates at extremely high temperatures. If the insulation is not sufficient there is the possibility that someone could receive a nasty burn.
At every examination, Thurra’s engineers assess the status of the insulation. This is carried out when the boiler is shut down and where insulation is exposed and can be carefully inspected, also, when the boiler is in operation when hot spots are very apparent. The results of any these examinations are communicated to the boiler owner before Thurra’s engineer leaves site.
If you require advice or help on any of the above, please speak to your Insurance Broker who will be happy to arrange a call or a visit from Thurra, or alternatively, get in touch.